When testing space_cache v2 on a large set of machines, we encountered a
few symptoms:
1. "unable to add free space :-17" (EEXIST) errors.
2. Missing free space info items, sometimes caught with a "missing free
space info for X" error.
3. Double-accounted space: ranges that were allocated in the extent tree
and also marked as free in the free space tree, ranges that were
marked as allocated twice in the extent tree, or ranges that were
marked as free twice in the free space tree. If the latter made it
onto disk, the next reboot would hit the BUG_ON() in
add_new_free_space().
4. On some hosts with no on-disk corruption or error messages, the
in-memory space cache (dumped with drgn) disagreed with the free
space tree.
All of these symptoms have the same underlying cause: a race between
caching the free space for a block group and returning free space to the
in-memory space cache for pinned extents causes us to double-add a free
range to the space cache. This race exists when free space is cached
from the free space tree (space_cache=v2) or the extent tree
(nospace_cache, or space_cache=v1 if the cache needs to be regenerated).
struct btrfs_block_group::last_byte_to_unpin and struct
btrfs_block_group::progress are supposed to protect against this race,
but commit d0c2f4fa55 ("btrfs: make concurrent fsyncs wait less when
waiting for a transaction commit") subtly broke this by allowing
multiple transactions to be unpinning extents at the same time.
Specifically, the race is as follows:
1. An extent is deleted from an uncached block group in transaction A.
2. btrfs_commit_transaction() is called for transaction A.
3. btrfs_run_delayed_refs() -> __btrfs_free_extent() runs the delayed
ref for the deleted extent.
4. __btrfs_free_extent() -> do_free_extent_accounting() ->
add_to_free_space_tree() adds the deleted extent back to the free
space tree.
5. do_free_extent_accounting() -> btrfs_update_block_group() ->
btrfs_cache_block_group() queues up the block group to get cached.
block_group->progress is set to block_group->start.
6. btrfs_commit_transaction() for transaction A calls
switch_commit_roots(). It sets block_group->last_byte_to_unpin to
block_group->progress, which is block_group->start because the block
group hasn't been cached yet.
7. The caching thread gets to our block group. Since the commit roots
were already switched, load_free_space_tree() sees the deleted extent
as free and adds it to the space cache. It finishes caching and sets
block_group->progress to U64_MAX.
8. btrfs_commit_transaction() advances transaction A to
TRANS_STATE_SUPER_COMMITTED.
9. fsync calls btrfs_commit_transaction() for transaction B. Since
transaction A is already in TRANS_STATE_SUPER_COMMITTED and the
commit is for fsync, it advances.
10. btrfs_commit_transaction() for transaction B calls
switch_commit_roots(). This time, the block group has already been
cached, so it sets block_group->last_byte_to_unpin to U64_MAX.
11. btrfs_commit_transaction() for transaction A calls
btrfs_finish_extent_commit(), which calls unpin_extent_range() for
the deleted extent. It sees last_byte_to_unpin set to U64_MAX (by
transaction B!), so it adds the deleted extent to the space cache
again!
This explains all of our symptoms above:
* If the sequence of events is exactly as described above, when the free
space is re-added in step 11, it will fail with EEXIST.
* If another thread reallocates the deleted extent in between steps 7
and 11, then step 11 will silently re-add that space to the space
cache as free even though it is actually allocated. Then, if that
space is allocated *again*, the free space tree will be corrupted
(namely, the wrong item will be deleted).
* If we don't catch this free space tree corruption, it will continue
to get worse as extents are deleted and reallocated.
The v1 space_cache is synchronously loaded when an extent is deleted
(btrfs_update_block_group() with alloc=0 calls btrfs_cache_block_group()
with load_cache_only=1), so it is not normally affected by this bug.
However, as noted above, if we fail to load the space cache, we will
fall back to caching from the extent tree and may hit this bug.
The easiest fix for this race is to also make caching from the free
space tree or extent tree synchronous. Josef tested this and found no
performance regressions.
A few extra changes fall out of this change. Namely, this fix does the
following, with step 2 being the crucial fix:
1. Factor btrfs_caching_ctl_wait_done() out of
btrfs_wait_block_group_cache_done() to allow waiting on a caching_ctl
that we already hold a reference to.
2. Change the call in btrfs_cache_block_group() of
btrfs_wait_space_cache_v1_finished() to
btrfs_caching_ctl_wait_done(), which makes us wait regardless of the
space_cache option.
3. Delete the now unused btrfs_wait_space_cache_v1_finished() and
space_cache_v1_done().
4. Change btrfs_cache_block_group()'s `int load_cache_only` parameter to
`bool wait` to more accurately describe its new meaning.
5. Change a few callers which had a separate call to
btrfs_wait_block_group_cache_done() to use wait = true instead.
6. Make btrfs_wait_block_group_cache_done() static now that it's not
used outside of block-group.c anymore.
Fixes: d0c2f4fa55 ("btrfs: make concurrent fsyncs wait less when waiting for a transaction commit")
CC: stable@vger.kernel.org # 5.12+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
With the automatic block group reclaim code we will preemptively try to
mark the block group RO before we start the relocation. We do this to
make sure we should actually try to relocate the block group.
However if we hit an error during the actual relocation we won't clean
up our RO counter and the block group will remain RO. This was observed
internally with file systems reporting less space available from df when
we had failed background relocations.
Fix this by doing the dec_ro in the error case.
Fixes: 18bb8bbf13 ("btrfs: zoned: automatically reclaim zones")
CC: stable@vger.kernel.org # 5.15+
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There are two places where allocating a chunk is not enough. These two
places are trying to ensure the space by allocating a chunk. To meet the
condition for active_total_bytes, we also need to activate a block group
there.
CC: stable@vger.kernel.org # 5.16+
Fixes: afba2bc036 ("btrfs: zoned: implement active zone tracking")
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The active_total_bytes, like the total_bytes, accounts for the total bytes
of active block groups in the space_info.
With an introduction of active_total_bytes, we can check if the reserved
bytes can be written to the block groups without activating a new block
group. The check is necessary for metadata allocation on zoned
filesystem. We cannot finish a block group, which may require waiting
for the current transaction, from the metadata allocation context.
Instead, we need to ensure the ongoing allocation (reserved bytes) fits
in active block groups.
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Use the same expression for stripe_nr for RAID0 (map->sub_stripes is 1)
and RAID10 (map->sub_stripes is 2), with equivalent results.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If you try to force a chunk allocation, but you race with another chunk
allocation, you will end up waiting on the chunk allocation that just
occurred and then allocate another chunk. If you have many threads all
doing this at once you can way over-allocate chunks.
