For use by the EFI loader, we will want to split off the file path
within a device from the device path.

As we have no function that generates a path relative to a mountpoint's
root, add a function that does this.

Signed-off-by: Ahmad Fatoum <[email protected]>
---
 fs/fs.c      | 25 +++++++++++++++++++++++++
 include/fs.h |  1 +
 2 files changed, 26 insertions(+)

diff --git a/fs/fs.c b/fs/fs.c
index 28378989f91b..77f22d69ea49 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -2454,6 +2454,31 @@ struct fs_device *get_fsdevice_by_path(int dirfd, const 
char *pathname)
        return fsdev;
 }
 
+struct fs_device *resolve_fsdevice_path(int dirfd, const char *pathname, char 
**filepath)
+{
+       struct fs_device *fsdev;
+       char *res = NULL;
+       struct path path;
+       int ret;
+
+       fsdev = get_fsdevice_by_path(dirfd, pathname);
+       if (!fsdev)
+               return NULL;
+
+       ret = filename_lookup(dirfd, getname(pathname), LOOKUP_FOLLOW, &path);
+       if (ret)
+               goto out;
+
+       res = dpath(path.dentry, fsdev->vfsmount.mnt_root);
+       if (res)
+               *filepath = res;
+
+       path_put(&path);
+out:
+       errno_set(ret);
+       return res ? fsdev : NULL;
+}
+
 static int vfs_rmdir(struct inode *dir, struct dentry *dentry)
 {
        int error;
diff --git a/include/fs.h b/include/fs.h
index b9bd14da81a7..9c3c8d95123a 100644
--- a/include/fs.h
+++ b/include/fs.h
@@ -141,6 +141,7 @@ void cdev_print(const struct cdev *cdev);
 char *canonicalize_path(int dirfd, const char *pathname);
 
 struct fs_device *get_fsdevice_by_path(int dirfd, const char *path);
+struct fs_device *resolve_fsdevice_path(int dirfd, const char *pathname, char 
**filepath);
 
 const char *get_mounted_path(const char *path);
 
-- 
2.47.3


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