We have a few flags that are inconsistently used to describe the fs in
different states of failure. As of 5963ffcaf3 ("btrfs: always abort
the transaction if we abort a trans handle") we will always set
BTRFS_FS_STATE_ERROR if we abort, so we don't have to check both ABORTED
and ERROR to see if things have gone wrong. Add a helper to check
BTRFS_FS_STATE_ERROR and then convert all checkers of FS_STATE_ERROR to
use the helper.
The TRANS_ABORTED bit check was added in af72273381 ("Btrfs: clean up
resources during umount after trans is aborted") but is not actually
specific.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Commit eafa4fd0ad ("btrfs: fix exhaustion of the system chunk array
due to concurrent allocations") fixed a problem that resulted in
exhausting the system chunk array in the superblock when there are many
tasks allocating chunks in parallel. Basically too many tasks enter the
first phase of chunk allocation without previous tasks having finished
their second phase of allocation, resulting in too many system chunks
being allocated. That was originally observed when running the fallocate
tests of stress-ng on a PowerPC machine, using a node size of 64K.
However that commit also introduced a deadlock where a task in phase 1 of
the chunk allocation waited for another task that had allocated a system
chunk to finish its phase 2, but that other task was waiting on an extent
buffer lock held by the first task, therefore resulting in both tasks not
making any progress. That change was later reverted by a patch with the
subject "btrfs: fix deadlock with concurrent chunk allocations involving
system chunks", since there is no simple and short solution to address it
and the deadlock is relatively easy to trigger on zoned filesystems, while
the system chunk array exhaustion is not so common.
This change reworks the chunk allocation to avoid the system chunk array
exhaustion. It accomplishes that by making the first phase of chunk
allocation do the updates of the device items in the chunk btree and the
insertion of the new chunk item in the chunk btree. This is done while
under the protection of the chunk mutex (fs_info->chunk_mutex), in the
same critical section that checks for available system space, allocates
a new system chunk if needed and reserves system chunk space. This way
we do not have chunk space reserved until the second phase completes.
The same logic is applied to chunk removal as well, since it keeps
reserved system space long after it is done updating the chunk btree.
For direct allocation of system chunks, the previous behaviour remains,
because otherwise we would deadlock on extent buffers of the chunk btree.
Changes to the chunk btree are by large done by chunk allocation and chunk
removal, which first reserve chunk system space and then later do changes
to the chunk btree. The other remaining cases are uncommon and correspond
to adding a device, removing a device and resizing a device. All these
other cases do not pre-reserve system space, they modify the chunk btree
right away, so they don't hold reserved space for a long period like chunk
allocation and chunk removal do.
The diff of this change is huge, but more than half of it is just addition
of comments describing both how things work regarding chunk allocation and
removal, including both the new behavior and the parts of the old behavior
that did not change.
CC: stable@vger.kernel.org # 5.12+
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Tested-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Tested-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When a task attempting to allocate a new chunk verifies that there is not
currently enough free space in the system space_info and there is another
task that allocated a new system chunk but it did not finish yet the
creation of the respective block group, it waits for that other task to
finish creating the block group. This is to avoid exhaustion of the system
chunk array in the superblock, which is limited, when we have a thundering
herd of tasks allocating new chunks. This problem was described and fixed
by commit eafa4fd0ad ("btrfs: fix exhaustion of the system chunk array
due to concurrent allocations").
However there are two very similar scenarios where this can lead to a
deadlock:
1) Task B allocated a new system chunk and task A is waiting on task B
to finish creation of the respective system block group. However before
task B ends its transaction handle and finishes the creation of the
system block group, it attempts to allocate another chunk (like a data
chunk for an fallocate operation for a very large range). Task B will
be unable to progress and allocate the new chunk, because task A set
space_info->chunk_alloc to 1 and therefore it loops at
btrfs_chunk_alloc() waiting for task A to finish its chunk allocation
and set space_info->chunk_alloc to 0, but task A is waiting on task B
to finish creation of the new system block group, therefore resulting
in a deadlock;
2) Task B allocated a new system chunk and task A is waiting on task B to
finish creation of the respective system block group. By the time that
task B enter the final phase of block group allocation, which happens
at btrfs_create_pending_block_groups(), when it modifies the extent
tree, the device tree or the chunk tree to insert the items for some
new block group, it needs to allocate a new chunk, so it ends up at
btrfs_chunk_alloc() and keeps looping there because task A has set
space_info->chunk_alloc to 1, but task A is waiting for task B to
finish creation of the new system block group and release the reserved
system space, therefore resulting in a deadlock.
In short, the problem is if a task B needs to allocate a new chunk after
it previously allocated a new system chunk and if another task A is
currently waiting for task B to complete the allocation of the new system
chunk.
Unfortunately this deadlock scenario introduced by the previous fix for
the system chunk array exhaustion problem does not have a simple and short
fix, and requires a big change to rework the chunk allocation code so that
chunk btree updates are all made in the first phase of chunk allocation.
And since this deadlock regression is being frequently hit on zoned
filesystems and the system chunk array exhaustion problem is triggered
in more extreme cases (originally observed on PowerPC with a node size
of 64K when running the fallocate tests from stress-ng), revert the
changes from that commit. The next patch in the series, with a subject
of "btrfs: rework chunk allocation to avoid exhaustion of the system
chunk array" does the necessary changes to fix the system chunk array
exhaustion problem.
Reported-by: Naohiro Aota <naohiro.aota@wdc.com>
Link: https://lore.kernel.org/linux-btrfs/20210621015922.ewgbffxuawia7liz@naota-xeon/
Fixes: eafa4fd0ad ("btrfs: fix exhaustion of the system chunk array due to concurrent allocations")
CC: stable@vger.kernel.org # 5.12+
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Tested-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Tested-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When doing a send we don't expect the task to ever start a transaction
after the initial check that verifies if commit roots match the regular
roots. This is because after that we set current->journal_info with a
stub (special value) that signals we are in send context, so that we take
a read lock on an extent buffer when reading it from disk and verifying
it is valid (its generation matches the generation stored in the parent).
This stub was introduced in 2014 by commit a26e8c9f75 ("Btrfs: don't
clear uptodate if the eb is under IO") in order to fix a concurrency issue
between send and balance.
However there is one particular exception where we end up needing to start
a transaction and when this happens it results in a crash with a stack
trace like the following:
[60015.902283] kernel: WARNING: CPU: 3 PID: 58159 at arch/x86/include/asm/kfence.h:44 kfence_protect_page+0x21/0x80
[60015.902292] kernel: Modules linked in: uinput rfcomm snd_seq_dummy (...)
[60015.902384] kernel: CPU: 3 PID: 58159 Comm: btrfs Not tainted 5.12.9-300.fc34.x86_64 #1
[60015.902387] kernel: Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./F2A88XN-WIFI, BIOS F6 12/24/2015
[60015.902389] kernel: RIP: 0010:kfence_protect_page+0x21/0x80
[60015.902393] kernel: Code: ff 0f 1f 84 00 00 00 00 00 55 48 89 fd (...)
[60015.902396] kernel: RSP: 0018:ffff9fb583453220 EFLAGS: 00010246
[60015.902399] kernel: RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff9fb583453224
[60015.902401] kernel: RDX: ffff9fb583453224 RSI: 0000000000000000 RDI: 0000000000000000
[60015.902402] kernel: RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
[60015.902404] kernel: R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
[60015.902406] kernel: R13: ffff9fb583453348 R14: 0000000000000000 R15: 0000000000000001
[60015.902408] kernel: FS: 00007f158e62d8c0(0000) GS:ffff93bd37580000(0000) knlGS:0000000000000000
[60015.902410] kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[60015.902412] kernel: CR2: 0000000000000039 CR3: 00000001256d2000 CR4: 00000000000506e0
[60015.902414] kernel: Call Trace:
[60015.902419] kernel: kfence_unprotect+0x13/0x30
[60015.902423] kernel: page_fault_oops+0x89/0x270
[60015.902427] kernel: ? search_module_extables+0xf/0x40
[60015.902431] kernel: ? search_bpf_extables+0x57/0x70
[60015.902435] kernel: kernelmode_fixup_or_oops+0xd6/0xf0
[60015.902437] kernel: __bad_area_nosemaphore+0x142/0x180
[60015.902440] kernel: exc_page_fault+0x67/0x150
[60015.902445] kernel: asm_exc_page_fault+0x1e/0x30
[60015.902450] kernel: RIP: 0010:start_transaction+0x71/0x580
[60015.902454] kernel: Code: d3 0f 84 92 00 00 00 80 e7 06 0f 85 63 (...)
