The path cache used during fiemap used to determine the sharedness of
extent buffers in a path from a leaf containing a file extent item
pointing to our data extent up to the root node of the tree, is meant to
be used for a single path. Having a single path is by far the most common
case, and therefore worth to optimize for, but it's possible to actually
have multiple paths because we have 2 or more leaves.
If we have multiple leaves, the 'level' variable keeps getting incremented
in each iteration of the while loop at btrfs_is_data_extent_shared(),
which means we will treat the second leaf in the 'tmp' ulist as a level 1
node, and so forth. In the worst case this can lead to getting a level
greater than or equals to BTRFS_MAX_LEVEL (8), which will trigger a
WARN_ON_ONCE() in the functions to lookup from or store in the path cache
(lookup_backref_shared_cache() and store_backref_shared_cache()). If the
current level never goes beyond 8, due to shared nodes in the paths and
a fs tree height smaller than 8, it can still result in incorrectly
marking one leaf as shared because some other leaf is shared and is stored
one level below that other leaf, as when storing a true sharedness value
in the cache results in updating the sharedness to true of all entries in
the cache below the current level.
Having multiple leaves happens in a case like the following:
- We have a file extent item point to data extent at bytenr X, for
a file range [0, 1M[ for example;
- At this moment we have an extent data ref for the extent, with
an offset of 0 and a count of 1;
- A write into the middle of the extent happens, file range [64K, 128K)
so the file extent item is split into two (at btrfs_drop_extents()):
1) One for file range [0, 64K), with a length (num_bytes field) of
64K and an extent offset of 0;
2) Another one for file range [128K, 1M), with a length of 896K
(1M - 128K) and an extent offset of 128K.
- At this moment the two file extent items are located in the same
leaf;
- A new file extent item for the range [64K, 128K), pointing to a new
data extent, is inserted in the leaf. This results in a leaf split
and now those two file extent items pointing to data extent X end
up located in different leaves;
- Once delayed refs are run, we still have a single extent data ref
item for our data extent at bytenr X, for offset 0, but now with a
count of 2 instead of 1;
- So during fiemap, at btrfs_is_data_extent_shared(), after we call
find_parent_nodes() for the data extent, we get two leaves, since
we have two file extent items point to data extent at bytenr X that
are located in two different leaves.
So skip the use of the path cache when we get more than one leaf.
Fixes: 12a824dc67 ("btrfs: speedup checking for extent sharedness during fiemap")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
During fiemap, for each file extent we find, we must check if it's shared
or not. The sharedness check starts by verifying if the extent is directly
shared (its refcount in the extent tree is > 1), and if it is not directly
shared, then we will check if every node in the subvolume b+tree leading
from the root to the leaf that has the file extent item (in reverse order),
is shared (through snapshots).
However this second step is not needed if our extent was created in a
transaction more recent than the last transaction where a snapshot of the
inode's root happened, because it can't be shared indirectly (through
shared subtrees) without a snapshot created in a more recent transaction.
So grab the generation of the extent from the extent map and pass it to
btrfs_is_data_extent_shared(), which will skip this second phase when the
generation is more recent than the root's last snapshot value. Note that
we skip this optimization if the extent map is the result of merging 2
or more extent maps, because in this case its generation is the maximum
of the generations of all merged extent maps.
The fact the we use extent maps and they can be merged despite the
underlying extents being distinct (different file extent items in the
subvolume b+tree and different extent items in the extent b+tree), can
result in some bugs when reporting shared extents. But this is a problem
of the current implementation of fiemap relying on extent maps.
One example where we get incorrect results is:
$ cat fiemap-bug.sh
#!/bin/bash
DEV=/dev/sdj
MNT=/mnt/sdj
mkfs.btrfs -f $DEV
mount $DEV $MNT
# Create a file with two 256K extents.
# Since there is no other write activity, they will be contiguous,
# and their extent maps merged, despite having two distinct extents.
xfs_io -f -c "pwrite -S 0xab 0 256K" \
-c "fsync" \
-c "pwrite -S 0xcd 256K 256K" \
-c "fsync" \
$MNT/foo
# Now clone only the second extent into another file.
xfs_io -f -c "reflink $MNT/foo 256K 0 256K" $MNT/bar
# Filefrag will report a single 512K extent, and say it's not shared.
echo
filefrag -v $MNT/foo
umount $MNT
Running the reproducer:
$ ./fiemap-bug.sh
wrote 262144/262144 bytes at offset 0
256 KiB, 64 ops; 0.0038 sec (65.479 MiB/sec and 16762.7030 ops/sec)
wrote 262144/262144 bytes at offset 262144
256 KiB, 64 ops; 0.0040 sec (61.125 MiB/sec and 15647.9218 ops/sec)
linked 262144/262144 bytes at offset 0
256 KiB, 1 ops; 0.0002 sec (1.034 GiB/sec and 4237.2881 ops/sec)
Filesystem type is: 9123683e
File size of /mnt/sdj/foo is 524288 (128 blocks of 4096 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 127: 3328.. 3455: 128: last,eof
/mnt/sdj/foo: 1 extent found
We end up reporting that we have a single 512K that is not shared, however
we have two 256K extents, and the second one is shared. Changing the
reproducer to clone instead the first extent into file 'bar', makes us
report a single 512K extent that is shared, which is algo incorrect since
we have two 256K extents and only the first one is shared.
