[XFS] Return case-insensitive match for dentry cache

This implements the code to store the actual filename found during a
lookup in the dentry cache and to avoid multiple entries in the dcache
pointing to the same inode.

To avoid polluting the dcache, we implement a new directory inode
operations for lookup. xfs_vn_ci_lookup() stores the correct case name in
the dcache.

The "actual name" is only allocated and returned for a case- insensitive
match and not an actual match.

Another unusual interaction with the dcache is not storing negative
dentries like other filesystems doing a d_add(dentry, NULL) when an ENOENT
is returned. During the VFS lookup, if a dentry returned has no inode,
dput is called and ENOENT is returned. By not doing a d_add, this actually
removes it completely from the dcache to be reused. create/rename have to
be modified to support unhashed dentries being passed in.

SGI-PV: 981521
SGI-Modid: xfs-linux-melb:xfs-kern:31208a

Signed-off-by: Barry Naujok <bnaujok@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>

1 files changed, 11 insertions, 5 deletions

diff --git a/fs/xfs/xfs_dir2_node.c b/fs/xfs/xfs_dir2_node.c
index c71cff85950c..1b5430223461 100644
--- a/fs/xfs/xfs_dir2_node.c
+++ b/fs/xfs/xfs_dir2_node.c
@@ -549,7 +549,7 @@ xfs_dir2_leafn_lookup_for_entry(
 	xfs_dir2_data_entry_t	*dep;		/* data block entry */
 	xfs_inode_t		*dp;		/* incore directory inode */
 	int			error;		/* error return value */
-	int			di;		/* data entry index */
+	int			di = -1;	/* data entry index */
 	int			index;		/* leaf entry index */
 	xfs_dir2_leaf_t		*leaf;		/* leaf structure */
 	xfs_dir2_leaf_entry_t	*lep;		/* leaf entry */
@@ -577,6 +577,7 @@ xfs_dir2_leafn_lookup_for_entry(
 	if (state->extravalid) {
 		curbp = state->extrablk.bp;
 		curdb = state->extrablk.blkno;
+		di = state->extrablk.index;
 	}
 	/*
 	 * Loop over leaf entries with the right hash value.
@@ -637,7 +638,6 @@ xfs_dir2_leafn_lookup_for_entry(
 	}
 	/* Didn't find an exact match. */
 	error = ENOENT;
-	di = -1;
 	ASSERT(index == be16_to_cpu(leaf->hdr.count) ||
 					(args->op_flags & XFS_DA_OP_OKNOENT));
 out:
@@ -652,7 +652,7 @@ out:
 		state->extravalid = 0;
 	}
 	/*
-	 * Return the index, that will be the insertion point.
+	 * Return the index, that will be the deletion point for remove/replace.
 	 */
 	*indexp = index;
 	return XFS_ERROR(error);
@@ -1820,8 +1820,14 @@ xfs_dir2_node_lookup(
 	error = xfs_da_node_lookup_int(state, &rval);
 	if (error)
 		rval = error;
-	else if (rval == ENOENT && args->cmpresult == XFS_CMP_CASE)
-		rval = EEXIST;	/* a case-insensitive match was found */
+	else if (rval == ENOENT && args->cmpresult == XFS_CMP_CASE) {
+		/* If a CI match, dup the actual name and return EEXIST */
+		xfs_dir2_data_entry_t	*dep;
+
+		dep = (xfs_dir2_data_entry_t *)((char *)state->extrablk.bp->
+						data + state->extrablk.index);
+		rval = xfs_dir_cilookup_result(args, dep->name, dep->namelen);
+	}
 	/*
 	 * Release the btree blocks and leaf block.
 	 */