[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.
          */