Re: [PATCH] ext4: don't over-report free space or inodes in statvfs

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Mar 18, 2025 at 12:23:47AM -0400, Theodore Ts'o wrote:
> This fixes an analogus bug that was fixed in xfs in commit
> 4b8d867ca6e2 ("xfs: don't over-report free space or inodes in
> statvfs") where statfs can report misleading / incorrect information
> where project quota is enabled, and the free space is less than the
> remaining quota.
> 
> This commit will resolve a test failure in generic/762 which tests for
> this bug.
> 
> Cc: stable@kernel.org
> Fixes: 689c958cbe6b ("ext4: add project quota support")
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Yeah, that looks exactly like the xfs solution to this problem...
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/ext4/super.c | 27 +++++++++++++++++----------
>  1 file changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 4768770715ca..8cafcd3e9f5f 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -6820,22 +6820,29 @@ static int ext4_statfs_project(struct super_block *sb,
>  			     dquot->dq_dqb.dqb_bhardlimit);
>  	limit >>= sb->s_blocksize_bits;
>  
> -	if (limit && buf->f_blocks > limit) {
> +	if (limit) {
> +		uint64_t	remaining = 0;
> +
>  		curblock = (dquot->dq_dqb.dqb_curspace +
>  			    dquot->dq_dqb.dqb_rsvspace) >> sb->s_blocksize_bits;
> -		buf->f_blocks = limit;
> -		buf->f_bfree = buf->f_bavail =
> -			(buf->f_blocks > curblock) ?
> -			 (buf->f_blocks - curblock) : 0;
> +		if (limit > curblock)
> +			remaining = limit - curblock;
> +
> +		buf->f_blocks = min(buf->f_blocks, limit);
> +		buf->f_bfree = min(buf->f_bfree, remaining);
> +		buf->f_bavail = min(buf->f_bavail, remaining);
>  	}
>  
>  	limit = min_not_zero(dquot->dq_dqb.dqb_isoftlimit,
>  			     dquot->dq_dqb.dqb_ihardlimit);
> -	if (limit && buf->f_files > limit) {
> -		buf->f_files = limit;
> -		buf->f_ffree =
> -			(buf->f_files > dquot->dq_dqb.dqb_curinodes) ?
> -			 (buf->f_files - dquot->dq_dqb.dqb_curinodes) : 0;
> +	if (limit) {
> +		uint64_t	remaining = 0;
> +
> +		if (limit > dquot->dq_dqb.dqb_curinodes)
> +			remaining = limit - dquot->dq_dqb.dqb_curinodes;
> +
> +		buf->f_files = min(buf->f_files, limit);
> +		buf->f_ffree = min(buf->f_ffree, remaining);
>  	}
>  
>  	spin_unlock(&dquot->dq_dqb_lock);
> -- 
> 2.47.2
> 
>