Signed-off-by: NChristoph Hellwig <hch@lst.de>

Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: NChristoph Hellwig <hch@lst.de>

Signed-off-by: NChristoph Hellwig <hch@lst.de>

Now that sock_poll handles a NULL ->poll or ->poll_mask there is no need
for a stub.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

The socket file operations still implement ->poll until all protocols are
switched over.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

Factor out two busy poll related helpers for late reuse, and remove
a command that isn't very helpful, especially with the __poll_t
annotations in place.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

If we can acquire ctx_lock without spinning we can just remove our
iocb from the active_reqs list, and thus complete the iocbs from the
wakeup context.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

Simple one-shot poll through the io_submit() interface.  To poll for
a file descriptor the application should submit an iocb of type
IOCB_CMD_POLL.  It will poll the fd for the events specified in the
the first 32 bits of the aio_buf field of the iocb.

Unlike poll or epoll without EPOLLONESHOT this interface always works
in one shot mode, that is once the iocb is completed, it will have to be
resubmitted.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

With the current aio code there is no need for the magic KIOCB_CANCELLED
value, as a cancelation just kicks the driver to queue the completion
ASAP, with all actual completion handling done in another thread. Given
that both the completion path and cancelation take the context lock there
is no need for magic cmpxchg loops either.  If we remove iocbs from the
active list after calling ->ki_cancel (but with ctx_lock still held), we
can also rely on the invariant thay anything found on the list has a
->ki_cancel callback and can be cancelled, further simplifing the code.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

No need to pass the key field to lookup_iocb to compare it with KIOCB_KEY,
as we can do that right after retrieving it from userspace.  Also move the
KIOCB_KEY definition to aio.c as it is an internal value not used by any
other place in the kernel.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

->get_poll_head returns the waitqueue that the poll operation is going
to sleep on.  Note that this means we can only use a single waitqueue
for the poll, unlike some current drivers that use two waitqueues for
different events.  But now that we have keyed wakeups and heavily use
those for poll there aren't that many good reason left to keep the
multiple waitqueues, and if there are any ->poll is still around, the
driver just won't support aio poll.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

These abstract out calls to the poll method in preparation for changes
in how we poll.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Use straightline code with failure handling gotos instead of a lot
of nested conditionals.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

No users outside of select.c.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

Signed-off-by: NChristoph Hellwig <hch@lst.de>

If io_destroy() gets to cancelling everything that can be cancelled and
gets to kiocb_cancel() calling the function driver has left in ->ki_cancel,
it becomes vulnerable to a race with IO completion.  At that point req
is already taken off the list and aio_complete() does *NOT* spin until
we (in free_ioctx_users()) releases ->ctx_lock.  As the result, it proceeds
to kiocb_free(), freing req just it gets passed to ->ki_cancel().

Fix is simple - remove from the list after the call of kiocb_cancel().  All
instances of ->ki_cancel() already have to cope with the being called with
iocb still on list - that's what happens in io_cancel(2).

Cc: stable@kernel.org
Fixes: 0460fef2 "aio: use cancellation list lazily"
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

kill_ioctx() used to have an explicit RCU delay between removing the
reference from ->ioctx_table and percpu_ref_kill() dropping the refcount.
At some point that delay had been removed, on the theory that
percpu_ref_kill() itself contained an RCU delay.  Unfortunately, that was
the wrong kind of RCU delay and it didn't care about rcu_read_lock() used
by lookup_ioctx().  As the result, we could get ctx freed right under
lookup_ioctx().  Tejun has fixed that in a6d7cff4 ("fs/aio: Add explicit
RCU grace period when freeing kioctx"); however, that fix is not enough.

Suppose io_destroy() from one thread races with e.g. io_setup() from another;
CPU1 removes the reference from current->mm->ioctx_table[...] just as CPU2
has picked it (under rcu_read_lock()).  Then CPU1 proceeds to drop the
refcount, getting it to 0 and triggering a call of free_ioctx_users(),
which proceeds to drop the secondary refcount and once that reaches zero
calls free_ioctx_reqs().  That does
        INIT_RCU_WORK(&ctx->free_rwork, free_ioctx);
        queue_rcu_work(system_wq, &ctx->free_rwork);
and schedules freeing the whole thing after RCU delay.

In the meanwhile CPU2 has gotten around to percpu_ref_get(), bumping the
refcount from 0 to 1 and returned the reference to io_setup().

