xfs: Directory's data fork extent counter can never overflow

The maximum file size that can be represented by the data fork extent counter
in the worst case occurs when all extents are 1 block in length and each block
is 1KB in size.

With XFS_MAX_EXTCNT_DATA_FORK_SMALL representing maximum extent count and with
1KB sized blocks, a file can reach upto,
(2^31) * 1KB = 2TB

This is much larger than the theoretical maximum size of a directory
i.e. XFS_DIR2_SPACE_SIZE * 3 = ~96GB.

Since a directory's inode can never overflow its data fork extent counter,
this commit removes all the overflow checks associated with
it. xfs_dinode_verify() now performs a rough check to verify if a diretory's
data fork is larger than 96GB.

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

7 files changed, 26 insertions, 33 deletions

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 1254d4d4821e..4fab0c92ab70 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -5147,26 +5147,6 @@ xfs_bmap_del_extent_real(
 		 * Deleting the middle of the extent.
 		 */
 
-		/*
-		 * For directories, -ENOSPC is returned since a directory entry
-		 * remove operation must not fail due to low extent count
-		 * availability. -ENOSPC will be handled by higher layers of XFS
-		 * by letting the corresponding empty Data/Free blocks to linger
-		 * until a future remove operation. Dabtree blocks would be
-		 * swapped with the last block in the leaf space and then the
-		 * new last block will be unmapped.
-		 *
-		 * The above logic also applies to the source directory entry of
-		 * a rename operation.
-		 */
-		error = xfs_iext_count_may_overflow(ip, whichfork, 1);
-		if (error) {
-			ASSERT(S_ISDIR(VFS_I(ip)->i_mode) &&
-				whichfork == XFS_DATA_FORK);
-			error = -ENOSPC;
-			goto done;
-		}
-
 		old = got;
 
 		got.br_blockcount = del->br_startoff - got.br_startoff;
diff --git a/fs/xfs/libxfs/xfs_da_btree.h b/fs/xfs/libxfs/xfs_da_btree.h
index 0faf7d9ac241..7f08f6de48bf 100644
--- a/fs/xfs/libxfs/xfs_da_btree.h
+++ b/fs/xfs/libxfs/xfs_da_btree.h
@@ -30,6 +30,7 @@ struct xfs_da_geometry {
 	unsigned int	free_hdr_size;	/* dir2 free header size */
 	unsigned int	free_max_bests;	/* # of bests entries in dir2 free */
 	xfs_dablk_t	freeblk;	/* blockno of free data v2 */
+	xfs_extnum_t	max_extents;	/* Max. extents in corresponding fork */
 
 	xfs_dir2_data_aoff_t data_first_offset;
 	size_t		data_entry_offset;
diff --git a/fs/xfs/libxfs/xfs_da_format.h b/fs/xfs/libxfs/xfs_da_format.h
index 5a49caa5c9df..95354b7ab7f5 100644
--- a/fs/xfs/libxfs/xfs_da_format.h
+++ b/fs/xfs/libxfs/xfs_da_format.h
@@ -277,6 +277,7 @@ xfs_dir2_sf_firstentry(struct xfs_dir2_sf_hdr *hdr)
  * Directory address space divided into sections,
  * spaces separated by 32GB.
  */
+#define	XFS_DIR2_MAX_SPACES	3
 #define	XFS_DIR2_SPACE_SIZE	(1ULL << (32 + XFS_DIR2_DATA_ALIGN_LOG))
 #define	XFS_DIR2_DATA_SPACE	0
 #define	XFS_DIR2_DATA_OFFSET	(XFS_DIR2_DATA_SPACE * XFS_DIR2_SPACE_SIZE)
diff --git a/fs/xfs/libxfs/xfs_dir2.c b/fs/xfs/libxfs/xfs_dir2.c
index 5f1e4799e8fa..3cd51fa3837b 100644
--- a/fs/xfs/libxfs/xfs_dir2.c
+++ b/fs/xfs/libxfs/xfs_dir2.c
@@ -150,6 +150,8 @@ xfs_da_mount(
 	dageo->freeblk = xfs_dir2_byte_to_da(dageo, XFS_DIR2_FREE_OFFSET);
 	dageo->node_ents = (dageo->blksize - dageo->node_hdr_size) /
 				(uint)sizeof(xfs_da_node_entry_t);
+	dageo->max_extents = (XFS_DIR2_MAX_SPACES * XFS_DIR2_SPACE_SIZE) >>
+					mp->m_sb.sb_blocklog;
 	dageo->magicpct = (dageo->blksize * 37) / 100;
 
 	/* set up attribute geometry - single fsb only */
@@ -161,6 +163,12 @@ xfs_da_mount(
 	dageo->node_hdr_size = mp->m_dir_geo->node_hdr_size;
 	dageo->node_ents = (dageo->blksize - dageo->node_hdr_size) /
 				(uint)sizeof(xfs_da_node_entry_t);
+
+	if (xfs_has_large_extent_counts(mp))
+		dageo->max_extents = XFS_MAX_EXTCNT_ATTR_FORK_LARGE;
+	else
+		dageo->max_extents = XFS_MAX_EXTCNT_ATTR_FORK_SMALL;
+
 	dageo->magicpct = (dageo->blksize * 37) / 100;
 	return 0;
 }
diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 82b404c99b80..43de892d0305 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -915,6 +915,19 @@ enum xfs_dinode_fmt {
  *
  * 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.
+ *
+ * The maximum file size that can be represented by the data fork extent counter
+ * in the worst case occurs when all extents are 1 block in length and each
+ * block is 1KB in size.
+ *
+ * With XFS_MAX_EXTCNT_DATA_FORK_SMALL representing maximum extent count and
+ * with 1KB sized blocks, a file can reach upto,
+ * 1KB * (2^31) = 2TB
+ *
+ * This is much larger than the theoretical maximum size of a directory
+ * i.e. XFS_DIR2_SPACE_SIZE * XFS_DIR2_MAX_SPACES = ~96GB.
+ *
+ * Hence, a directory inode can never overflow its data fork extent counter.
  */
 #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))
diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index ee8d4eb7d048..74b82ec80f8e 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -491,6 +491,9 @@ xfs_dinode_verify(
 	if (mode && nextents + naextents > nblocks)
 		return __this_address;
 
+	if (S_ISDIR(mode) && nextents > mp->m_dir_geo->max_extents)
+		return __this_address;
+
 	if (mode && XFS_DFORK_BOFF(dip) > mp->m_sb.sb_inodesize)
 		return __this_address;
 
diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index fd5c3c2d77e0..6f9d69f8896e 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -40,19 +40,6 @@ struct xfs_ifork {
 #define XFS_IEXT_PUNCH_HOLE_CNT		(1)
 
 /*
- * Directory entry addition can cause the following,
- * 1. Data block can be added/removed.
- *    A new extent can cause extent count to increase by 1.
- * 2. Free disk block can be added/removed.
- *    Same behaviour as described above for Data block.
- * 3. Dabtree blocks.
- *    XFS_DA_NODE_MAXDEPTH blocks can be added. Each of these can be new
- *    extents. Hence extent count can increase by XFS_DA_NODE_MAXDEPTH.
- */
-#define XFS_IEXT_DIR_MANIP_CNT(mp) \
-	((XFS_DA_NODE_MAXDEPTH + 1 + 1) * (mp)->m_dir_geo->fsbcount)
-
-/*
  * Adding/removing an xattr can cause XFS_DA_NODE_MAXDEPTH extents to
  * be added. One extra extent for dabtree in case a local attr is
  * large enough to cause a double split.  It can also cause extent