Fix this by resetting force to NO_FORCE, that way if we think we need to
allocate we can, otherwise we don't force another chunk allocation if
one is already happening.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
CC: stable@vger.kernel.org # 5.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
While the active zones within an active block group are reset, and their
active resource is released, the block group itself is kept in the active
block group list and marked as active. As a result, the list will contain
more than max_active_zones block groups. That itself is not fatal for the
device as the zones are properly reset.
However, that inflated list is, of course, strange. Also, a to-appear
patch series, which deactivates an active block group on demand, gets
confused with the wrong list.
So, fix the issue by finishing the unused block group once it gets
read-only, so that we can release the active resource in an early stage.
Fixes: be1a1d7a5d ("btrfs: zoned: finish fully written block group")
CC: stable@vger.kernel.org # 5.16+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When doing a NOCOW write, either through direct IO or buffered IO, we do
two lookups for the block group that contains the target extent: once
when we call btrfs_inc_nocow_writers() and then later again when we call
btrfs_dec_nocow_writers() after creating the ordered extent.
The lookups require taking a lock and navigating the red black tree used
to track all block groups, which can take a non-negligible amount of time
for a large filesystem with thousands of block groups, as well as lock
contention and cache line bouncing.
Improve on this by having a single block group search: making
btrfs_inc_nocow_writers() return the block group to its caller and then
have the caller pass that block group to btrfs_dec_nocow_writers().
This is part of a patchset comprised of the following patches:
btrfs: remove search start argument from first_logical_byte()
btrfs: use rbtree with leftmost node cached for tracking lowest block group
btrfs: use a read/write lock for protecting the block groups tree
btrfs: return block group directly at btrfs_next_block_group()
btrfs: avoid double search for block group during NOCOW writes
The following test was used to test these changes from a performance
perspective:
$ cat test.sh
#!/bin/bash
modprobe null_blk nr_devices=0
NULL_DEV_PATH=/sys/kernel/config/nullb/nullb0
mkdir $NULL_DEV_PATH
if [ $? -ne 0 ]; then
echo "Failed to create nullb0 directory."
exit 1
fi
echo 2 > $NULL_DEV_PATH/submit_queues
echo 16384 > $NULL_DEV_PATH/size # 16G
echo 1 > $NULL_DEV_PATH/memory_backed
echo 1 > $NULL_DEV_PATH/power
DEV=/dev/nullb0
MNT=/mnt/nullb0
LOOP_MNT="$MNT/loop"
MOUNT_OPTIONS="-o ssd -o nodatacow"
MKFS_OPTIONS="-R free-space-tree -O no-holes"
cat <<EOF > /tmp/fio-job.ini
[io_uring_writes]
rw=randwrite
fsync=0
fallocate=posix
group_reporting=1
direct=1
ioengine=io_uring
iodepth=64
bs=64k
filesize=1g
runtime=300
time_based
directory=$LOOP_MNT
numjobs=8
thread
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 &> /dev/null
mount $MOUNT_OPTIONS $DEV $MNT
mkdir $LOOP_MNT
truncate -s 4T $MNT/loopfile
mkfs.btrfs -f $MKFS_OPTIONS $MNT/loopfile &> /dev/null
mount $MOUNT_OPTIONS $MNT/loopfile $LOOP_MNT
# Trigger the allocation of about 3500 data block groups, without
# actually consuming space on underlying filesystem, just to make
# the tree of block group large.
fallocate -l 3500G $LOOP_MNT/filler
fio /tmp/fio-job.ini
umount $LOOP_MNT
umount $MNT
echo 0 > $NULL_DEV_PATH/power
rmdir $NULL_DEV_PATH
The test was run on a non-debug kernel (Debian's default kernel config),
the result were the following.
Before patchset:
WRITE: bw=1455MiB/s (1526MB/s), 1455MiB/s-1455MiB/s (1526MB/s-1526MB/s), io=426GiB (458GB), run=300006-300006msec
After patchset:
WRITE: bw=1503MiB/s (1577MB/s), 1503MiB/s-1503MiB/s (1577MB/s-1577MB/s), io=440GiB (473GB), run=300006-300006msec
+3.3% write throughput and +3.3% IO done in the same time period.
The test has somewhat limited coverage scope, as with only NOCOW writes
we get less contention on the red black tree of block groups, since we
don't have the extra contention caused by COW writes, namely when
allocating data extents, pinning and unpinning data extents, but on the
hand there's access to tree in the NOCOW path, when incrementing a block
group's number of NOCOW writers.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
At btrfs_next_block_group(), we have this long line with two statements:
cache = btrfs_lookup_first_block_group(...); return cache;
This makes it a bit harder to read due to two statements on the same
line, so change that to directly return the result of the call to
btrfs_lookup_first_block_group().
Reviewed-by: Nikolay Borisov <nborisov@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>
Currently we use a spin lock to protect the red black tree that we use to
track block groups. Most accesses to that tree are actually read only and
for large filesystems, with thousands of block groups, it actually has
a bad impact on performance, as concurrent read only searches on the tree
are serialized.
Read only searches on the tree are very frequent and done when:
1) Pinning and unpinning extents, as we need to lookup the respective
block group from the tree;
2) Freeing the last reference of a tree block, regardless if we pin the
underlying extent or add it back to free space cache/tree;
3) During NOCOW writes, both buffered IO and direct IO, we need to check
if the block group that contains an extent is read only or not and to
increment the number of NOCOW writers in the block group. For those
operations we need to search for the block group in the tree.
Similarly, after creating the ordered extent for the NOCOW write, we
need to decrement the number of NOCOW writers from the same block
group, which requires searching for it in the tree;
4) Decreasing the number of extent reservations in a block group;
5) When allocating extents and freeing reserved extents;
6) Adding and removing free space to the free space tree;
7) When releasing delalloc bytes during ordered extent completion;
8) When relocating a block group;
9) During fitrim, to iterate over the block groups;
10) etc;
Write accesses to the tree, to add or remove block groups, are much less
frequent as they happen only when allocating a new block group or when
deleting a block group.
We also use the same spin lock to protect the list of currently caching
block groups. Additions to this list are made when we need to cache a
block group, because we don't have a free space cache for it (or we have
but it's invalid), and removals from this list are done when caching of
the block group's free space finishes. These cases are also not very
common, but when they happen, they happen only once when the filesystem
is mounted.
So switch the lock that protects the tree of block groups from a spinning
lock to a read/write lock.
