inotify uses bits called IN_* and fsnotify uses bits called FS_*.  These
need to line up.  This patch adds build time checks to make sure noone can
change these bits so they are not the same.

Signed-off-by: Eric Paris <eparis@redhat.com>

An inotify watch on a directory will send events for children even if those
children have been unlinked.  This patch add a new inotify flag IN_EXCL_UNLINK
which allows a watch to specificy they don't care about unlinked children.
This should fix performance problems seen by tasks which add a watch to
/tmp and then are overrun with events when other processes are reading and
writing to unlinked files they created in /tmp.

https://bugzilla.kernel.org/show_bug.cgi?id=16296

Requested-by: Matthias Clasen <mclasen@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

Extern declarations in sysctl.c should be move to their own head file, and
then include them in relavant .c files.

Move inotify_table extern declaration to linux/inotify.h

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Eric Paris <eparis@redhat.com>

nothing uses inotify in the kernel, drop it!

Signed-off-by: Eric Paris <eparis@redhat.com>

Inotify watch removals suck violently.

To kick the watch out we need (in this order) inode->inotify_mutex and
ih->mutex.  That's fine if we have a hold on inode; however, for all
other cases we need to make damn sure we don't race with umount.  We can
*NOT* just grab a reference to a watch - inotify_unmount_inodes() will
happily sail past it and we'll end with reference to inode potentially
outliving its superblock.

Ideally we just want to grab an active reference to superblock if we
can; that will make sure we won't go into inotify_umount_inodes() until
we are done.  Cleanup is just deactivate_super().

However, that leaves a messy case - what if we *are* racing with
umount() and active references to superblock can't be acquired anymore?
We can bump ->s_count, grab ->s_umount, which will almost certainly wait
until the superblock is shut down and the watch in question is pining
for fjords.  That's fine, but there is a problem - we might have hit the
window between ->s_active getting to 0 / ->s_count - below S_BIAS (i.e.
the moment when superblock is past the point of no return and is heading
for shutdown) and the moment when deactivate_super() acquires
->s_umount.

We could just do drop_super() yield() and retry, but that's rather
antisocial and this stuff is luser-triggerable.  OTOH, having grabbed
->s_umount and having found that we'd got there first (i.e.  that
->s_root is non-NULL) we know that we won't race with
inotify_umount_inodes().

So we could grab a reference to watch and do the rest as above, just
with drop_super() instead of deactivate_super(), right? Wrong.  We had
to drop ih->mutex before we could grab ->s_umount.  So the watch
could've been gone already.

That still can be dealt with - we need to save watch->wd, do idr_find()
and compare its result with our pointer.  If they match, we either have
the damn thing still alive or we'd lost not one but two races at once,
the watch had been killed and a new one got created with the same ->wd
at the same address.  That couldn't have happened in inotify_destroy(),
but inotify_rm_wd() could run into that.  Still, "new one got created"
is not a problem - we have every right to kill it or leave it alone,
whatever's more convenient.

So we can use idr_find(...) == watch && watch->inode->i_sb == sb as
"grab it and kill it" check.  If it's been our original watch, we are
fine, if it's a newcomer - nevermind, just pretend that we'd won the
race and kill the fscker anyway; we are safe since we know that its
superblock won't be going away.

And yes, this is far beyond mere "not very pretty"; so's the entire
concept of inotify to start with.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Greg KH <greg@kroah.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This patch adds non-blocking support for inotify_init1.  The
additional changes needed are minimal.

The following test must be adjusted for architectures other than x86 and
x86-64 and in case the syscall numbers changed.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/syscall.h>

#ifndef __NR_inotify_init1
# ifdef __x86_64__
#  define __NR_inotify_init1 294
# elif defined __i386__
#  define __NR_inotify_init1 332
# else
#  error "need __NR_inotify_init1"
# endif
#endif

#define IN_NONBLOCK O_NONBLOCK

int
main (void)
{
  int fd = syscall (__NR_inotify_init1, 0);
  if (fd == -1)
    {
      puts ("inotify_init1(0) failed");
      return 1;
    }
  int fl = fcntl (fd, F_GETFL);
  if (fl == -1)
    {
      puts ("fcntl failed");
      return 1;
    }
  if (fl & O_NONBLOCK)
    {
      puts ("inotify_init1(0) set non-blocking mode");
      return 1;
    }
  close (fd);

  fd = syscall (__NR_inotify_init1, IN_NONBLOCK);
  if (fd == -1)
    {
      puts ("inotify_init1(IN_NONBLOCK) failed");
      return 1;
    }
  fl = fcntl (fd, F_GETFL);
  if (fl == -1)
    {
      puts ("fcntl failed");
      return 1;
    }
  if ((fl & O_NONBLOCK) == 0)
    {
      puts ("inotify_init1(IN_NONBLOCK) set non-blocking mode");
      return 1;
    }
  close (fd);

  puts ("OK");

  return 0;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This patch introduces the new syscall inotify_init1 (note: the 1 stands for
the one parameter the syscall takes, as opposed to no parameter before).  The
values accepted for this parameter are function-specific and defined in the
inotify.h header.  Here the values must match the O_* flags, though.  In this
patch CLOEXEC support is introduced.

The following test must be adjusted for architectures other than x86 and
x86-64 and in case the syscall numbers changed.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/syscall.h>

#ifndef __NR_inotify_init1
# ifdef __x86_64__
#  define __NR_inotify_init1 294
# elif defined __i386__
#  define __NR_inotify_init1 332
# else
#  error "need __NR_inotify_init1"
# endif
#endif

#define IN_CLOEXEC O_CLOEXEC

int
main (void)
{
  int fd;
  fd = syscall (__NR_inotify_init1, 0);
  if (fd == -1)
    {
      puts ("inotify_init1(0) failed");
      return 1;
    }
  int coe = fcntl (fd, F_GETFD);
  if (coe == -1)
    {
      puts ("fcntl failed");
      return 1;
    }
  if (coe & FD_CLOEXEC)
    {
      puts ("inotify_init1(0) set close-on-exit");
      return 1;
    }
  close (fd);

  fd = syscall (__NR_inotify_init1, IN_CLOEXEC);
  if (fd == -1)
    {
      puts ("inotify_init1(IN_CLOEXEC) failed");
      return 1;
    }
  coe = fcntl (fd, F_GETFD);
  if (coe == -1)
    {
      puts ("fcntl failed");
      return 1;
    }
  if ((coe & FD_CLOEXEC) == 0)
    {
      puts ("inotify_init1(O_CLOEXEC) does not set close-on-exit");
      return 1;
    }
  close (fd);

  puts ("OK");

  return 0;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[akpm@linux-foundation.org: add sys_ni stub]
Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Kicks the watch out without dropping it.  Called under ->inotify_mutex

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

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

Allow callers to remove watches from their event handler via
inotify_remove_watch_locked().  This functionality can be used to
achieve IN_ONESHOT-like functionality for a subset of events in the
mask.

Signed-off-by: Amy Griffis <amy.griffis@hp.com>
Acked-by: Robert Love <rml@novell.com>
Acked-by: John McCutchan <john@johnmccutchan.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>