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>

8 files changed, 64 insertions, 59 deletions

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index b52ed339727f..f2a918ed7b8a 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -2511,7 +2511,7 @@ __xfs_free_extent_later(
 
 	ASSERT(bno != NULLFSBLOCK);
 	ASSERT(len > 0);
-	ASSERT(len <= MAXEXTLEN);
+	ASSERT(len <= XFS_MAX_BMBT_EXTLEN);
 	ASSERT(!isnullstartblock(bno));
 	agno = XFS_FSB_TO_AGNO(mp, bno);
 	agbno = XFS_FSB_TO_AGBNO(mp, bno);
diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 74198dd82b03..00b8e6e1c404 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -1452,7 +1452,7 @@ xfs_bmap_add_extent_delay_real(
 	    LEFT.br_startoff + LEFT.br_blockcount == new->br_startoff &&
 	    LEFT.br_startblock + LEFT.br_blockcount == new->br_startblock &&
 	    LEFT.br_state == new->br_state &&
-	    LEFT.br_blockcount + new->br_blockcount <= MAXEXTLEN)
+	    LEFT.br_blockcount + new->br_blockcount <= XFS_MAX_BMBT_EXTLEN)
 		state |= BMAP_LEFT_CONTIG;
 
 	/*
@@ -1470,13 +1470,13 @@ xfs_bmap_add_extent_delay_real(
 	    new_endoff == RIGHT.br_startoff &&
 	    new->br_startblock + new->br_blockcount == RIGHT.br_startblock &&
 	    new->br_state == RIGHT.br_state &&
-	    new->br_blockcount + RIGHT.br_blockcount <= MAXEXTLEN &&
+	    new->br_blockcount + RIGHT.br_blockcount <= XFS_MAX_BMBT_EXTLEN &&
 	    ((state & (BMAP_LEFT_CONTIG | BMAP_LEFT_FILLING |
 		       BMAP_RIGHT_FILLING)) !=
 		      (BMAP_LEFT_CONTIG | BMAP_LEFT_FILLING |
 		       BMAP_RIGHT_FILLING) ||
 	     LEFT.br_blockcount + new->br_blockcount + RIGHT.br_blockcount
-			<= MAXEXTLEN))
+			<= XFS_MAX_BMBT_EXTLEN))
 		state |= BMAP_RIGHT_CONTIG;
 
 	error = 0;
@@ -2000,7 +2000,7 @@ xfs_bmap_add_extent_unwritten_real(
 	    LEFT.br_startoff + LEFT.br_blockcount == new->br_startoff &&
 	    LEFT.br_startblock + LEFT.br_blockcount == new->br_startblock &&
 	    LEFT.br_state == new->br_state &&
-	    LEFT.br_blockcount + new->br_blockcount <= MAXEXTLEN)
+	    LEFT.br_blockcount + new->br_blockcount <= XFS_MAX_BMBT_EXTLEN)
 		state |= BMAP_LEFT_CONTIG;
 
 	/*
@@ -2018,13 +2018,13 @@ xfs_bmap_add_extent_unwritten_real(
 	    new_endoff == RIGHT.br_startoff &&
 	    new->br_startblock + new->br_blockcount == RIGHT.br_startblock &&
 	    new->br_state == RIGHT.br_state &&
-	    new->br_blockcount + RIGHT.br_blockcount <= MAXEXTLEN &&
+	    new->br_blockcount + RIGHT.br_blockcount <= XFS_MAX_BMBT_EXTLEN &&
 	    ((state & (BMAP_LEFT_CONTIG | BMAP_LEFT_FILLING |
 		       BMAP_RIGHT_FILLING)) !=
 		      (BMAP_LEFT_CONTIG | BMAP_LEFT_FILLING |
 		       BMAP_RIGHT_FILLING) ||
 	     LEFT.br_blockcount + new->br_blockcount + RIGHT.br_blockcount
-			<= MAXEXTLEN))
+			<= XFS_MAX_BMBT_EXTLEN))
 		state |= BMAP_RIGHT_CONTIG;
 