[60015.902456] kernel: RSP: 0018:ffff9fb5834533f8 EFLAGS: 00010246
[60015.902458] kernel: RAX: 0000000000000001 RBX: 0000000000000001 RCX: 0000000000000000
[60015.902460] kernel: RDX: 0000000000000801 RSI: 0000000000000000 RDI: 0000000000000039
[60015.902462] kernel: RBP: ffff93bc0a7eb800 R08: 0000000000000001 R09: 0000000000000000
[60015.902463] kernel: R10: 0000000000098a00 R11: 0000000000000001 R12: 0000000000000001
[60015.902464] kernel: R13: 0000000000000000 R14: ffff93bc0c92b000 R15: ffff93bc0c92b000
[60015.902468] kernel: btrfs_commit_inode_delayed_inode+0x5d/0x120
[60015.902473] kernel: btrfs_evict_inode+0x2c5/0x3f0
[60015.902476] kernel: evict+0xd1/0x180
[60015.902480] kernel: inode_lru_isolate+0xe7/0x180
[60015.902483] kernel: __list_lru_walk_one+0x77/0x150
[60015.902487] kernel: ? iput+0x1a0/0x1a0
[60015.902489] kernel: ? iput+0x1a0/0x1a0
[60015.902491] kernel: list_lru_walk_one+0x47/0x70
[60015.902495] kernel: prune_icache_sb+0x39/0x50
[60015.902497] kernel: super_cache_scan+0x161/0x1f0
[60015.902501] kernel: do_shrink_slab+0x142/0x240
[60015.902505] kernel: shrink_slab+0x164/0x280
[60015.902509] kernel: shrink_node+0x2c8/0x6e0
[60015.902512] kernel: do_try_to_free_pages+0xcb/0x4b0
[60015.902514] kernel: try_to_free_pages+0xda/0x190
[60015.902516] kernel: __alloc_pages_slowpath.constprop.0+0x373/0xcc0
[60015.902521] kernel: ? __memcg_kmem_charge_page+0xc2/0x1e0
[60015.902525] kernel: __alloc_pages_nodemask+0x30a/0x340
[60015.902528] kernel: pipe_write+0x30b/0x5c0
[60015.902531] kernel: ? set_next_entity+0xad/0x1e0
[60015.902534] kernel: ? switch_mm_irqs_off+0x58/0x440
[60015.902538] kernel: __kernel_write+0x13a/0x2b0
[60015.902541] kernel: kernel_write+0x73/0x150
[60015.902543] kernel: send_cmd+0x7b/0xd0
[60015.902545] kernel: send_extent_data+0x5a3/0x6b0
[60015.902549] kernel: process_extent+0x19b/0xed0
[60015.902551] kernel: btrfs_ioctl_send+0x1434/0x17e0
[60015.902554] kernel: ? _btrfs_ioctl_send+0xe1/0x100
[60015.902557] kernel: _btrfs_ioctl_send+0xbf/0x100
[60015.902559] kernel: ? enqueue_entity+0x18c/0x7b0
[60015.902562] kernel: btrfs_ioctl+0x185f/0x2f80
[60015.902564] kernel: ? psi_task_change+0x84/0xc0
[60015.902569] kernel: ? _flat_send_IPI_mask+0x21/0x40
[60015.902572] kernel: ? check_preempt_curr+0x2f/0x70
[60015.902576] kernel: ? selinux_file_ioctl+0x137/0x1e0
[60015.902579] kernel: ? expand_files+0x1cb/0x1d0
[60015.902582] kernel: ? __x64_sys_ioctl+0x82/0xb0
[60015.902585] kernel: __x64_sys_ioctl+0x82/0xb0
[60015.902588] kernel: do_syscall_64+0x33/0x40
[60015.902591] kernel: entry_SYSCALL_64_after_hwframe+0x44/0xae
[60015.902595] kernel: RIP: 0033:0x7f158e38f0ab
[60015.902599] kernel: Code: ff ff ff 85 c0 79 9b (...)
[60015.902602] kernel: RSP: 002b:00007ffcb2519bf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[60015.902605] kernel: RAX: ffffffffffffffda RBX: 00007ffcb251ae00 RCX: 00007f158e38f0ab
[60015.902607] kernel: RDX: 00007ffcb2519cf0 RSI: 0000000040489426 RDI: 0000000000000004
[60015.902608] kernel: RBP: 0000000000000004 R08: 00007f158e297640 R09: 00007f158e297640
[60015.902610] kernel: R10: 0000000000000008 R11: 0000000000000246 R12: 0000000000000000
[60015.902612] kernel: R13: 0000000000000002 R14: 00007ffcb251aee0 R15: 0000558c1a83e2a0
[60015.902615] kernel: ---[ end trace 7bbc33e23bb887ae ]---
This happens because when writing to the pipe, by calling kernel_write(),
we end up doing page allocations using GFP_HIGHUSER | __GFP_ACCOUNT as the
gfp flags, which allow reclaim to happen if there is memory pressure. This
allocation happens at fs/pipe.c:pipe_write().
If the reclaim is triggered, inode eviction can be triggered and that in
turn can result in starting a transaction if the inode has a link count
of 0. The transaction start happens early on during eviction, when we call
btrfs_commit_inode_delayed_inode() at btrfs_evict_inode(). This happens if
there is currently an open file descriptor for an inode with a link count
of 0 and the reclaim task gets a reference on the inode before that
descriptor is closed, in which case the reclaim task ends up doing the
final iput that triggers the inode eviction.
When we have assertions enabled (CONFIG_BTRFS_ASSERT=y), this triggers
the following assertion at transaction.c:start_transaction():
/* Send isn't supposed to start transactions. */
ASSERT(current->journal_info != BTRFS_SEND_TRANS_STUB);
And when assertions are not enabled, it triggers a crash since after that
assertion we cast current->journal_info into a transaction handle pointer
and then dereference it:
if (current->journal_info) {
WARN_ON(type & TRANS_EXTWRITERS);
h = current->journal_info;
refcount_inc(&h->use_count);
(...)
Which obviously results in a crash due to an invalid memory access.
The same type of issue can happen during other memory allocations we
do directly in the send code with kmalloc (and friends) as they use
GFP_KERNEL and therefore may trigger reclaim too, which started to
happen since 2016 after commit e780b0d1c1 ("btrfs: send: use
GFP_KERNEL everywhere").
The issue could be solved by setting up a NOFS context for the entire
send operation so that reclaim could not be triggered when allocating
memory or pages through kernel_write(). However that is not very friendly
and we can in fact get rid of the send stub because:
1) The stub was introduced way back in 2014 by commit a26e8c9f75
("Btrfs: don't clear uptodate if the eb is under IO") to solve an
issue exclusive to when send and balance are running in parallel,
however there were other problems between balance and send and we do
not allow anymore to have balance and send run concurrently since
commit 9e967495e0 ("Btrfs: prevent send failures and crashes due
to concurrent relocation"). More generically the issues are between
send and relocation, and that last commit eliminated only the
possibility of having send and balance run concurrently, but shrinking
a device also can trigger relocation, and on zoned filesystems we have
relocation of partially used block groups triggered automatically as
well. The previous patch that has a subject of:
"btrfs: ensure relocation never runs while we have send operations running"
Addresses all the remaining cases that can trigger relocation.
2) We can actually allow starting and even committing transactions while
in a send context if needed because send is not holding any locks that
would block the start or the commit of a transaction.
So get rid of all the logic added by commit a26e8c9f75 ("Btrfs: don't
clear uptodate if the eb is under IO"). We can now always call
clear_extent_buffer_uptodate() at verify_parent_transid() since send is
the only case that uses commit roots without having a transaction open or
without holding the commit_root_sem.
Reported-by: Chris Murphy <lists@colorremedies.com>
Link: https://lore.kernel.org/linux-btrfs/CAJCQCtRQ57=qXo3kygwpwEBOU_CA_eKvdmjP52sU=eFvuVOEGw@mail.gmail.com/
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
qgroup_account_snapshot() is trying to unlock the not taken
tree_log_mutex in a error path. Since ret != 0 in this case, we can
just return from here.
Fixes: 2a4d84c11a ("btrfs: move delayed ref flushing for qgroup into qgroup helper")
CC: stable@vger.kernel.org # 5.12+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Function wait_current_trans_commit_start is now fairly trivial so it can
be inlined in its only caller.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There's only one caller left btrfs_ioctl_start_sync that passes 0, so we
can remove the switch in btrfs_commit_transaction_async.
A cleanup 9babda9f33 ("btrfs: Remove async_transid from
btrfs_mksubvol/create_subvol/create_snapshot") removed calls that passed
1, so this is a followup.
As this removes last call of wait_current_trans_commit_start_and_unblock,
remove the function as well.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The defrag loop processes leaves in batches and starting transaction for
each. The whole defragmentation on a given root is protected by a bit
but in case the transaction fails, the bit is not cleared
In case the transaction fails the bit would prevent starting
defragmentation again, so make sure it's cleared.
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
While stress testing our error handling I noticed that sometimes we
would still commit the transaction even though we had aborted the
transaction.
Currently we track if a trans handle has dirtied any metadata, and if it
hasn't we mark the filesystem as having an error (so no new transactions
can be started), but we will allow the current transaction to complete
as we do not mark the transaction itself as having been aborted.
This sounds good in theory, but we were not properly tracking IO errors
in btrfs_finish_ordered_io, and thus committing the transaction with
bogus free space data. This isn't necessarily a problem per-se with the
free space cache, as the other guards in place would have kept us from
accepting the free space cache as valid, but highlights a real world
case where we had a bug and could have corrupted the filesystem because
of it.
This "skip abort on empty trans handle" is nice in theory, but assumes
we have perfect error handling everywhere, which we clearly do not.
Also we do not allow further transactions to be started, so all this
does is save the last transaction that was happening, which doesn't
necessarily gain us anything other than the potential for real
corruption.
Remove this particular bit of code, if we decide we need to abort the
transaction then abort the current one and keep us from doing real harm
to the file system, regardless of whether this specific trans handle
dirtied anything or not.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There is a race between a task aborting a transaction during a commit,
a task doing an fsync and the transaction kthread, which leads to an
use-after-free of the log root tree. When this happens, it results in a
stack trace like the following:
BTRFS info (device dm-0): forced readonly
BTRFS warning (device dm-0): Skipping commit of aborted transaction.
BTRFS: error (device dm-0) in cleanup_transaction:1958: errno=-5 IO failure
BTRFS warning (device dm-0): lost page write due to IO error on /dev/mapper/error-test (-5)
BTRFS warning (device dm-0): Skipping commit of aborted transaction.
BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0xa4e8 len 4096 err no 10
BTRFS error (device dm-0): error writing primary super block to device 1
BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e000 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e008 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e010 len 4096 err no 10
BTRFS: error (device dm-0) in write_all_supers:4110: errno=-5 IO failure (1 errors while writing supers)
BTRFS: error (device dm-0) in btrfs_sync_log:3308: errno=-5 IO failure
general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b68: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
CPU: 2 PID: 2458471 Comm: fsstress Not tainted 5.12.0-rc5-btrfs-next-84 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
RIP: 0010:__mutex_lock+0x139/0xa40
Code: c0 74 19 (...)
