Re: [PATCH 1/4] xfs: remove xfs_tosspages

[Andrew Dahl <adahl@sgi.com>]

On 11/09/2012 04:10 AM, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> It's a buggy, unnecessary wrapper that is duplicating
> truncate_pagecache_range().
> 
> When replacing the call in xfs_change_file_space(), also ensure that
> the length being allocated/freed is always positive before making
> any changes. These checks are done in the lower extent manipulation
> functions, too, but we need to do them before any page cache
> operations.
> 
> Reported-by: Andrew Dahl <adahl@sgi.com>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/xfs_dfrag.c    |    3 +--
>  fs/xfs/xfs_fs_subr.c  |   12 ------------
>  fs/xfs/xfs_vnodeops.c |   28 +++++++++++++++++++++++-----
>  fs/xfs/xfs_vnodeops.h |    2 --
>  4 files changed, 24 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/xfs/xfs_dfrag.c b/fs/xfs/xfs_dfrag.c
> index b9b8646..b2c63a2 100644
> --- a/fs/xfs/xfs_dfrag.c
> +++ b/fs/xfs/xfs_dfrag.c
> @@ -315,8 +315,7 @@ xfs_swap_extents(
>  	 * are safe.  We don't really care if non-io related
>  	 * fields change.
>  	 */
> -
> -	xfs_tosspages(ip, 0, -1, FI_REMAPF);
> +	truncate_pagecache_range(VFS_I(ip), 0, -1);
>  
>  	tp = xfs_trans_alloc(mp, XFS_TRANS_SWAPEXT);
>  	if ((error = xfs_trans_reserve(tp, 0,
> diff --git a/fs/xfs/xfs_fs_subr.c b/fs/xfs/xfs_fs_subr.c
> index 652b875..d49de3d 100644
> --- a/fs/xfs/xfs_fs_subr.c
> +++ b/fs/xfs/xfs_fs_subr.c
> @@ -25,18 +25,6 @@
>   * note: all filemap functions return negative error codes. These
>   * need to be inverted before returning to the xfs core functions.
>   */
> -void
> -xfs_tosspages(
> -	xfs_inode_t	*ip,
> -	xfs_off_t	first,
> -	xfs_off_t	last,
> -	int		fiopt)
> -{
> -	/* can't toss partial tail pages, so mask them out */
> -	last &= ~(PAGE_SIZE - 1);
> -	truncate_inode_pages_range(VFS_I(ip)->i_mapping, first, last - 1);
> -}
> -
>  int
>  xfs_flushinval_pages(
>  	xfs_inode_t	*ip,
> diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
> index c2ddd7a..f7de578 100644
> --- a/fs/xfs/xfs_vnodeops.c
> +++ b/fs/xfs/xfs_vnodeops.c
> @@ -2118,7 +2118,6 @@ xfs_change_file_space(
>  	xfs_fsize_t	fsize;
>  	int		setprealloc;
>  	xfs_off_t	startoffset;
> -	xfs_off_t	llen;
>  	xfs_trans_t	*tp;
>  	struct iattr	iattr;
>  	int		prealloc_type;
> @@ -2139,12 +2138,30 @@ xfs_change_file_space(
>  		return XFS_ERROR(EINVAL);
>  	}
>  
> -	llen = bf->l_len > 0 ? bf->l_len - 1 : bf->l_len;
> +	/*
> +	 * length of <= 0 for resv/unresv/zero is invalid.  length for
> +	 * alloc/free is ignored completely and we have no idea what userspace
> +	 * might have set it to, so set it to zero to allow range
> +	 * checks to pass.
> +	 */
> +	switch (cmd) {
> +	case XFS_IOC_ZERO_RANGE:
> +	case XFS_IOC_RESVSP:
> +	case XFS_IOC_RESVSP64:
> +	case XFS_IOC_UNRESVSP:
> +	case XFS_IOC_UNRESVSP64:
> +		if (bf->l_len <= 0)
> +			return XFS_ERROR(EINVAL);
> +		break;
> +	default:
> +		bf->l_len = 0;
> +		break;
> +	}
>  
>  	if (bf->l_start < 0 ||
>  	    bf->l_start > mp->m_super->s_maxbytes ||
> -	    bf->l_start + llen < 0 ||
> -	    bf->l_start + llen > mp->m_super->s_maxbytes)
> +	    bf->l_start + bf->l_len < 0 ||
> +	    bf->l_start + bf->l_len >= mp->m_super->s_maxbytes)
>  		return XFS_ERROR(EINVAL);
>  
>  	bf->l_whence = 0;
> @@ -2169,7 +2186,8 @@ xfs_change_file_space(
>  	switch (cmd) {
>  	case XFS_IOC_ZERO_RANGE:
>  		prealloc_type |= XFS_BMAPI_CONVERT;
> -		xfs_tosspages(ip, startoffset, startoffset + bf->l_len, 0);
> +		truncate_pagecache_range(VFS_I(ip), startoffset,
> +			 round_down(startoffset + bf->l_len, PAGE_SIZE) - 1);

When calling XFS_IOC_ZERO_RANGE with a range [0, 4095] or [0,1] it's
tossing pages because the call to round_down() is returning 0 and
passing -1 in for the end will toss all pages.  So, we need to make sure
round_down() isn't going to return a 0, or that (startoffset +
bf->l_len) > PAGE_SIZE.

So, something like...


xfs_off_t       end;

[...]

if((end = round_down(startoffset + bf->l_len, PAGE_SIZE)) > 0) {
	truncate_pagecache_range(VFS_I(ip), startoffset, end - 1);
}


>  		/* FALLTHRU */
>  	case XFS_IOC_RESVSP:
>  	case XFS_IOC_RESVSP64:
> diff --git a/fs/xfs/xfs_vnodeops.h b/fs/xfs/xfs_vnodeops.h
> index 52fafc4..d48141d 100644
> --- a/fs/xfs/xfs_vnodeops.h
> +++ b/fs/xfs/xfs_vnodeops.h
> @@ -48,8 +48,6 @@ int xfs_attr_set(struct xfs_inode *dp, const unsigned char *name,
>  int xfs_attr_remove(struct xfs_inode *dp, const unsigned char *name, int flags);
>  int xfs_attr_list(struct xfs_inode *dp, char *buffer, int bufsize,
>  		int flags, struct attrlist_cursor_kern *cursor);
> -void xfs_tosspages(struct xfs_inode *inode, xfs_off_t first,
> -		xfs_off_t last, int fiopt);
>  int xfs_flushinval_pages(struct xfs_inode *ip, xfs_off_t first,
>  		xfs_off_t last, int fiopt);
>  int xfs_flush_pages(struct xfs_inode *ip, xfs_off_t first,
> 

Beyond that one change, it looks good!

-Andrew

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