 	/*
@@ -2510,15 +2510,15 @@ xfs_bmap_add_extent_hole_delay(
 	 */
 	if ((state & BMAP_LEFT_VALID) && (state & BMAP_LEFT_DELAY) &&
 	    left.br_startoff + left.br_blockcount == new->br_startoff &&
-	    left.br_blockcount + new->br_blockcount <= MAXEXTLEN)
+	    left.br_blockcount + new->br_blockcount <= XFS_MAX_BMBT_EXTLEN)
 		state |= BMAP_LEFT_CONTIG;
 
 	if ((state & BMAP_RIGHT_VALID) && (state & BMAP_RIGHT_DELAY) &&
 	    new->br_startoff + new->br_blockcount == right.br_startoff &&
-	    new->br_blockcount + right.br_blockcount <= MAXEXTLEN &&
+	    new->br_blockcount + right.br_blockcount <= XFS_MAX_BMBT_EXTLEN &&
 	    (!(state & BMAP_LEFT_CONTIG) ||
 	     (left.br_blockcount + new->br_blockcount +
-	      right.br_blockcount <= MAXEXTLEN)))
+	      right.br_blockcount <= XFS_MAX_BMBT_EXTLEN)))
 		state |= BMAP_RIGHT_CONTIG;
 
 	/*
@@ -2661,17 +2661,17 @@ xfs_bmap_add_extent_hole_real(
 	    left.br_startoff + left.br_blockcount == new->br_startoff &&
 	    left.br_startblock + left.br_blockcount == new->br_startblock &&
 	    left.br_state == new->br_state &&
-	    left.br_blockcount + new->br_blockcount <= MAXEXTLEN)
+	    left.br_blockcount + new->br_blockcount <= XFS_MAX_BMBT_EXTLEN)
 		state |= BMAP_LEFT_CONTIG;
 
 	if ((state & BMAP_RIGHT_VALID) && !(state & BMAP_RIGHT_DELAY) &&
 	    new->br_startoff + new->br_blockcount == right.br_startoff &&
 	    new->br_startblock + new->br_blockcount == right.br_startblock &&
 	    new->br_state == right.br_state &&
-	    new->br_blockcount + right.br_blockcount <= MAXEXTLEN &&
+	    new->br_blockcount + right.br_blockcount <= XFS_MAX_BMBT_EXTLEN &&
 	    (!(state & BMAP_LEFT_CONTIG) ||
 	     left.br_blockcount + new->br_blockcount +
-	     right.br_blockcount <= MAXEXTLEN))
+	     right.br_blockcount <= XFS_MAX_BMBT_EXTLEN))
 		state |= BMAP_RIGHT_CONTIG;
 
 	error = 0;
@@ -2906,15 +2906,15 @@ xfs_bmap_extsize_align(
 
 	/*
 	 * For large extent hint sizes, the aligned extent might be larger than
-	 * MAXEXTLEN. In that case, reduce the size by an extsz so that it pulls
-	 * the length back under MAXEXTLEN. The outer allocation loops handle
-	 * short allocation just fine, so it is safe to do this. We only want to
-	 * do it when we are forced to, though, because it means more allocation
-	 * operations are required.
+	 * XFS_BMBT_MAX_EXTLEN. In that case, reduce the size by an extsz so
+	 * that it pulls the length back under XFS_BMBT_MAX_EXTLEN. The outer
+	 * allocation loops handle short allocation just fine, so it is safe to
+	 * do this. We only want to do it when we are forced to, though, because
+	 * it means more allocation operations are required.
 	 */
-	while (align_alen > MAXEXTLEN)
+	while (align_alen > XFS_MAX_BMBT_EXTLEN)
 		align_alen -= extsz;
-	ASSERT(align_alen <= MAXEXTLEN);
+	ASSERT(align_alen <= XFS_MAX_BMBT_EXTLEN);
 