RSP: 0018:ffff9f18830d7b00 EFLAGS: 00010202
RAX: 6b6b6b6b6b6b6b68 RBX: 0000000000000001 RCX: 0000000000000002
RDX: ffffffffb9c54d13 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff9f18830d7bc0 R08: 0000000000000000 R09: 0000000000000000
R10: ffff9f18830d7be0 R11: 0000000000000001 R12: ffff8c6cd199c040
R13: ffff8c6c95821358 R14: 00000000fffffffb R15: ffff8c6cbcf01358
FS: 00007fa9140c2b80(0000) GS:ffff8c6fac600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa913d52000 CR3: 000000013d2b4003 CR4: 0000000000370ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
? __btrfs_handle_fs_error+0xde/0x146 [btrfs]
? btrfs_sync_log+0x7c1/0xf20 [btrfs]
? btrfs_sync_log+0x7c1/0xf20 [btrfs]
btrfs_sync_log+0x7c1/0xf20 [btrfs]
btrfs_sync_file+0x40c/0x580 [btrfs]
do_fsync+0x38/0x70
__x64_sys_fsync+0x10/0x20
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7fa9142a55c3
Code: 8b 15 09 (...)
RSP: 002b:00007fff26278d48 EFLAGS: 00000246 ORIG_RAX: 000000000000004a
RAX: ffffffffffffffda RBX: 0000563c83cb4560 RCX: 00007fa9142a55c3
RDX: 00007fff26278cb0 RSI: 00007fff26278cb0 RDI: 0000000000000005
RBP: 0000000000000005 R08: 0000000000000001 R09: 00007fff26278d5c
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000340
R13: 00007fff26278de0 R14: 00007fff26278d96 R15: 0000563c83ca57c0
Modules linked in: btrfs dm_zero dm_snapshot dm_thin_pool (...)
---[ end trace ee2f1b19327d791d ]---
The steps that lead to this crash are the following:
1) We are at transaction N;
2) We have two tasks with a transaction handle attached to transaction N.
Task A and Task B. Task B is doing an fsync;
3) Task B is at btrfs_sync_log(), and has saved fs_info->log_root_tree
into a local variable named 'log_root_tree' at the top of
btrfs_sync_log(). Task B is about to call write_all_supers(), but
before that...
4) Task A calls btrfs_commit_transaction(), and after it sets the
transaction state to TRANS_STATE_COMMIT_START, an error happens before
it waits for the transaction's 'num_writers' counter to reach a value
of 1 (no one else attached to the transaction), so it jumps to the
label "cleanup_transaction";
5) Task A then calls cleanup_transaction(), where it aborts the
transaction, setting BTRFS_FS_STATE_TRANS_ABORTED on fs_info->fs_state,
setting the ->aborted field of the transaction and the handle to an
errno value and also setting BTRFS_FS_STATE_ERROR on fs_info->fs_state.
After that, at cleanup_transaction(), it deletes the transaction from
the list of transactions (fs_info->trans_list), sets the transaction
to the state TRANS_STATE_COMMIT_DOING and then waits for the number
of writers to go down to 1, as it's currently 2 (1 for task A and 1
for task B);
6) The transaction kthread is running and sees that BTRFS_FS_STATE_ERROR
is set in fs_info->fs_state, so it calls btrfs_cleanup_transaction().
There it sees the list fs_info->trans_list is empty, and then proceeds
into calling btrfs_drop_all_logs(), which frees the log root tree with
a call to btrfs_free_log_root_tree();
7) Task B calls write_all_supers() and, shortly after, under the label
'out_wake_log_root', it deferences the pointer stored in
'log_root_tree', which was already freed in the previous step by the
transaction kthread. This results in a use-after-free leading to a
crash.
Fix this by deleting the transaction from the list of transactions at
cleanup_transaction() only after setting the transaction state to
TRANS_STATE_COMMIT_DOING and waiting for all existing tasks that are
attached to the transaction to release their transaction handles.
This makes the transaction kthread wait for all the tasks attached to
the transaction to be done with the transaction before dropping the
log roots and doing other cleanups.
Fixes: ef67963dac ("btrfs: drop logs when we've aborted a transaction")
CC: stable@vger.kernel.org # 5.10+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_update_reloc_root will will return errors in the future, so handle
the error properly in commit_fs_roots.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We can create a reloc root when we record the root in the trans, which
can fail for all sorts of different reasons. Propagate this error up
the chain of callers. Future patches will fix the callers of
btrfs_record_root_in_trans() to handle the error.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
record_root_in_trans can currently fail, so handle this failure
properly.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
record_root_in_trans can fail currently, handle this failure properly.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
record_root_in_trans can fail currently, so handle this failure
properly.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_record_root_in_trans will return errors in the future, so handle
the error properly in start_transaction.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add comment ]
Signed-off-by: David Sterba <dsterba@suse.com>
When we are running out of space for updating the chunk tree, that is,
when we are low on available space in the system space info, if we have
many task concurrently allocating block groups, via fallocate for example,
many of them can end up all allocating new system chunks when only one is
needed. In extreme cases this can lead to exhaustion of the system chunk
array, which has a size limit of 2048 bytes, and results in a transaction
abort with errno EFBIG, producing a trace in dmesg like the following,
which was triggered on a PowerPC machine with a node/leaf size of 64K:
[1359.518899] ------------[ cut here ]------------
[1359.518980] BTRFS: Transaction aborted (error -27)
[1359.519135] WARNING: CPU: 3 PID: 16463 at ../fs/btrfs/block-group.c:1968 btrfs_create_pending_block_groups+0x340/0x3c0 [btrfs]
[1359.519152] Modules linked in: (...)
[1359.519239] Supported: Yes, External
[1359.519252] CPU: 3 PID: 16463 Comm: stress-ng Tainted: G X 5.3.18-47-default #1 SLE15-SP3
[1359.519274] NIP: c008000000e36fe8 LR: c008000000e36fe4 CTR: 00000000006de8e8
[1359.519293] REGS: c00000056890b700 TRAP: 0700 Tainted: G X (5.3.18-47-default)
[1359.519317] MSR: 800000000282b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 48008222 XER: 00000007
[1359.519356] CFAR: c00000000013e170 IRQMASK: 0
[1359.519356] GPR00: c008000000e36fe4 c00000056890b990 c008000000e83200 0000000000000026
[1359.519356] GPR04: 0000000000000000 0000000000000000 0000d52a3b027651 0000000000000007
[1359.519356] GPR08: 0000000000000003 0000000000000001 0000000000000007 0000000000000000
[1359.519356] GPR12: 0000000000008000 c00000063fe44600 000000001015e028 000000001015dfd0
[1359.519356] GPR16: 000000000000404f 0000000000000001 0000000000010000 0000dd1e287affff
[1359.519356] GPR20: 0000000000000001 c000000637c9a000 ffffffffffffffe5 0000000000000000
[1359.519356] GPR24: 0000000000000004 0000000000000000 0000000000000100 ffffffffffffffc0
[1359.519356] GPR28: c000000637c9a000 c000000630e09230 c000000630e091d8 c000000562188b08
[1359.519561] NIP [c008000000e36fe8] btrfs_create_pending_block_groups+0x340/0x3c0 [btrfs]
[1359.519613] LR [c008000000e36fe4] btrfs_create_pending_block_groups+0x33c/0x3c0 [btrfs]
[1359.519626] Call Trace:
[1359.519671] [c00000056890b990] [c008000000e36fe4] btrfs_create_pending_block_groups+0x33c/0x3c0 [btrfs] (unreliable)
[1359.519729] [c00000056890ba90] [c008000000d68d44] __btrfs_end_transaction+0xbc/0x2f0 [btrfs]
[1359.519782] [c00000056890bae0] [c008000000e309ac] btrfs_alloc_data_chunk_ondemand+0x154/0x610 [btrfs]
[1359.519844] [c00000056890bba0] [c008000000d8a0fc] btrfs_fallocate+0xe4/0x10e0 [btrfs]
[1359.519891] [c00000056890bd00] [c0000000004a23b4] vfs_fallocate+0x174/0x350
[1359.519929] [c00000056890bd50] [c0000000004a3cf8] ksys_fallocate+0x68/0xf0
[1359.519957] [c00000056890bda0] [c0000000004a3da8] sys_fallocate+0x28/0x40
[1359.519988] [c00000056890bdc0] [c000000000038968] system_call_exception+0xe8/0x170
[1359.520021] [c00000056890be20] [c00000000000cb70] system_call_common+0xf0/0x278
[1359.520037] Instruction dump:
[1359.520049] 7d0049ad 40c2fff4 7c0004ac 71490004 40820024 2f83fffb 419e0048 3c620000
[1359.520082] e863bcb8 7ec4b378 48010d91 e8410018 <0fe00000> 3c820000 e884bcc8 7ec6b378
[1359.520122] ---[ end trace d6c186e151022e20 ]---
The following steps explain how we can end up in this situation:
1) Task A is at check_system_chunk(), either because it is allocating a
new data or metadata block group, at btrfs_chunk_alloc(), or because
it is removing a block group or turning a block group RO. It does not
matter why;
2) Task A sees that there is not enough free space in the system
space_info object, that is 'left' is < 'thresh'. And at this point
the system space_info has a value of 0 for its 'bytes_may_use'
counter;
3) As a consequence task A calls btrfs_alloc_chunk() in order to allocate
a new system block group (chunk) and then reserves 'thresh' bytes in
the chunk block reserve with the call to btrfs_block_rsv_add(). This
changes the chunk block reserve's 'reserved' and 'size' counters by an
amount of 'thresh', and changes the 'bytes_may_use' counter of the
system space_info object from 0 to 'thresh'.
