4 files changed, 44 insertions, 50 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 0a926e2ba3ab..6a34a0f4d37c 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -50,8 +50,8 @@ prototypes:
         int (*rename2) (struct inode *, struct dentry *,
                         struct inode *, struct dentry *, unsigned int);
         int (*readlink) (struct dentry *, char __user *,int);
-        void * (*follow_link) (struct dentry *, struct nameidata *);
-        void (*put_link) (struct dentry *, struct nameidata *, void *);
+        const char *(*follow_link) (struct dentry *, void **);
+        void (*put_link) (struct inode *, void *);
         void (*truncate) (struct inode *);
         int (*permission) (struct inode *, int, unsigned int);
         int (*get_acl)(struct inode *, int);
diff --git a/Documentation/filesystems/automount-support.txt b/Documentation/filesystems/automount-support.txt
index 7cac200e2a85..7eb762eb3136 100644
--- a/Documentation/filesystems/automount-support.txt
+++ b/Documentation/filesystems/automount-support.txt
@@ -1,41 +1,15 @@
-Support is available for filesystems that wish to do automounting support (such
-as kAFS which can be found in fs/afs/). This facility includes allowing
-in-kernel mounts to be performed and mountpoint degradation to be
-requested. The latter can also be requested by userspace.
+Support is available for filesystems that wish to do automounting
+support (such as kAFS which can be found in fs/afs/ and NFS in
+fs/nfs/). This facility includes allowing in-kernel mounts to be
+performed and mountpoint degradation to be requested. The latter can
+also be requested by userspace.
 
 
 ======================
 IN-KERNEL AUTOMOUNTING
 ======================
 
-A filesystem can now mount another filesystem on one of its directories by the
-following procedure:
-
- (1) Give the directory a follow_link() operation.
-
-     When the directory is accessed, the follow_link op will be called, and
-     it will be provided with the location of the mountpoint in the nameidata
-     structure (vfsmount and dentry).
-
- (2) Have the follow_link() op do the following steps:
-
-     (a) Call vfs_kern_mount() to call the appropriate filesystem to set up a
-         superblock and gain a vfsmount structure representing it.
-
-     (b) Copy the nameidata provided as an argument and substitute the dentry
-         argument into it the copy.
-
-     (c) Call do_add_mount() to install the new vfsmount into the namespace's
-         mountpoint tree, thus making it accessible to userspace. Use the
-         nameidata set up in (b) as the destination.
-
-         If the mountpoint will be automatically expired, then do_add_mount()
-         should also be given the location of an expiration list (see further
-         down).
-
-     (d) Release the path in the nameidata argument and substitute in the new
-         vfsmount and its root dentry. The ref counts on these will need
-         incrementing.
+See section "Mount Traps" of  Documentation/filesystems/autofs4.txt
 
 Then from userspace, you can just do something like:
 
@@ -61,17 +35,18 @@ AUTOMATIC MOUNTPOINT EXPIRY
 ===========================
 
 Automatic expiration of mountpoints is easy, provided you've mounted the
-mountpoint to be expired in the automounting procedure outlined above.
+mountpoint to be expired in the automounting procedure outlined separately.
 
 To do expiration, you need to follow these steps:
 
- (3) Create at least one list off which the vfsmounts to be expired can be
-     hung. Access to this list will be governed by the vfsmount_lock.
+ (1) Create at least one list off which the vfsmounts to be expired can be
+     hung.
 
- (4) In step (2c) above, the call to do_add_mount() should be provided with a
-     pointer to this list. It will hang the vfsmount off of it if it succeeds.
+ (2) When a new mountpoint is created in the ->d_automount method, add
+     the mnt to the list using mnt_set_expiry()
+             mnt_set_expiry(newmnt, &afs_vfsmounts);
 
- (5) When you want mountpoints to be expired, call mark_mounts_for_expiry()
+ (3) When you want mountpoints to be expired, call mark_mounts_for_expiry()
      with a pointer to this list. This will process the list, marking every
      vfsmount thereon for potential expiry on the next call.
 
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index e69274de8d0c..3eae250254d5 100644
--- 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 5d833b32bbcd..b403b29ef710 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -350,8 +350,8 @@ struct inode_operations {
         int (*rename2) (struct inode *, struct dentry *,
                         struct inode *, struct dentry *, unsigned int);
         int (*readlink) (struct dentry *, char __user *,int);
-        void * (*follow_link) (struct dentry *, struct nameidata *);
-        void (*put_link) (struct dentry *, struct nameidata *, void *);
+        const char *(*follow_link) (struct dentry *, void **);
+        void (*put_link) (struct inode *, void *);
         int (*permission) (struct inode *, int);
         int (*get_acl)(struct inode *, int);
         int (*setattr) (struct dentry *, struct iattr *);
@@ -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.