Re: [PATCH 5.10] btrfs: fix region size in count_bitmap_extents

[Анастасия Любимова]

03/10/23 15:39, Anastasia Belova пишет:
> 14/09/23 12:45, Anastasia Belova пишет:
> > count_bitmap_extents was deleted in version 5.11, but
> > there is possible mistake in versions 5.6-5.10.
> >
> > Region size should be calculated by subtracting
> > the end from the beginning.
> Do I understand correctly that bytes should decrease and
> (rs - re) is always negative and should be replaced by (re - rs)?
> > Found by Linux Verification Center (linuxtesting.org) with SVACE.
> >
> > Fixes: dfb79ddb130e ("btrfs: track discardable extents for async discard")
> > Signed-off-by: Anastasia Belova<abelova@xxxxxxxxxxxxx>
> > ---
> >   fs/btrfs/free-space-cache.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> > index 4989c60b1df9..a34e266a0969 100644
> > --- a/fs/btrfs/free-space-cache.c
> > +++ b/fs/btrfs/free-space-cache.c
> > @@ -1930,7 +1930,7 @@ static int count_bitmap_extents(struct btrfs_free_space_ctl *ctl,
> >   
> >   	bitmap_for_each_set_region(bitmap_info->bitmap, rs, re, 0,
> >   				   BITS_PER_BITMAP) {
> > -		bytes -= (rs - re) * ctl->unit;
> > +		bytes -= (re - rs) * ctl->unit;
> >   		count++;
> >   
> >   		if (!bytes)
> Anastasia
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