This is z problem that existed before this change, and remains after this
change, as it can't be easily fixed. The next patch in the series reworks
fiemap to primarily use file extent items instead of extent maps (except
for checking for delalloc ranges), with the goal of improving its
scalability and performance, but it also ends up fixing this particular
bug caused by extent map merging.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
One of the most expensive tasks performed during fiemap is to check if
an extent is shared. This task has two major steps:
1) Check if the data extent is shared. This implies checking the extent
item in the extent tree, checking delayed references, etc. If we
find the data extent is directly shared, we terminate immediately;
2) If the data extent is not directly shared (its extent item has a
refcount of 1), then it may be shared if we have snapshots that share
subtrees of the inode's subvolume b+tree. So we check if the leaf
containing the file extent item is shared, then its parent node, then
the parent node of the parent node, etc, until we reach the root node
or we find one of them is shared - in which case we stop immediately.
During fiemap we process the extents of a file from left to right, from
file offset 0 to EOF. This means that we iterate b+tree leaves from left
to right, and has the implication that we keep repeating that second step
above several times for the same b+tree path of the inode's subvolume
b+tree.
For example, if we have two file extent items in leaf X, and the path to
leaf X is A -> B -> C -> X, then when we try to determine if the data
extent referenced by the first extent item is shared, we check if the data
extent is shared - if it's not, then we check if leaf X is shared, if not,
then we check if node C is shared, if not, then check if node B is shared,
if not than check if node A is shared. When we move to the next file
extent item, after determining the data extent is not shared, we repeat
the checks for X, C, B and A - doing all the expensive searches in the
extent tree, delayed refs, etc. If we have thousands of tile extents, then
we keep repeating the sharedness checks for the same paths over and over.
On a file that has no shared extents or only a small portion, it's easy
to see that this scales terribly with the number of extents in the file
and the sizes of the extent and subvolume b+trees.
This change eliminates the repeated sharedness check on extent buffers
by caching the results of the last path used. The results can be used as
long as no snapshots were created since they were cached (for not shared
extent buffers) or no roots were dropped since they were cached (for
shared extent buffers). This greatly reduces the time spent by fiemap for
files with thousands of extents and/or large extent and subvolume b+trees.
Example performance test:
$ cat fiemap-perf-test.sh
#!/bin/bash
DEV=/dev/sdi
MNT=/mnt/sdi
mkfs.btrfs -f $DEV
mount -o compress=lzo $DEV $MNT
# 40G gives 327680 128K file extents (due to compression).
xfs_io -f -c "pwrite -S 0xab -b 1M 0 40G" $MNT/foobar
umount $MNT
mount -o compress=lzo $DEV $MNT
start=$(date +%s%N)
filefrag $MNT/foobar
end=$(date +%s%N)
dur=$(( (end - start) / 1000000 ))
echo "fiemap took $dur milliseconds (metadata not cached)"
start=$(date +%s%N)
filefrag $MNT/foobar
end=$(date +%s%N)
dur=$(( (end - start) / 1000000 ))
echo "fiemap took $dur milliseconds (metadata cached)"
umount $MNT
Before this patch:
$ ./fiemap-perf-test.sh
(...)
/mnt/sdi/foobar: 327680 extents found
fiemap took 3597 milliseconds (metadata not cached)
/mnt/sdi/foobar: 327680 extents found
fiemap took 2107 milliseconds (metadata cached)
After this patch:
$ ./fiemap-perf-test.sh
(...)
/mnt/sdi/foobar: 327680 extents found
fiemap took 1646 milliseconds (metadata not cached)
/mnt/sdi/foobar: 327680 extents found
fiemap took 698 milliseconds (metadata cached)
That's about 2.2x faster when no metadata is cached, and about 3x faster
when all metadata is cached. On a real filesystem with many other files,
data, directories, etc, the b+trees will be 2 or 3 levels higher,
therefore this optimization will have a higher impact.
Several reports of a slow fiemap show up often, the two Link tags below
refer to two recent reports of such slowness. This patch, together with
the next ones in the series, is meant to address that.
