With the addition of memfd hugetlbfs support, we now have the situation
where memfd depends on TMPFS -or- HUGETLBFS.  Previously, memfd was only
supported on tmpfs, so it made sense that the code resided in shmem.c.
In the current code, memfd is only functional if TMPFS is defined.  If
HUGETLFS is defined and TMPFS is not defined, then memfd functionality
will not be available for hugetlbfs.  This does not cause BUGs, just a
lack of potentially desired functionality.

Code is restructured in the following way:
- include/linux/memfd.h is a new file containing memfd specific
  definitions previously contained in shmem_fs.h.
- mm/memfd.c is a new file containing memfd specific code previously
  contained in shmem.c.
- memfd specific code is removed from shmem_fs.h and shmem.c.
- A new config option MEMFD_CREATE is added that is defined if TMPFS
  or HUGETLBFS is defined.

No functional changes are made to the code: restructuring only.

Link: http://lkml.kernel.org/r/20180415182119.4517-4-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Marc-Andr Lureau <marcandre.lureau@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

I observed the following deadlock between them:

[task 1]                          [task 2]                         [task 3]
kill_fasync()                     mm_update_next_owner()           copy_process()
 spin_lock_irqsave(&fa->fa_lock)   read_lock(&tasklist_lock)        write_lock_irq(&tasklist_lock)
  send_sigio()                    <IRQ>                             ...
   read_lock(&fown->lock)         kill_fasync()                     ...
    read_lock(&tasklist_lock)      spin_lock_irqsave(&fa->fa_lock)  ...

Task 1 can't acquire read locked tasklist_lock, since there is
already task 3 expressed its wish to take the lock exclusive.
Task 2 holds the read locked lock, but it can't take the spin lock.

Also, there is possible another deadlock (which I haven't observed):

[task 1]                            [task 2]
f_getown()                          kill_fasync()
 read_lock(&f_own->lock)             spin_lock_irqsave(&fa->fa_lock,)
 <IRQ>                               send_sigio()                     write_lock_irq(&f_own->lock)
  kill_fasync()                       read_lock(&fown->lock)
   spin_lock_irqsave(&fa->fa_lock,)

Actually, we do not need exclusive fa->fa_lock in kill_fasync_rcu(),
as it guarantees fa->fa_file->f_owner integrity only. It may seem,
that it used to give a task a small possibility to receive two sequential
signals, if there are two parallel kill_fasync() callers, and task
handles the first signal fastly, but the behaviour won't become
different, since there is exclusive sighand lock in do_send_sig_info().

The patch converts fa_lock into rwlock_t, and this fixes two above
deadlocks, as rwlock is allowed to be taken from interrupt handler
by qrwlock design.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>

Using the fs-internal do_compat_fcntl64() helper allows us to get rid of
the fs-internal call to the compat_sys_fcntl64() syscall.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

This is the mindless scripted replacement of kernel use of POLL*
variables as described by Al, done by this script:

    for V in IN OUT PRI ERR RDNORM RDBAND WRNORM WRBAND HUP RDHUP NVAL MSG; do
        L=`git grep -l -w POLL$V | grep -v '^t' | grep -v /um/ | grep -v '^sa' | grep -v '/poll.h$'|grep -v '^D'`
        for f in $L; do sed -i "-es/^\([^\"]*\)\(\<POLL$V\>\)/\\1E\\2/" $f; done
    done

with de-mangling cleanups yet to come.

NOTE! On almost all architectures, the EPOLL* constants have the same
values as the POLL* constants do.  But they keyword here is "almost".
For various bad reasons they aren't the same, and epoll() doesn't
actually work quite correctly in some cases due to this on Sparc et al.

The next patch from Al will sort out the final differences, and we
should be all done.

Scripted-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull more poll annotation updates from Al Viro:
 "This is preparation to solving the problems you've mentioned in the
  original poll series.

  After this series, the kernel is ready for running

      for V in IN OUT PRI ERR RDNORM RDBAND WRNORM WRBAND HUP RDHUP NVAL MSG; do
            L=`git grep -l -w POLL$V | grep -v '^t' | grep -v /um/ | grep -v '^sa' | grep -v '/poll.h$'|grep -v '^D'`
            for f in $L; do sed -i "-es/^\([^\"]*\)\(\<POLL$V\>\)/\\1E\\2/" $f; done
      done

  as a for bulk search-and-replace.

  After that, the kernel is ready to apply the patch to unify
  {de,}mangle_poll(), and then get rid of kernel-side POLL... uses
  entirely, and we should be all done with that stuff.

  Basically, that's what you suggested wrt KPOLL..., except that we can
  use EPOLL... instead - they already are arch-independent (and equal to
  what is currently kernel-side POLL...).

