Revert commit f6422f17, due to

Valdis.Kletnieks@vt.edu wrote:
>
> There seems to have been a bug introduced in this changeset:
>
> Am running 2.6.17-rc3-mm1.  When this changeset is applied, 'mount --bind'
> misbehaves:
>
> > # mkdir /foo
> > # mount -t tmpfs -o rw,nosuid,nodev,noexec,noatime,nodiratime none /foo
> > # mkdir /foo/bar
> > # mount --bind /foo/bar /foo
> > # tail -2 /proc/mounts
> > none /foo tmpfs rw,nosuid,nodev,noexec,noatime,nodiratime 0 0
> > none /foo tmpfs rw 0 0
>
> Reverting this changeset causes both mounts to have the same options.
>
> (Thanks to Stephen Smalley for tracking down the changeset...)
>

Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: <Valdis.Kletnieks@vt.edu>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The mnt_flags are propagated into do_loopback(), so that they can be stored
with the vfsmount
Signed-off-by: NHerbert Poetzl <herbert@13thfloor.at>
Acked-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Change the functions may_umount and may_umount_tree to boolean functions to
aid code readability.
Signed-off-by: NIan Kent <raven@themaw.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

I discovered on oprofile hunting on a SMP platform that dentry lookups were
slowed down because d_hash_mask, d_hash_shift and dentry_hashtable were in
a cache line that contained inodes_stat.  So each time inodes_stats is
changed by a cpu, other cpus have to refill their cache line.

This patch moves some variables to the __read_mostly section, in order to
avoid false sharing.  RCU dentry lookups can go full speed.
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Create a new file under /proc/self, called mountstats, where mounted file
systems can export information (configuration options, performance counters,
and so on).  Use a mechanism similar to /proc/mounts and s_ops->show_options.

This mechanism does not violate namespace security, and is safe to use while
other processes are unmounting file systems.

Thanks to Mike Waychison for his review and comments.

Test-plan:
Test concurrent mount/unmount operations while cat'ing /proc/self/mountstats.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

The Coverity checker spotted the following bug in dup_namespace():

<--  snip  -->

        if (!new_ns->root) {
                up_write(&namespace_sem);
                kfree(new_ns);
                goto out;
        }
...
out:
        return new_ns;

<--  snip  -->

Callers expect a non-NULL result to not be freed.
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

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

If the namespace structure is being shared, allocate a new one and copy
information from the current, shared, structure.
Signed-off-by: NJanak Desai <janak@us.ibm.com>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Cc: Andi Kleen <ak@muc.de>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch adds an empty /sys/fs, which filesystems can use.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

fs: Use <linux/capability.h> where capable() is used.
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Acked-by: NTim Schmielau <tim@physik3.uni-rostock.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Turn noatime and nodiratime into per-mount instead of per-sb flags.

After all the preparations this is a rather trivial patch.  The mount code
needs to treat the two options as per-mount instead of per-superblock, and
touch_atime needs to be changed to check the new MNT_ flags in addition to
the MS_ flags that are kept for filesystems that are always
noatime/nodiratime but not user settable anymore.  Besides that core code
only nfs needed an update because it's leaving atime updates to the server
and thus sets the S_NOATIME flag on every inode, but needs to know whether
it's a real noatime mount for an getattr optimization.

While we're at it I've killed the IS_NOATIME/IS_NODIRATIME macros that were
only used by touch_atime.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch converts the inode semaphore to a mutex. I have tested it on
XFS and compiled as much as one can consider on an ia64. Anyway your
luck with it might be different.
Modified-by: NIngo Molnar <mingo@elte.hu>

(finished the conversion)
Signed-off-by: NJes Sorensen <jes@sgi.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Small cleanups in shared mounts code.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Signed-off-by: NNeil Brown <neilb@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Most permission() calls have a struct nameidata * available.  This helper
takes that as an argument and thus makes sure we pass it down for lookup
intents and prepares for per-mount read-only support where we need a struct
vfsmount for checking whether a file is writeable.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

An unbindable mount does not forward or receive propagation.  Also
unbindable mount disallows bind mounts.  The semantics is as follows.

