fs: remove redundant ".." handling after VFS canonicalization

Since _inode_canonicalize() now resolves all "." and ".." segments
in the common VFS layer before inode search, the relpath passed to
each filesystem will never contain ".." segments.  Remove the
now-dead ".." handling code from individual filesystem layers and
the inode search internals.

Files modified (redundant ".." path resolution removed):
- fs/hostfs/hostfs.c: remove depth-tracking escape check in
  hostfs_mkpath(), simplify to direct path concatenation.
- fs/rpmsgfs/rpmsgfs.c: same as hostfs, remove depth-tracking in
  rpmsgfs_mkpath().
- fs/smartfs/smartfs_utils.c: remove "." and ".." segment checks
  in smartfs_finddirentry(), de-indent the remaining search logic.
- fs/inode/fs_inodesearch.c: remove _inode_isdotdot() function,
  simplify _compute_path_depth() to only count forward segments,
  remove dead else-if branch in _inode_search().

Files NOT modified (and why):
- fs/littlefs/littlefs/lfs.c: third-party upstream library (git
  submodule), must not be modified locally.
- fs/fatfs/fatfs/source/ff.c: third-party upstream library.
- fs/lwext4/lwext4/src/ext4*.c: third-party upstream library.
- fs/cromfs/fs_cromfs.c: handles "." and ".." as directory entries
  (structural, not path resolution), so its code stays.
- fs/vfs/fs_symlink.c: constructs relative paths containing ".."
  (writes, not parses relpath).

Signed-off-by: yukangzhi <yukangzhi@xiaomi.com>

fs/hostfs/hostfs.c

@@ -201,54 +201,14 @@ static void hostfs_mkpath(FAR struct hostfs_mountpt_s  *fs,
                           FAR const char *relpath,
                           FAR char *path, int pathlen)
 {
-  int depth = 0;
-  int first;
-  int x;
-
-  /* Copy base host path to output */
-
-  strlcpy(path, fs->fs_root, pathlen);
-
-  /* Be sure we aren't trying to use ".." to display outside of our
-   * mounted path.
+  /* Copy base host path to output and append relative path directly.
+   * Note: Both ".." segments and leading slashes are already resolved
+   * by the VFS layer (_inode_canonicalize + inode_nextname) before
+   * relpath reaches here.
    */
 
-  x = 0;
-  while (relpath[x] == '/')
-    {
-      x++;
-    }
-
-  first = x;
-
-  while (relpath[x] != '\0')
-    {
-      /* Test for ".." occurrence */
-
-      if (strncmp(&relpath[x], "..", 2) == 0)
-        {
-          /* Reduce depth by 1 */
-
-          depth--;
-          x += 2;
-        }
-
-      else if (relpath[x] == '/' && relpath[x + 1] != '/' &&
-               relpath[x + 1] != '\0')
-        {
-          depth++;
-          x++;
-        }
-      else
-        {
-          x++;
-        }
-    }
-
-  if (depth >= 0)
-    {
-      strlcat(path, &relpath[first], pathlen);
-    }
+  strlcpy(path, fs->fs_root, pathlen);
+  strlcat(path, relpath, pathlen);
 }
 
 /****************************************************************************

fs/inode/fs_inodesearch.c

@@ -60,16 +60,6 @@ FAR struct inode *g_root_inode = NULL;
  * Private Functions
  ****************************************************************************/
 
-/****************************************************************************
- * Name: _inode_isdotdot
- ****************************************************************************/
-
-static inline bool _inode_isdotdot(FAR const char *name)
-{
-  return name[0] == '.' && name[1] == '.' &&
-         (name[2] == '\0' || name[2] == '/');
-}
-
 /****************************************************************************
  * Name: _inode_isdot
  ****************************************************************************/
@@ -221,20 +211,13 @@ static int _compute_path_depth(FAR const char *path)
   FAR const char *name = path;
   int depth = 0;
 
+  /* After _inode_canonicalize(), path never contains ".." segments,
+   * so we only need to count path components.
+   */
+
   while (*name != '\0')
     {
-      if (_inode_isdotdot(name))
-        {
-          if (--depth < 0)
-            {
-              break;
-            }
-        }
-      else
-        {
-          depth++;
-        }
-
+      depth++;
       name = inode_nextname(name);
     }
 
@@ -512,31 +495,6 @@ static int _inode_search(FAR struct inode_search_s *desc)
               ret = OK;
               break;
             }
-          else if (_inode_isdotdot(name))
-            {
-              do
-                {
-                  if (above != NULL)
-                    {
-                      inode = above;
-                      above = above->i_parent;
-                    }
-
-                  name = inode_nextname(name);
-                }
-              while (_inode_isdotdot(name));
-
-              if (*name == '\0')
-                {
-                  relpath = name;
-                  ret = OK;
-                  break;
-                }
-
-              above = inode;
-              left  = NULL;
-              inode = inode->i_child;
-            }
           else
             {
               /* More nodes to be examined in the path "below" this one. */

fs/rpmsgfs/rpmsgfs.c

@@ -232,54 +232,14 @@ static void rpmsgfs_mkpath(FAR struct rpmsgfs_mountpt_s *fs,
                            FAR const char *relpath,
                            FAR char *path, int pathlen)
 {
-  int depth = 0;
-  int first;
-  int x;
-
-  /* Copy base host path to output */
-
-  strlcpy(path, fs->fs_root, pathlen);
-
-  /* Be sure we aren't trying to use ".." to display outside of our
-   * mounted path.
+  /* Copy base host path to output and append relative path directly.
+   * Note: Both ".." segments and leading slashes are already resolved
+   * by the VFS layer (_inode_canonicalize + inode_nextname) before
+   * relpath reaches here.
    */
 
-  x = 0;
-  while (relpath[x] == '/')
-    {
-      x++;
-    }
-
-  first = x;
-
-  while (relpath[x] != '\0')
-    {
-      /* Test for ".." occurrence */
-
-      if (strncmp(&relpath[x], "..", 2) == 0)
-        {
-          /* Reduce depth by 1 */
-
-          depth--;
-          x += 2;
-        }
-
-      else if (relpath[x] == '/' && relpath[x + 1] != '/' &&
-               relpath[x + 1] != '\0')
-        {
-          depth++;
-          x++;
-        }
-      else
-        {
-          x++;
-        }
-    }
-
-  if (depth >= 0)
-    {
-      strlcat(path, &relpath[first], pathlen - strlen(path));
-    }
+  strlcpy(path, fs->fs_root, pathlen);
+  strlcat(path, relpath, pathlen);
 
   while (fs->timeout > 0)
     {