Link: https://lore.kernel.org/linux-btrfs/21dd32c6-f1f9-f44a-466a-e18fdc6788a7@virtuozzo.com/
Link: https://lore.kernel.org/linux-btrfs/Ysace25wh5BbLd5f@atmark-techno.com/
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The function btrfs_check_shared() is supposed to be used to check if a
data extent is shared, but its name is too generic, may easily cause
confusion in the sense that it may be used for metadata extents.
So rename it to btrfs_is_data_extent_shared(), which will also make it
less confusing after the next change that adds a backref lookup cache for
the b+tree nodes that lead to the leaf that contains the file extent item
that points to the target data extent.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There's only one function we pass to iterate_inodes_from_logical as
iterator, so we can drop the indirection and call it directly, after
moving the function to backref.c
Signed-off-by: David Sterba <dsterba@suse.com>
Currently all the callers of btrfs_find_all_roots() pass a value of false
for its ignore_offset argument. This makes the argument pointless and we
can remove it and make btrfs_find_all_roots() always pass false as the
ignore_offset argument for btrfs_find_all_roots_safe(). So just do that.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
At btrfs_qgroup_trace_extent_post() we call btrfs_find_all_roots() with a
NULL value as the transaction handle argument, which makes that function
take the commit_root_sem semaphore, which is necessary when we don't hold
a transaction handle or any other mechanism to prevent a transaction
commit from wiping out commit roots.
However btrfs_qgroup_trace_extent_post() can be called in a context where
we are holding a write lock on an extent buffer from a subvolume tree,
namely from btrfs_truncate_inode_items(), called either during truncate
or unlink operations. In this case we end up with a lock inversion problem
because the commit_root_sem is a higher level lock, always supposed to be
acquired before locking any extent buffer.
Lockdep detects this lock inversion problem since we switched the extent
buffer locks from custom locks to semaphores, and when running btrfs/158
from fstests, it reported the following trace:
[ 9057.626435] ======================================================
[ 9057.627541] WARNING: possible circular locking dependency detected
[ 9057.628334] 5.14.0-rc2-btrfs-next-93 #1 Not tainted
[ 9057.628961] ------------------------------------------------------
[ 9057.629867] kworker/u16:4/30781 is trying to acquire lock:
[ 9057.630824] ffff8e2590f58760 (btrfs-tree-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x24/0x110 [btrfs]
[ 9057.632542]
but task is already holding lock:
[ 9057.633551] ffff8e25582d4b70 (&fs_info->commit_root_sem){++++}-{3:3}, at: iterate_extent_inodes+0x10b/0x280 [btrfs]
[ 9057.635255]
which lock already depends on the new lock.
[ 9057.636292]
the existing dependency chain (in reverse order) is:
[ 9057.637240]
-> #1 (&fs_info->commit_root_sem){++++}-{3:3}:
[ 9057.638138] down_read+0x46/0x140
[ 9057.638648] btrfs_find_all_roots+0x41/0x80 [btrfs]
[ 9057.639398] btrfs_qgroup_trace_extent_post+0x37/0x70 [btrfs]
[ 9057.640283] btrfs_add_delayed_data_ref+0x418/0x490 [btrfs]
[ 9057.641114] btrfs_free_extent+0x35/0xb0 [btrfs]
[ 9057.641819] btrfs_truncate_inode_items+0x424/0xf70 [btrfs]
[ 9057.642643] btrfs_evict_inode+0x454/0x4f0 [btrfs]
[ 9057.643418] evict+0xcf/0x1d0
[ 9057.643895] do_unlinkat+0x1e9/0x300
[ 9057.644525] do_syscall_64+0x3b/0xc0
[ 9057.645110] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 9057.645835]
