[PATCH V9 12/19] xfs: Introduce macros to represent new maximum extent counts for data/attr forks

Chandan Babu R
2022-04-06T09:38:55Z

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

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
---
fs/xfs/libxfs/xfs_bmap.c | 9 ++++-----
fs/xfs/libxfs/xfs_bmap_btree.c | 3 ++-
fs/xfs/libxfs/xfs_format.h | 24 ++++++++++++++++++++++--
fs/xfs/libxfs/xfs_inode_buf.c | 4 +++-
fs/xfs/libxfs/xfs_inode_fork.c | 3 ++-
fs/xfs/libxfs/xfs_inode_fork.h | 21 +++++++++++++++++----
6 files changed, 50 insertions(+), 14 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index b317226fb4ba..1254d4d4821e 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/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 +72,8 @@ 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_large_extent_counts(mp),
+ whichfork);
if (whichfork == XFS_DATA_FORK)
sz = XFS_BMDR_SPACE_CALC(MINDBTPTRS);
else
diff --git a/fs/xfs/libxfs/xfs_bmap_btree.c b/fs/xfs/libxfs/xfs_bmap_btree.c
index 453309fc85f2..7aabeccea9ab 100644
--- a/fs/xfs/libxfs/xfs_bmap_btree.c
+++ b/fs/xfs/libxfs/xfs_bmap_btree.c
@@ -611,7 +611,8 @@ 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_LARGE) + 1;
}

/*
diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 57b24744a7c2..eb85bc9b229b 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -872,9 +872,29 @@ enum xfs_dinode_fmt {

/*
* Max values for extnum and aextnum.
+ *
+ * The original on-disk extent counts were held in signed fields, resulting in
+ * maximum extent counts of 2^31 and 2^15 for the data and attr forks
+ * respectively. Similarly the maximum extent length is limited to 2^21 blocks
+ * by the 21-bit wide blockcount field of a BMBT extent record.
+ *
+ * The newly introduced data fork extent counter can hold a 64-bit value,
+ * however the maximum number of extents in a file is also limited to 2^54
+ * extents by the 54-bit wide startoff field of a BMBT extent record.
+ *
+ * It is further limited by the maximum supported file size of 2^63
+ * *bytes*. This leads to a maximum extent count for maximally sized filesystem
+ * blocks (64kB) of:
+ *
+ * 2^63 bytes / 2^16 bytes per block = 2^47 blocks
+ *
+ * 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 MAXEXTNUM ((xfs_extnum_t)0x7fffffff) /* signed int */
-#define MAXAEXTNUM ((xfs_aextnum_t)0x7fff) /* signed short */
+#define XFS_MAX_EXTCNT_DATA_FORK_LARGE ((xfs_extnum_t)((1ULL << 48) - 1))
+#define XFS_MAX_EXTCNT_ATTR_FORK_LARGE ((xfs_extnum_t)((1ULL << 32) - 1))
+#define XFS_MAX_EXTCNT_DATA_FORK_SMALL ((xfs_extnum_t)((1ULL << 31) - 1))
+#define XFS_MAX_EXTCNT_ATTR_FORK_SMALL ((xfs_extnum_t)((1ULL << 15) - 1))

/*
* Inode minimum and maximum sizes.
diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index f0e063835318..e0d3140c3622 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -361,7 +361,9 @@ 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_large_extent_counts(dip),
+ whichfork);
if (di_nextents > max_extents)
return __this_address;
break;
diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
index 004b205d87b8..bb5d841aac58 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.c
+++ b/fs/xfs/libxfs/xfs_inode_fork.c
@@ -744,7 +744,8 @@ 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_large_extent_counts(ip),
+ whichfork);

if (XFS_TEST_ERROR(false, ip->i_mount, XFS_ERRTAG_REDUCE_MAX_IEXTENTS))
max_exts = 10;
diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index 4a8b77d425df..967837a88860 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -133,12 +133,25 @@ 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_large_extent_counts,
+ int whichfork)
{
- if (whichfork == XFS_DATA_FORK || whichfork == XFS_COW_FORK)
- return MAXEXTNUM;
+ switch (whichfork) {
+ case XFS_DATA_FORK:
+ case XFS_COW_FORK:
+ if (has_large_extent_counts)
+ return XFS_MAX_EXTCNT_DATA_FORK_LARGE;
+ return XFS_MAX_EXTCNT_DATA_FORK_SMALL;
+
+ case XFS_ATTR_FORK:
+ if (has_large_extent_counts)
+ return XFS_MAX_EXTCNT_ATTR_FORK_LARGE;
+ return XFS_MAX_EXTCNT_ATTR_FORK_SMALL;

- return MAXAEXTNUM;
+ default:
+ ASSERT(0);
+ return 0;
+ }
}

static inline xfs_extnum_t
--
2.30.2