cifs: switch build_path_from_dentry() to using dentry_path_raw()

The cost is that we might need to flip '/' to '\\' in more than
just the prefix.  Needs profiling, but I suspect that we won't
get slowdown on that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 6e855f0..03afad8 100644 (file)
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -93,20 +93,16 @@ char *
 build_path_from_dentry_optional_prefix(struct dentry *direntry, void *page,
                                       bool prefix)
 {
-       struct dentry *temp;
-       int namelen;
        int dfsplen;
        int pplen = 0;
-       char *full_path = page;
-       char dirsep;
        struct cifs_sb_info *cifs_sb = CIFS_SB(direntry->d_sb);
        struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
-       unsigned seq;
+       char dirsep = CIFS_DIR_SEP(cifs_sb);
+       char *s;
 
        if (unlikely(!page))
                return ERR_PTR(-ENOMEM);
 
-       dirsep = CIFS_DIR_SEP(cifs_sb);
        if (prefix)
                dfsplen = strnlen(tcon->treeName, MAX_TREE_SIZE + 1);
        else
@@ -115,74 +111,39 @@ build_path_from_dentry_optional_prefix(struct dentry *direntry, void *page,
        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH)
                pplen = cifs_sb->prepath ? strlen(cifs_sb->prepath) + 1 : 0;
 
-cifs_bp_rename_retry:
-       namelen = dfsplen + pplen;
-       seq = read_seqbegin(&rename_lock);
-       rcu_read_lock();
-       for (temp = direntry; !IS_ROOT(temp);) {
-               namelen += (1 + temp->d_name.len);
-               temp = temp->d_parent;
-       }
-       rcu_read_unlock();
-
-       if (namelen >= PAGE_SIZE)
+       s = dentry_path_raw(direntry, page, PAGE_SIZE);
+       if (IS_ERR(s))
+               return s;
+       if (!s[1])      // for root we want "", not "/"
+               s++;
+       if (s < (char *)page + pplen + dfsplen)
                return ERR_PTR(-ENAMETOOLONG);
-
-       full_path[namelen] = 0; /* trailing null */
-       rcu_read_lock();
-       for (temp = direntry; !IS_ROOT(temp);) {
-               spin_lock(&temp->d_lock);
-               namelen -= 1 + temp->d_name.len;
-               if (namelen < 0) {
-                       spin_unlock(&temp->d_lock);
-                       break;
-               } else {
-                       full_path[namelen] = dirsep;
-                       strncpy(full_path + namelen + 1, temp->d_name.name,
-                               temp->d_name.len);
-                       cifs_dbg(FYI, "name: %s\n", full_path + namelen);
-               }
-               spin_unlock(&temp->d_lock);
-               temp = temp->d_parent;
-       }
-       rcu_read_unlock();
-       if (namelen != dfsplen + pplen || read_seqretry(&rename_lock, seq)) {
-               cifs_dbg(FYI, "did not end path lookup where expected. namelen=%ddfsplen=%d\n",
-                        namelen, dfsplen);
-               /* presumably this is only possible if racing with a rename
-               of one of the parent directories  (we can not lock the dentries
-               above us to prevent this, but retrying should be harmless) */
-               goto cifs_bp_rename_retry;
-       }
-       /* DIR_SEP already set for byte  0 / vs \ but not for
-          subsequent slashes in prepath which currently must
-          be entered the right way - not sure if there is an alternative
-          since the '\' is a valid posix character so we can not switch
-          those safely to '/' if any are found in the middle of the prepath */
-       /* BB test paths to Windows with '/' in the midst of prepath */
-
        if (pplen) {
-               int i;
-
                cifs_dbg(FYI, "using cifs_sb prepath <%s>\n", cifs_sb->prepath);
-               memcpy(full_path+dfsplen+1, cifs_sb->prepath, pplen-1);
-               full_path[dfsplen] = dirsep;
-               for (i = 0; i < pplen-1; i++)
-                       if (full_path[dfsplen+1+i] == '/')
-                               full_path[dfsplen+1+i] = CIFS_DIR_SEP(cifs_sb);
+               s -= pplen;
+               memcpy(s + 1, cifs_sb->prepath, pplen - 1);
+               *s = '/';
        }
+       if (dirsep != '/') {
+               /* BB test paths to Windows with '/' in the midst of prepath */
+               char *p;
 
+               for (p = s; *p; p++)
+                       if (*p == '/')
+                               *p = dirsep;
+       }
        if (dfsplen) {
-               strncpy(full_path, tcon->treeName, dfsplen);
+               s -= dfsplen;
+               memcpy(s, tcon->treeName, dfsplen);
                if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) {
                        int i;
                        for (i = 0; i < dfsplen; i++) {
-                               if (full_path[i] == '\\')
-                                       full_path[i] = '/';
+                               if (s[i] == '\\')
+                                       s[i] = '/';
                        }
                }
        }
-       return full_path;
+       return s;
 }
 
 /*