-> #0 (btrfs-tree-00){++++}-{3:3}:
[ 9057.646600] __lock_acquire+0x130e/0x2210
[ 9057.647248] lock_acquire+0xd7/0x310
[ 9057.647773] down_read_nested+0x4b/0x140
[ 9057.648350] __btrfs_tree_read_lock+0x24/0x110 [btrfs]
[ 9057.649175] btrfs_read_lock_root_node+0x31/0x40 [btrfs]
[ 9057.650010] btrfs_search_slot+0x537/0xc00 [btrfs]
[ 9057.650849] scrub_print_warning_inode+0x89/0x370 [btrfs]
[ 9057.651733] iterate_extent_inodes+0x1e3/0x280 [btrfs]
[ 9057.652501] scrub_print_warning+0x15d/0x2f0 [btrfs]
[ 9057.653264] scrub_handle_errored_block.isra.0+0x135f/0x1640 [btrfs]
[ 9057.654295] scrub_bio_end_io_worker+0x101/0x2e0 [btrfs]
[ 9057.655111] btrfs_work_helper+0xf8/0x400 [btrfs]
[ 9057.655831] process_one_work+0x247/0x5a0
[ 9057.656425] worker_thread+0x55/0x3c0
[ 9057.656993] kthread+0x155/0x180
[ 9057.657494] ret_from_fork+0x22/0x30
[ 9057.658030]
other info that might help us debug this:
[ 9057.659064] Possible unsafe locking scenario:
[ 9057.659824] CPU0 CPU1
[ 9057.660402] ---- ----
[ 9057.660988] lock(&fs_info->commit_root_sem);
[ 9057.661581] lock(btrfs-tree-00);
[ 9057.662348] lock(&fs_info->commit_root_sem);
[ 9057.663254] lock(btrfs-tree-00);
[ 9057.663690]
*** DEADLOCK ***
[ 9057.664437] 4 locks held by kworker/u16:4/30781:
[ 9057.665023] #0: ffff8e25922a1148 ((wq_completion)btrfs-scrub){+.+.}-{0:0}, at: process_one_work+0x1c7/0x5a0
[ 9057.666260] #1: ffffabb3451ffe70 ((work_completion)(&work->normal_work)){+.+.}-{0:0}, at: process_one_work+0x1c7/0x5a0
[ 9057.667639] #2: ffff8e25922da198 (&ret->mutex){+.+.}-{3:3}, at: scrub_handle_errored_block.isra.0+0x5d2/0x1640 [btrfs]
[ 9057.669017] #3: ffff8e25582d4b70 (&fs_info->commit_root_sem){++++}-{3:3}, at: iterate_extent_inodes+0x10b/0x280 [btrfs]
[ 9057.670408]
stack backtrace:
[ 9057.670976] CPU: 7 PID: 30781 Comm: kworker/u16:4 Not tainted 5.14.0-rc2-btrfs-next-93 #1
[ 9057.672030] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[ 9057.673492] Workqueue: btrfs-scrub btrfs_work_helper [btrfs]
[ 9057.674258] Call Trace:
[ 9057.674588] dump_stack_lvl+0x57/0x72
[ 9057.675083] check_noncircular+0xf3/0x110
[ 9057.675611] __lock_acquire+0x130e/0x2210
[ 9057.676132] lock_acquire+0xd7/0x310
[ 9057.676605] ? __btrfs_tree_read_lock+0x24/0x110 [btrfs]
[ 9057.677313] ? lock_is_held_type+0xe8/0x140
[ 9057.677849] down_read_nested+0x4b/0x140
[ 9057.678349] ? __btrfs_tree_read_lock+0x24/0x110 [btrfs]
[ 9057.679068] __btrfs_tree_read_lock+0x24/0x110 [btrfs]
[ 9057.679760] btrfs_read_lock_root_node+0x31/0x40 [btrfs]
[ 9057.680458] btrfs_search_slot+0x537/0xc00 [btrfs]
[ 9057.681083] ? _raw_spin_unlock+0x29/0x40
[ 9057.681594] ? btrfs_find_all_roots_safe+0x11f/0x140 [btrfs]
[ 9057.682336] scrub_print_warning_inode+0x89/0x370 [btrfs]
[ 9057.683058] ? btrfs_find_all_roots_safe+0x11f/0x140 [btrfs]
[ 9057.683834] ? scrub_write_block_to_dev_replace+0xb0/0xb0 [btrfs]
[ 9057.684632] iterate_extent_inodes+0x1e3/0x280 [btrfs]
[ 9057.685316] scrub_print_warning+0x15d/0x2f0 [btrfs]
[ 9057.685977] ? ___ratelimit+0xa4/0x110
[ 9057.686460] scrub_handle_errored_block.isra.0+0x135f/0x1640 [btrfs]
[ 9057.687316] scrub_bio_end_io_worker+0x101/0x2e0 [btrfs]
[ 9057.688021] btrfs_work_helper+0xf8/0x400 [btrfs]
[ 9057.688649] ? lock_is_held_type+0xe8/0x140
[ 9057.689180] process_one_work+0x247/0x5a0
[ 9057.689696] worker_thread+0x55/0x3c0
[ 9057.690175] ? process_one_work+0x5a0/0x5a0
[ 9057.690731] kthread+0x155/0x180
[ 9057.691158] ? set_kthread_struct+0x40/0x40
[ 9057.691697] ret_from_fork+0x22/0x30
Fix this by making btrfs_find_all_roots() never attempt to lock the
commit_root_sem when it is called from btrfs_qgroup_trace_extent_post().