Reviewed-by: Nikolay Borisov <nborisov@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>
We keep track of the start offset of the block group with the lowest start
offset at fs_info->first_logical_byte. This requires explicitly updating
that field every time we add, delete or lookup a block group to/from the
red black tree at fs_info->block_group_cache_tree.
Since the block group with the lowest start address happens to always be
the one that is the leftmost node of the tree, we can use a red black tree
that caches the left most node. Then when we need the start address of
that block group, we can just quickly get the leftmost node in the tree
and extract the start offset of that node's block group. This avoids the
need to explicitly keep track of that address in the dedicated member
fs_info->first_logical_byte, and it also allows the next patch in the
series to switch the lock that protects the red black tree from a spin
lock to a read/write lock - without this change it would be tricky
because block group searches also update fs_info->first_logical_byte.
Reviewed-by: Nikolay Borisov <nborisov@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>
The current auto-reclaim algorithm starts reclaiming all block groups
with a zone_unusable value above a configured threshold. This is causing
a lot of reclaim IO even if there would be enough free zones on the
device.
Instead of only accounting a block groups zone_unusable value, also take
the ratio of free and not usable (written as well as zone_unusable)
bytes a device has into account.
Tested-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This will allow us to set a threshold for block groups to be
automatically relocated even if we don't have zoned devices.
We have found this feature invaluable at Facebook due to how our
workload interacts with the allocator. We have been using this in
production for months with only a single problem that has already been
fixed.
Tested-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This function can be simplified by refactoring to use the new iterator
macro. No functional changes.
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In btrfs_make_block_group(), we activate the allocated block group,
expecting that the block group is soon used for allocation. However, the
chunk allocation from flush_space() context broke the assumption. There
can be a large time gap between the chunk allocation time and the extent
allocation time from the chunk.
Activating the empty block groups pre-allocated from flush_space()
context can exhaust the active zone counter of a device. Once we use all
the active zone counts for empty pre-allocated block groups, we cannot
activate new block group for the other things: metadata, tree-log, or
data relocation block group. That failure results in a fake -ENOSPC.
This patch introduces CHUNK_ALLOC_FORCE_FOR_EXTENT to distinguish the
chunk allocation from find_free_extent(). Now, the new block group is
activated only in that context.
Fixes: eb66a010d5 ("btrfs: zoned: activate new block group")
CC: stable@vger.kernel.org # 5.16+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Tested-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Return the allocated block group from do_chunk_alloc(). This is a
preparation patch for the next patch.
CC: stable@vger.kernel.org # 5.16+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Tested-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Clang's version of -Wunused-but-set-variable recently gained support for
unary operations, which reveals two unused variables:
fs/btrfs/block-group.c:2949:6: error: variable 'num_started' set but not used [-Werror,-Wunused-but-set-variable]
int num_started = 0;
^
fs/btrfs/block-group.c:3116:6: error: variable 'num_started' set but not used [-Werror,-Wunused-but-set-variable]
int num_started = 0;
^
2 errors generated.
These variables appear to be unused from their introduction, so just
remove them to silence the warnings.
Fixes: c9dc4c6578 ("Btrfs: two stage dirty block group writeout")
Fixes: 1bbc621ef2 ("Btrfs: allow block group cache writeout outside critical section in commit")
CC: stable@vger.kernel.org # 5.4+
Link: https://github.com/ClangBuiltLinux/linux/issues/1614
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: David Sterba <dsterba@suse.com>
There is a hung_task issue with running generic/068 on an SMR
device. The hang occurs while a process is trying to thaw the
filesystem. The process is trying to take sb->s_umount to thaw the
FS. The lock is held by fsstress, which calls btrfs_sync_fs() and is
waiting for an ordered extent to finish. However, as the FS is frozen,
the ordered extents never finish.
Having an ordered extent while the FS is frozen is the root cause of
the hang. The ordered extent is initiated from btrfs_relocate_chunk()
which is called from btrfs_reclaim_bgs_work().
This commit adds sb_*_write() around btrfs_relocate_chunk() call
site. For the usual "btrfs balance" command, we already call it with
mnt_want_file() in btrfs_ioctl_balance().
Fixes: 18bb8bbf13 ("btrfs: zoned: automatically reclaim zones")
CC: stable@vger.kernel.org # 5.13+
Link: https://github.com/naota/linux/issues/56
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.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>
With extent tree v2 you will be able to create multiple csum, extent,
and free space trees. They will be used based on the block group, which
will now use the block_group_item->chunk_objectid to point to the set of
global roots that it will use. When allocating new block groups we'll
simply mod the gigabyte offset of the block group against the number of
global roots we have and that will be the block groups global id.
>From there we can take the bytenr that we're modifying in the respective
tree, look up the block group and get that block groups corresponding
global root id. From there we can get to the appropriate global root
for that bytenr.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
After the recent changes made by commit c2e3930529 ("btrfs: clear
extent buffer uptodate when we fail to write it") and its followup fix,
commit 651740a502 ("btrfs: check WRITE_ERR when trying to read an
extent buffer"), we can now end up not cleaning up space reservations of
log tree extent buffers after a transaction abort happens, as well as not
cleaning up still dirty extent buffers.
This happens because if writeback for a log tree extent buffer failed,
then we have cleared the bit EXTENT_BUFFER_UPTODATE from the extent buffer
and we have also set the bit EXTENT_BUFFER_WRITE_ERR on it. Later on,
when trying to free the log tree with free_log_tree(), which iterates
over the tree, we can end up getting an -EIO error when trying to read
a node or a leaf, since read_extent_buffer_pages() returns -EIO if an
extent buffer does not have EXTENT_BUFFER_UPTODATE set and has the
EXTENT_BUFFER_WRITE_ERR bit set. Getting that -EIO means that we return
immediately as we can not iterate over the entire tree.
In that case we never update the reserved space for an extent buffer in
the respective block group and space_info object.
When this happens we get the following traces when unmounting the fs:
[174957.284509] BTRFS: error (device dm-0) in cleanup_transaction:1913: errno=-5 IO failure
[174957.286497] BTRFS: error (device dm-0) in free_log_tree:3420: errno=-5 IO failure
[174957.399379] ------------[ cut here ]------------
[174957.402497] WARNING: CPU: 2 PID: 3206883 at fs/btrfs/block-group.c:127 btrfs_put_block_group+0x77/0xb0 [btrfs]
[174957.407523] Modules linked in: btrfs overlay dm_zero (...)
[174957.424917] CPU: 2 PID: 3206883 Comm: umount Tainted: G W 5.16.0-rc5-btrfs-next-109 #1
[174957.426689] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[174957.428716] RIP: 0010:btrfs_put_block_group+0x77/0xb0 [btrfs]
[174957.429717] Code: 21 48 8b bd (...)
