[RFC PATCH 02/24] libfs: allow custom validation of stashed inode data

[Li Chen]

path_from_stashed() assumes that inode->i_private is identical to the
caller data used to find or create a dentry. That is too strict for an
inode whose stable identity can later resolve through another object.

Add an optional data_matches() callback to stashed_operations. Existing
users retain the pointer-identity check when no callback is provided.

Assisted-by: Codex:gpt-5.6-sol
Signed-off-by: Li Chen <me@linux.beauty>
---
 fs/internal.h | 1 +
 fs/libfs.c    | 5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/internal.h b/fs/internal.h
index 174f063575558..71cc43e72b33e 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -334,6 +334,7 @@ struct stashed_operations {
 				       struct dentry *dentry);
 	void (*put_data)(void *data);
 	int (*init_inode)(struct inode *inode, void *data);
+	bool (*data_matches)(const struct inode *inode, const void *data);
 };
 int path_from_stashed(struct dentry **stashed, struct vfsmount *mnt, void *data,
 		      struct path *path);
diff --git a/fs/libfs.c b/fs/libfs.c
index 5a0d276379d13..68cc1671b4699 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -2260,7 +2260,10 @@ int path_from_stashed(struct dentry **stashed, struct vfsmount *mnt, void *data,
 	path->dentry = res;
 	path->mnt = mntget(mnt);
 	VFS_WARN_ON_ONCE(path->dentry->d_fsdata != stashed);
-	VFS_WARN_ON_ONCE(d_inode(path->dentry)->i_private != data);
+	if (sops->data_matches)
+		VFS_WARN_ON_ONCE(!sops->data_matches(d_inode(path->dentry), data));
+	else
+		VFS_WARN_ON_ONCE(d_inode(path->dentry)->i_private != data);
 	return 0;
 }
 
-- 
2.52.0