update Documentation/filesystems/ regarding the follow_link/put_link changes

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index e69274de8d0c9c1754cc40b8d99d78a724e63e50..3eae250254d581d253dd035109d568f8ef0c7873 100644 (file)
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -483,3 +483,20 @@ in your dentry operations instead.
 --
 [mandatory]
        ->aio_read/->aio_write are gone.  Use ->read_iter/->write_iter.
+---
+[recommended]
+       for embedded ("fast") symlinks just set inode->i_link to wherever the
+       symlink body is and use simple_follow_link() as ->follow_link().
+--
+[mandatory]
+       calling conventions for ->follow_link() have changed.  Instead of returning
+       cookie and using nd_set_link() to store the body to traverse, we return
+       the body to traverse and store the cookie using explicit void ** argument.
+       nameidata isn't passed at all - nd_jump_link() doesn't need it and
+       nd_[gs]et_link() is gone.
+--
+[mandatory]
+       calling conventions for ->put_link() have changed.  It gets inode instead of
+       dentry,  it does not get nameidata at all and it gets called only when cookie
+       is non-NULL.  Note that link body isn't available anymore, so if you need it,
+       store it as cookie.

diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 542d9352d0f2a9932a91db0559a5269f2a59eab3..b403b29ef7107cd9bfad4a4d0d509cbeb22f145e 100644 (file)
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -436,16 +436,18 @@ otherwise noted.
 
   follow_link: called by the VFS to follow a symbolic link to the
        inode it points to.  Only required if you want to support
-       symbolic links.  This method returns a void pointer cookie
-       that is passed to put_link().
+       symbolic links.  This method returns the symlink body
+       to traverse (and possibly resets the current position with
+       nd_jump_link()).  If the body won't go away until the inode
+       is gone, nothing else is needed; if it needs to be otherwise
+       pinned, the data needed to release whatever we'd grabbed
+       is to be stored in void * variable passed by address to
+       follow_link() instance.
 
   put_link: called by the VFS to release resources allocated by
-       follow_link().  The cookie returned by follow_link() is passed
-       to this method as the last parameter.  It is used by
-       filesystems such as NFS where page cache is not stable
-       (i.e. page that was installed when the symbolic link walk
-       started might not be in the page cache at the end of the
-       walk).
+       follow_link().  The cookie stored by follow_link() is passed
+       to this method as the last parameter; only called when
+       cookie isn't NULL.
 
   permission: called by the VFS to check for access rights on a POSIX-like
        filesystem.