6.15-stable review patch. If anyone has any objections, please let me know.
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From: Chao Yu chao@kernel.org
[ Upstream commit c836d3b8d94e3dd381e7d4bb918875084f85715e ]
Syzbot reports a f2fs bug as below:
INFO: task syz-executor328:5856 blocked for more than 144 seconds. Not tainted 6.15.0-rc6-syzkaller-00208-g3c21441eeffc #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor328 state:D stack:24392 pid:5856 tgid:5832 ppid:5826 task_flags:0x400040 flags:0x00004006 Call Trace: <TASK> context_switch kernel/sched/core.c:5382 [inline] __schedule+0x168f/0x4c70 kernel/sched/core.c:6767 __schedule_loop kernel/sched/core.c:6845 [inline] schedule+0x165/0x360 kernel/sched/core.c:6860 io_schedule+0x81/0xe0 kernel/sched/core.c:7742 f2fs_balance_fs+0x4b4/0x780 fs/f2fs/segment.c:444 f2fs_map_blocks+0x3af1/0x43b0 fs/f2fs/data.c:1791 f2fs_expand_inode_data+0x653/0xaf0 fs/f2fs/file.c:1872 f2fs_fallocate+0x4f5/0x990 fs/f2fs/file.c:1975 vfs_fallocate+0x6a0/0x830 fs/open.c:338 ioctl_preallocate fs/ioctl.c:290 [inline] file_ioctl fs/ioctl.c:-1 [inline] do_vfs_ioctl+0x1b8f/0x1eb0 fs/ioctl.c:885 __do_sys_ioctl fs/ioctl.c:904 [inline] __se_sys_ioctl+0x82/0x170 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f
The root cause is after commit 84b5bb8bf0f6 ("f2fs: modify f2fs_is_checkpoint_ready logic to allow more data to be written with the CP disable"), we will get chance to allow f2fs_is_checkpoint_ready() to return true once below conditions are all true: 1. checkpoint is disabled 2. there are not enough free segments 3. there are enough free blocks
Then it will cause f2fs_balance_fs() to trigger foreground GC.
void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need) ... if (!f2fs_is_checkpoint_ready(sbi)) return;
And the testcase mounts f2fs image w/ gc_merge,checkpoint=disable, so deadloop will happen through below race condition:
- f2fs_do_shutdown - vfs_fallocate - gc_thread_func - file_start_write - __sb_start_write(SB_FREEZE_WRITE) - f2fs_fallocate - f2fs_expand_inode_data - f2fs_map_blocks - f2fs_balance_fs - prepare_to_wait - wake_up(gc_wait_queue_head) - io_schedule - bdev_freeze - freeze_super - sb->s_writers.frozen = SB_FREEZE_WRITE; - sb_wait_write(sb, SB_FREEZE_WRITE); - if (sbi->sb->s_writers.frozen >= SB_FREEZE_WRITE) continue; : cause deadloop
This patch fix to add check condition in f2fs_balance_fs(), so that if checkpoint is disabled, we will just skip trigger foreground GC to avoid such deadloop issue.
Meanwhile let's remove f2fs_is_checkpoint_ready() check condition in f2fs_balance_fs(), since it's redundant, due to the main logic in the function is to check: a) whether checkpoint is disabled b) there is enough free segments
f2fs_balance_fs() still has all logics after f2fs_is_checkpoint_ready()'s removal.
Reported-by: syzbot+aa5bb5f6860e08a60450@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-f2fs-devel/682d743a.a00a0220.29bc26.0289.GAE@g... Fixes: 84b5bb8bf0f6 ("f2fs: modify f2fs_is_checkpoint_ready logic to allow more data to be written with the CP disable") Cc: Qi Han hanqi@vivo.com Signed-off-by: Chao Yu chao@kernel.org Reviewed-by: Zhiguo Niu zhiguo.niu@unisoc.com Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/f2fs/segment.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index 2a71e70c9ac97..41ca73622c8d4 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -424,7 +424,7 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need) if (need && excess_cached_nats(sbi)) f2fs_balance_fs_bg(sbi, false);
- if (!f2fs_is_checkpoint_ready(sbi)) + if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) return;
/*