[XFS] Fix speculative allocation beyond eof

Speculative allocation beyond eof doesn't work properly.  It was
broken some time ago after a code cleanup that moved what is now
xfs_iomap_eof_align_last_fsb() and xfs_iomap_eof_want_preallocate()
out of xfs_iomap_write_delay() into separate functions.  The code
used to use the current file size in various checks but got changed
to be max(file_size, i_new_size).  Since i_new_size is the result
of 'offset + count' then in xfs_iomap_eof_want_preallocate() the
check for '(offset + count) <= isize' will always be true.

ie if 'offset + count' is > ip->i_size then isize will be i_new_size
and equal to 'offset + count'.

This change fixes all the places that used to use the current file
size.

Reviewed-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

fs/xfs/xfs_iomap.c

@@ -290,7 +290,6 @@ STATIC int
 xfs_iomap_eof_align_last_fsb(
 	xfs_mount_t	*mp,
 	xfs_inode_t	*ip,
-	xfs_fsize_t	isize,
 	xfs_extlen_t	extsize,
 	xfs_fileoff_t	*last_fsb)
 {
@@ -306,14 +305,14 @@ xfs_iomap_eof_align_last_fsb(
 	 * stripe width and we are allocating past the allocation eof.
 	 */
 	else if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC) &&
-	        (isize >= XFS_FSB_TO_B(mp, mp->m_swidth)))
+	        (ip->i_size >= XFS_FSB_TO_B(mp, mp->m_swidth)))
 		new_last_fsb = roundup_64(*last_fsb, mp->m_swidth);
 	/*
 	 * Roundup the allocation request to a stripe unit (m_dalign) boundary
 	 * if the file size is >= stripe unit size, and we are allocating past
 	 * the allocation eof.
 	 */
-	else if (mp->m_dalign && (isize >= XFS_FSB_TO_B(mp, mp->m_dalign)))
+	else if (mp->m_dalign && (ip->i_size >= XFS_FSB_TO_B(mp, mp->m_dalign)))
 		new_last_fsb = roundup_64(*last_fsb, mp->m_dalign);
 
 	/*
@@ -403,7 +402,6 @@ xfs_iomap_write_direct(
 	xfs_filblks_t	count_fsb, resaligned;
 	xfs_fsblock_t	firstfsb;
 	xfs_extlen_t	extsz, temp;
-	xfs_fsize_t	isize;
 	int		nimaps;
 	int		bmapi_flag;
 	int		quota_flag;
@@ -426,15 +424,10 @@ xfs_iomap_write_direct(
 	rt = XFS_IS_REALTIME_INODE(ip);
 	extsz = xfs_get_extsz_hint(ip);
 
-	isize = ip->i_size;
-	if (ip->i_new_size > isize)
-		isize = ip->i_new_size;
-
 	offset_fsb = XFS_B_TO_FSBT(mp, offset);
 	last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));
-	if ((offset + count) > isize) {
-		error = xfs_iomap_eof_align_last_fsb(mp, ip, isize, extsz,
-							&last_fsb);
+	if ((offset + count) > ip->i_size) {
+		error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
 		if (error)
 			goto error_out;
 	} else {
@@ -559,7 +552,6 @@ STATIC int
 xfs_iomap_eof_want_preallocate(
 	xfs_mount_t	*mp,
 	xfs_inode_t	*ip,
-	xfs_fsize_t	isize,
 	xfs_off_t	offset,
 	size_t		count,
 	int		ioflag,
@@ -573,7 +565,7 @@ xfs_iomap_eof_want_preallocate(
 	int		n, error, imaps;
 
 	*prealloc = 0;
-	if ((ioflag & BMAPI_SYNC) || (offset + count) <= isize)
+	if ((ioflag & BMAPI_SYNC) || (offset + count) <= ip->i_size)
 		return 0;
 
 	/*
@@ -617,7 +609,6 @@ xfs_iomap_write_delay(
 	xfs_fileoff_t	ioalign;
 	xfs_fsblock_t	firstblock;
 	xfs_extlen_t	extsz;
-	xfs_fsize_t	isize;
 	int		nimaps;
 	xfs_bmbt_irec_t imap[XFS_WRITE_IMAPS];
 	int		prealloc, fsynced = 0;
@@ -637,11 +628,7 @@ xfs_iomap_write_delay(
 	offset_fsb = XFS_B_TO_FSBT(mp, offset);
 
 retry:
-	isize = ip->i_size;
-	if (ip->i_new_size > isize)
-		isize = ip->i_new_size;
-
-	error = xfs_iomap_eof_want_preallocate(mp, ip, isize, offset, count,
+	error = xfs_iomap_eof_want_preallocate(mp, ip, offset, count,
 				ioflag, imap, XFS_WRITE_IMAPS, &prealloc);
 	if (error)
 		return error;
@@ -655,8 +642,7 @@ xfs_iomap_write_delay(
 	}
 
 	if (prealloc || extsz) {
-		error = xfs_iomap_eof_align_last_fsb(mp, ip, isize, extsz,
-							&last_fsb);
+		error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
 		if (error)
 			return error;
 	}