Make file->f_path always point to the overlay dentry so that the path in
/proc/pid/fd is correct and to ensure that label-based LSMs have access to the
overlay as well as the underlay (path-based LSMs probably don't need it).

Using my union testsuite to set things up, before the patch I see:

	[root@andromeda union-testsuite]# bash 5</mnt/a/foo107
	[root@andromeda union-testsuite]# ls -l /proc/$$/fd/
	...
	lr-x------. 1 root root 64 Jun  5 14:38 5 -> /a/foo107
	[root@andromeda union-testsuite]# stat /mnt/a/foo107
	...
	Device: 23h/35d Inode: 13381       Links: 1
	...
	[root@andromeda union-testsuite]# stat -L /proc/$$/fd/5
	...
	Device: 23h/35d Inode: 13381       Links: 1
	...

After the patch:

	[root@andromeda union-testsuite]# bash 5</mnt/a/foo107
	[root@andromeda union-testsuite]# ls -l /proc/$$/fd/
	...
	lr-x------. 1 root root 64 Jun  5 14:22 5 -> /mnt/a/foo107
	[root@andromeda union-testsuite]# stat /mnt/a/foo107
	...
	Device: 23h/35d Inode: 40346       Links: 1
	...
	[root@andromeda union-testsuite]# stat -L /proc/$$/fd/5
	...
	Device: 23h/35d Inode: 40346       Links: 1
	...

Note the change in where /proc/$$/fd/5 points to in the ls command.  It was
pointing to /a/foo107 (which doesn't exist) and now points to /mnt/a/foo107
(which is correct).

The inode accessed, however, is the lower layer.  The union layer is on device
25h/37d and the upper layer on 24h/36d.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Call ovl_drop_write() earlier in ovl_dentry_open() before we call vfs_open()
as we've done the copy up for which we needed the freeze-write lock by that
point.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Add last missing line in commit "cdd9eefd"
("fs/ufs: restore s_lock mutex")
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

See "ext2: Do not update mtime of a moved directory" (and followup in
"ext2: fix unbalanced kmap()/kunmap()") for background; this is UFS
equivalent - the same problem exists here.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

We are already serialized by ->i_mutex and operations on different
directories are independent.  These calls are just rudiments of
blind BKL conversion and they should've been removed back then.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Commit e4502c63 (ufs: deal with nfsd/iget races) made ufs
create inodes with I_NEW flag set. However ufs_mkdir() never cleared
this flag. Thus if someone ever tried to lookup the directory by inode
number, he would deadlock waiting for I_NEW to be cleared. Luckily this
mostly happens only if the filesystem is exported over NFS since
otherwise we have the inode attached to dentry and don't look it up by
inode number. In rare cases dentry can get freed without inode being
freed and then we'd hit the deadlock even without NFS export.

Fix the problem by clearing I_NEW before instantiating new directory
inode.

Fixes: e4502c63Reported-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Commit e4502c63 (ufs: deal with nfsd/iget races) introduced
unlock_new_inode() call into ufs_add_nondir(). However that function
gets called also from ufs_link() which hands it already initialized
inode and thus unlock_new_inode() complains. The problem is harmless but
annoying.

Fix the problem by opencoding necessary stuff in ufs_link()

Fixes: e4502c63Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Commit 0244756e ("ufs: sb mutex merge + mutex_destroy") generated
deadlocks in read/write mode on mkdir.

This patch partially reverts it keeping fixes by Andrew Morton and
mutex_destroy()

[AV: fixed a missing bit in ufs_remount()]
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Reported-by: Ian Campbell <ian.campbell@citrix.com>
Suggested-by: Jan Kara <jack@suse.cz>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Cc: Alexey Khoroshilov <khoroshilov@ispras.ru>
Cc: Roger Pau Monne <roger.pau@citrix.com>
Cc: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

This reverts commit 9ef7db7f ("ufs: fix deadlocks introduced by sb
mutex merge") That patch tried to solve commit 0244756e ("ufs: sb
mutex merge + mutex_destroy") which is itself partially reverted due to
multiple deadlocks.
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Suggested-by: Jan Kara <jack@suse.cz>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Cc: Alexey Khoroshilov <khoroshilov@ispras.ru>
Cc: Roger Pau Monne <roger.pau@citrix.com>
Cc: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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

when we find that a child has died while we'd been trying to ascend,
we should go into the first live sibling itself, rather than its sibling.

Off-by-one in question had been introduced in "deal with deadlock in
d_walk()" and the fix needs to be backported to all branches this one
has been backported to.

Cc: stable@vger.kernel.org # 3.2 and later
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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

these guys are always declared next to each other; might as well put
the former (pointer to previous instance) into the latter and simplify
the calling conventions for {set,restore}_nameidata()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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

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

now that struct filename is stashed in nameidata we have no need to
pass it in
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fewer arguments to pass around...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

they are always called next to each other; moreover,
terminate_walk() is more symmetrical that way.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

a) make it reject ERR_PTR() for name
b) make it putname(name) on all other failure exits
c) make it return name on success

again, simplifies the callers
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

a) make it reject ERR_PTR() for name
b) make it putname(name) upon return in all other cases.

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

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

makes for much easier life in callers
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

pass root instead; non-NULL => copy to nd.root and
set LOOKUP_ROOT in flags
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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

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

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

Otherwise we are risking a hard error where nonlazy restart would be the right
thing to do; it's a very narrow race with mount --move and most of the time it
ends up being completely harmless, but it's possible to construct a case when
we'll get a bogus hard error instead of falling back to non-lazy walk...

For one thing, when crossing _into_ overmount of parent we need to check for
mount_lock bumps when we get NULL from __lookup_mnt() as well.

For another, and less exotically, we need to make sure that the data fetched
in follow_up_rcu() had been consistent.  ->mnt_mountpoint is pinned for as
long as it is a mountpoint, but we need to check mount_lock after fetching
to verify that.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

The guidelines for adding automount support to a filesystem
in filesystems/automount-support.txt is out or date.
filesystems/autofs4.txt contains more current text, so replace
the out-of-date content with a reference to that.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

pointless forward declarations, stale comments
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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

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

now that we have ->root_seq, legitimize_path(&nd->root, nd->root_seq)
will do just fine...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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

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

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

touch_atime is not RCU-safe, and so cannot be called on an RCU walk.
However, in situations where RCU-walk makes a difference, the symlink
will likely to accessed much more often than it is useful to update
the atime.

So split out the test of "Does the atime actually need to be updated"
into  atime_needs_update(), and have get_link() unlazy if it finds that
it will need to do that update.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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

We are almost done - primitives for leaving RCU mode are aware of nd->stack
now, a new primitive for going to non-RCU mode when we have a symlink on hands
added.

The thing we are heavily relying upon is that *any* unlazy failure will be
shortly followed by terminate_walk(), with no access to nameidata in between.
So it's enough to leave the things in a state terminate_walk() would cope with.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

we'll need them for unlazy_walk()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>