  After the preparations (in this series) switch to returning EPOLL...
  from ->poll() instances is completely mechanical and kernel-side
  POLL... can go away. The last step (killing kernel-side POLL... and
  unifying {de,}mangle_poll() has to be done after the
  search-and-replace job, since we need userland-side POLL... for
  unified {de,}mangle_poll(), thus the cherry-pick at the last step.

  After that we will have:

   - POLL{IN,OUT,...} *not* in __poll_t, so any stray instances of
     ->poll() still using those will be caught by sparse.

   - eventpoll.c and select.c warning-free wrt __poll_t

   - no more kernel-side definitions of POLL... - userland ones are
     visible through the entire kernel (and used pretty much only for
     mangle/demangle)

   - same behavior as after the first series (i.e. sparc et.al. epoll(2)
     working correctly)"

* 'work.poll2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  annotate ep_scan_ready_list()
  ep_send_events_proc(): return result via esed->res
  preparation to switching ->poll() to returning EPOLL...
  add EPOLLNVAL, annotate EPOLL... and event_poll->event
  use linux/poll.h instead of asm/poll.h
  xen: fix poll misannotation
  smc: missing poll annotations

The only place that has any business including asm/poll.h
is linux/poll.h.  Fortunately, asm/poll.h had only been
included in 3 places beyond that one, and all of them
are trivial to switch to using linux/poll.h.

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

Those functions are called for memfd files, backed by shmem or hugetlb
(the next patches will handle hugetlb).

Link: http://lkml.kernel.org/r/20171107122800.25517-3-marcandre.lureau@redhat.com
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull poll annotations from Al Viro:
 "This introduces a __bitwise type for POLL### bitmap, and propagates
  the annotations through the tree. Most of that stuff is as simple as
  'make ->poll() instances return __poll_t and do the same to local
  variables used to hold the future return value'.

  Some of the obvious brainos found in process are fixed (e.g. POLLIN
  misspelled as POLL_IN). At that point the amount of sparse warnings is
  low and most of them are for genuine bugs - e.g. ->poll() instance
  deciding to return -EINVAL instead of a bitmap. I hadn't touched those
  in this series - it's large enough as it is.

  Another problem it has caught was eventpoll() ABI mess; select.c and
  eventpoll.c assumed that corresponding POLL### and EPOLL### were
  equal. That's true for some, but not all of them - EPOLL### are
  arch-independent, but POLL### are not.

  The last commit in this series separates userland POLL### values from
  the (now arch-independent) kernel-side ones, converting between them
  in the few places where they are copied to/from userland. AFAICS, this
  is the least disruptive fix preserving poll(2) ABI and making epoll()
  work on all architectures.

  As it is, it's simply broken on sparc - try to give it EPOLLWRNORM and
  it will trigger only on what would've triggered EPOLLWRBAND on other
  architectures. EPOLLWRBAND and EPOLLRDHUP, OTOH, are never triggered
  at all on sparc. With this patch they should work consistently on all
  architectures"

* 'misc.poll' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (37 commits)
  make kernel-side POLL... arch-independent
  eventpoll: no need to mask the result of epi_item_poll() again
  eventpoll: constify struct epoll_event pointers
  debugging printk in sg_poll() uses %x to print POLL... bitmap
  annotate poll(2) guts
  9p: untangle ->poll() mess
  ->si_band gets POLL... bitmap stored into a user-visible long field
  ring_buffer_poll_wait() return value used as return value of ->poll()
  the rest of drivers/*: annotate ->poll() instances
  media: annotate ->poll() instances
  fs: annotate ->poll() instances
  ipc, kernel, mm: annotate ->poll() instances
  net: annotate ->poll() instances
  apparmor: annotate ->poll() instances
  tomoyo: annotate ->poll() instances
  sound: annotate ->poll() instances
  acpi: annotate ->poll() instances
  crypto: annotate ->poll() instances
  block: annotate ->poll() instances
  x86: annotate ->poll() instances
  ...

Call clear_siginfo to ensure stack allocated siginfos are fully
initialized before being passed to the signal sending functions.

This ensures that if there is the kind of confusion documented by
TRAP_FIXME, FPE_FIXME, or BUS_FIXME the kernel won't send unitialized
data to userspace when the kernel generates a signal with SI_USER but
the copy to userspace assumes it is a different kind of signal, and
different fields are initialized.

This also prepares the way for turning copy_siginfo_to_user
into a copy_to_user, by removing the need in many cases to perform
a field by field copy simply to skip the uninitialized fields.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

mangle/demangle on the way to/from userland

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