xfs: Define max extent length based on on-disk format definition

The maximum extent length depends on maximum block count that can be stored in
a BMBT record. Hence this commit defines MAXEXTLEN based on
BMBT_BLOCKCOUNT_BITLEN.

While at it, the commit also renames MAXEXTLEN to XFS_MAX_BMBT_EXTLEN.

Suggested-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>

1 files changed, 14 insertions, 14 deletions

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index e552ce541ec2..87e1cf5060bd 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -402,7 +402,7 @@ xfs_iomap_prealloc_size(
 	 */
 	plen = prev.br_blockcount;
 	while (xfs_iext_prev_extent(ifp, &ncur, &got)) {
-		if (plen > MAXEXTLEN / 2 ||
+		if (plen > XFS_MAX_BMBT_EXTLEN / 2 ||
 		    isnullstartblock(got.br_startblock) ||
 		    got.br_startoff + got.br_blockcount != prev.br_startoff ||
 		    got.br_startblock + got.br_blockcount != prev.br_startblock)
@@ -414,23 +414,23 @@ xfs_iomap_prealloc_size(
 	/*
 	 * If the size of the extents is greater than half the maximum extent
 	 * length, then use the current offset as the basis.  This ensures that
-	 * for large files the preallocation size always extends to MAXEXTLEN
-	 * rather than falling short due to things like stripe unit/width
-	 * alignment of real extents.
+	 * for large files the preallocation size always extends to
+	 * XFS_BMBT_MAX_EXTLEN rather than falling short due to things like stripe
+	 * unit/width alignment of real extents.
 	 */
 	alloc_blocks = plen * 2;
-	if (alloc_blocks > MAXEXTLEN)
+	if (alloc_blocks > XFS_MAX_BMBT_EXTLEN)
 		alloc_blocks = XFS_B_TO_FSB(mp, offset);
 	qblocks = alloc_blocks;
 
 	/*
-	 * MAXEXTLEN is not a power of two value but we round the prealloc down
-	 * to the nearest power of two value after throttling. To prevent the
-	 * round down from unconditionally reducing the maximum supported
-	 * prealloc size, we round up first, apply appropriate throttling,
-	 * round down and cap the value to MAXEXTLEN.
+	 * XFS_BMBT_MAX_EXTLEN is not a power of two value but we round the prealloc
+	 * down to the nearest power of two value after throttling. To prevent
+	 * the round down from unconditionally reducing the maximum supported
+	 * prealloc size, we round up first, apply appropriate throttling, round
+	 * down and cap the value to XFS_BMBT_MAX_EXTLEN.
 	 */
-	alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(MAXEXTLEN),
+	alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(XFS_MAX_BMBT_EXTLEN),
 				       alloc_blocks);
 
 	freesp = percpu_counter_read_positive(&mp->m_fdblocks);
@@ -478,14 +478,14 @@ xfs_iomap_prealloc_size(
 	 */
 	if (alloc_blocks)
 		alloc_blocks = rounddown_pow_of_two(alloc_blocks);
-	if (alloc_blocks > MAXEXTLEN)
-		alloc_blocks = MAXEXTLEN;
+	if (alloc_blocks > XFS_MAX_BMBT_EXTLEN)
+		alloc_blocks = XFS_MAX_BMBT_EXTLEN;
 
 	/*
 	 * If we are still trying to allocate more space than is
 	 * available, squash the prealloc hard. This can happen if we
 	 * have a large file on a small filesystem and the above
-	 * lowspace thresholds are smaller than MAXEXTLEN.
+	 * lowspace thresholds are smaller than XFS_BMBT_MAX_EXTLEN.
 	 */
 	while (alloc_blocks && alloc_blocks >= freesp)
 		alloc_blocks >>= 4;