On Wed 30-04-25 16:44:25, Zhang Yi wrote:
> On 2025/4/30 16:18, Jan Kara wrote:
> > On Wed 30-04-25 09:12:59, Zhang Yi wrote:
> >> From: Zhang Yi <yi.zhang@xxxxxxxxxx>
> >>
> >> For the extents inodes, the maxbytes should be sb->s_maxbytes instead of
> >> sbi->s_bitmap_maxbytes. Correct the maxbytes value to correct the
> >> behavior of punch hole.
> >>
> >> Fixes: 2da376228a24 ("ext4: limit length to bitmap_maxbytes - blocksize in punch_hole")
> >> Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
> >
> > Thinking about this some more...
> >
> >> @@ -4015,6 +4015,12 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
> >> trace_ext4_punch_hole(inode, offset, length, 0);
> >> WARN_ON_ONCE(!inode_is_locked(inode));
> >>
> >> + if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
> >> + max_end = sb->s_maxbytes;
> >> + else
> >> + max_end = EXT4_SB(sb)->s_bitmap_maxbytes;
> >> + max_end -= sb->s_blocksize;
> >
> > I think the -= sb->s_blocksize is needed only for indirect-block based
> > scheme (due to an implementation quirk in ext4_ind_remove_space()). But
> > ext4_ext_remove_space() should be fine with punch hole ending right at
> > sb->s_maxbytes. And since I find it somewhat odd that you can create file
> > upto s_maxbytes but cannot punch hole to the end, it'd limit that behavior
> > as much as possible. Ideally we'd fix ext4_ind_remove_space() but I can't
> > be really bothered for the ancient format...
> >
>
> Yes, I share your feelings. Currently, we do not seem to have any
> practical issues. To maintain consistent behavior between the two inode
> types and to keep the code simple, I retained the -= sb->s_blocksize
> operation. Would you suggest that we should at least address the extents
> inodes by removing the -=sb->s_blocksize now?
Yes, what I'm suggesting is that we keep -=sb->s_blocksize specific for the
case !ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS).
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
