Re: [PATCH v2] xfs: fix fallocate functions when rtextsize is larger than 1

[Chandan Babu R <chandanrlinux@gmail.com>]

On Sunday 18 October 2020 3:20:11 AM IST Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> In commit fe341eb151ec, I forgot that xfs_free_file_space isn't strictly
> a "remove mapped blocks" function.  It is actually a function to zero
> file space by punching out the middle and writing zeroes to the
> unaligned ends of the specified range.  Therefore, putting a rtextsize
> alignment check in that function is wrong because that breaks unaligned
> ZERO_RANGE on the realtime volume.
> 
> Furthermore, xfs_file_fallocate already has alignment checks for the
> functions require the file range to be aligned to the size of a
> fundamental allocation unit (which is 1 FSB on the data volume and 1 rt
> extent on the realtime volume).  Create a new helper to check fallocate
> arguments against the realtiem allocation unit size, fix the fallocate
> frontend to use it, fix free_file_space to delete the correct range, and
> remove a now redundant check from insert_file_space.
> 
> NOTE: The realtime extent size is not required to be a power of two!
>

Looks good to me.

Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>

> Fixes: fe341eb151ec ("xfs: ensure that fpunch, fcollapse, and finsert operations are aligned to rt extent size")
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
> v2: fix this to actually handle rtextsize not being a power of 2, add
> testcase
> ---
>  fs/xfs/xfs_bmap_util.c |   17 ++++-------------
>  fs/xfs/xfs_file.c      |   40 +++++++++++++++++++++++++++++++++++-----
>  2 files changed, 39 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index f2a8a0e75e1f..52cddcfee8a1 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -947,11 +947,10 @@ xfs_free_file_space(
>  	endoffset_fsb = XFS_B_TO_FSBT(mp, offset + len);
>  
>  	/* We can only free complete realtime extents. */
> -	if (XFS_IS_REALTIME_INODE(ip)) {
> -		xfs_extlen_t	extsz = xfs_get_extsz_hint(ip);
> -
> -		if ((startoffset_fsb | endoffset_fsb) & (extsz - 1))
> -			return -EINVAL;
> +	if (XFS_IS_REALTIME_INODE(ip) && mp->m_sb.sb_rextsize > 0) {
> +		startoffset_fsb = round_up(startoffset_fsb,
> +					   mp->m_sb.sb_rextsize);
> +		endoffset_fsb = round_down(endoffset_fsb, mp->m_sb.sb_rextsize);
>  	}
>  
>  	/*
> @@ -1147,14 +1146,6 @@ xfs_insert_file_space(
>  
>  	trace_xfs_insert_file_space(ip);
>  
> -	/* We can only insert complete realtime extents. */
> -	if (XFS_IS_REALTIME_INODE(ip)) {
> -		xfs_extlen_t	extsz = xfs_get_extsz_hint(ip);
> -
> -		if ((stop_fsb | shift_fsb) & (extsz - 1))
> -			return -EINVAL;
> -	}
> -
>  	error = xfs_bmap_can_insert_extents(ip, stop_fsb, shift_fsb);
>  	if (error)
>  		return error;
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 3d1b95124744..9e97815887c5 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -785,6 +785,39 @@ xfs_break_layouts(
>  	return error;
>  }
>  
> +/*
> + * Decide if the given file range is aligned to the size of the fundamental
> + * allocation unit for the file.
> + */
> +static bool
> +xfs_is_falloc_aligned(
> +	struct xfs_inode	*ip,
> +	loff_t			pos,
> +	long long int		len)
> +{
> +	struct xfs_mount	*mp = ip->i_mount;
> +	uint64_t		mask;
> +
> +	if (XFS_IS_REALTIME_INODE(ip)) {
> +		if (!is_power_of_2(mp->m_sb.sb_rextsize)) {
> +			u64	rextbytes;
> +			u32	mod;
> +
> +			rextbytes = XFS_FSB_TO_B(mp, mp->m_sb.sb_rextsize);
> +			div_u64_rem(pos, rextbytes, &mod);
> +			if (mod)
> +				return false;
> +			div_u64_rem(len, rextbytes, &mod);
> +			return mod == 0;
> +		}
> +		mask = XFS_FSB_TO_B(mp, mp->m_sb.sb_rextsize) - 1;
> +	} else {
> +		mask = mp->m_sb.sb_blocksize - 1;
> +	}
> +
> +	return !((pos | len) & mask);
> +}
> +
>  #define	XFS_FALLOC_FL_SUPPORTED						\
>  		(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |		\
>  		 FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |	\
> @@ -850,9 +883,7 @@ xfs_file_fallocate(
>  		if (error)
>  			goto out_unlock;
>  	} else if (mode & FALLOC_FL_COLLAPSE_RANGE) {
> -		unsigned int blksize_mask = i_blocksize(inode) - 1;
> -
> -		if (offset & blksize_mask || len & blksize_mask) {
> +		if (!xfs_is_falloc_aligned(ip, offset, len)) {
>  			error = -EINVAL;
>  			goto out_unlock;
>  		}
> @@ -872,10 +903,9 @@ xfs_file_fallocate(
>  		if (error)
>  			goto out_unlock;
>  	} else if (mode & FALLOC_FL_INSERT_RANGE) {
> -		unsigned int	blksize_mask = i_blocksize(inode) - 1;
>  		loff_t		isize = i_size_read(inode);
>  
> -		if (offset & blksize_mask || len & blksize_mask) {
> +		if (!xfs_is_falloc_aligned(ip, offset, len)) {
>  			error = -EINVAL;
>  			goto out_unlock;
>  		}
> 


-- 
chandan