commit 49d31c2f389acfe83417083e1208422b4091cd9e upstream.

take_dentry_name_snapshot() takes a safe snapshot of dentry name;
if the name is a short one, it gets copied into caller-supplied
structure, otherwise an extra reference to external name is grabbed
(those are never modified).  In either case the pointer to stable
string is stored into the same structure.

dentry must be held by the caller of take_dentry_name_snapshot(),
but may be freely dropped afterwards - the snapshot will stay
until destroyed by release_dentry_name_snapshot().

Intended use:
	struct name_snapshot s;

	take_dentry_name_snapshot(&s, dentry);
	...
	access s.name
	...
	release_dentry_name_snapshot(&s);

Replaces fsnotify_oldname_...(), gets used in fsnotify to obtain the name
to pass down with event.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

d_op->d_real() leaves the dentry alone except if the third argument is
non-zero.  Unfortunately very difficult to explain to the compiler without
a cast.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: Jeff Layton <jlayton@poochiereds.net>

Pull more vfs updates from Al Viro:
 "Assorted cleanups and fixes.

  In the "trivial API change" department - ->d_compare() losing 'parent'
  argument"

* 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  cachefiles: Fix race between inactivating and culling a cache object
  9p: use clone_fid()
  9p: fix braino introduced in "9p: new helper - v9fs_parent_fid()"
  vfs: make dentry_needs_remove_privs() internal
  vfs: remove file_needs_remove_privs()
  vfs: fix deadlock in file_remove_privs() on overlayfs
  get rid of 'parent' argument of ->d_compare()
  cifs, msdos, vfat, hfs+: don't bother with parent in ->d_compare()
  affs ->d_compare(): don't bother with ->d_inode
  fold _d_rehash() and __d_rehash() together
  fold dentry_rcuwalk_invalidate() into its only remaining caller

Pull qstr constification updates from Al Viro:
 "Fairly self-contained bunch - surprising lot of places passes struct
  qstr * as an argument when const struct qstr * would suffice; it
  complicates analysis for no good reason.

  I'd prefer to feed that separately from the assorted fixes (those are
  in #for-linus and with somewhat trickier topology)"

* 'work.const-qstr' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  qstr: constify instances in adfs
  qstr: constify instances in lustre
  qstr: constify instances in f2fs
  qstr: constify instances in ext2
  qstr: constify instances in vfat
  qstr: constify instances in procfs
  qstr: constify instances in fuse
  qstr constify instances in fs/dcache.c
  qstr: constify instances in nfs
  qstr: constify instances in ocfs2
  qstr: constify instances in autofs4
  qstr: constify instances in hfs
  qstr: constify instances in hfsplus
  qstr: constify instances in logfs
  qstr: constify dentry_init_security

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

Allow filesystem to initialize dentry at allocation time.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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

Add missing documentation for the d_op->d_real() method and d_real()
helper.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The two methods essentially do the same: find the real dentry/inode
belonging to an overlay dentry.  The difference is in the usage:

vfs_open() uses ->d_select_inode() and expects the function to perform
copy-up if necessary based on the open flags argument.

file_dentry() uses ->d_real() passing in the overlay dentry as well as the
underlying inode.

vfs_rename() uses ->d_select_inode() but passes zero flags.  ->d_real()
with a zero inode would have worked just as well here.

This patch merges the functionality of ->d_select_inode() into ->d_real()
by adding an 'open_flags' argument to the latter.

[Al Viro] Make the signature of d_real() match that of ->d_real() again.
And constify the inode argument, while we are at it.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Pull vfs fixes from Al Viro:
 "A couple more of d_walk()/d_subdirs reordering fixes (stable fodder;
  ought to solve that crap for good) and a fix for a brown paperbag bug
  in d_alloc_parallel() (this cycle)"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fix idiotic braino in d_alloc_parallel()
  autofs races
  much milder d_walk() race