[174957.432867] RSP: 0018:ffffb70d41cffdd0 EFLAGS: 00010206
[174957.433632] RAX: 0000000000000001 RBX: ffff8b09c3848000 RCX: ffff8b0758edd1c8
[174957.434689] RDX: 0000000000000001 RSI: ffffffffc0b467e7 RDI: ffff8b0758edd000
[174957.436068] RBP: ffff8b0758edd000 R08: 0000000000000000 R09: 0000000000000000
[174957.437114] R10: 0000000000000246 R11: 0000000000000000 R12: ffff8b09c3848148
[174957.438140] R13: ffff8b09c3848198 R14: ffff8b0758edd188 R15: dead000000000100
[174957.439317] FS: 00007f328fb82800(0000) GS:ffff8b0a2d200000(0000) knlGS:0000000000000000
[174957.440402] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[174957.441164] CR2: 00007fff13563e98 CR3: 0000000404f4e005 CR4: 0000000000370ee0
[174957.442117] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[174957.443076] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[174957.443948] Call Trace:
[174957.444264] <TASK>
[174957.444538] btrfs_free_block_groups+0x255/0x3c0 [btrfs]
[174957.445238] close_ctree+0x301/0x357 [btrfs]
[174957.445803] ? call_rcu+0x16c/0x290
[174957.446250] generic_shutdown_super+0x74/0x120
[174957.446832] kill_anon_super+0x14/0x30
[174957.447305] btrfs_kill_super+0x12/0x20 [btrfs]
[174957.447890] deactivate_locked_super+0x31/0xa0
[174957.448440] cleanup_mnt+0x147/0x1c0
[174957.448888] task_work_run+0x5c/0xa0
[174957.449336] exit_to_user_mode_prepare+0x1e5/0x1f0
[174957.449934] syscall_exit_to_user_mode+0x16/0x40
[174957.450512] do_syscall_64+0x48/0xc0
[174957.450980] entry_SYSCALL_64_after_hwframe+0x44/0xae
[174957.451605] RIP: 0033:0x7f328fdc4a97
[174957.452059] Code: 03 0c 00 f7 (...)
[174957.454320] RSP: 002b:00007fff13564ec8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
[174957.455262] RAX: 0000000000000000 RBX: 00007f328feea264 RCX: 00007f328fdc4a97
[174957.456131] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000560b8ae51dd0
[174957.457118] RBP: 0000560b8ae51ba0 R08: 0000000000000000 R09: 00007fff13563c40
[174957.458005] R10: 00007f328fe49fc0 R11: 0000000000000246 R12: 0000000000000000
[174957.459113] R13: 0000560b8ae51dd0 R14: 0000560b8ae51cb0 R15: 0000000000000000
[174957.460193] </TASK>
[174957.460534] irq event stamp: 0
[174957.461003] hardirqs last enabled at (0): [<0000000000000000>] 0x0
[174957.461947] hardirqs last disabled at (0): [<ffffffffb0e94214>] copy_process+0x934/0x2040
[174957.463147] softirqs last enabled at (0): [<ffffffffb0e94214>] copy_process+0x934/0x2040
[174957.465116] softirqs last disabled at (0): [<0000000000000000>] 0x0
[174957.466323] ---[ end trace bc7ee0c490bce3af ]---
[174957.467282] ------------[ cut here ]------------
[174957.468184] WARNING: CPU: 2 PID: 3206883 at fs/btrfs/block-group.c:3976 btrfs_free_block_groups+0x330/0x3c0 [btrfs]
[174957.470066] Modules linked in: btrfs overlay dm_zero (...)
[174957.483137] CPU: 2 PID: 3206883 Comm: umount Tainted: G W 5.16.0-rc5-btrfs-next-109 #1
[174957.484691] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[174957.486853] RIP: 0010:btrfs_free_block_groups+0x330/0x3c0 [btrfs]
[174957.488050] Code: 00 00 00 ad de (...)
[174957.491479] RSP: 0018:ffffb70d41cffde0 EFLAGS: 00010206
[174957.492520] RAX: ffff8b08d79310b0 RBX: ffff8b09c3848000 RCX: 0000000000000000
[174957.493868] RDX: 0000000000000001 RSI: fffff443055ee600 RDI: ffffffffb1131846
[174957.495183] RBP: ffff8b08d79310b0 R08: 0000000000000000 R09: 0000000000000000
[174957.496580] R10: 0000000000000001 R11: 0000000000000000 R12: ffff8b08d7931000
[174957.498027] R13: ffff8b09c38492b0 R14: dead000000000122 R15: dead000000000100
[174957.499438] FS: 00007f328fb82800(0000) GS:ffff8b0a2d200000(0000) knlGS:0000000000000000
[174957.500990] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[174957.502117] CR2: 00007fff13563e98 CR3: 0000000404f4e005 CR4: 0000000000370ee0
[174957.503513] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[174957.504864] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[174957.506167] Call Trace:
[174957.506654] <TASK>
[174957.507047] close_ctree+0x301/0x357 [btrfs]
[174957.507867] ? call_rcu+0x16c/0x290
[174957.508567] generic_shutdown_super+0x74/0x120
[174957.509447] kill_anon_super+0x14/0x30
[174957.510194] btrfs_kill_super+0x12/0x20 [btrfs]
[174957.511123] deactivate_locked_super+0x31/0xa0
[174957.511976] cleanup_mnt+0x147/0x1c0
[174957.512610] task_work_run+0x5c/0xa0
[174957.513309] exit_to_user_mode_prepare+0x1e5/0x1f0
[174957.514231] syscall_exit_to_user_mode+0x16/0x40
[174957.515069] do_syscall_64+0x48/0xc0
[174957.515718] entry_SYSCALL_64_after_hwframe+0x44/0xae
[174957.516688] RIP: 0033:0x7f328fdc4a97
[174957.517413] Code: 03 0c 00 f7 d8 (...)
