On Thu, Nov 29, 2018 at 05:31:32PM +0800, Lu Fengqi wrote:
> The btrfs/001 with inode_cache mount option will encounter the following
> warning:
>
> WARNING: CPU: 1 PID: 23700 at fs/btrfs/inode.c:956
> cow_file_range.isra.19+0x32b/0x430 [btrfs]
> CPU: 1 PID: 23700 Comm: btrfs Kdump: loaded Tainted: G W O
> 4.20.0-rc4-custom+ #30
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
> RIP: 0010:cow_file_range.isra.19+0x32b/0x430 [btrfs]
> Call Trace:
> ? free_extent_buffer+0x46/0x90 [btrfs]
> run_delalloc_nocow+0x455/0x900 [btrfs]
> btrfs_run_delalloc_range+0x1a7/0x360 [btrfs]
> writepage_delalloc+0xf9/0x150 [btrfs]
> __extent_writepage+0x125/0x3e0 [btrfs]
> extent_write_cache_pages+0x1b6/0x3e0 [btrfs]
> ? __wake_up_common_lock+0x63/0xc0
> extent_writepages+0x50/0x80 [btrfs]
> do_writepages+0x41/0xd0
> ? __filemap_fdatawrite_range+0x9e/0xf0
> __filemap_fdatawrite_range+0xbe/0xf0
> btrfs_fdatawrite_range+0x1b/0x50 [btrfs]
> __btrfs_write_out_cache+0x42c/0x480 [btrfs]
> btrfs_write_out_ino_cache+0x84/0xd0 [btrfs]
> btrfs_save_ino_cache+0x551/0x660 [btrfs]
> commit_fs_roots+0xc5/0x190 [btrfs]
> btrfs_commit_transaction+0x2bf/0x8d0 [btrfs]
> btrfs_mksubvol+0x48d/0x4d0 [btrfs]
> btrfs_ioctl_snap_create_transid+0x170/0x180 [btrfs]
> btrfs_ioctl_snap_create_v2+0x124/0x180 [btrfs]
> btrfs_ioctl+0x123f/0x3030 [btrfs]
>
> The file extent generation of the free space inode is equal to the last
> snapshot of the file root, so the inode will be passed to cow_file_rage.
> But the inode was created and its extents were preallocated in
> btrfs_save_ino_cache, there are no cow copies on disk.
>
> The preallocated extents don't present on disk, and the
> btrfs_cross_ref_exist will ignore the -ENOENT returned by
> check_committed_ref, so we can directly write the inode to the disk.
>
> Fixes: 78d4295b1eee ("btrfs: lift some btrfs_cross_ref_exist checks in nocow
> path")
> Signed-off-by: Lu Fengqi <lufq.f...@cn.fujitsu.com>
With updated changelog and reviewed-by added to misc-next, thanks.