Also during its call to btrfs_alloc_chunk(), we end up increasing the
value of the 'total_bytes' counter of the system space_info object by
8MiB (the size of a system chunk stripe). This happens through the
call chain:
btrfs_alloc_chunk()
create_chunk()
btrfs_make_block_group()
btrfs_update_space_info()
4) After it finishes the first phase of the block group allocation, at
btrfs_chunk_alloc(), task A unlocks the chunk mutex;
5) At this point the new system block group was added to the transaction
handle's list of new block groups, but its block group item, device
items and chunk item were not yet inserted in the extent, device and
chunk trees, respectively. That only happens later when we call
btrfs_finish_chunk_alloc() through a call to
btrfs_create_pending_block_groups();
Note that only when we update the chunk tree, through the call to
btrfs_finish_chunk_alloc(), we decrement the 'reserved' counter
of the chunk block reserve as we COW/allocate extent buffers,
through:
btrfs_alloc_tree_block()
btrfs_use_block_rsv()
btrfs_block_rsv_use_bytes()
And the system space_info's 'bytes_may_use' is decremented everytime
we allocate an extent buffer for COW operations on the chunk tree,
through:
btrfs_alloc_tree_block()
btrfs_reserve_extent()
find_free_extent()
btrfs_add_reserved_bytes()
If we end up COWing less chunk btree nodes/leaves than expected, which
is the typical case since the amount of space we reserve is always
pessimistic to account for the worst possible case, we release the
unused space through:
btrfs_create_pending_block_groups()
btrfs_trans_release_chunk_metadata()
btrfs_block_rsv_release()
block_rsv_release_bytes()
btrfs_space_info_free_bytes_may_use()
But before task A gets into btrfs_create_pending_block_groups()...
6) Many other tasks start allocating new block groups through fallocate,
each one does the first phase of block group allocation in a
serialized way, since btrfs_chunk_alloc() takes the chunk mutex
before calling check_system_chunk() and btrfs_alloc_chunk().
However before everyone enters the final phase of the block group
allocation, that is, before calling btrfs_create_pending_block_groups(),
new tasks keep coming to allocate new block groups and while at
check_system_chunk(), the system space_info's 'bytes_may_use' keeps
increasing each time a task reserves space in the chunk block reserve.
This means that eventually some other task can end up not seeing enough
free space in the system space_info and decide to allocate yet another
system chunk.
This may repeat several times if yet more new tasks keep allocating
new block groups before task A, and all the other tasks, finish the
creation of the pending block groups, which is when reserved space
in excess is released. Eventually this can result in exhaustion of
system chunk array in the superblock, with btrfs_add_system_chunk()
returning EFBIG, resulting later in a transaction abort.
Even when we don't reach the extreme case of exhausting the system
array, most, if not all, unnecessarily created system block groups
end up being unused since when finishing creation of the first
pending system block group, the creation of the following ones end
up not needing to COW nodes/leaves of the chunk tree, so we never
allocate and deallocate from them, resulting in them never being
added to the list of unused block groups - as a consequence they
don't get deleted by the cleaner kthread - the only exceptions are
if we unmount and mount the filesystem again, which adds any unused
block groups to the list of unused block groups, if a scrub is
run, which also adds unused block groups to the unused list, and
under some circumstances when using a zoned filesystem or async
discard, which may also add unused block groups to the unused list.
So fix this by:
*) Tracking the number of reserved bytes for the chunk tree per
transaction, which is the sum of reserved chunk bytes by each
transaction handle currently being used;
*) When there is not enough free space in the system space_info,
if there are other transaction handles which reserved chunk space,
wait for some of them to complete in order to have enough excess
reserved space released, and then try again. Otherwise proceed with
the creation of a new system chunk.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Tree manipulating operations like merging nodes often release
once-allocated tree nodes. Such nodes are cleaned so that pages in the
node are not uselessly written out. On zoned volumes, however, such
optimization blocks the following IOs as the cancellation of the write
out of the freed blocks breaks the sequential write sequence expected by
the device.
Introduce a list of clean and unwritten extent buffers that have been
released in a transaction. Redirty the buffers so that
btree_write_cache_pages() can send proper bios to the devices.
Besides it clears the entire content of the extent buffer not to confuse
raw block scanners e.g. 'btrfs check'. By clearing the content,
csum_dirty_buffer() complains about bytenr mismatch, so avoid the
checking and checksum using newly introduced buffer flag
EXTENT_BUFFER_NO_CHECK.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Often an fsync needs to fallback to a transaction commit for several
reasons (to ensure consistency after a power failure, a new block group
was allocated or a temporary error such as ENOMEM or ENOSPC happened).
In that case the log is marked as needing a full commit and any concurrent
tasks attempting to log inodes or commit the log will also fallback to the
transaction commit. When this happens they all wait for the task that first
started the transaction commit to finish the transaction commit - however
they wait until the full transaction commit happens, which is not needed,
as they only need to wait for the superblocks to be persisted and not for
unpinning all the extents pinned during the transaction's lifetime, which
even for short lived transactions can be a few thousand and take some
significant amount of time to complete - for dbench workloads I have
observed up to 4~5 milliseconds of time spent unpinning extents in the
worst cases, and the number of pinned extents was between 2 to 3 thousand.
So allow fsync tasks to skip waiting for the unpinning of extents when
they call btrfs_commit_transaction() and they were not the task that
started the transaction commit (that one has to do it, the alternative
would be to offload the transaction commit to another task so that it
could avoid waiting for the extent unpinning or offload the extent
unpinning to another task).
This patch is part of a patchset comprised of the following patches:
btrfs: remove unnecessary directory inode item update when deleting dir entry
btrfs: stop setting nbytes when filling inode item for logging
btrfs: avoid logging new ancestor inodes when logging new inode
btrfs: skip logging directories already logged when logging all parents
btrfs: skip logging inodes already logged when logging new entries
btrfs: remove unnecessary check_parent_dirs_for_sync()
btrfs: make concurrent fsyncs wait less when waiting for a transaction commit
After applying the entire patchset, dbench shows improvements in respect
to throughput and latency. The script used to measure it is the following:
$ cat dbench-test.sh
#!/bin/bash
DEV=/dev/sdk
MNT=/mnt/sdk
MOUNT_OPTIONS="-o ssd"
MKFS_OPTIONS="-m single -d single"
echo "performance" | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
umount $DEV &> /dev/null
mkfs.btrfs -f $MKFS_OPTIONS $DEV
mount $MOUNT_OPTIONS $DEV $MNT
dbench -D $MNT -t 300 64
umount $MNT
The test was run on a physical machine with 12 cores (Intel corei7), 64G
of ram, using a NVMe device and a non-debug kernel configuration (Debian's
default configuration).
Before applying patchset, 32 clients:
Operation Count AvgLat MaxLat
----------------------------------------
NTCreateX 9627107 0.153 61.938
Close 7072076 0.001 3.175
Rename 407633 1.222 44.439
Unlink 1943895 0.658 44.440
Deltree 256 17.339 110.891
Mkdir 128 0.003 0.009
Qpathinfo 8725406 0.064 17.850
Qfileinfo 1529516 0.001 2.188
Qfsinfo 1599884 0.002 1.457
Sfileinfo 784200 0.005 3.562
Find 3373513 0.411 30.312
WriteX 4802132 0.053 29.054
ReadX 15089959 0.002 5.801
LockX 31344 0.002 0.425
UnlockX 31344 0.001 0.173
Flush 674724 5.952 341.830
Throughput 1008.02 MB/sec 32 clients 32 procs max_latency=341.833 ms
After applying patchset, 32 clients:
After patchset, with 32 clients:
Operation Count AvgLat MaxLat
----------------------------------------
NTCreateX 9931568 0.111 25.597
Close 7295730 0.001 2.171
Rename 420549 0.982 49.714
Unlink 2005366 0.497 39.015
Deltree 256 11.149 89.242
Mkdir 128 0.002 0.014
Qpathinfo 9001863 0.049 20.761
Qfileinfo 1577730 0.001 2.546
Qfsinfo 1650508 0.002 3.531
Sfileinfo 809031 0.005 5.846
Find 3480259 0.309 23.977
WriteX 4952505 0.043 41.283
ReadX 15568127 0.002 5.476
LockX 32338 0.002 0.978
UnlockX 32338 0.001 2.032
Flush 696017 7.485 228.835
Throughput 1049.91 MB/sec 32 clients 32 procs max_latency=228.847 ms
--> +4.1% throughput, -39.6% max latency
Before applying patchset, 64 clients:
Operation Count AvgLat MaxLat
----------------------------------------
NTCreateX 8956748 0.342 108.312
Close 6579660 0.001 3.823
Rename 379209 2.396 81.897
Unlink 1808625 1.108 131.148
Deltree 256 25.632 172.176
Mkdir 128 0.003 0.018
Qpathinfo 8117615 0.131 55.916
Qfileinfo 1423495 0.001 2.635
Qfsinfo 1488496 0.002 5.412
Sfileinfo 729472 0.007 8.643
Find 3138598 0.855 78.321
WriteX 4470783 0.102 79.442
ReadX 14038139 0.002 7.578
LockX 29158 0.002 0.844
UnlockX 29158 0.001 0.567
Flush 627746 14.168 506.151
Throughput 924.738 MB/sec 64 clients 64 procs max_latency=506.154 ms
After applying patchset, 64 clients:
Operation Count AvgLat MaxLat
----------------------------------------
NTCreateX 9069003 0.303 43.193
Close 6662328 0.001 3.888
Rename 383976 2.194 46.418
Unlink 1831080 1.022 43.873
Deltree 256 24.037 155.763
Mkdir 128 0.002 0.005
Qpathinfo 8219173 0.137 30.233
Qfileinfo 1441203 0.001 3.204
Qfsinfo 1507092 0.002 4.055
Sfileinfo 738775 0.006 5.431
Find 3177874 0.936 38.170
WriteX 4526152 0.084 39.518
ReadX 14213562 0.002 24.760
LockX 29522 0.002 1.221
UnlockX 29522 0.001 0.694
Flush 635652 14.358 422.039
Throughput 990.13 MB/sec 64 clients 64 procs max_latency=422.043 ms
--> +6.8% throughput, -18.1% max latency
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We love running delayed refs in commit_cowonly_roots, but it is a bit
excessive. I was seeing cases of running 3 or 4 refs a few times in a
row during this time. Instead simply:
- update all of the roots first
- then run delayed refs
- then handle the empty block groups case
- and then if we have any more dirty roots do the whole thing again
This allows us to be much more efficient with our delayed ref running,
as we can batch a few more operations at once.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This was added in commit 361048f586 ("Btrfs: fix full backref problem
when inserting shared block reference") to address a problem where we
hit the following BUG_ON() in alloc_reserved_tree_block
if (node->type == BTRFS_SHARED_BLOCK_REF_KEY) {
BUG_ON(!(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF));
However this BUG_ON() is bogus, and was removed by previous commit:
btrfs: remove bogus BUG_ON in alloc_reserved_tree_block
We no longer need to run delayed refs because of this, and can remove
this flushing here.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The commit d672633545 ("btrfs: qgroup: Make snapshot accounting work
with new extent-oriented qgroup.") added a flush of the delayed refs
during snapshot creation in order to get the qgroup accounting properly.