[174957.521052] RSP: 002b:00007fff13564ec8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
[174957.522514] RAX: 0000000000000000 RBX: 00007f328feea264 RCX: 00007f328fdc4a97
[174957.523950] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000560b8ae51dd0
[174957.525375] RBP: 0000560b8ae51ba0 R08: 0000000000000000 R09: 00007fff13563c40
[174957.526763] R10: 00007f328fe49fc0 R11: 0000000000000246 R12: 0000000000000000
[174957.528058] R13: 0000560b8ae51dd0 R14: 0000560b8ae51cb0 R15: 0000000000000000
[174957.529404] </TASK>
[174957.529843] irq event stamp: 0
[174957.530256] hardirqs last enabled at (0): [<0000000000000000>] 0x0
[174957.531061] hardirqs last disabled at (0): [<ffffffffb0e94214>] copy_process+0x934/0x2040
[174957.532075] softirqs last enabled at (0): [<ffffffffb0e94214>] copy_process+0x934/0x2040
[174957.533083] softirqs last disabled at (0): [<0000000000000000>] 0x0
[174957.533865] ---[ end trace bc7ee0c490bce3b0 ]---
[174957.534452] BTRFS info (device dm-0): space_info 4 has 1070841856 free, is not full
[174957.535404] BTRFS info (device dm-0): space_info total=1073741824, used=2785280, pinned=0, reserved=49152, may_use=0, readonly=65536 zone_unusable=0
[174957.537029] BTRFS info (device dm-0): global_block_rsv: size 0 reserved 0
[174957.537859] BTRFS info (device dm-0): trans_block_rsv: size 0 reserved 0
[174957.538697] BTRFS info (device dm-0): chunk_block_rsv: size 0 reserved 0
[174957.539552] BTRFS info (device dm-0): delayed_block_rsv: size 0 reserved 0
[174957.540403] BTRFS info (device dm-0): delayed_refs_rsv: size 0 reserved 0
This also means that in case we have log tree extent buffers that are
still dirty, we can end up not cleaning them up in case we find an
extent buffer with EXTENT_BUFFER_WRITE_ERR set on it, as in that case
we have no way for iterating over the rest of the tree.
This issue is very often triggered with test cases generic/475 and
generic/648 from fstests.
The issue could almost be fixed by iterating over the io tree attached to
each log root which keeps tracks of the range of allocated extent buffers,
log_root->dirty_log_pages, however that does not work and has some
inconveniences:
1) After we sync the log, we clear the range of the extent buffers from
the io tree, so we can't find them after writeback. We could keep the
ranges in the io tree, with a separate bit to signal they represent
extent buffers already written, but that means we need to hold into
more memory until the transaction commits.
How much more memory is used depends a lot on whether we are able to
allocate contiguous extent buffers on disk (and how often) for a log
tree - if we are able to, then a single extent state record can
represent multiple extent buffers, otherwise we need multiple extent
state record structures to track each extent buffer.
In fact, my earlier approach did that:
https://lore.kernel.org/linux-btrfs/3aae7c6728257c7ce2279d6660ee2797e5e34bbd.1641300250.git.fdmanana@suse.com/
However that can cause a very significant negative impact on
performance, not only due to the extra memory usage but also because
we get a larger and deeper dirty_log_pages io tree.
We got a report that, on beefy machines at least, we can get such
performance drop with fsmark for example:
https://lore.kernel.org/linux-btrfs/20220117082426.GE32491@xsang-OptiPlex-9020/
2) We would be doing it only to deal with an unexpected and exceptional
case, which is basically failure to read an extent buffer from disk
due to IO failures. On a healthy system we don't expect transaction
aborts to happen after all;
3) Instead of relying on iterating the log tree or tracking the ranges
of extent buffers in the dirty_log_pages io tree, using the radix
tree that tracks extent buffers (fs_info->buffer_radix) to find all
log tree extent buffers is not reliable either, because after writeback
of an extent buffer it can be evicted from memory by the release page
callback of the btree inode (btree_releasepage()).
Since there's no way to be able to properly cleanup a log tree without
being able to read its extent buffers from disk and without using more
memory to track the logical ranges of the allocated extent buffers do
the following:
1) When we fail to cleanup a log tree, setup a flag that indicates that
failure;
2) Trigger writeback of all log tree extent buffers that are still dirty,
and wait for the writeback to complete. This is just to cleanup their
state, page states, page leaks, etc;
3) When unmounting the fs, ignore if the number of bytes reserved in a
block group and in a space_info is not 0 if, and only if, we failed to
cleanup a log tree. Also ignore only for metadata block groups and the
metadata space_info object.
This is far from a perfect solution, but it serves to silence test
failures such as those from generic/475 and generic/648. However having
a non-zero value for the reserved bytes counters on unmount after a
transaction abort, is not such a terrible thing and it's completely
harmless, it does not affect the filesystem integrity in any way.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
The following super simple script would crash btrfs at unmount time, if
CONFIG_BTRFS_ASSERT() is set.
mkfs.btrfs -f $dev
mount $dev $mnt
xfs_io -f -c "pwrite 0 4k" $mnt/file
umount $mnt
mount -r ro $dev $mnt
btrfs scrub start -Br $mnt
umount $mnt
This will trigger the following ASSERT() introduced by commit
0a31daa4b6 ("btrfs: add assertion for empty list of transactions at
late stage of umount").
That patch is definitely not the cause, it just makes enough noise for
developers.
[CAUSE]
We will start transaction for the following call chain during scrub:
scrub_enumerate_chunks()
|- btrfs_inc_block_group_ro()
|- btrfs_join_transaction()
However for RO mount, there is no running transaction at all, thus
btrfs_join_transaction() will start a new transaction.
Furthermore, since it's read-only mount, btrfs_sync_fs() will not call
btrfs_commit_super() to commit the new but empty transaction.
And leads to the ASSERT().
The bug has been there for a long time. Only the new ASSERT() makes it
noisy enough to be noticed.
[FIX]
For read-only scrub on read-only mount, there is no need to start a
transaction nor to allocate new chunks in btrfs_inc_block_group_ro().
Just do extra read-only mount check in btrfs_inc_block_group_ro(), and
if it's read-only, skip all chunk allocation and go inc_block_group_ro()
directly.
CC: stable@vger.kernel.org # 5.4+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't allow send and balance/relocation to run in parallel in order
to prevent send failing or silently producing some bad stream. This is
because while send is using an extent (specially metadata) or about to
read a metadata extent and expecting it belongs to a specific parent
node, relocation can run, the transaction used for the relocation is
committed and the extent gets reallocated while send is still using the
extent, so it ends up with a different content than expected. This can
result in just failing to read a metadata extent due to failure of the
validation checks (parent transid, level, etc), failure to find a
backreference for a data extent, and other unexpected failures. Besides
reallocation, there's also a similar problem of an extent getting
discarded when it's unpinned after the transaction used for block group
relocation is committed.
The restriction between balance and send was added in commit 9e967495e0
("Btrfs: prevent send failures and crashes due to concurrent relocation"),
kernel 5.3, while the more general restriction between send and relocation
was added in commit 1cea5cf0e6 ("btrfs: ensure relocation never runs
while we have send operations running"), kernel 5.14.
