btrfs: fix re-dirty process of tree-log nodes

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix re-dirty process of tree-log nodes

There is a report of a transaction abort of -EAGAIN with the following

script.

#!/bin/sh

for d in sda sdb; do

mkfs.btrfs -d single -m single -f /dev/\${d}

done

mount /dev/sda /mnt/test

mount /dev/sdb /mnt/scratch

for dir in test scratch; do

echo 3 >/proc/sys/vm/drop_caches

fio --directory=/mnt/\${dir} --name=fio.\${dir} --rw=read --size=50G --bs=64m \

--numjobs=$(nproc) --time_based --ramp_time=5 --runtime=480 \

--group_reporting |& tee /dev/shm/fio.\${dir}

echo 3 >/proc/sys/vm/drop_caches

done

for d in sda sdb; do

umount /dev/\${d}

done

The stack trace is shown in below.

[3310.967991] BTRFS: error (device sda) in btrfs_commit_transaction:2341: errno=-11 unknown (Error while writing out transaction)

[3310.968060] BTRFS info (device sda): forced readonly

[3310.968064] BTRFS warning (device sda): Skipping commit of aborted transaction.

[3310.968065] ------------[ cut here ]------------

[3310.968066] BTRFS: Transaction aborted (error -11)

[3310.968074] WARNING: CPU: 14 PID: 1684 at fs/btrfs/transaction.c:1946 btrfs_commit_transaction.cold+0x209/0x2c8

[3310.968131] CPU: 14 PID: 1684 Comm: fio Not tainted 5.14.10-300.fc35.x86_64 #1

[3310.968135] Hardware name: DIAWAY Tartu/Tartu, BIOS V2.01.B10 04/08/2021

[3310.968137] RIP: 0010:btrfs_commit_transaction.cold+0x209/0x2c8

[3310.968144] RSP: 0018:ffffb284ce393e10 EFLAGS: 00010282

[3310.968147] RAX: 0000000000000026 RBX: ffff973f147b0f60 RCX: 0000000000000027

[3310.968149] RDX: ffff974ecf098a08 RSI: 0000000000000001 RDI: ffff974ecf098a00

[3310.968150] RBP: ffff973f147b0f08 R08: 0000000000000000 R09: ffffb284ce393c48

[3310.968151] R10: ffffb284ce393c40 R11: ffffffff84f47468 R12: ffff973f101bfc00

[3310.968153] R13: ffff971f20cf2000 R14: 00000000fffffff5 R15: ffff973f147b0e58

[3310.968154] FS: 00007efe65468740(0000) GS:ffff974ecf080000(0000) knlGS:0000000000000000

[3310.968157] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

[3310.968158] CR2: 000055691bcbe260 CR3: 000000105cfa4001 CR4: 0000000000770ee0

[3310.968160] PKRU: 55555554

[3310.968161] Call Trace:

[3310.968167] ? dput+0xd4/0x300

[3310.968174] btrfs_sync_file+0x3f1/0x490

[3310.968180] __x64_sys_fsync+0x33/0x60

[3310.968185] do_syscall_64+0x3b/0x90

[3310.968190] entry_SYSCALL_64_after_hwframe+0x44/0xae

[3310.968194] RIP: 0033:0x7efe6557329b

[3310.968200] RSP: 002b:00007ffe0236ebc0 EFLAGS: 00000293 ORIG_RAX: 000000000000004a

[3310.968203] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007efe6557329b

[3310.968204] RDX: 0000000000000000 RSI: 00007efe58d77010 RDI: 0000000000000006

[3310.968205] RBP: 0000000004000000 R08: 0000000000000000 R09: 00007efe58d77010

[3310.968207] R10: 0000000016cacc0c R11: 0000000000000293 R12: 00007efe5ce95980

[3310.968208] R13: 0000000000000000 R14: 00007efe6447c790 R15: 0000000c80000000

[3310.968212] ---[ end trace 1a346f4d3c0d96ba ]---

[3310.968214] BTRFS: error (device sda) in cleanup_transaction:1946: errno=-11 unknown

The abort occurs because of a write hole while writing out freeing tree

nodes of a tree-log tree. For zoned btrfs, we re-dirty a freed tree

node to ensure btrfs can write the region and does not leave a hole on

write on a zoned device. The current code fails to re-dirty a node

when the tree-log tree's depth is greater or equal to 2. That leads to

a transaction abort with -EAGAIN.

Fix the issue by properly re-dirtying a node on walking up the tree.