Re: [PATCH] btrfs-progs: fix false alert on tree block crossing 64K page boundary

[David Sterba <dsterba@suse.cz>]

On Sat, Mar 06, 2021 at 08:40:19AM +0800, Qu Wenruo wrote:
> [BUG]
> When btrfs-check is executed on even newly created fs, it can report
> tree blocks crossing 64K page boundary like this:
> 
>   Opening filesystem to check...
>   Checking filesystem on /dev/test/test
>   UUID: 80d734c8-dcbc-411b-9623-a10bd9e7767f
>   [1/7] checking root items
>   [2/7] checking extents
>   WARNING: tree block [30523392, 30539776) crosses 64K page boudnary, may cause problem for 64K page system
>   [3/7] checking free space cache
>   [4/7] checking fs roots
>   [5/7] checking only csums items (without verifying data)
>   [6/7] checking root refs
>   [7/7] checking quota groups skipped (not enabled on this FS)
>   found 131072 bytes used, no error found
>   total csum bytes: 0
>   total tree bytes: 131072
>   total fs tree bytes: 32768
>   total extent tree bytes: 16384
>   btree space waste bytes: 125199
>   file data blocks allocated: 0
>    referenced 0
> 
> [CAUSE]
> Tree block [30523392, 30539776) is at the last 16K slot of page.
> As 30523392 % 65536 = 49152, and 30539776 % 65536 = 0.
> 
> The cross boundary check is using exclusive end, which causes false
> alerts.
> 
> [FIX]
> Use inclusive end to do the cross 64K boundary check.
> 
> Reported-by: Wang Yugui <wangyugui@e16-tech.com>
> Fixes: fc38ae7f4826 ("btrfs-progs: check: detect and warn about tree blocks crossing 64K page boundary")
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Thanks. I've extended the 001 test for mkfs to actually check for any
check warnings right after mkfs, covering all profiles and
single/multiple setups.