Both send and relocation can be very long running operations. Relocation
because it has to do a lot of IO and expensive backreference lookups in
case there are many snapshots, and send due to read IO when operating on
very large trees. This makes it inconvenient for users and tools to deal
with scheduling both operations.
For zoned filesystem we also have automatic block group relocation, so
send can fail with -EAGAIN when users least expect it or send can end up
delaying the block group relocation for too long. In the future we might
also get the automatic block group relocation for non zoned filesystems.
This change makes it possible for send and relocation to run in parallel.
This is achieved the following way:
1) For all tree searches, send acquires a read lock on the commit root
semaphore;
2) After each tree search, and before releasing the commit root semaphore,
the leaf is cloned and placed in the search path (struct btrfs_path);
3) After releasing the commit root semaphore, the changed_cb() callback
is invoked, which operates on the leaf and writes commands to the pipe
(or file in case send/receive is not used with a pipe). It's important
here to not hold a lock on the commit root semaphore, because if we did
we could deadlock when sending and receiving to the same filesystem
using a pipe - the send task blocks on the pipe because it's full, the
receive task, which is the only consumer of the pipe, triggers a
transaction commit when attempting to create a subvolume or reserve
space for a write operation for example, but the transaction commit
blocks trying to write lock the commit root semaphore, resulting in a
deadlock;
4) Before moving to the next key, or advancing to the next change in case
of an incremental send, check if a transaction used for relocation was
committed (or is about to finish its commit). If so, release the search
path(s) and restart the search, to where we were before, so that we
don't operate on stale extent buffers. The search restarts are always
possible because both the send and parent roots are RO, and no one can
add, remove of update keys (change their offset) in RO trees - the
only exception is deduplication, but that is still not allowed to run
in parallel with send;
5) Periodically check if there is contention on the commit root semaphore,
which means there is a transaction commit trying to write lock it, and
release the semaphore and reschedule if there is contention, so as to
avoid causing any significant delays to transaction commits.
This leaves some room for optimizations for send to have less path
releases and re searching the trees when there's relocation running, but
for now it's kept simple as it performs quite well (on very large trees
with resulting send streams in the order of a few hundred gigabytes).
Test case btrfs/187, from fstests, stresses relocation, send and
deduplication attempting to run in parallel, but without verifying if send
succeeds and if it produces correct streams. A new test case will be added
that exercises relocation happening in parallel with send and then checks
that send succeeds and the resulting streams are correct.
A final note is that for now this still leaves the mutual exclusion
between send operations and deduplication on files belonging to a root
used by send operations. A solution for that will be slightly more complex
but it will eventually be built on top of this change.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When we start having multiple extent roots we'll need to use a helper to
get to the correct extent_root. Rename fs_info->extent_root to
_extent_root and convert all of the users of the extent root to using
the btrfs_extent_root() helper. This will allow us to easily clean up
the remaining direct accesses in the future.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
With extent tree v2 we will have a separate root to hold the block group
items. Add a btrfs_block_group_root() that will return the appropriate
root given the flags of the fs, and convert all functions that need to
modify block group items to use the helper.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We used to need the root for btrfs_reserve_metadata_bytes to check the
orphan cleanup state, but we no longer need that, we simply need the
fs_info. Change btrfs_reserve_metadata_bytes() to use the fs_info, and
change both btrfs_block_rsv_refill() and btrfs_block_rsv_add() to do the
same as they simply call btrfs_reserve_metadata_bytes() and then
manipulate the block_rsv that is being used.
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>
Since both unused block groups and reclaim bgs lists are protected by
unused_bgs_lock then free them in the same critical section without
doing an extra unlock/lock pair.
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>
Update the comments at btrfs_chunk_alloc() and do_chunk_alloc() that
describe which cases can lead to a failure to allocate metadata and system
space despite having previously reserved space. This adds one more reason
that I previously forgot to mention.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When a task is doing some modification to the chunk btree and it is not in
the context of a chunk allocation or a chunk removal, it can deadlock with
another task that is currently allocating a new data or metadata chunk.
These contexts are the following:
* When relocating a system chunk, when we need to COW the extent buffers
that belong to the chunk btree;
* When adding a new device (ioctl), where we need to add a new device item
to the chunk btree;
* When removing a device (ioctl), where we need to remove a device item
from the chunk btree;
* When resizing a device (ioctl), where we need to update a device item in
the chunk btree and may need to relocate a system chunk that lies beyond
the new device size when shrinking a device.
The problem happens due to a sequence of steps like the following:
1) Task A starts a data or metadata chunk allocation and it locks the
chunk mutex;
2) Task B is relocating a system chunk, and when it needs to COW an extent
buffer of the chunk btree, it has locked both that extent buffer as
well as its parent extent buffer;
3) Since there is not enough available system space, either because none
of the existing system block groups have enough free space or because
the only one with enough free space is in RO mode due to the relocation,
task B triggers a new system chunk allocation. It blocks when trying to
acquire the chunk mutex, currently held by task A;
4) Task A enters btrfs_chunk_alloc_add_chunk_item(), in order to insert
the new chunk item into the chunk btree and update the existing device
items there. But in order to do that, it has to lock the extent buffer
that task B locked at step 2, or its parent extent buffer, but task B
is waiting on the chunk mutex, which is currently locked by task A,
therefore resulting in a deadlock.
One example report when the deadlock happens with system chunk relocation:
INFO: task kworker/u9:5:546 blocked for more than 143 seconds.
Not tainted 5.15.0-rc3+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u9:5 state:D stack:25936 pid: 546 ppid: 2 flags:0x00004000
Workqueue: events_unbound btrfs_async_reclaim_metadata_space
Call Trace:
context_switch kernel/sched/core.c:4940 [inline]
__schedule+0xcd9/0x2530 kernel/sched/core.c:6287
schedule+0xd3/0x270 kernel/sched/core.c:6366
rwsem_down_read_slowpath+0x4ee/0x9d0 kernel/locking/rwsem.c:993
__down_read_common kernel/locking/rwsem.c:1214 [inline]
__down_read kernel/locking/rwsem.c:1223 [inline]
down_read_nested+0xe6/0x440 kernel/locking/rwsem.c:1590
__btrfs_tree_read_lock+0x31/0x350 fs/btrfs/locking.c:47
btrfs_tree_read_lock fs/btrfs/locking.c:54 [inline]
btrfs_read_lock_root_node+0x8a/0x320 fs/btrfs/locking.c:191
btrfs_search_slot_get_root fs/btrfs/ctree.c:1623 [inline]
btrfs_search_slot+0x13b4/0x2140 fs/btrfs/ctree.c:1728
btrfs_update_device+0x11f/0x500 fs/btrfs/volumes.c:2794
btrfs_chunk_alloc_add_chunk_item+0x34d/0xea0 fs/btrfs/volumes.c:5504
do_chunk_alloc fs/btrfs/block-group.c:3408 [inline]
btrfs_chunk_alloc+0x84d/0xf50 fs/btrfs/block-group.c:3653
flush_space+0x54e/0xd80 fs/btrfs/space-info.c:670
btrfs_async_reclaim_metadata_space+0x396/0xa90 fs/btrfs/space-info.c:953
process_one_work+0x9df/0x16d0 kernel/workqueue.c:2297
worker_thread+0x90/0xed0 kernel/workqueue.c:2444
kthread+0x3e5/0x4d0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
INFO: task syz-executor:9107 blocked for more than 143 seconds.