Tejun's fix (that queue_rcu_work() in there) guarantees that ctx won't get
freed until after percpu_ref_get().  Sure, we'd increment the counter before
ctx can be freed.  Now we are out of rcu_read_lock() and there's nothing to
stop freeing of the whole thing.  Unfortunately, CPU2 assumes that since it
has grabbed the reference, ctx is *NOT* going away until it gets around to
dropping that reference.

The fix is obvious - use percpu_ref_tryget_live() and treat failure as miss.
It's not costlier than what we currently do in normal case, it's safe to
call since freeing *is* delayed and it closes the race window - either
lookup_ioctx() comes before percpu_ref_kill() (in which case ctx->users
won't reach 0 until the caller of lookup_ioctx() drops it) or lookup_ioctx()
fails, ctx->users is unaffected and caller of lookup_ioctx() doesn't see
the object in question at all.

Cc: stable@kernel.org
Fixes: a6d7cff4 "fs/aio: Add explicit RCU grace period when freeing kioctx"
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

open file, unlink it, then use ioctl(2) to make it immutable or
append only.  Now close it and watch the blocks *not* freed...

Immutable/append-only checks belong in ->setattr().
Note: the bug is old and backport to anything prior to 737f2e93
("ext2: convert to use the new truncate convention") will need
these checks lifted into ext2_setattr().

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

That can (and does, on some filesystems) happen - ->mkdir() (and thus
vfs_mkdir()) can legitimately leave its argument negative and just
unhash it, counting upon the lookup to pick the object we'd created
next time we try to look at that name.

Some vfs_mkdir() callers forget about that possibility...
Acked-by: NJ. Bruce Fields <bfields@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

That can (and does, on some filesystems) happen - ->mkdir() (and thus
vfs_mkdir()) can legitimately leave its argument negative and just
unhash it, counting upon the lookup to pick the object we'd created
next time we try to look at that name.

Some vfs_mkdir() callers forget about that possibility...
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

new_sb is left uninitialized in case of early failures in kernfs_mount_ns(),
and while IS_ERR(root) is true in all such cases, using IS_ERR(root) || !new_sb
is not a solution - IS_ERR(root) is true in some cases when new_sb is true.

Make sure new_sb is initialized (and matches the reality) in all cases and
fix the condition for dropping kobj reference - we want it done precisely
in those situations where the reference has not been transferred into a new
super_block instance.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

make sure that info->node is initialized early, so that kernfs_kill_sb()
can list_del() it safely.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

There's an extra C here...

Fixes: 99c18ce5 ("cramfs: direct memory access support")
Acked-by: NNicolas Pitre <nico@linaro.org>
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

RTFS(Documentation/filesystems/nfs/Exporting) if you try to make
something exportable.

Fixes: ac632f5b "befs: add NFS export support"
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Making something exportable takes more than providing ->s_export_ops.
In particular, ->lookup() *MUST* use d_splice_alias() instead of
d_add().

Reading Documentation/filesystems/nfs/Exporting would've been a good idea;
as it is, exporting AFFS is badly (and exploitably) broken.

Partially-Fixes: ed4433d7 "fs/affs: make affs exportable"
Acked-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

we unlock the directory hash too early - if we are looking at secondary
link and primary (in another directory) gets removed just as we unlock,
we could have the old primary moved in place of the secondary, leaving
us to look into freed entry (and leaving our dentry with ->d_fsdata
pointing to a freed entry).

Cc: stable@vger.kernel.org # 2.4.4+
Acked-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

"VFS: don't keep disconnected dentries on d_anon" had a non-trivial
side-effect - d_unhashed() now returns true for those dentries,
making d_find_alias() skip them altogether.  For most of its callers
that's fine - we really want a connected alias there.  However,
there is a codepath where we relied upon picking such aliases
if nothing else could be found - selinux delayed initialization
of contexts for inodes on already mounted filesystems used to
rely upon that.