We can't just pass a non-NULL transaction handle to btrfs_find_all_roots()
from btrfs_qgroup_trace_extent_post(), because that would make backref
lookup not use commit roots and acquire read locks on extent buffers, and
therefore could deadlock when btrfs_qgroup_trace_extent_post() is called
from the btrfs_truncate_inode_items() code path which has acquired a write
lock on an extent buffer of the subvolume btree.
CC: stable@vger.kernel.org # 4.19+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
A weird KASAN problem that Zygo reported could have been easily caught
if we checked for basic things in our backref freeing code. We have two
methods of freeing a backref node
- btrfs_backref_free_node: this just is kfree() essentially.
- btrfs_backref_drop_node: this actually unlinks the node and cleans up
everything and then calls btrfs_backref_free_node().
We should mostly be using btrfs_backref_drop_node(), to make sure the
node is properly unlinked from the backref cache, and only use
btrfs_backref_free_node() when we know the node isn't actually linked to
the backref cache. We made a mistake here and thus got the KASAN splat.
Make this style of issue easier to find by adding some ASSERT()'s to
btrfs_backref_free_node() and adjusting our deletion stuff to properly
init the list so we can rely on list_empty() checks working properly.
BUG: KASAN: use-after-free in btrfs_backref_cleanup_node+0x18a/0x420
Read of size 8 at addr ffff888112402950 by task btrfs/28836
CPU: 0 PID: 28836 Comm: btrfs Tainted: G W 5.10.0-e35f27394290-for-next+ #23
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
dump_stack+0xbc/0xf9
? btrfs_backref_cleanup_node+0x18a/0x420
print_address_description.constprop.8+0x21/0x210
? record_print_text.cold.34+0x11/0x11
? btrfs_backref_cleanup_node+0x18a/0x420
? btrfs_backref_cleanup_node+0x18a/0x420
kasan_report.cold.10+0x20/0x37
? btrfs_backref_cleanup_node+0x18a/0x420
__asan_load8+0x69/0x90
btrfs_backref_cleanup_node+0x18a/0x420
btrfs_backref_release_cache+0x83/0x1b0
relocate_block_group+0x394/0x780
? merge_reloc_roots+0x4a0/0x4a0
btrfs_relocate_block_group+0x26e/0x4c0
btrfs_relocate_chunk+0x52/0x120
btrfs_balance+0xe2e/0x1900
? check_flags.part.50+0x6c/0x1e0
? btrfs_relocate_chunk+0x120/0x120
? kmem_cache_alloc_trace+0xa06/0xcb0
? _copy_from_user+0x83/0xc0
btrfs_ioctl_balance+0x3a7/0x460
btrfs_ioctl+0x24c8/0x4360
? __kasan_check_read+0x11/0x20
? check_chain_key+0x1f4/0x2f0
? __asan_loadN+0xf/0x20
? btrfs_ioctl_get_supported_features+0x30/0x30
? kvm_sched_clock_read+0x18/0x30
? check_chain_key+0x1f4/0x2f0
? lock_downgrade+0x3f0/0x3f0
? handle_mm_fault+0xad6/0x2150
? do_vfs_ioctl+0xfc/0x9d0
? ioctl_file_clone+0xe0/0xe0
? check_flags.part.50+0x6c/0x1e0
? check_flags.part.50+0x6c/0x1e0
? check_flags+0x26/0x30
? lock_is_held_type+0xc3/0xf0
? syscall_enter_from_user_mode+0x1b/0x60
? do_syscall_64+0x13/0x80
? rcu_read_lock_sched_held+0xa1/0xd0
? __kasan_check_read+0x11/0x20
? __fget_light+0xae/0x110
__x64_sys_ioctl+0xc3/0x100
do_syscall_64+0x37/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f4c4bdfe427
RSP: 002b:00007fff33ee6df8 EFLAGS: 00000202 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fff33ee6e98 RCX: 00007f4c4bdfe427
RDX: 00007fff33ee6e98 RSI: 00000000c4009420 RDI: 0000000000000003
RBP: 0000000000000003 R08: 0000000000000003 R09: 0000000000000078
R10: fffffffffffff59d R11: 0000000000000202 R12: 0000000000000001
R13: 0000000000000000 R14: 00007fff33ee8a34 R15: 0000000000000001
Allocated by task 28836:
kasan_save_stack+0x21/0x50
__kasan_kmalloc.constprop.18+0xbe/0xd0
kasan_kmalloc+0x9/0x10
kmem_cache_alloc_trace+0x410/0xcb0
btrfs_backref_alloc_node+0x46/0xf0
btrfs_backref_add_tree_node+0x60d/0x11d0
build_backref_tree+0xc5/0x700
relocate_tree_blocks+0x2be/0xb90
relocate_block_group+0x2eb/0x780
btrfs_relocate_block_group+0x26e/0x4c0
btrfs_relocate_chunk+0x52/0x120
btrfs_balance+0xe2e/0x1900
btrfs_ioctl_balance+0x3a7/0x460
btrfs_ioctl+0x24c8/0x4360
__x64_sys_ioctl+0xc3/0x100
do_syscall_64+0x37/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 28836:
kasan_save_stack+0x21/0x50
kasan_set_track+0x20/0x30
kasan_set_free_info+0x1f/0x30
__kasan_slab_free+0xf3/0x140
kasan_slab_free+0xe/0x10
kfree+0xde/0x200
btrfs_backref_error_cleanup+0x452/0x530
build_backref_tree+0x1a5/0x700
relocate_tree_blocks+0x2be/0xb90
relocate_block_group+0x2eb/0x780
btrfs_relocate_block_group+0x26e/0x4c0
btrfs_relocate_chunk+0x52/0x120
btrfs_balance+0xe2e/0x1900
btrfs_ioctl_balance+0x3a7/0x460
btrfs_ioctl+0x24c8/0x4360
__x64_sys_ioctl+0xc3/0x100
do_syscall_64+0x37/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xa9
The buggy address belongs to the object at ffff888112402900