Not tainted 5.15.0-rc3+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor state:D stack:23200 pid: 9107 ppid: 7792 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4940 [inline]
__schedule+0xcd9/0x2530 kernel/sched/core.c:6287
schedule+0xd3/0x270 kernel/sched/core.c:6366
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6425
__mutex_lock_common kernel/locking/mutex.c:669 [inline]
__mutex_lock+0xc96/0x1680 kernel/locking/mutex.c:729
btrfs_chunk_alloc+0x31a/0xf50 fs/btrfs/block-group.c:3631
find_free_extent_update_loop fs/btrfs/extent-tree.c:3986 [inline]
find_free_extent+0x25cb/0x3a30 fs/btrfs/extent-tree.c:4335
btrfs_reserve_extent+0x1f1/0x500 fs/btrfs/extent-tree.c:4415
btrfs_alloc_tree_block+0x203/0x1120 fs/btrfs/extent-tree.c:4813
__btrfs_cow_block+0x412/0x1620 fs/btrfs/ctree.c:415
btrfs_cow_block+0x2f6/0x8c0 fs/btrfs/ctree.c:570
btrfs_search_slot+0x1094/0x2140 fs/btrfs/ctree.c:1768
relocate_tree_block fs/btrfs/relocation.c:2694 [inline]
relocate_tree_blocks+0xf73/0x1770 fs/btrfs/relocation.c:2757
relocate_block_group+0x47e/0xc70 fs/btrfs/relocation.c:3673
btrfs_relocate_block_group+0x48a/0xc60 fs/btrfs/relocation.c:4070
btrfs_relocate_chunk+0x96/0x280 fs/btrfs/volumes.c:3181
__btrfs_balance fs/btrfs/volumes.c:3911 [inline]
btrfs_balance+0x1f03/0x3cd0 fs/btrfs/volumes.c:4301
btrfs_ioctl_balance+0x61e/0x800 fs/btrfs/ioctl.c:4137
btrfs_ioctl+0x39ea/0x7b70 fs/btrfs/ioctl.c:4949
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
So fix this by making sure that whenever we try to modify the chunk btree
and we are neither in a chunk allocation context nor in a chunk remove
context, we reserve system space before modifying the chunk btree.
Reported-by: Hao Sun <sunhao.th@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/CACkBjsax51i4mu6C0C3vJqQN3NR_iVuucoeG3U1HXjrgzn5FFQ@mail.gmail.com/
Fixes: 79bd37120b ("btrfs: rework chunk allocation to avoid exhaustion of the system chunk array")
CC: stable@vger.kernel.org # 5.14+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently auto reclaim of unusable zones reclaims the block-groups in
the order they have been added to the reclaim list.
Change this to a greedy algorithm by sorting the list so we have the
block-groups with the least amount of valid bytes reclaimed first.
Note: we can't splice the block groups from reclaim_bgs to let the sort
happen outside of the lock. The block groups can be still in use by
other parts eg. via bg_list and we must hold unused_bgs_lock while
processing them.
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ write note and comment why we can't splice the list ]
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_update_block_group() accounts for the number of bytes allocated or
freed. Argument @alloc specifies whether the call is for alloc or free.
Convert the argument @alloc type from int to bool.
Reviewed-by: Su Yue <l@damenly.su>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Relocation in a zoned filesystem can fail with a transaction abort with
error -22 (EINVAL). This happens because the relocation code assumes that
the extents we relocated the data to have the same size the source extents
had and ensures this by preallocating the extents.
But in a zoned filesystem we currently can't preallocate the extents as
this would break the sequential write required rule. Therefore it can
happen that the writeback process kicks in while we're still adding pages
to a delalloc range and starts writing out dirty pages.
This then creates destination extents that are smaller than the source
extents, triggering the following safety check in get_new_location():
1034 if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) {
1035 ret = -EINVAL;
1036 goto out;
1037 }
Temporarily create a dedicated block group for the relocation process, so
no non-relocation data writes can interfere with the relocation writes.
This is needed that we can switch the relocation process on a zoned
filesystem from the REQ_OP_ZONE_APPEND writing we use for data to a scheme
like in a non-zoned filesystem using REQ_OP_WRITE and preallocation.
Fixes: 32430c6148 ("btrfs: zoned: enable relocation on a zoned filesystem")
Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Activate new block group at btrfs_make_block_group(). We do not check the
return value. If failed, we can try again later at the actual extent
allocation phase.
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Add zone_is_active flag to btrfs_block_group. This flag indicates the
underlying zones are all active. Such zone active block groups are tracked
by fs_info->active_bg_list.
btrfs_dev_{set,clear}_active_zone() take responsibility for the underlying
device part. They set/clear the bitmap to indicate zone activeness and
count the number of zones we can activate left.
btrfs_zone_{activate,finish}() take responsibility for the logical part and
the list management. In addition, btrfs_zone_finish() wait for any writes
on it and send REQ_OP_ZONE_FINISH to the zone.
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We will use a block group's physical location to track active zones and
finish fully written zones in the following commits. Since the zone
activation is done in the extent allocation context which already holding
the tree locks, we can't query the chunk tree for the physical locations.
So, copy the location info into a block group and use it for activation.
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Now that we introduced capacity in a block group, we need to calculate free
space using the capacity instead of the length. Thus, bytes we account
capacity - alloc_pointer as free, and account bytes [capacity, length] as
zone unusable.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_free_excluded_extents() is not neccessary for
btrfs_calc_zone_unusable() and it makes btrfs_calc_zone_unusable()
difficult to reuse. Move it out and call btrfs_free_excluded_extents()
in proper context.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_chunk_readonly() checks if the given chunk is writeable. It
returns 1 for readonly, and 0 for writeable. So the return argument type
bool shall suffice instead of the current type int.