Cc: stable@kernel.org # f1ee6162 "VFS: don't keep disconnected dentries on d_anon"
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

We recently had an oops reported on a 4.14 kernel in
xfs_reclaim_inodes_count() where sb->s_fs_info pointed to garbage
and so the m_perag_tree lookup walked into lala land.  It produces
an oops down this path during the failed mount:

  radix_tree_gang_lookup_tag+0xc4/0x130
  xfs_perag_get_tag+0x37/0xf0
  xfs_reclaim_inodes_count+0x32/0x40
  xfs_fs_nr_cached_objects+0x11/0x20
  super_cache_count+0x35/0xc0
  shrink_slab.part.66+0xb1/0x370
  shrink_node+0x7e/0x1a0
  try_to_free_pages+0x199/0x470
  __alloc_pages_slowpath+0x3a1/0xd20
  __alloc_pages_nodemask+0x1c3/0x200
  cache_grow_begin+0x20b/0x2e0
  fallback_alloc+0x160/0x200
  kmem_cache_alloc+0x111/0x4e0

The problem is that the superblock shrinker is running before the
filesystem structures it depends on have been fully set up. i.e.
the shrinker is registered in sget(), before ->fill_super() has been
called, and the shrinker can call into the filesystem before
fill_super() does it's setup work. Essentially we are exposed to
both use-after-free and use-before-initialisation bugs here.

To fix this, add a check for the SB_BORN flag in super_cache_count.
In general, this flag is not set until ->fs_mount() completes
successfully, so we know that it is set after the filesystem
setup has completed. This matches the trylock_super() behaviour
which will not let super_cache_scan() run if SB_BORN is not set, and
hence will not allow the superblock shrinker from entering the
filesystem while it is being set up or after it has failed setup
and is being torn down.

Cc: stable@kernel.org
Signed-Off-By: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

For anything NFS-exported we do _not_ want to unlock new inode
before it has grown an alias; original set of fixes got the
ordering right, but missed the nasty complication in case of
lockdep being enabled - unlock_new_inode() does
	lockdep_annotate_inode_mutex_key(inode)
which can only be done before anyone gets a chance to touch
->i_mutex.  Unfortunately, flipping the order and doing
unlock_new_inode() before d_instantiate() opens a window when
mkdir can race with open-by-fhandle on a guessed fhandle, leading
to multiple aliases for a directory inode and all the breakage
that follows from that.

	Correct solution: a new primitive (d_instantiate_new())
combining these two in the right order - lockdep annotate, then
d_instantiate(), then the rest of unlock_new_inode().  All
combinations of d_instantiate() with unlock_new_inode() should
be converted to that.

Cc: stable@kernel.org	# 2.6.29 and later
Tested-by: NMike Marshall <hubcap@omnibond.com>
Reviewed-by: NAndreas Dilger <adilger@dilger.ca>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Make n signed to avoid leaking the pages array if __pipe_get_pages()
fails to allocate any pages.
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

It returns -EFAULT and happens to be a helper for pipe_get_pages()
whose return type is ssize_t.
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

This is the io_getevents equivalent of ppoll/pselect and allows to
properly mix signals and aio completions (especially with IOCB_CMD_POLL)
and atomically executes the following sequence:

	sigset_t origmask;

	pthread_sigmask(SIG_SETMASK, &sigmask, &origmask);
	ret = io_getevents(ctx, min_nr, nr, events, timeout);
	pthread_sigmask(SIG_SETMASK, &origmask, NULL);

Note that unlike many other signal related calls we do not pass a sigmask
size, as that would get us to 7 arguments, which aren't easily supported
by the syscall infrastructure.  It seems a lot less painful to just add a
new syscall variant in the unlikely case we're going to increase the
sigset size.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

Simple workqueue offload for now, but prepared for adding a real aio_fsync
method if the need arises.  Based on an earlier patch from Dave Chinner.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

Don't reference the kiocb structure from the common aio code, and move
any use of it into helper specific to the read/write path.  This is in
preparation for aio_poll support that wants to use the space for different
fields.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NJeff Moyer <jmoyer@redhat.com>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

If we release the lockdep write protection token before calling into
->write_iter and thus never access the file pointer after an -EIOCBQUEUED
return from ->write_iter or ->read_iter we don't need this extra
reference.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

Instead of handcoded non-null checks always initialize ki_list to an
empty list and use list_empty / list_empty_careful on it.  While we're
at it also error out on a double call to kiocb_set_cancel_fn instead
of ignoring it.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NJeff Moyer <jmoyer@redhat.com>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

These days we don't treat sync iocbs special in the aio completion code as
they never use it.  Remove the old comment and BUG_ON given that the
current definition of is_sync_kiocb makes it impossible to hit.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>