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?
Thanks,
Yi.