 	/*
 	 * If the previous block overlaps with this proposed allocation
@@ -3004,9 +3004,9 @@ xfs_bmap_extsize_align(
 			return -EINVAL;
 	} else {
 		ASSERT(orig_off >= align_off);
-		/* see MAXEXTLEN handling above */
+		/* see XFS_BMBT_MAX_EXTLEN handling above */
 		ASSERT(orig_end <= align_off + align_alen ||
-		       align_alen + extsz > MAXEXTLEN);
+		       align_alen + extsz > XFS_MAX_BMBT_EXTLEN);
 	}
 
 #ifdef DEBUG
@@ -3971,7 +3971,7 @@ xfs_bmapi_reserve_delalloc(
 	 * Cap the alloc length. Keep track of prealloc so we know whether to
 	 * tag the inode before we return.
 	 */
-	alen = XFS_FILBLKS_MIN(len + prealloc, MAXEXTLEN);
+	alen = XFS_FILBLKS_MIN(len + prealloc, XFS_MAX_BMBT_EXTLEN);
 	if (!eof)
 		alen = XFS_FILBLKS_MIN(alen, got->br_startoff - aoff);
 	if (prealloc && alen >= len)
@@ -4104,7 +4104,7 @@ xfs_bmapi_allocate(
 		if (!xfs_iext_peek_prev_extent(ifp, &bma->icur, &bma->prev))
 			bma->prev.br_startoff = NULLFILEOFF;
 	} else {
-		bma->length = XFS_FILBLKS_MIN(bma->length, MAXEXTLEN);
+		bma->length = XFS_FILBLKS_MIN(bma->length, XFS_MAX_BMBT_EXTLEN);
 		if (!bma->eof)
 			bma->length = XFS_FILBLKS_MIN(bma->length,
 					bma->got.br_startoff - bma->offset);
@@ -4424,8 +4424,8 @@ xfs_bmapi_write(
 			 * xfs_extlen_t and therefore 32 bits. Hence we have to
 			 * check for 32-bit overflows and handle them here.
 			 */
-			if (len > (xfs_filblks_t)MAXEXTLEN)
-				bma.length = MAXEXTLEN;
+			if (len > (xfs_filblks_t)XFS_MAX_BMBT_EXTLEN)
+				bma.length = XFS_MAX_BMBT_EXTLEN;
 			else
 				bma.length = len;
 
@@ -4560,7 +4560,8 @@ xfs_bmapi_convert_delalloc(
 	bma.ip = ip;
 	bma.wasdel = true;
 	bma.offset = bma.got.br_startoff;
-	bma.length = max_t(xfs_filblks_t, bma.got.br_blockcount, MAXEXTLEN);
+	bma.length = max_t(xfs_filblks_t, bma.got.br_blockcount,
+			XFS_MAX_BMBT_EXTLEN);
 	bma.minleft = xfs_bmapi_minleft(tp, ip, whichfork);
 
 	/*
@@ -4641,7 +4642,7 @@ xfs_bmapi_remap(
 
 	ifp = XFS_IFORK_PTR(ip, whichfork);
 	ASSERT(len > 0);
-	ASSERT(len <= (xfs_filblks_t)MAXEXTLEN);
+	ASSERT(len <= (xfs_filblks_t)XFS_MAX_BMBT_EXTLEN);
 	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
 	ASSERT(!(flags & ~(XFS_BMAPI_ATTRFORK | XFS_BMAPI_PREALLOC |
 			   XFS_BMAPI_NORMAP)));
@@ -5641,7 +5642,7 @@ xfs_bmse_can_merge(
 	if ((left->br_startoff + left->br_blockcount != startoff) ||
 	    (left->br_startblock + left->br_blockcount != got->br_startblock) ||
 	    (left->br_state != got->br_state) ||
-	    (left->br_blockcount + got->br_blockcount > MAXEXTLEN))
+	    (left->br_blockcount + got->br_blockcount > XFS_MAX_BMBT_EXTLEN))
 		return false;
 
 	return true;
diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index d75e5b16da7e..66594853a88b 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -870,9 +870,8 @@ enum xfs_dinode_fmt {
 	{ XFS_DINODE_FMT_UUID,		"uuid" }
 
