From f32800568b368edc102c61ef9d8be6792cc36dd5 Mon Sep 17 00:00:00 2001
From: zhaoxingyu1 <zhaoxingyu1@xiaomi.com>
Date: Thu, 30 Oct 2025 11:40:50 +0800
Subject: [PATCH] fs/inode: support relative path when inode_search

Add support for resolving relative path components (in particular the
".." parent references) during the inode search.  A helper
_compute_path_depth() computes the remaining path depth so that a mount
point is only treated as the terminal node when the depth is positive,
and "../" components walk back up to the parent inode.

Signed-off-by: zhaoxingyu1 <zhaoxingyu1@xiaomi.com>
---
 fs/inode/fs_inodesearch.c | 48 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 47 insertions(+), 1 deletion(-)

diff --git a/fs/inode/fs_inodesearch.c b/fs/inode/fs_inodesearch.c
index fa02871984e..640dee936fc 100644
--- a/fs/inode/fs_inodesearch.c
+++ b/fs/inode/fs_inodesearch.c
@@ -192,6 +192,35 @@ static int _inode_linktarget(FAR struct inode *inode,
 }
 #endif
 
+/****************************************************************************
+ * Name: _compute_path_depth
+ ****************************************************************************/
+
+static int _compute_path_depth(FAR const char *path)
+{
+  FAR const char *name = path;
+  int depth = 0;
+
+  while (*name != '\0')
+    {
+      if (strncmp(name, "../", 3) == 0)
+        {
+          if (--depth < 0)
+            {
+              break;
+            }
+        }
+      else
+        {
+          depth++;
+        }
+
+      name = inode_nextname(name);
+    }
+
+  return depth;
+}
+
 /****************************************************************************
  * Name: _inode_search
  *
@@ -280,7 +309,8 @@ static int _inode_search(FAR struct inode_search_s *desc)
            */
 
           name = inode_nextname(name);
-          if (*name == '\0' || INODE_IS_MOUNTPT(inode))
+          if (*name == '\0' ||
+              (INODE_IS_MOUNTPT(inode) && _compute_path_depth(name) > 0))
             {
               /* Either (1) we are at the end of the path, so this must be
                * the node we are looking for or else (2) this node is a
@@ -292,6 +322,22 @@ static int _inode_search(FAR struct inode_search_s *desc)
               ret = OK;
               break;
             }
+          else if (strncmp(name, "../", 3) == 0)
+            {
+              above = inode;
+              left  = NULL;
+              inode = inode->i_child;
+
+              while (strncmp(name, "../", 3) == 0)
+                {
+                  name = inode_nextname(name);
+                  if (above != g_root_inode)
+                    {
+                      above = above->i_parent;
+                      inode = above->i_child;
+                    }
+                }
+            }
           else
             {
               /* More nodes to be examined in the path "below" this one. */