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 80 bytes inside of
128-byte region [ffff888112402900, ffff888112402980)
The buggy address belongs to the page:
page:0000000028b1cd08 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888131c810c0 pfn:0x112402
flags: 0x17ffe0000000200(slab)
raw: 017ffe0000000200 ffffea000424f308 ffffea0007d572c8 ffff888100040440
raw: ffff888131c810c0 ffff888112402000 0000000100000009 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888112402800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888112402880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888112402900: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888112402980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888112402a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
Link: https://lore.kernel.org/linux-btrfs/20201208194607.GI31381@hungrycats.org/
CC: stable@vger.kernel.org # 5.10+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
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>
The error cleanup will be extracted as a new function,
btrfs_backref_error_cleanup(), and moved to backref.c and exported for
later usage.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This the the 2nd major part of generic backref cache. Move it to
backref.c so we can reuse it.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This function is the major part of backref cache build process, move it
to backref.c so we can reuse it later.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Also change the parameter, since all callers can easily grab an fs_info,
there is no need for all the pointer chasing.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Since we're releasing all existing nodes/edges, other than cleanup the
mess after error, "release" is a more proper naming here.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Also add comment explaining the cleanup progress, to differ it from
btrfs_backref_drop_node().
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
With extra comment for drop_backref_node() as it has some similarity
with remove_backref_node(), thus we need extra comment explaining the
difference.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Structure tree_entry provides a very simple rb_tree which only uses
bytenr as search index.
That tree_entry is used in 3 structures: backref_node, mapping_node and
tree_block.
Since we're going to make backref_node independnt from relocation, it's
a good time to extract the tree_entry into rb_simple_node, and export it
into misc.h.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
These 3 structures are the main part of btrfs backref cache, move them
to backref.h to build the basis for later reuse.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This function will go to the next inline/keyed backref for
btrfs_backref_iter infrastructure.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
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>
Due to the complex nature of btrfs extent tree, when we want to iterate
all backrefs of one extent, this involves quite a lot of work, like
searching the EXTENT_ITEM/METADATA_ITEM, iteration through inline and keyed
backrefs.
Normally this would result in a complex code, something like:
btrfs_search_slot()
/* Ensure we are at EXTENT_ITEM/METADATA_ITEM */
while (1) { /* Loop for extent tree items */
while (ptr < end) { /* Loop for inlined items */
/* Real work here */
}
next:
ret = btrfs_next_item()
/* Ensure we're still at keyed item for specified bytenr */
}
The idea of btrfs_backref_iter is to avoid such complex and hard to
read code structure, but something like the following:
iter = btrfs_backref_iter_alloc();
ret = btrfs_backref_iter_start(iter, bytenr);
if (ret < 0)
goto out;
for (; ; ret = btrfs_backref_iter_next(iter)) {
/* Real work here */
}
out:
btrfs_backref_iter_free(iter);
This patch is just the skeleton + btrfs_backref_iter_start() code.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
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>
In relocation, we need to locate all parent tree leaves referring to one
data extent, thus we have a complex mechanism to iterate throught extent
tree and subvolume trees to locate the related leaves.
However this is already done in backref.c, we have
btrfs_find_all_leafs(), which can return a ulist containing all leaves
referring to that data extent.
Use btrfs_find_all_leafs() to replace find_data_references().
There is a special handling for v1 space cache data extents, where we
need to delete the v1 space cache data extents, to avoid those data
extents to hang the data relocation.