Also, rename btrfs_chunk_readonly() to btrfs_chunk_writeable() as we
check if the bg is writeable, and helps to keep the logic at the parent
function simpler to understand.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The user facing function used to allocate new chunks is
btrfs_chunk_alloc, unfortunately there is yet another similar sounding
function - btrfs_alloc_chunk. This creates confusion, especially since
the latter function can be considered "private" in the sense that it
implements the first stage of chunk creation and as such is called by
btrfs_chunk_alloc.
To avoid the awkwardness that comes with having similarly named but
distinctly different in their purpose function rename btrfs_alloc_chunk
to btrfs_create_chunk, given that the main purpose of this function is
to orchestrate the whole process of allocating a chunk - reserving space
into devices, deciding on characteristics of the stripe size and
creating the in-memory structures.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_relocate_chunk() can fail with -EAGAIN when e.g. send operations are
running. The message can fail btrfs/187 and it's unnecessary because we
anyway add it back to the reclaim list.
btrfs_reclaim_bgs_work()
`-> btrfs_relocate_chunk()
`-> btrfs_relocate_block_group()
`-> reloc_chunk_start()
`-> if (fs_info->send_in_progress)
`-> return -EAGAIN
CC: stable@vger.kernel.org # 5.13+
Fixes: 18bb8bbf13 ("btrfs: zoned: automatically reclaim zones")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.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>
When extent tree gets corrupted, normally it's not extent tree root, but
one toasted tree leaf/node.
In that case, rescue=ibadroots mount option won't help as it can only
handle the extent tree root corruption.
This patch will enhance the behavior by:
- Allow fill_dummy_bgs() to ignore -EEXIST error
This means we may have some block group items read from disk, but
then hit some error halfway.
- Fallback to fill_dummy_bgs() if any error gets hit in
btrfs_read_block_groups()
Of course, this still needs rescue=ibadroots mount option.
With that, rescue=ibadroots can handle extent tree corruption more
gracefully and allow a better recover chance.
Reported-by: Zhenyu Wu <wuzy001@gmail.com>
Link: https://www.spinics.net/lists/linux-btrfs/msg114424.html
Reviewed-by: Su Yue <l@damenly.su>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
One of the final things that must be done to add a new chunk is
inserting its device extent items in the device tree. They describe
the portion of allocated device physical space during phase 1 of
chunk allocation. This is currently done in btrfs_finish_chunk_alloc
whose name isn't very informative. What's more, this function is only
used in block-group.c but is defined as public. There isn't anything
special about it that would warrant it being defined in volumes.c.
Just move btrfs_finish_chunk_alloc and alloc_chunk_dev_extent to
block-group.c, make the former static and rename both functions to
insert_dev_extents and insert_dev_extent respectively.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If we can't acquire the reclaim_bgs_lock on block group reclaim, we
block until it is free. This can potentially stall for a long time.
While reclaim of block groups is necessary for a good user experience on
a zoned file system, there still is no need to block as it is best
effort only, just like when we're deleting unused block groups.
CC: stable@vger.kernel.org # 5.13
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.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 we're automatically reclaiming a zone, because its zone_unusable
value is above the reclaim threshold, we're only logging how much
percent of the zone's capacity are used, but not how much of the
capacity is unusable.
Also print the percentage of the unusable space in the block group
before we're reclaiming it.
Example:
BTRFS info (device sdg): reclaiming chunk 230686720 with 13% used 86% unusable
CC: stable@vger.kernel.org # 5.13
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The types in calculation of the used percentage in the reclaiming
messages are both u64, though bg->length is either 1GiB (non-zoned) or
the zone size in the zoned mode. The upper limit on zone size is 8GiB so
this could theoretically overflow in the future, right now the values
fit.
Fixes: 18bb8bbf13 ("btrfs: zoned: automatically reclaim zones")
CC: stable@vger.kernel.org # 5.13
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We used this in may_commit_transaction() in order to determine if we
needed to commit the transaction. However we no longer have that logic
and thus have no use of this counter anymore, so delete it.
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>
Relocation and send do not play well together because while send is
running a block group can be relocated, a transaction committed and
the respective disk extents get re-allocated and written to or discarded
while send is about to do something with the extents.
This was explained in commit 9e967495e0 ("Btrfs: prevent send failures
and crashes due to concurrent relocation"), which prevented balance and
send from running in parallel but it did not address one remaining case
where chunk relocation can happen: shrinking a device (and device deletion
which shrinks a device's size to 0 before deleting the device).
We also have now one more case where relocation is triggered: on zoned
filesystems partially used block groups get relocated by a background
thread, introduced in commit 18bb8bbf13 ("btrfs: zoned: automatically
reclaim zones").
So make sure that instead of preventing balance from running when there
are ongoing send operations, we prevent relocation from happening.
This uses the infrastructure recently added by a patch that has the
subject: "btrfs: add cancellable chunk relocation support".
Also it adds a spinlock used exclusively for the exclusivity between
send and relocation, as before fs_info->balance_mutex was used, which
would make an attempt to run send to block waiting for balance to
finish, which can take a lot of time on large filesystems.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently free space cache inode size is determined by two factors:
- block group size
- PAGE_SIZE
This means, for the same sized block groups, with different PAGE_SIZE,
it will result in different inode sizes.
This will not be a good thing for subpage support, so change the
requirement for PAGE_SIZE to sectorsize.
Now for the same 4K sectorsize btrfs, it should result the same inode
size no matter what the PAGE_SIZE is.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Consider we have a using block group on zoned btrfs.
|<- ZU ->|<- used ->|<---free--->|
`- Alloc offset
ZU: Zone unusable
Marking the block group read-only will migrate the zone unusable bytes
to the read-only bytes. So, we will have this.
|<- RO ->|<- used ->|<--- RO --->|
RO: Read only
When marking it back to read-write, btrfs_dec_block_group_ro()
subtracts the above "RO" bytes from the
space_info->bytes_readonly. And, it moves the zone unusable bytes back
and again subtracts those bytes from the space_info->bytes_readonly,
leading to negative bytes_readonly.
This can be observed in the output as eg.:
Data, single: total=512.00MiB, used=165.21MiB, zone_unusable=16.00EiB
Data, single: total=536870912, used=173256704, zone_unusable=18446744073603186688
This commit fixes the issue by reordering the operations.
Link: https://github.com/naota/linux/issues/37
Reported-by: David Sterba <dsterba@suse.com>
Fixes: 169e0da91a ("btrfs: zoned: track unusable bytes for zones")
CC: stable@vger.kernel.org # 5.12+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Omar Sandoval