cifs: fix dentry lookups in directory handle cache

Get rid of any prefix paths in @path before lookup_positive_unlocked()
as it will call ->lookup() which already adds those prefix paths
through build_path_from_dentry().

This has caused a performance regression when mounting shares with a
prefix path where readdir(2) would end up retrying several times to
open bad directory names that contained duplicate prefix paths.

Fix this by skipping any prefix paths in @path before calling
lookup_positive_unlocked().

Fixes: e4029e072673 ("cifs: find and use the dentry for cached non-root directories also")
Cc: stable@vger.kernel.org # 6.1+
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/cached_dir.c b/fs/cifs/cached_dir.c
index 71fabb4c09a4bb74ddcf17fecb807e3606747613..bfc964b36c72ecaa9da088892be7349731b327dc 100644 (file)
--- a/fs/cifs/cached_dir.c
+++ b/fs/cifs/cached_dir.c
@@ -99,6 +99,23 @@ path_to_dentry(struct cifs_sb_info *cifs_sb, const char *path)
        return dentry;
 }
 
+static const char *path_no_prefix(struct cifs_sb_info *cifs_sb,
+                                 const char *path)
+{
+       size_t len = 0;
+
+       if (!*path)
+               return path;
+
+       if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH) &&
+           cifs_sb->prepath) {
+               len = strlen(cifs_sb->prepath) + 1;
+               if (unlikely(len > strlen(path)))
+                       return ERR_PTR(-EINVAL);
+       }
+       return path + len;
+}
+
 /*
  * Open the and cache a directory handle.
  * If error then *cfid is not initialized.
@@ -125,6 +142,7 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
        struct dentry *dentry = NULL;
        struct cached_fid *cfid;
        struct cached_fids *cfids;
+       const char *npath;
 
        if (tcon == NULL || tcon->cfids == NULL || tcon->nohandlecache ||
            is_smb1_server(tcon->ses->server))
@@ -160,6 +178,20 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
                return 0;
        }
 
+       /*
+        * Skip any prefix paths in @path as lookup_positive_unlocked() ends up
+        * calling ->lookup() which already adds those through
+        * build_path_from_dentry().  Also, do it earlier as we might reconnect
+        * below when trying to send compounded request and then potentially
+        * having a different prefix path (e.g. after DFS failover).
+        */
+       npath = path_no_prefix(cifs_sb, path);
+       if (IS_ERR(npath)) {
+               rc = PTR_ERR(npath);
+               kfree(utf16_path);
+               return rc;
+       }
+
        /*
         * We do not hold the lock for the open because in case
         * SMB2_open needs to reconnect.
@@ -252,10 +284,10 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
                                (char *)&cfid->file_all_info))
                cfid->file_all_info_is_valid = true;
 
-       if (!path[0])
+       if (!npath[0])
                dentry = dget(cifs_sb->root);
        else {
-               dentry = path_to_dentry(cifs_sb, path);
+               dentry = path_to_dentry(cifs_sb, npath);
                if (IS_ERR(dentry)) {
                        rc = -ENOENT;
                        goto oshr_free;