Bind semantics:
  It is invalid to bind mount an unbindable mount.

Move semantics:
  It is invalid to move an unbindable mount under shared mount.

Clone-namespace semantics:
  If a mount is unbindable in the parent namespace, the corresponding
  cloned mount in the child namespace becomes unbindable too.  Note:
  there is subtle difference, unbindable mounts cannot be bind mounted
  but can be cloned during clone-namespace.
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This makes bind, rbind, move, clone namespace and umount operations
aware of the semantics of slave mount (see Documentation/sharedsubtree.txt
in the last patch of the series for detailed description).
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

A slave mount always has a master mount from which it receives
mount/umount events.  Unlike shared mount the event propagation does not
flow from the slave mount to the master.
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

An unmount of a mount creates a umount event on the parent.  If the
parent is a shared mount, it gets propagated to all mounts in the peer
group.
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Implement handling of mount --move in presense of shared mounts (see
Documentation/sharedsubtree.txt in the end of patch series for detailed
description).
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Implement handling of MS_BIND in presense of shared mounts (see
Documentation/sharedsubtree.txt in the end of patch series for detailed
description).
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This creates shared mounts.  A shared mount when bind-mounted to some
mountpoint, propagates mount/umount events to each other.  All the
shared mounts that propagate events to each other belong to the same
peer-group.
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

A private mount does not forward or receive propagation.  This patch
provides user the ability to convert any mount to private.
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This removes the per-namespace semaphore in favor of a global semaphore.
This can have an effect on namespace scalability.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

 - clean up the ugliness in may_umount_tree()

 - fix a bug in do_loopback().  after cloning a tree, do_loopback()
   unlinks only the topmost mount of the cloned tree, leaving behind the
   children mounts on their corresponding expiry list.
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

umount is done under the protection of the namespace semaphore.  This
can lead to intresting deadlocks when the last reference to a mount is
released, if filesystem code is in sufficiently nasty state.

This collects all the to-be-released-mounts and releases them after
releasing the namespace semaphore.  That both reduces the time we are
holding namespace semaphore and gets the things more robust.

Idea proposed by Al Viro.
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Old semantics: graft_tree() grabs a reference on the vfsmount before
returning success.

New one: graft_tree() leaves that to caller.

All the callers of graft_tree() immediately dropped that reference
anyway.  Changing the interface takes care of this unnecessary overhead.

Idea proposed by Al Viro.
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

 - check_mnt() on the source of binding should've been unconditional
   from the very beginning.  My fault - as far I could've trace it,
   that's an old thinko made back in 2001.  Kudos to Miklos for spotting
   it...

   Fixed.

 - code cleaned up.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The way we currently deal with quota and process accounting that might
keep vfsmount busy at umount time is inherently broken; we try to turn
them off just in case (not quite correctly, at that) and

  a) pray umount doesn't fail (otherwise they'll stay turned off)
  b) pray nobody doesn anything funny just as we turn quota off

Moreover, LSM provides hooks for doing the same sort of broken logics.

The proper way to deal with that is to introduce the second kind of
reference to vfsmount.  Semantics:

 - when the last normal reference is dropped, all special ones are
   converted to normal ones and if there had been any, cleanup is done.
 - normal reference can be cloned into a special one
 - special reference can be converted to normal one; that's a no-op if
   we'd already passed the point of no return (i.e.  mntput() had
   converted special references to normal and started cleanup).

The way it works: e.g. starting process accounting converts the vfsmount
reference pinned by the opened file into special one and turns it back
to normal when it gets shut down; acct_auto_close() is done when no
normal references are left.  That way it does *not* obstruct umount(2)
and it silently gets turned off when the last normal reference to
vfsmount is gone.  Which is exactly what we want...