 /*
- * Max values for extlen, extnum, aextnum.
+ * Max values for extnum and aextnum.
  */
-#define	MAXEXTLEN	((xfs_extlen_t)0x001fffff)	/* 21 bits */
 #define	MAXEXTNUM	((xfs_extnum_t)0x7fffffff)	/* signed int */
 #define	MAXAEXTNUM	((xfs_aextnum_t)0x7fff)		/* signed short */
 
@@ -1603,6 +1602,8 @@ typedef struct xfs_bmdr_block {
 #define BMBT_STARTOFF_MASK	((1ULL << BMBT_STARTOFF_BITLEN) - 1)
 #define BMBT_BLOCKCOUNT_MASK	((1ULL << BMBT_BLOCKCOUNT_BITLEN) - 1)
 
+#define XFS_MAX_BMBT_EXTLEN	((xfs_extlen_t)(BMBT_BLOCKCOUNT_MASK))
+
 /*
  * bmbt records have a file offset (block) field that is 54 bits wide, so this
  * is the largest xfs_fileoff_t that we ever expect to see.
diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index cae9708c8587..87781a5d5a45 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -639,7 +639,7 @@ xfs_inode_validate_extsize(
 	if (extsize_bytes % blocksize_bytes)
 		return __this_address;
 
-	if (extsize > MAXEXTLEN)
+	if (extsize > XFS_MAX_BMBT_EXTLEN)
 		return __this_address;
 
 	if (!rt_flag && extsize > mp->m_sb.sb_agblocks / 2)
@@ -696,7 +696,7 @@ xfs_inode_validate_cowextsize(
 	if (cowextsize_bytes % mp->m_sb.sb_blocksize)
 		return __this_address;
 
-	if (cowextsize > MAXEXTLEN)
+	if (cowextsize > XFS_MAX_BMBT_EXTLEN)
 		return __this_address;
 
 	if (cowextsize > mp->m_sb.sb_agblocks / 2)
diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
index 6f83d9b306ee..8e1d09e8cc9a 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.c
+++ b/fs/xfs/libxfs/xfs_trans_resv.c
@@ -199,8 +199,8 @@ xfs_calc_inode_chunk_res(
 /*
  * Per-extent log reservation for the btree changes involved in freeing or
  * allocating a realtime extent.  We have to be able to log as many rtbitmap
- * blocks as needed to mark inuse MAXEXTLEN blocks' worth of realtime extents,
- * as well as the realtime summary block.
+ * blocks as needed to mark inuse XFS_BMBT_MAX_EXTLEN blocks' worth of realtime
+ * extents, as well as the realtime summary block.
  */
 static unsigned int
 xfs_rtalloc_log_count(
@@ -210,7 +210,7 @@ xfs_rtalloc_log_count(
 	unsigned int		blksz = XFS_FSB_TO_B(mp, 1);
 	unsigned int		rtbmp_bytes;
 
-	rtbmp_bytes = (MAXEXTLEN / mp->m_sb.sb_rextsize) / NBBY;
+	rtbmp_bytes = (XFS_MAX_BMBT_EXTLEN / mp->m_sb.sb_rextsize) / NBBY;
 	return (howmany(rtbmp_bytes, blksz) + 1) * num_ops;
 }
 