In this patch, the special handling is done by re-iterating the root
tree leaf. Although it's a little less efficient than the old handling,
considering we can reuse a lot of code, it should be acceptable.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_check_shared looks up parents of a given extent and uses ulists
for that. These are allocated and freed repeatedly. Preallocation in the
caller will avoid the overhead and also allow us to use the GFP_KERNEL
as it is happens before the extent locks are taken.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Remove GPL boilerplate text (long, short, one-line) and keep the rest,
ie. personal, company or original source copyright statements. Add the
SPDX header.
Unify the include protection macros to match the file names.
Signed-off-by: David Sterba <dsterba@suse.com>
The __cold functions are placed to a special section, as they're
expected to be called rarely. This could help i-cache prefetches or help
compiler to decide which branches are more/less likely to be taken
without any other annotations needed.
Though we can't add more __exit annotations, it's still possible to add
__cold (that's also added with __exit). That way the following function
categories are tagged:
- printf wrappers, error messages
- exit helpers
Signed-off-by: David Sterba <dsterba@suse.com>
The LOGICAL_INO ioctl provides a backward mapping from extent bytenr and
offset (encoded as a single logical address) to a list of extent refs.
LOGICAL_INO complements TREE_SEARCH, which provides the forward mapping
(extent ref -> extent bytenr and offset, or logical address). These are
useful capabilities for programs that manipulate extents and extent
references from userspace (e.g. dedup and defrag utilities).
When the extents are uncompressed (and not encrypted and not other),
check_extent_in_eb performs filtering of the extent refs to remove any
extent refs which do not contain the same extent offset as the 'logical'
parameter's extent offset. This prevents LOGICAL_INO from returning
references to more than a single block.
To find the set of extent references to an uncompressed extent from [a, b),
userspace has to run a loop like this pseudocode:
for (i = a; i < b; ++i)
extent_ref_set += LOGICAL_INO(i);
At each iteration of the loop (up to 32768 iterations for a 128M extent),
data we are interested in is collected in the kernel, then deleted by
the filter in check_extent_in_eb.
When the extents are compressed (or encrypted or other), the 'logical'
parameter must be an extent bytenr (the 'a' parameter in the loop).
No filtering by extent offset is done (or possible?) so the result is
the complete set of extent refs for the entire extent. This removes
the need for the loop, since we get all the extent refs in one call.
Add an 'ignore_offset' argument to iterate_inodes_from_logical,
[...several levels of function call graph...], and check_extent_in_eb, so
that we can disable the extent offset filtering for uncompressed extents.
This flag can be set by an improved version of the LOGICAL_INO ioctl to
get either behavior as desired.
There is no functional change in this patch. The new flag is always
false.
Signed-off-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Reviewed-by: David Sterba <dsterba@suse.com>
[ minor coding style fixes ]
Signed-off-by: David Sterba <dsterba@suse.com>
This patch adds a tracepoint event for prelim_ref insertion and
merging. For each, the ref being inserted or merged and the count
of tree nodes is issued.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Commit afce772e87 ("btrfs: fix check_shared for fiemap ioctl") added
transaction semantics around calls to btrfs_check_shared() in order to
provide accurate accounting of delayed refs. The transaction management
should be done inside btrfs_check_shared(), so that callers do not need
to manage transactions individually.
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We have been iterating all references for each extent we have in a file when we
do fiemap to see if it is shared. This is fine when you have a few clones or a
few snapshots, but when you have 5k snapshots suddenly fiemap just sits there
and stares at you. So add btrfs_check_shared which will use the backref walking
code but will short circuit as soon as it finds a root or inode that doesn't
match the one we currently have. This makes fiemap on my testbox go from
looking at me blankly for a day to spitting out actual output in a reasonable
amount of time. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
The skinny extents are intepreted incorrectly in scrub_print_warning(),
and end up hitting the BUG() in btrfs_extent_inline_ref_size.
Reported-by: Konstantinos Skarlatos <k.skarlatos@gmail.com>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <clm@fb.com>
Currently qgroups account for space by intercepting delayed ref updates to fs
trees. It does this by adding sequence numbers to delayed ref updates so that
it can figure out how the tree looked before the update so we can adjust the
counters properly. The problem with this is that it does not allow delayed refs
to be merged, so if you say are defragging an extent with 5k snapshots pointing
to it we will thrash the delayed ref lock because we need to go back and
manually merge these things together. Instead we want to process quota changes
when we know they are going to happen, like when we first allocate an extent, we
free a reference for an extent, we add new references etc. This patch
accomplishes this by only adding qgroup operations for real ref changes. We
only modify the sequence number when we need to lookup roots for bytenrs, this
reduces the amount of churn on the sequence number and allows us to merge
delayed refs as we add them most of the time. This patch encompasses a bunch of
architectural changes
1) qgroup ref operations: instead of tracking qgroup operations through the
delayed refs we simply add new ref operations whenever we notice that we need to
when we've modified the refs themselves.
