[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, 10 insertions, 7 deletions

diff --git a/fs/xfs/xfs_dir2_sf.c b/fs/xfs/xfs_dir2_sf.c
index 9409fd3e565f..b46af0013ec9 100644
--- a/fs/xfs/xfs_dir2_sf.c
+++ b/fs/xfs/xfs_dir2_sf.c
@@ -812,9 +812,11 @@ xfs_dir2_sf_lookup(
 {
         xfs_inode_t             *dp;            /* incore directory inode */
         int                     i;              /* entry index */
+        int                     error;
         xfs_dir2_sf_entry_t     *sfep;          /* shortform directory entry */
         xfs_dir2_sf_t           *sfp;           /* shortform structure */
         enum xfs_dacmp          cmp;            /* comparison result */
+        xfs_dir2_sf_entry_t     *ci_sfep;       /* case-insens. entry */
 
         xfs_dir2_trace_args("sf_lookup", args);
         xfs_dir2_sf_check(args);
@@ -852,6 +854,7 @@ xfs_dir2_sf_lookup(
         /*
          * Loop over all the entries trying to match ours.
          */
+        ci_sfep = NULL;
         for (i = 0, sfep = xfs_dir2_sf_firstentry(sfp); i < sfp->hdr.count;
                                 i++, sfep = xfs_dir2_sf_nextentry(sfp, sfep)) {
                 /*
@@ -867,19 +870,19 @@ xfs_dir2_sf_lookup(
                                                 xfs_dir2_sf_inumberp(sfep));
                         if (cmp == XFS_CMP_EXACT)
                                 return XFS_ERROR(EEXIST);
+                        ci_sfep = sfep;
                 }
         }
         ASSERT(args->op_flags & XFS_DA_OP_OKNOENT);
         /*
          * Here, we can only be doing a lookup (not a rename or replace).
-         * If a case-insensitive match was found earlier, return "found".
+         * If a case-insensitive match was not found, return ENOENT.
          */
-        if (args->cmpresult == XFS_CMP_CASE)
-                return XFS_ERROR(EEXIST);
-        /*
-         * Didn't find it.
-         */
-        return XFS_ERROR(ENOENT);
+        if (!ci_sfep)
+                return XFS_ERROR(ENOENT);
+        /* otherwise process the CI match as required by the caller */
+        error = xfs_dir_cilookup_result(args, ci_sfep->name, ci_sfep->namelen);
+        return XFS_ERROR(error);
 }
 
 /*