@@ -247,7 +247,7 @@ xfs_rtalloc_log_count(
  *    the inode's bmap btree: max depth * block size
  *    the agfs of the ags from which the extents are allocated: 2 * sector
  *    the superblock free block counter: sector size
- *    the realtime bitmap: ((MAXEXTLEN / rtextsize) / NBBY) bytes
+ *    the realtime bitmap: ((XFS_BMBT_MAX_EXTLEN / rtextsize) / NBBY) bytes
  *    the realtime summary: 1 block
  *    the allocation btrees: 2 trees * (2 * max depth - 1) * block size
  * And the bmap_finish transaction can free bmap blocks in a join (t3):
@@ -299,7 +299,8 @@ xfs_calc_write_reservation(
  *    the agf for each of the ags: 2 * sector size
  *    the agfl for each of the ags: 2 * sector size
  *    the super block to reflect the freed blocks: sector size
- *    the realtime bitmap: 2 exts * ((MAXEXTLEN / rtextsize) / NBBY) bytes
+ *    the realtime bitmap:
+ *		2 exts * ((XFS_BMBT_MAX_EXTLEN / rtextsize) / NBBY) bytes
  *    the realtime summary: 2 exts * 1 block
  *    worst case split in allocation btrees per extent assuming 2 extents:
  *		2 exts * 2 trees * (2 * max depth - 1) * block size
diff --git a/fs/xfs/scrub/bmap.c b/fs/xfs/scrub/bmap.c
index a4cbbc346f60..c357593e0a02 100644
--- a/fs/xfs/scrub/bmap.c
+++ b/fs/xfs/scrub/bmap.c
@@ -350,7 +350,7 @@ xchk_bmap_iextent(
 				irec->br_startoff);
 
 	/* Make sure the extent points to a valid place. */
-	if (irec->br_blockcount > MAXEXTLEN)
+	if (irec->br_blockcount > XFS_MAX_BMBT_EXTLEN)
 		xchk_fblock_set_corrupt(info->sc, info->whichfork,
 				irec->br_startoff);
 	if (info->is_rt &&
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index eb2e387ba528..18c1b99311a8 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -119,14 +119,14 @@ retry:
 	 */
 	ralen = ap->length / mp->m_sb.sb_rextsize;
 	/*
-	 * If the old value was close enough to MAXEXTLEN that
+	 * If the old value was close enough to XFS_BMBT_MAX_EXTLEN that
 	 * we rounded up to it, cut it back so it's valid again.
 	 * Note that if it's a really large request (bigger than
-	 * MAXEXTLEN), we don't hear about that number, and can't
+	 * XFS_BMBT_MAX_EXTLEN), we don't hear about that number, and can't
 	 * adjust the starting point to match it.
 	 */
-	if (ralen * mp->m_sb.sb_rextsize >= MAXEXTLEN)
-		ralen = MAXEXTLEN / mp->m_sb.sb_rextsize;
+	if (ralen * mp->m_sb.sb_rextsize >= XFS_MAX_BMBT_EXTLEN)
+		ralen = XFS_MAX_BMBT_EXTLEN / mp->m_sb.sb_rextsize;
 
 	/*
 	 * Lock out modifications to both the RT bitmap and summary inodes
@@ -839,9 +839,11 @@ xfs_alloc_file_space(
 		 * count, hence we need to limit the number of blocks we are
 		 * trying to reserve to avoid an overflow. We can't allocate
 		 * more than @nimaps extents, and an extent is limited on disk
-		 * to MAXEXTLEN (21 bits), so use that to enforce the limit.
+		 * to XFS_BMBT_MAX_EXTLEN (21 bits), so use that to enforce the
+		 * limit.
 		 */
-		resblks = min_t(xfs_fileoff_t, (e - s), (MAXEXTLEN * nimaps));
+		resblks = min_t(xfs_fileoff_t, (e - s),
+				(XFS_MAX_BMBT_EXTLEN * nimaps));
 		if (unlikely(rt)) {
 			dblocks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
 			rblocks = resblks;
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;