However this code has changed and been moved to it's own helper that is
skipped if qgroups are turned off. Move the flushing to the helper, as
we do not need it when qgroups are turned off.
Also add a comment explaining why it exists, and why it doesn't actually
save us. This will be helpful later when we try to fix qgroup
accounting properly.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We try to pre-flush the delayed refs when committing, because we want to
do as little work as possible in the critical section of the transaction
commit.
However doing this twice can lead to very long transaction commit delays
as other threads are allowed to continue to generate more delayed refs,
which potentially delays the commit by multiple minutes in very extreme
cases.
So simply stick to one pre-flush, and then continue the rest of the
transaction commit.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
I've been running a stress test that runs 20 workers in their own
subvolume, which are running an fsstress instance with 4 threads per
worker, which is 80 total fsstress threads. In addition to this I'm
running balance in the background as well as creating and deleting
snapshots. This test takes around 12 hours to run normally, going
slower and slower as the test goes on.
The reason for this is because fsstress is running fsync sometimes, and
because we're messing with block groups we often fall through to
btrfs_commit_transaction, so will often have 20-30 threads all calling
btrfs_commit_transaction at the same time.
These all get stuck contending on the extent tree while they try to run
delayed refs during the initial part of the commit.
This is suboptimal, really because the extent tree is a single point of
failure we only want one thread acting on that tree at once to reduce
lock contention.
Fix this by making the flushing mechanism a bit operation, to make it
easy to use test_and_set_bit() in order to make sure only one task does
this initial flush.
Once we're into the transaction commit we only have one thread doing
delayed ref running, it's just this initial pre-flush that is
problematic. With this patch my stress test takes around 90 minutes to
run, instead of 12 hours.
The memory barrier is not necessary for the flushing bit as it's
ordered, unlike plain int. The transaction state accessed in
btrfs_should_end_transaction could be affected by that too as it's not
always used under transaction lock. Upon Nikolay's analysis in [1]
it's not necessary:
In should_end_transaction it's read without holding any locks. (U)
It's modified in btrfs_cleanup_transaction without holding the
fs_info->trans_lock (U), but the STATE_ERROR flag is going to be set.
set in cleanup_transaction under fs_info->trans_lock (L)
set in btrfs_commit_trans to COMMIT_START under fs_info->trans_lock.(L)
set in btrfs_commit_trans to COMMIT_DOING under fs_info->trans_lock.(L)
set in btrfs_commit_trans to COMMIT_UNBLOCK under
fs_info->trans_lock.(L)
set in btrfs_commit_trans to COMMIT_COMPLETED without locks but at this
point the transaction is finished and fs_info->running_trans is NULL (U
but irrelevant).
So by the looks of it we can have a concurrent READ race with a WRITE,
due to reads not taking a lock. In this case what we want to ensure is
we either see new or old state. I consulted with Will Deacon and he said
that in such a case we'd want to annotate the accesses to ->state with
(READ|WRITE)_ONCE so as to avoid a theoretical tear, in this case I
don't think this could happen but I imagine at some point KCSAN would
flag such an access as racy (which it is).
[1] https://lore.kernel.org/linux-btrfs/e1fd5cc1-0f28-f670-69f4-e9958b4964e6@suse.com
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
[ add comments regarding memory barrier ]
Signed-off-by: David Sterba <dsterba@suse.com>
This better reflects the semantics of the function i.e no search is
performed whatsoever.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
While doing error injection I would sometimes get a corrupt file system.
This is because I was injecting errors at btrfs_search_slot, but would
only do it one time per stack. This uncovered a problem in
commit_fs_roots, where if we get an error we would just break. However
we're in a nested loop, the first loop being a loop to find all the
dirty fs roots, and then subsequent root updates would succeed clearing
the error value.
This isn't likely to happen in real scenarios, however we could
potentially get a random ENOMEM once and then not again, and we'd end up
with a corrupted file system. Fix this by moving the error checking
around a bit to the main loop, as this is the only place where something
will fail, and return the error as soon as it occurs.
With this patch my reproducer no longer corrupts the file system.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The inode number cache has been removed in this dev cycle, there's one
more leftover. We don't need to run the delayed refs again after
commit_fs_roots as stated in the comment, because btrfs_save_ino_cache
is no more since 5297199a8b ("btrfs: remove inode number cache
feature").
Nothing else between commit_fs_roots and btrfs_qgroup_account_extents
could create new delayed refs so the qgroup consistency should be safe.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When mounting, btrfs uses the cache_generation in the super block to
determine if space cache v1 is in use. However, by mounting with
nospace_cache or space_cache=v2, it is possible to disable space cache
v1, which does not result in un-setting cache_generation back to 0.
In order to base some logic, like mount option printing in /proc/mounts,
on the current state of the space cache rather than just the values of
the mount option, keep the value of cache_generation consistent with the
status of space cache v1.
We ensure that cache_generation > 0 iff the file system is using
space_cache v1. This requires committing a transaction on any mount
which changes whether we are using v1. (v1->nospace_cache, v1->v2,
nospace_cache->v1, v2->v1).
Since the mechanism for writing out the cache generation is transaction
commit, but we want some finer grained control over when we un-set it,
we can't just rely on the SPACE_CACHE mount option, and introduce an
fs_info flag that mount can use when it wants to unset the generation.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
It's been deprecated since commit b547a88ea5 ("btrfs: start
deprecation of mount option inode_cache") which enumerates the reasons.
A filesystem that uses the feature (mount -o inode_cache) tracks the
inode numbers in bitmaps, that data stay on the filesystem after this
patch. The size is roughly 5MiB for 1M inodes [1], which is considered
small enough to be left there. Removal of the change can be implemented
in btrfs-progs if needed.
[1] https://lore.kernel.org/linux-btrfs/20201127145836.GZ6430@twin.jikos.cz/
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
While writing an explanation for the need of the commit_root_sem for
btrfs_prepare_extent_commit, I realized we have a slight hole that could
result in leaked space if we have to do the old style caching. Consider
the following scenario
commit root
+----+----+----+----+----+----+----+
|\\\\| |\\\\|\\\\| |\\\\|\\\\|
+----+----+----+----+----+----+----+
0 1 2 3 4 5 6 7
new commit root
+----+----+----+----+----+----+----+
| | | |\\\\| | |\\\\|
+----+----+----+----+----+----+----+
0 1 2 3 4 5 6 7
Prior to this patch, we run btrfs_prepare_extent_commit, which updates
the last_byte_to_unpin, and then we subsequently run
switch_commit_roots. In this example lets assume that
caching_ctl->progress == 1 at btrfs_prepare_extent_commit() time, which
means that cache->last_byte_to_unpin == 1. Then we go and do the
switch_commit_roots(), but in the meantime the caching thread has made
some more progress, because we drop the commit_root_sem and re-acquired
it. Now caching_ctl->progress == 3. We swap out the commit root and
carry on to unpin.
The race can happen like:
1) The caching thread was running using the old commit root when it
found the extent for [2, 3);
2) Then it released the commit_root_sem because it was in the last
item of a leaf and the semaphore was contended, and set ->progress
to 3 (value of 'last'), as the last extent item in the current leaf
was for the extent for range [2, 3);
3) Next time it gets the commit_root_sem, will start using the new
commit root and search for a key with offset 3, so it never finds
the hole for [2, 3).
So the caching thread never saw [2, 3) as free space in any of the
commit roots, and by the time finish_extent_commit() was called for
the range [0, 3), ->last_byte_to_unpin was 1, so it only returned the
subrange [0, 1) to the free space cache, skipping [2, 3).
In the unpin code we have last_byte_to_unpin == 1, so we unpin [0,1),
but do not unpin [2,3). However because caching_ctl->progress == 3 we
do not see the newly freed section of [2,3), and thus do not add it to
our free space cache. This results in us missing a chunk of free space
in memory (on disk too, unless we have a power failure before writing
the free space cache to disk).
Fix this by making sure the ->last_byte_to_unpin is set at the same time
that we swap the commit roots, this ensures that we will always be
consistent.
