To avoid potential problems with an empty /dev open /dev/console
from rootfs instead of waiting to mount our root filesystem and
mounting it there.   This effectively guarantees that there will
be a device node, and it won't be on a filesystem that we will
ever unmount, so there are no issues with leaving /dev/console
open and pinning the filesystem.

This is actually more effective than automatically mounting
devtmpfs on /dev because it removes removes the occasionally
problematic assumption that /dev/console exists from the boot
code.

With this patch I was able to throw busybox on my /boot partition
(which has no /dev directory) and boot into userspace without
problems.

The only possible negative consequence I can think of is that
someone out there deliberately used did not use a character device
that is major 5 minor 2 for /dev/console.  Does anyone know of a
situation in which that could make sense?
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

... postponing assignments until they're needed. Doesn't change code size.
Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

It reduces code size:
text    data     bss     dec     hex filename
9925      72      16   10013    271d ipc/mqueue-BEFORE.o
9885      72      16    9973    26f5 ipc/mqueue-AFTER.o
Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Code size reduction:
   text    data     bss     dec     hex filename
   9941      72      16   10029    272d ipc/mqueue-BEFORE.o
   9925      72      16   10013    271d ipc/mqueue-AFTER.o
Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

... and abort earlier if we couldn't allocate the message pointers array,
avoiding the u->mq_bytes accounting logic.

It reduces code size:
   text    data     bss     dec     hex filename
   9949      72      16   10037    2735 ipc/mqueue-BEFORE.o
   9941      72      16   10029    272d ipc/mqueue-AFTER.o
Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

We leak fd on lookup_one_len() failure
Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

rehashing the negative placeholder opens a race with d_lookup();
we unhash it almost immediately (by d_move()), but the race
window is there.  Since d_move() doesn't rely on target being
hashed, we don't need that d_rehash() at all.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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

Add a new UMOUNT_NOFOLLOW flag to umount(2).  This is needed to prevent
symlink attacks in unprivileged unmounts (fuse, samba, ncpfs).

Additionally, return -EINVAL if an unknown flag is used (and specify
an explicitly unused flag: UMOUNT_UNUSED).  This makes it possible for
the caller to determine if a flag is supported or not.

CC: Eugene Teo <eugene@redhat.com>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
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>

It hadn't been needed since we'd sanitized the logics in
mark_mounts_for_expiry() (which, in turn, used to be a
rudiment of bad old times when namespace_sem was per-ns).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

no more users left outside of fs/*.c (and very few outside of
fs/namespace.c, actually)
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

passing *any* namespace root to __d_path() as root is equivalent
to just passing it {NULL, NULL}; no need to bother with finding
the root of our namespace in there.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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

Just use dentry_unhash() there
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>

... especially when it only needs (and initializes) .d_name of it
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>

apply function to vfsmounts in set returned by collect_mounts(),
stop if it returns non-zero.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

RFC says we need to follow the chain of mounts if there's more
than one stacked on that point.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

No need to open-code follow_up() in it and locking can be lighter.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

(mnt,mnt_mountpoint) pair is conceptually wrong; if you want
to use it for generating pathname and for nothing else *and*
if you know that vfsmount tree is unchanging, you can get
away with that, but the right solution for that is (mnt,mnt_root).
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>

Analog of is_subdir for vfsmount,dentry pairs, moved from audit_tree.c
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

The handling of mount flags in set_mnt_shared() got a little tangled
up during previous cleanups, with the following problems:

* MNT_PNODE_MASK is defined as a literal constant when it should be a
bitwise xor of other MNT_* flags
* set_mnt_shared() clears and then sets MNT_SHARED (part of MNT_PNODE_MASK)
* MNT_PNODE_MASK could use a comment in mount.h
* MNT_PNODE_MASK is a terrible name, change to MNT_SHARED_MASK

This patch fixes these problems.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

No one is calling this anymore as everyone has switched to
invalidate_mapping_pages long time ago.  Also update a few
references to it in comments.  nfs has two more, but I can't
easily figure what they are actually referring to, so I left
them as-is.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

re-order structure super_block to remove 16 bytes of alignment padding
on 64bit builds.

This shrinks the size of super_block from 712 to 696 bytes so requiring
one fewer 64 byte cache lines.
Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>

-----
patch against 2.6.33-rc5
compiled & tested on x86_64 AMDX2 desktop machine.

I've been running with this patch applied for several weeks with no
problems.

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

->kill_sb() will be called after any failure exit, so no need
to duplicate what it can do.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

kill_litter_super() from ->kill_sb() will take care of the junk

... and get rid of open-coding its guts (i.e. RIP autofs4_force_release())
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

path to mnt/mnt->mnt_root is no worse than that to
mnt->mnt_parent/mnt->mnt_mountpoint *and* needs no
pinning the sucker down (mnt is not going away and
mnt->mnt_root won't change)
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>

* document locking
* add the missing part of data structure invariants (relationship
between mnt_share and mnt_slave lists in case of a peer group
among slaves).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>