The same should be done by LSM module that holds some internal
references to vfsmount and wants to shut them down on umount - it should
make them special and security_sb_umount_close() will be called exactly
when the last normal reference to vfsmount is gone.

quota handling is even simpler - we don't use normal file IO anymore, so
there's no need to hold vfsmounts at all.  DQUOT_OFF() is done from
deactivate_super(), where it really belongs.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Make code more readable with list_for_each_entry.
Signed-off-by: NMaximilian Attems <janitor@sternwelten.at>
Signed-off-by: NDomen Puncer <domen@coderock.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Fix http://bugzilla.kernel.org/show_bug.cgi?id=4857

When pivot_root is called from an init script in an initramfs environment,
it causes a circular reference in the mount tree.

The cause of this is that pivot_root() is not prepared to handle pivoting
an unattached mount.  In an initramfs environment, rootfs is the root of
the namespace, and so it is not attached.

This patch fixes this and related problems, by returning -EINVAL if either
the current root or the new root is detached.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Acked-by: NAl Viro <viro@parcelfarce.linux.theplanet.co.uk>
Cc: <bigfish@asmallpond.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Mark variables which are usually accessed for reads with __readmostly.
Signed-off-by: NAlok N Kataria <alokk@calsoftinc.com>
Signed-off-by: NShai Fultheim <shai@scalex86.org>
Signed-off-by: NRavikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

I'm resending this patch, because I still believe it's the correct fix.

Tested before/after applying the patch with a test application
available from:

  http://www.inf.bme.hu/~mszeredi/nstest.c

Bind mount from a foreign namespace results in an un-removable mount.
The reason is that mnt->mnt_namespace is copied from the old mount in
clone_mnt().  Because of this check_mnt() in sys_umount() will fail.

The solution is to set mnt->mnt_namespace to current->namespace in
clone_mnt().  clone_mnt() is either called from do_loopback() or
copy_tree().  copy_tree() is called from do_loopback() or
copy_namespace().

When called (directly or indirectly) from do_loopback(), always
current->namspace is being modified: check_mnt(nd->mnt).  So setting
mnt->mnt_namespace to current->namspace is the right thing to do.

When called from copy_namespace(), the setting of mnt_namespace is
irrelevant, since mnt_namespace is reset later in that function for
all copied mounts.

Jamie said:

  This patch is correct.  The old code was buggy for more fundamental and
  serious reason: it broke the invariant that a tree of vfsmnts all have the
  same value of mnt_namespace (and the same for the mnt_list list).
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Acked-by: NJamie Lokier <jamie@shareable.org>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch renames vfsmount->mnt_fslink to something a little more
descriptive: vfsmount->mnt_expire.
Signed-off-by: NMike Waychison <michael.waychison@sun.com>
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Acked-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch sets ->mnt_namespace where it's actually added to the
namespace.

Previously mnt_namespace was set in do_kern_mount() even if the filesystem
was never added to any process's namespace (most kernel-internal
filesystems).

This discrepancy doesn't actually cause any problems, but it's cleaner if
mnt_namespace is NULL for these non exported filesystems.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Acked-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch clears mnt_namespace in an expired mount.

If mnt_namespace is not cleared, it's possible to attach a new mount to the
already detached mount, because check_mnt() can return true.

The effect is a resource leak, since the resulting tree will never be
freed.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Acked-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch fixes a bug noticed by Al Viro:

   However, we still have a problem here - just what would
   happen if vfsmount is detached while we were grabbing namespace
   semaphore?  Refcount alone is not useful here - we might be held by
   whoever had detached the vfsmount.  IOW, we should check that it's
   still attached (i.e. that mnt->mnt_parent != mnt).  If it's not -
   just leave it alone, do mntput() and let whoever holds it deal with
   the sucker.  No need to put it back on lists.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Acked-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch splits the mark_mounts_for_expiry() function.  It's too complex and
too deeply nested, even without the bugfix in the following patch.

Otherwise code is completely the same.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Acked-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>