CC: stable@vger.kernel.org # 5.8+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
[ update changelog with Filipe's review comments ]
Signed-off-by: David Sterba <dsterba@suse.com>
Now that we're using a rw_semaphore we no longer need to indicate if a
lock is blocking or not, nor do we need to flip the entire path from
blocking to spinning. Remove these helpers and all the places they are
called.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We do not need anymore to start writeback for delalloc of roots that are
being snapshotted and wait for it to complete. This was done in commit
609e804d77 ("Btrfs: fix file corruption after snapshotting due to mix
of buffered/DIO writes") to fix a type of file corruption where files in a
snapshot end up having their i_size updated in a non-ordered way, leaving
implicit file holes, when buffered IO writes that increase a file's size
are followed by direct IO writes that also increase the file's size.
This is not needed anymore because we now have a more generic mechanism
to prevent a non-ordered i_size update since commit 9ddc959e80
("btrfs: use the file extent tree infrastructure"), which addresses this
scenario involving snapshots as well.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When we COW a block we are holding a lock on the original block, and
then we lock the new COW block. Because our lockdep maps are based on
root + level, this will make lockdep complain. We need a way to
indicate a subclass for locking the COW'ed block, so plumb through our
btrfs_lock_nesting from btrfs_cow_block down to the btrfs_init_buffer,
and then introduce BTRFS_NESTING_COW to be used for cow'ing blocks.
The reason I've added all this extra infrastructure is because there
will be need of different nesting classes in follow up patches.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently regardless of a full or a fast fsync we always wait for ordered
extents to complete, and then start logging the inode after that. However
for fast fsyncs we can just wait for the writeback to complete, we don't
need to wait for the ordered extents to complete since we use the list of
modified extents maps to figure out which extents we must log and we can
get their checksums directly from the ordered extents that are still in
flight, otherwise look them up from the checksums tree.
Until commit b5e6c3e170 ("btrfs: always wait on ordered extents at
fsync time"), for fast fsyncs, we used to start logging without even
waiting for the writeback to complete first, we would wait for it to
complete after logging, while holding a transaction open, which lead to
performance issues when using cgroups and probably for other cases too,
as wait for IO while holding a transaction handle should be avoided as
much as possible. After that, for fast fsyncs, we started to wait for
ordered extents to complete before starting to log, which adds some
latency to fsyncs and we even got at least one report about a performance
drop which bisected to that particular change:
https://lore.kernel.org/linux-btrfs/20181109215148.GF23260@techsingularity.net/
This change makes fast fsyncs only wait for writeback to finish before
starting to log the inode, instead of waiting for both the writeback to
finish and for the ordered extents to complete. This brings back part of
the logic we had that extracts checksums from in flight ordered extents,
which are not yet in the checksums tree, and making sure transaction
commits wait for the completion of ordered extents previously logged
(by far most of the time they have already completed by the time a
transaction commit starts, resulting in no wait at all), to avoid any
data loss if an ordered extent completes after the transaction used to
log an inode is committed, followed by a power failure.
When there are no other tasks accessing the checksums and the subvolume
btrees, the ordered extent completion is pretty fast, typically taking
100 to 200 microseconds only in my observations. However when there are
other tasks accessing these btrees, ordered extent completion can take a
lot more time due to lock contention on nodes and leaves of these btrees.
I've seen cases over 2 milliseconds, which starts to be significant. In
particular when we do have concurrent fsyncs against different files there
is a lot of contention on the checksums btree, since we have many tasks
writing the checksums into the btree and other tasks that already started
the logging phase are doing lookups for checksums in the btree.
This change also turns all ranged fsyncs into full ranged fsyncs, which
is something we already did when not using the NO_HOLES features or when
doing a full fsync. This is to guarantee we never miss checksums due to
writeback having been triggered only for a part of an extent, and we end
up logging the full extent but only checksums for the written range, which
results in missing checksums after log replay. Allowing ranged fsyncs to
operate again only in the original range, when using the NO_HOLES feature
and doing a fast fsync is doable but requires some non trivial changes to
the writeback path, which can always be worked on later if needed, but I
don't think they are a very common use case.
Several tests were performed using fio for different numbers of concurrent
jobs, each writing and fsyncing its own file, for both sequential and
random file writes. The tests were run on bare metal, no virtualization,
on a box with 12 cores (Intel i7-8700), 64Gb of RAM and a NVMe device,
with a kernel configuration that is the default of typical distributions
(debian in this case), without debug options enabled (kasan, kmemleak,
slub debug, debug of page allocations, lock debugging, etc).
The following script that calls fio was used:
$ cat test-fsync.sh
#!/bin/bash
DEV=/dev/nvme0n1
MNT=/mnt/btrfs
MOUNT_OPTIONS="-o ssd -o space_cache=v2"
MKFS_OPTIONS="-d single -m single"
if [ $# -ne 5 ]; then
echo "Use $0 NUM_JOBS FILE_SIZE FSYNC_FREQ BLOCK_SIZE [write|randwrite]"
exit 1
fi
NUM_JOBS=$1
FILE_SIZE=$2
FSYNC_FREQ=$3
BLOCK_SIZE=$4
WRITE_MODE=$5
if [ "$WRITE_MODE" != "write" ] && [ "$WRITE_MODE" != "randwrite" ]; then
echo "Invalid WRITE_MODE, must be 'write' or 'randwrite'"
exit 1
fi
cat <<EOF > /tmp/fio-job.ini
[writers]
rw=$WRITE_MODE
fsync=$FSYNC_FREQ
fallocate=none
group_reporting=1
direct=0
bs=$BLOCK_SIZE
ioengine=sync
size=$FILE_SIZE
directory=$MNT
numjobs=$NUM_JOBS
EOF
echo "performance" | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
echo
echo "Using config:"
echo
cat /tmp/fio-job.ini
echo
umount $MNT &> /dev/null
mkfs.btrfs -f $MKFS_OPTIONS $DEV
mount $MOUNT_OPTIONS $DEV $MNT
fio /tmp/fio-job.ini
umount $MNT
The results were the following:
*************************
*** sequential writes ***
*************************
==== 1 job, 8GiB file, fsync frequency 1, block size 64KiB ====
Before patch:
WRITE: bw=36.6MiB/s (38.4MB/s), 36.6MiB/s-36.6MiB/s (38.4MB/s-38.4MB/s), io=8192MiB (8590MB), run=223689-223689msec
After patch:
WRITE: bw=40.2MiB/s (42.1MB/s), 40.2MiB/s-40.2MiB/s (42.1MB/s-42.1MB/s), io=8192MiB (8590MB), run=203980-203980msec
(+9.8%, -8.8% runtime)
==== 2 jobs, 4GiB files, fsync frequency 1, block size 64KiB ====
Before patch:
WRITE: bw=35.8MiB/s (37.5MB/s), 35.8MiB/s-35.8MiB/s (37.5MB/s-37.5MB/s), io=8192MiB (8590MB), run=228950-228950msec
After patch:
WRITE: bw=43.5MiB/s (45.6MB/s), 43.5MiB/s-43.5MiB/s (45.6MB/s-45.6MB/s), io=8192MiB (8590MB), run=188272-188272msec
(+21.5% throughput, -17.8% runtime)
==== 4 jobs, 2GiB files, fsync frequency 1, block size 64KiB ====
Before patch:
WRITE: bw=50.1MiB/s (52.6MB/s), 50.1MiB/s-50.1MiB/s (52.6MB/s-52.6MB/s), io=8192MiB (8590MB), run=163446-163446msec
After patch:
WRITE: bw=64.5MiB/s (67.6MB/s), 64.5MiB/s-64.5MiB/s (67.6MB/s-67.6MB/s), io=8192MiB (8590MB), run=126987-126987msec
(+28.7% throughput, -22.3% runtime)
==== 8 jobs, 1GiB files, fsync frequency 1, block size 64KiB ====
Before patch:
WRITE: bw=64.0MiB/s (68.1MB/s), 64.0MiB/s-64.0MiB/s (68.1MB/s-68.1MB/s), io=8192MiB (8590MB), run=126075-126075msec
After patch:
WRITE: bw=86.8MiB/s (91.0MB/s), 86.8MiB/s-86.8MiB/s (91.0MB/s-91.0MB/s), io=8192MiB (8590MB), run=94358-94358msec
(+35.6% throughput, -25.2% runtime)
==== 16 jobs, 512MiB files, fsync frequency 1, block size 64KiB ====
Before patch:
WRITE: bw=79.8MiB/s (83.6MB/s), 79.8MiB/s-79.8MiB/s (83.6MB/s-83.6MB/s), io=8192MiB (8590MB), run=102694-102694msec
After patch:
WRITE: bw=107MiB/s (112MB/s), 107MiB/s-107MiB/s (112MB/s-112MB/s), io=8192MiB (8590MB), run=76446-76446msec
(+34.1% throughput, -25.6% runtime)
==== 32 jobs, 512MiB files, fsync frequency 1, block size 64KiB ====
Before patch:
WRITE: bw=93.2MiB/s (97.7MB/s), 93.2MiB/s-93.2MiB/s (97.7MB/s-97.7MB/s), io=16.0GiB (17.2GB), run=175836-175836msec
After patch:
WRITE: bw=111MiB/s (117MB/s), 111MiB/s-111MiB/s (117MB/s-117MB/s), io=16.0GiB (17.2GB), run=147001-147001msec
(+19.1% throughput, -16.4% runtime)
==== 64 jobs, 512MiB files, fsync frequency 1, block size 64KiB ====
Before patch:
WRITE: bw=108MiB/s (114MB/s), 108MiB/s-108MiB/s (114MB/s-114MB/s), io=32.0GiB (34.4GB), run=302656-302656msec
After patch:
WRITE: bw=133MiB/s (140MB/s), 133MiB/s-133MiB/s (140MB/s-140MB/s), io=32.0GiB (34.4GB), run=246003-246003msec
(+23.1% throughput, -18.7% runtime)
************************
*** random writes ***
************************
==== 1 job, 8GiB file, fsync frequency 16, block size 4KiB ====
Before patch:
WRITE: bw=11.5MiB/s (12.0MB/s), 11.5MiB/s-11.5MiB/s (12.0MB/s-12.0MB/s), io=8192MiB (8590MB), run=714281-714281msec
After patch:
WRITE: bw=11.6MiB/s (12.2MB/s), 11.6MiB/s-11.6MiB/s (12.2MB/s-12.2MB/s), io=8192MiB (8590MB), run=705959-705959msec
(+0.9% throughput, -1.7% runtime)
==== 2 jobs, 4GiB files, fsync frequency 16, block size 4KiB ====
Before patch:
WRITE: bw=12.8MiB/s (13.5MB/s), 12.8MiB/s-12.8MiB/s (13.5MB/s-13.5MB/s), io=8192MiB (8590MB), run=638101-638101msec
After patch:
WRITE: bw=13.1MiB/s (13.7MB/s), 13.1MiB/s-13.1MiB/s (13.7MB/s-13.7MB/s), io=8192MiB (8590MB), run=625374-625374msec
(+2.3% throughput, -2.0% runtime)
==== 4 jobs, 2GiB files, fsync frequency 16, block size 4KiB ====
Before patch:
WRITE: bw=15.4MiB/s (16.2MB/s), 15.4MiB/s-15.4MiB/s (16.2MB/s-16.2MB/s), io=8192MiB (8590MB), run=531146-531146msec
After patch:
WRITE: bw=17.8MiB/s (18.7MB/s), 17.8MiB/s-17.8MiB/s (18.7MB/s-18.7MB/s), io=8192MiB (8590MB), run=460431-460431msec
(+15.6% throughput, -13.3% runtime)
==== 8 jobs, 1GiB files, fsync frequency 16, block size 4KiB ====
Before patch:
WRITE: bw=19.9MiB/s (20.8MB/s), 19.9MiB/s-19.9MiB/s (20.8MB/s-20.8MB/s), io=8192MiB (8590MB), run=412664-412664msec
After patch:
WRITE: bw=22.2MiB/s (23.3MB/s), 22.2MiB/s-22.2MiB/s (23.3MB/s-23.3MB/s), io=8192MiB (8590MB), run=368589-368589msec
(+11.6% throughput, -10.7% runtime)
==== 16 jobs, 512MiB files, fsync frequency 16, block size 4KiB ====
Before patch:
WRITE: bw=29.3MiB/s (30.7MB/s), 29.3MiB/s-29.3MiB/s (30.7MB/s-30.7MB/s), io=8192MiB (8590MB), run=279924-279924msec
After patch:
WRITE: bw=30.4MiB/s (31.9MB/s), 30.4MiB/s-30.4MiB/s (31.9MB/s-31.9MB/s), io=8192MiB (8590MB), run=269258-269258msec
(+3.8% throughput, -3.8% runtime)
==== 32 jobs, 512MiB files, fsync frequency 16, block size 4KiB ====
Before patch:
WRITE: bw=36.9MiB/s (38.7MB/s), 36.9MiB/s-36.9MiB/s (38.7MB/s-38.7MB/s), io=16.0GiB (17.2GB), run=443581-443581msec
After patch:
WRITE: bw=41.6MiB/s (43.6MB/s), 41.6MiB/s-41.6MiB/s (43.6MB/s-43.6MB/s), io=16.0GiB (17.2GB), run=394114-394114msec
(+12.7% throughput, -11.2% runtime)
==== 64 jobs, 512MiB files, fsync frequency 16, block size 4KiB ====
Before patch:
WRITE: bw=45.9MiB/s (48.1MB/s), 45.9MiB/s-45.9MiB/s (48.1MB/s-48.1MB/s), io=32.0GiB (34.4GB), run=714614-714614msec
After patch:
WRITE: bw=48.8MiB/s (51.1MB/s), 48.8MiB/s-48.8MiB/s (51.1MB/s-51.1MB/s), io=32.0GiB (34.4GB), run=672087-672087msec
(+6.3% throughput, -6.0% runtime)
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Eric reported seeing this message while running generic/475
BTRFS: error (device dm-3) in btrfs_sync_log:3084: errno=-117 Filesystem corrupted
Full stack trace:
BTRFS: error (device dm-0) in btrfs_commit_transaction:2323: errno=-5 IO failure (Error while writing out transaction)
BTRFS info (device dm-0): forced readonly
BTRFS warning (device dm-0): Skipping commit of aborted transaction.
------------[ cut here ]------------
BTRFS: error (device dm-0) in cleanup_transaction:1894: errno=-5 IO failure
BTRFS: Transaction aborted (error -117)
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c6480 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c6488 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c6490 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c6498 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c64a0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c64a8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c64b0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c64b8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3555 rw 0,0 sector 0x1c64c0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3572 rw 0,0 sector 0x1b85e8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3572 rw 0,0 sector 0x1b85f0 len 4096 err no 10
WARNING: CPU: 3 PID: 23985 at fs/btrfs/tree-log.c:3084 btrfs_sync_log+0xbc8/0xd60 [btrfs]
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d4288 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d4290 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d4298 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42a0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42a8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42b0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42b8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42c0 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42c8 len 4096 err no 10
BTRFS warning (device dm-0): direct IO failed ino 3548 rw 0,0 sector 0x1d42d0 len 4096 err no 10
CPU: 3 PID: 23985 Comm: fsstress Tainted: G W L 5.8.0-rc4-default+ #1181
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
RIP: 0010:btrfs_sync_log+0xbc8/0xd60 [btrfs]
RSP: 0018:ffff909a44d17bd0 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000001
RDX: ffff8f3be41cb940 RSI: ffffffffb0108d2b RDI: ffffffffb0108ff7
RBP: ffff909a44d17e70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000037988 R12: ffff8f3bd20e4000
R13: ffff8f3bd20e4428 R14: 00000000ffffff8b R15: ffff909a44d17c70
FS: 00007f6a6ed3fb80(0000) GS:ffff8f3c3dc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6a6ed3e000 CR3: 00000000525c0003 CR4: 0000000000160ee0
Call Trace:
? finish_wait+0x90/0x90
? __mutex_unlock_slowpath+0x45/0x2a0
? lock_acquire+0xa3/0x440
? lockref_put_or_lock+0x9/0x30
? dput+0x20/0x4a0
? dput+0x20/0x4a0
? do_raw_spin_unlock+0x4b/0xc0
? _raw_spin_unlock+0x1f/0x30
btrfs_sync_file+0x335/0x490 [btrfs]
do_fsync+0x38/0x70
__x64_sys_fsync+0x10/0x20
do_syscall_64+0x50/0xe0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f6a6ef1b6e3
Code: Bad RIP value.
RSP: 002b:00007ffd01e20038 EFLAGS: 00000246 ORIG_RAX: 000000000000004a
RAX: ffffffffffffffda RBX: 000000000007a120 RCX: 00007f6a6ef1b6e3
RDX: 00007ffd01e1ffa0 RSI: 00007ffd01e1ffa0 RDI: 0000000000000003
RBP: 0000000000000003 R08: 0000000000000001 R09: 00007ffd01e2004c
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000009f
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
irq event stamp: 0
hardirqs last enabled at (0): [<0000000000000000>] 0x0
hardirqs last disabled at (0): [<ffffffffb007fe0b>] copy_process+0x67b/0x1b00
softirqs last enabled at (0): [<ffffffffb007fe0b>] copy_process+0x67b/0x1b00
softirqs last disabled at (0): [<0000000000000000>] 0x0
---[ end trace af146e0e38433456 ]---
BTRFS: error (device dm-0) in btrfs_sync_log:3084: errno=-117 Filesystem corrupted
This ret came from btrfs_write_marked_extents(). If we get an aborted
transaction via EIO before, we'll see it in btree_write_cache_pages()
and return EUCLEAN, which gets printed as "Filesystem corrupted".
Except we shouldn't be returning EUCLEAN here, we need to be returning
EROFS because EUCLEAN is reserved for actual corruption, not IO errors.
We are inconsistent about our handling of BTRFS_FS_STATE_ERROR
elsewhere, but we want to use EROFS for this particular case. The
original transaction abort has the real error code for why we ended up
with an aborted transaction, all subsequent actions just need to return
EROFS because they may not have a trans handle and have no idea about
the original cause of the abort.
After patch "btrfs: don't WARN if we abort a transaction with EROFS" the
stacktrace will not be dumped either.
Reported-by: Eric Sandeen <esandeen@redhat.com>
CC: stable@vger.kernel.org # 5.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add full test stacktrace ]
Signed-off-by: David Sterba <dsterba@suse.com>
commit a514d63882 ("btrfs: qgroup: Commit transaction in advance to
reduce early EDQUOT") tries to reduce the early EDQUOT problems by
checking the qgroup free against threshold and tries to wake up commit
kthread to free some space.
The problem of that mechanism is, it can only free qgroup per-trans
metadata space, can't do anything to data, nor prealloc qgroup space.
Now since we have the ability to flush qgroup space, and implemented
retry-after-EDQUOT behavior, such mechanism can be completely replaced.