2) tree mod seq: we no longer have this separation of major/minor counters.
this makes the sequence number stuff much more sane and we can remove some
locking that was needed to protect the counter.
3) delayed ref seq: we now read the tree mod seq number and use that as our
sequence. This means each new delayed ref doesn't have it's own unique sequence
number, rather whenever we go to lookup backrefs we inc the sequence number so
we can make sure to keep any new operations from screwing up our world view at
that given point. This allows us to merge delayed refs during runtime.
With all of these changes the delayed ref stuff is a little saner and the qgroup
accounting stuff no longer goes negative in some cases like it was before.
Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
struct __prelim_ref is allocated and freed frequently when
walking backref tree, using slab allocater can not only
speed up allocating but also detect memory leaks.
Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
Looking into this backref problem I noticed we're using a macro to what turns
out to essentially be a NULL check to see if we need to search the commit root.
I'm killing this, let's just do what everybody else does and checks if trans ==
NULL. I've also made it so we pass in the path to __resolve_indirect_refs which
will have the search_commit_root flag set properly already and that way we can
avoid allocating another path when we have a perfectly good one to use. Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Big patch, but all it does is add statics to functions which
are in fact static, then remove the associated dead-code fallout.
removed functions:
btrfs_iref_to_path()
__btrfs_lookup_delayed_deletion_item()
__btrfs_search_delayed_insertion_item()
__btrfs_search_delayed_deletion_item()
find_eb_for_page()
btrfs_find_block_group()
range_straddles_pages()
extent_range_uptodate()
btrfs_file_extent_length()
btrfs_scrub_cancel_devid()
btrfs_start_transaction_lflush()
btrfs_print_tree() is left because it is used for debugging.
btrfs_start_transaction_lflush() and btrfs_reada_detach() are
left for symmetry.
ulist.c functions are left, another patch will take care of those.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
The header file will then be installed under /usr/include/linux so that
userspace applications can refer to Btrfs ioctls by name and use the same
structs used internally in the kernel.
Signed-off-by: Filipe Brandenburger <filbranden@google.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
The iterate_irefs in backref.c is used to build path components from inode
refs. This patch adds code to iterate extended refs as well.
I had modify the callback function signature to abstract out some of the
differences between ref structures. iref_to_path() also needed similar
changes.
Signed-off-by: Mark Fasheh <mfasheh@suse.de>
This patch adds basic support for extended inode refs. This includes support
for link and unlink of the refs, which basically gets us support for rename
as well.
Inode creation does not need changing - extended refs are only added after
the ref array is full.
Signed-off-by: Mark Fasheh <mfasheh@suse.de>
In logical resolve, we parse extent_from_logical()'s 'ret' as a kind of flag.
It is possible to lose our errors because
(-EXXXX & BTRFS_EXTENT_FLAG_TREE_BLOCK) is true.
I'm not sure if it is on purpose, it just looks too hacky if it is.
I'd rather use a real flag and a 'ret' to catch errors.
Acked-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Liu Bo <liub.liubo@gmail.com>
This is the kernel portion of btrfs send/receive
Conflicts:
fs/btrfs/Makefile
fs/btrfs/backref.h
fs/btrfs/ctree.c
fs/btrfs/ioctl.c
fs/btrfs/ioctl.h
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
We've got two mechanisms both required for reliable backref resolving (tree
mod log and holding back delayed refs). You cannot make use of one without
the other. So instead of requiring the user of this mechanism to setup both
correctly, we join them into a single interface.
Additionally, we stop inserting non-blockers into fs_info->tree_mod_seq_list
as we did before, which was of no value.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
This enables backref resolving on life trees while they are changing. This
is a prerequisite for quota groups and just nice to have for everything
else.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Before this patch we called find_all_leafs for a data extent, then called
find_all_roots and then looked into the extent to grab the information
we were seeking. This was done without holding the leaves locked to avoid
deadlocks. However, this can obviouly race with concurrent tree
modifications.
Instead, we now look into the extent while we're holding the lock during
find_all_leafs and store this information together with the leaf list.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
In commit 4692cf58 we introduced new backref walking code for btrfs. This
assumes we're searching live roots, which requires a transaction context.
While scrubbing, however, we must not join a transaction because this could
deadlock with the commit path. Additionally, what scrub really wants to do
is resolving a logical address in the commit root it's currently checking.
This patch adds support for logical to path resolving on commit roots and
makes scrub use that.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Filipe Manana