[PATCH 5.17 014/219] btrfs: release correct delalloc amount in direct IO write path

Greg Kroah-Hartman
2022-04-18T12:18:49Z

From: Naohiro Aota <naohiro.aota@wdc.com>

commit 6d82ad13c4110e73c7b0392f00534a1502a1b520 upstream.

Running generic/406 causes the following WARNING in btrfs_destroy_inode()
which tells there are outstanding extents left.

In btrfs_get_blocks_direct_write(), we reserve a temporary outstanding
extents with btrfs_delalloc_reserve_metadata() (or indirectly from
btrfs_delalloc_reserve_space(()). We then release the outstanding extents
with btrfs_delalloc_release_extents(). However, the "len" can be modified
in the COW case, which releases fewer outstanding extents than expected.

Fix it by calling btrfs_delalloc_release_extents() for the original length.

To reproduce the warning, the filesystem should be 1 GiB. It's
triggering a short-write, due to not being able to allocate a large
extent and instead allocating a smaller one.

WARNING: CPU: 0 PID: 757 at fs/btrfs/inode.c:8848 btrfs_destroy_inode+0x1e6/0x210 [btrfs]
Modules linked in: btrfs blake2b_generic xor lzo_compress
lzo_decompress raid6_pq zstd zstd_decompress zstd_compress xxhash zram
zsmalloc
CPU: 0 PID: 757 Comm: umount Not tainted 5.17.0-rc8+ #101
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS d55cb5a 04/01/2014
RIP: 0010:btrfs_destroy_inode+0x1e6/0x210 [btrfs]
RSP: 0018:ffffc9000327bda8 EFLAGS: 00010206
RAX: 0000000000000000 RBX: ffff888100548b78 RCX: 0000000000000000
RDX: 0000000000026900 RSI: 0000000000000000 RDI: ffff888100548b78
RBP: ffff888100548940 R08: 0000000000000000 R09: ffff88810b48aba8
R10: 0000000000000001 R11: ffff8881004eb240 R12: ffff88810b48a800
R13: ffff88810b48ec08 R14: ffff88810b48ed00 R15: ffff888100490c68
FS: 00007f8549ea0b80(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f854a09e733 CR3: 000000010a2e9003 CR4: 0000000000370eb0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
destroy_inode+0x33/0x70
dispose_list+0x43/0x60
evict_inodes+0x161/0x1b0
generic_shutdown_super+0x2d/0x110
kill_anon_super+0xf/0x20
btrfs_kill_super+0xd/0x20 [btrfs]
deactivate_locked_super+0x27/0x90
cleanup_mnt+0x12c/0x180
task_work_run+0x54/0x80
exit_to_user_mode_prepare+0x152/0x160
syscall_exit_to_user_mode+0x12/0x30
do_syscall_64+0x42/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f854a000fb7

Fixes: f0bfa76a11e9 ("btrfs: fix ENOSPC failure when attempting direct IO write into NOCOW range")
CC: stable@vger.kernel.org # 5.17
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Tested-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/inode.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7423,6 +7423,7 @@ static int btrfs_get_blocks_direct_write
u64 block_start, orig_start, orig_block_len, ram_bytes;
bool can_nocow = false;
bool space_reserved = false;
+ u64 prev_len;
int ret = 0;

/*
@@ -7450,6 +7451,7 @@ static int btrfs_get_blocks_direct_write
can_nocow = true;
}

+ prev_len = len;
if (can_nocow) {
struct extent_map *em2;

@@ -7479,8 +7481,6 @@ static int btrfs_get_blocks_direct_write
goto out;
}
} else {
- const u64 prev_len = len;
-
/* Our caller expects us to free the input extent map. */
free_extent_map(em);
*map = NULL;
@@ -7511,7 +7511,7 @@ static int btrfs_get_blocks_direct_write
* We have created our ordered extent, so we can now release our reservation
* for an outstanding extent.
*/
- btrfs_delalloc_release_extents(BTRFS_I(inode), len);
+ btrfs_delalloc_release_extents(BTRFS_I(inode), prev_len);

/*
* Need to update the i_size under the extent lock so buffered