So this patch will cleanup such mechanism in favor of
retry-after-EDQUOT.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
When the anonymous block device pool is exhausted, subvolume/snapshot
creation fails with EMFILE (Too many files open). This has been reported
by a user. The allocation happens in the second phase during transaction
commit where it's only way out is to abort the transaction
BTRFS: Transaction aborted (error -24)
WARNING: CPU: 17 PID: 17041 at fs/btrfs/transaction.c:1576 create_pending_snapshot+0xbc4/0xd10 [btrfs]
RIP: 0010:create_pending_snapshot+0xbc4/0xd10 [btrfs]
Call Trace:
create_pending_snapshots+0x82/0xa0 [btrfs]
btrfs_commit_transaction+0x275/0x8c0 [btrfs]
btrfs_mksubvol+0x4b9/0x500 [btrfs]
btrfs_ioctl_snap_create_transid+0x174/0x180 [btrfs]
btrfs_ioctl_snap_create_v2+0x11c/0x180 [btrfs]
btrfs_ioctl+0x11a4/0x2da0 [btrfs]
do_vfs_ioctl+0xa9/0x640
ksys_ioctl+0x67/0x90
__x64_sys_ioctl+0x1a/0x20
do_syscall_64+0x5a/0x110
entry_SYSCALL_64_after_hwframe+0x44/0xa9
---[ end trace 33f2f83f3d5250e9 ]---
BTRFS: error (device sda1) in create_pending_snapshot:1576: errno=-24 unknown
BTRFS info (device sda1): forced readonly
BTRFS warning (device sda1): Skipping commit of aborted transaction.
BTRFS: error (device sda1) in cleanup_transaction:1831: errno=-24 unknown
[CAUSE]
When the global anonymous block device pool is exhausted, the following
call chain will fail, and lead to transaction abort:
btrfs_ioctl_snap_create_v2()
|- btrfs_ioctl_snap_create_transid()
|- btrfs_mksubvol()
|- btrfs_commit_transaction()
|- create_pending_snapshot()
|- btrfs_get_fs_root()
|- btrfs_init_fs_root()
|- get_anon_bdev()
[FIX]
Although we can't enlarge the anonymous block device pool, at least we
can preallocate anon_dev for subvolume/snapshot in the first phase,
outside of transaction context and exactly at the moment the user calls
the creation ioctl.
Reported-by: Greed Rong <greedrong@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/CA+UqX+NTrZ6boGnWHhSeZmEY5J76CTqmYjO2S+=tHJX7nb9DPw@mail.gmail.com/
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The main function to lookup a root by its id btrfs_get_fs_root takes the
whole key, while only using the objectid. The value of offset is preset
to (u64)-1 but not actually used until btrfs_find_root that does the
actual search.
Switch btrfs_get_fs_root to use only objectid and remove all local
variables that existed just for the lookup. The actual key for search is
set up in btrfs_get_fs_root, reusing another key variable.
Signed-off-by: David Sterba <dsterba@suse.com>
The name BTRFS_ROOT_REF_COWS is not very clear about the meaning.
In fact, that bit can only be set to those trees:
- Subvolume roots
- Data reloc root
- Reloc roots for above roots
All other trees won't get this bit set. So just by the result, it is
obvious that, roots with this bit set can have tree blocks shared with
other trees. Either shared by snapshots, or by reloc roots (an special
snapshot created by relocation).
This patch will rename BTRFS_ROOT_REF_COWS to BTRFS_ROOT_SHAREABLE to
make it easier to understand, and update all comment mentioning
"reference counted" to follow the rename.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Back in 2014, commit 04216820fe ("Btrfs: fix race between fs trimming
and block group remove/allocation"), I added the 'trimming' member to the
block group structure. Its purpose was to prevent races between trimming
and block group deletion/allocation by pinning the block group in a way
that prevents its logical address and device extents from being reused
while trimming is in progress for a block group, so that if another task
deletes the block group and then another task allocates a new block group
that gets the same logical address and device extents while the trimming
task is still in progress.
After the previous fix for scrub (patch "btrfs: fix a race between scrub
and block group removal/allocation"), scrub now also has the same needs that
trimming has, so the member name 'trimming' no longer makes sense.
Since there is already a 'pinned' member in the block group that refers
to space reservations (pinned bytes), rename the member to 'frozen',
add a comment on top of it to describe its general purpose and rename
the helpers to increment and decrement the counter as well, to match
the new member name.
The next patch in the series will move the helpers into a more suitable
file (from free-space-cache.c to block-group.c).
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Nikolay noticed a bunch of test failures with my global rsv steal
patches. At first he thought they were introduced by them, but they've
been failing for a while with 64k nodes.
The problem is with 64k nodes we have a global reserve that calculates
out to 13MiB on a freshly made file system, which only has 8MiB of
metadata space. Because of changes I previously made we no longer
account for the global reserve in the overcommit logic, which means we
correctly allow overcommit to happen even though we are already
overcommitted.
However in some corner cases, for example btrfs/170, we will allocate
the entire file system up with data chunks before we have enough space
pressure to allocate a metadata chunk. Then once the fs is full we
ENOSPC out because we cannot overcommit and the global reserve is taking
up all of the available space.
The most ideal way to deal with this is to change our space reservation
stuff to take into account the height of the tree's that we're
modifying, so that our global reserve calculation does not end up so
obscenely large.
However that is a huge undertaking. Instead fix this by forcing a chunk
allocation if the global reserve is larger than the total metadata
space. This gives us essentially the same behavior that happened
before, we get a chunk allocated and these tests can pass.
This is meant to be a stop-gap measure until we can tackle the "tree
height only" project.
Fixes: 0096420adb ("btrfs: do not account global reserve in can_overcommit")
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Tested-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For unlink transactions and block group removal
btrfs_start_transaction_fallback_global_rsv will first try to start an
ordinary transaction and if it fails it will fall back to reserving the
required amount by stealing from the global reserve. This is problematic
because of all the same reasons we had with previous iterations of the
ENOSPC handling, thundering herd. We get a bunch of failures all at
once, everybody tries to allocate from the global reserve, some win and
some lose, we get an ENSOPC.
Fix this behavior by introducing BTRFS_RESERVE_FLUSH_ALL_STEAL. It's
used to mark unlink reservation. To fix this we need to integrate this
logic into the normal ENOSPC infrastructure. We still go through all of
the normal flushing work, and at the moment we begin to fail all the
tickets we try to satisfy any tickets that are allowed to steal by
stealing from the global reserve. If this works we start the flushing
system over again just like we would with a normal ticket satisfaction.
This serializes our global reserve stealing, so we don't have the
thundering herd problem.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Tested-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
One run of btrfs/063 triggered the following lockdep warning:
============================================
WARNING: possible recursive locking detected
5.6.0-rc7-custom+ #48 Not tainted
--------------------------------------------
kworker/u24:0/7 is trying to acquire lock:
ffff88817d3a46e0 (sb_internal#2){.+.+}, at: start_transaction+0x66c/0x890 [btrfs]
but task is already holding lock:
ffff88817d3a46e0 (sb_internal#2){.+.+}, at: start_transaction+0x66c/0x890 [btrfs]
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(sb_internal#2);
lock(sb_internal#2);
*** DEADLOCK ***
May be due to missing lock nesting notation
4 locks held by kworker/u24:0/7:
#0: ffff88817b495948 ((wq_completion)btrfs-endio-write){+.+.}, at: process_one_work+0x557/0xb80
#1: ffff888189ea7db8 ((work_completion)(&work->normal_work)){+.+.}, at: process_one_work+0x557/0xb80
#2: ffff88817d3a46e0 (sb_internal#2){.+.+}, at: start_transaction+0x66c/0x890 [btrfs]
#3: ffff888174ca4da8 (&fs_info->reloc_mutex){+.+.}, at: btrfs_record_root_in_trans+0x83/0xd0 [btrfs]
stack backtrace:
CPU: 0 PID: 7 Comm: kworker/u24:0 Not tainted 5.6.0-rc7-custom+ #48
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Workqueue: btrfs-endio-write btrfs_work_helper [btrfs]
Call Trace:
dump_stack+0xc2/0x11a
__lock_acquire.cold+0xce/0x214
lock_acquire+0xe6/0x210
__sb_start_write+0x14e/0x290
start_transaction+0x66c/0x890 [btrfs]
btrfs_join_transaction+0x1d/0x20 [btrfs]
find_free_extent+0x1504/0x1a50 [btrfs]
btrfs_reserve_extent+0xd5/0x1f0 [btrfs]
btrfs_alloc_tree_block+0x1ac/0x570 [btrfs]
btrfs_copy_root+0x213/0x580 [btrfs]
create_reloc_root+0x3bd/0x470 [btrfs]
btrfs_init_reloc_root+0x2d2/0x310 [btrfs]
record_root_in_trans+0x191/0x1d0 [btrfs]
btrfs_record_root_in_trans+0x90/0xd0 [btrfs]
start_transaction+0x16e/0x890 [btrfs]
btrfs_join_transaction+0x1d/0x20 [btrfs]
btrfs_finish_ordered_io+0x55d/0xcd0 [btrfs]
finish_ordered_fn+0x15/0x20 [btrfs]
btrfs_work_helper+0x116/0x9a0 [btrfs]
process_one_work+0x632/0xb80
worker_thread+0x80/0x690
kthread+0x1a3/0x1f0
ret_from_fork+0x27/0x50
It's pretty hard to reproduce, only one hit so far.
[CAUSE]
This is because we're calling btrfs_join_transaction() without re-using
the current running one:
btrfs_finish_ordered_io()
|- btrfs_join_transaction() <<< Call #1
|- btrfs_record_root_in_trans()
|- btrfs_reserve_extent()
|- btrfs_join_transaction() <<< Call #2
Normally such btrfs_join_transaction() call should re-use the existing
one, without trying to re-start a transaction.
But the problem is, in btrfs_join_transaction() call #1, we call
btrfs_record_root_in_trans() before initializing current::journal_info.
And in btrfs_join_transaction() call #2, we're relying on
current::journal_info to avoid such deadlock.
[FIX]
Call btrfs_record_root_in_trans() after we have initialized
current::journal_info.
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
At the point we add a root to the dead roots list we have no open inodes
for that root, so we need to hold a ref on that root to keep it from
disappearing.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We are going to make root life be controlled soley by refcounting, and
inodes will be one of the things that hold a ref on the root. This
means we need to handle dropping the ino_cache_inode outside of the root
freeing logic, so move it into btrfs_drop_and_free_fs_root() so it is
cleaned up properly on unmount.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik