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>

1 files changed, 2 insertions, 53 deletions

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index adc1355ce853..20f15a0393e1 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1024,11 +1024,6 @@ xfs_create(
 	xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
 	unlock_dp_on_error = true;
 
-	error = xfs_iext_count_may_overflow(dp, XFS_DATA_FORK,
-			XFS_IEXT_DIR_MANIP_CNT(mp));
-	if (error)
-		goto out_trans_cancel;
-
 	/*
 	 * A newly created regular or special file just has one directory
 	 * entry pointing to them, but a directory also the "." entry
@@ -1242,11 +1237,6 @@ xfs_link(
 	if (error)
 		goto std_return;
 
-	error = xfs_iext_count_may_overflow(tdp, XFS_DATA_FORK,
-			XFS_IEXT_DIR_MANIP_CNT(mp));
-	if (error)
-		goto error_return;
-
 	/*
 	 * If we are using project inheritance, we only allow hard link
 	 * creation in our tree when the project IDs are the same; else
@@ -3210,35 +3200,6 @@ retry:
 	/*
 	 * Check for expected errors before we dirty the transaction
 	 * so we can return an error without a transaction abort.
-	 *
-	 * Extent count overflow check:
-	 *
-	 * From the perspective of src_dp, a rename operation is essentially a
-	 * directory entry remove operation. Hence the only place where we check
-	 * for extent count overflow for src_dp is in
-	 * xfs_bmap_del_extent_real(). xfs_bmap_del_extent_real() returns
-	 * -ENOSPC when it detects a possible extent count overflow and in
-	 * response, the higher layers of directory handling code do the
-	 * following:
-	 * 1. Data/Free blocks: XFS lets these blocks linger until a
-	 *    future remove operation removes them.
-	 * 2. Dabtree blocks: XFS swaps the blocks with the last block in the
-	 *    Leaf space and unmaps the last block.
-	 *
-	 * For target_dp, there are two cases depending on whether the
-	 * destination directory entry exists or not.
-	 *
-	 * When destination directory entry does not exist (i.e. target_ip ==
-	 * NULL), extent count overflow check is performed only when transaction
-	 * has a non-zero sized space reservation associated with it.  With a
-	 * zero-sized space reservation, XFS allows a rename operation to
-	 * continue only when the directory has sufficient free space in its
-	 * data/leaf/free space blocks to hold the new entry.
-	 *
-	 * When destination directory entry exists (i.e. target_ip != NULL), all
-	 * we need to do is change the inode number associated with the already
-	 * existing entry. Hence there is no need to perform an extent count
-	 * overflow check.
 	 */
 	if (target_ip == NULL) {
 		/*
@@ -3249,12 +3210,6 @@ retry:
 			error = xfs_dir_canenter(tp, target_dp, target_name);
 			if (error)
 				goto out_trans_cancel;
-		} else {
-			error = xfs_iext_count_may_overflow(target_dp,
-					XFS_DATA_FORK,
-					XFS_IEXT_DIR_MANIP_CNT(mp));
-			if (error)
-				goto out_trans_cancel;
 		}
 	} else {
 		/*
@@ -3422,18 +3377,12 @@ retry:
 	 * inode number of the whiteout inode rather than removing it
 	 * altogether.
 	 */
-	if (wip) {
+	if (wip)
 		error = xfs_dir_replace(tp, src_dp, src_name, wip->i_ino,
 					spaceres);
-	} else {
-		/*
-		 * NOTE: We don't need to check for extent count overflow here
-		 * because the dir remove name code will leave the dir block in
-		 * place if the extent count would overflow.
-		 */
+	else
 		error = xfs_dir_removename(tp, src_dp, src_name, src_ip->i_ino,
 					   spaceres);
-	}
 
 	if (error)
 		goto out_trans_cancel;