xfs: Introduce macros to represent new maximum extent counts for data…

…/attr forks

This commit defines new macros to represent maximum extent counts allowed by
filesystems which have support for large per-inode extent counters.

Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>

fs/xfs/libxfs/xfs_bmap.c

@@ -61,10 +61,8 @@ xfs_bmap_compute_maxlevels(
 	int		sz;		/* root block size */
 
 	/*
-	 * The maximum number of extents in a file, hence the maximum number of
-	 * leaf entries, is controlled by the size of the on-disk extent count,
-	 * either a signed 32-bit number for the data fork, or a signed 16-bit
-	 * number for the attr fork.
+	 * The maximum number of extents in a fork, hence the maximum number of
+	 * leaf entries, is controlled by the size of the on-disk extent count.
 	 *
 	 * Note that we can no longer assume that if we are in ATTR1 that the
 	 * fork offset of all the inodes will be
@@ -74,7 +72,7 @@ xfs_bmap_compute_maxlevels(
 	 * ATTR2 we have to assume the worst case scenario of a minimum size
 	 * available.
 	 */
-	maxleafents = xfs_iext_max_nextents(whichfork);
+	maxleafents = xfs_iext_max_nextents(xfs_has_nrext64(mp), whichfork);
 	if (whichfork == XFS_DATA_FORK)
 		sz = XFS_BMDR_SPACE_CALC(MINDBTPTRS);
 	else

fs/xfs/libxfs/xfs_bmap_btree.c

@@ -611,7 +611,7 @@ xfs_bmbt_maxlevels_ondisk(void)
 	minrecs[1] = xfs_bmbt_block_maxrecs(blocklen, false) / 2;
 
 	/* One extra level for the inode root. */
-	return xfs_btree_compute_maxlevels(minrecs, MAXEXTNUM) + 1;
+	return xfs_btree_compute_maxlevels(minrecs, XFS_MAX_EXTCNT_DATA_FORK) + 1;
 }
 
 /*

fs/xfs/libxfs/xfs_format.h

@@ -872,10 +872,22 @@ enum xfs_dinode_fmt {
 
 /*
  * Max values for extlen, extnum, 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 */
+ *
+ * The newly introduced data fork extent counter is a 64-bit field. However, the
+ * maximum number of extents in a file is limited to 2^54 extents (assuming one
+ * blocks per extent) by the 54-bit wide startoff field of an extent record.
+ *
+ * A further limitation applies as shown below,
+ * 2^63 (max file size) / 64k (max block size) = 2^47
+ *
+ * Rounding up 47 to the nearest multiple of bits-per-byte results in 48. Hence
+ * 2^48 was chosen as the maximum data fork extent count.
+ */
+#define	MAXEXTLEN			((xfs_extlen_t)((1ULL << 21) - 1)) /* 21 bits */
+#define XFS_MAX_EXTCNT_DATA_FORK	((xfs_extnum_t)((1ULL << 48) - 1)) /* Unsigned 48-bits */
+#define XFS_MAX_EXTCNT_ATTR_FORK	((xfs_extnum_t)((1ULL << 32) - 1)) /* Unsigned 32-bits */
+#define XFS_MAX_EXTCNT_DATA_FORK_OLD	((xfs_extnum_t)((1ULL << 31) - 1)) /* Signed 32-bits */
+#define XFS_MAX_EXTCNT_ATTR_FORK_OLD	((xfs_extnum_t)((1ULL << 15) - 1)) /* Signed 16-bits */
 
 /*
  * Inode minimum and maximum sizes.

fs/xfs/libxfs/xfs_inode_buf.c

@@ -361,7 +361,8 @@ xfs_dinode_verify_fork(
 			return __this_address;
 		break;
 	case XFS_DINODE_FMT_BTREE:
-		max_extents = xfs_iext_max_nextents(whichfork);
+		max_extents = xfs_iext_max_nextents(xfs_dinode_has_nrext64(dip),
+					whichfork);
 		if (di_nextents > max_extents)
 			return __this_address;
 		break;

fs/xfs/libxfs/xfs_inode_fork.c

@@ -746,7 +746,7 @@ xfs_iext_count_may_overflow(
 	if (whichfork == XFS_COW_FORK)
 		return 0;
 
-	max_exts = xfs_iext_max_nextents(whichfork);
+	max_exts = xfs_iext_max_nextents(xfs_inode_has_nrext64(ip), whichfork);
 
 	if (XFS_TEST_ERROR(false, ip->i_mount, XFS_ERRTAG_REDUCE_MAX_IEXTENTS))
 		max_exts = 10;

fs/xfs/libxfs/xfs_inode_fork.h

@@ -133,12 +133,23 @@ static inline int8_t xfs_ifork_format(struct xfs_ifork *ifp)
 	return ifp->if_format;
 }
 
-static inline xfs_extnum_t xfs_iext_max_nextents(int whichfork)
+static inline xfs_extnum_t xfs_iext_max_nextents(bool has_nrext64,
+				int whichfork)
 {
-	if (whichfork == XFS_DATA_FORK || whichfork == XFS_COW_FORK)
-		return MAXEXTNUM;
+	switch (whichfork) {
+	case XFS_DATA_FORK:
+	case XFS_COW_FORK:
+		return has_nrext64 ? XFS_MAX_EXTCNT_DATA_FORK
+			: XFS_MAX_EXTCNT_DATA_FORK_OLD;
+
+	case XFS_ATTR_FORK:
+		return has_nrext64 ? XFS_MAX_EXTCNT_ATTR_FORK
+			: XFS_MAX_EXTCNT_ATTR_FORK_OLD;
 
-	return MAXAEXTNUM;
+	default:
+		ASSERT(0);
+		return 0;
+	}
 }
 
 static inline xfs_extnum_t