Since commit 74d60958 ("page cache: Add and replace pages using the
XArray") was merged, the replace_page_cache_page() can not fail and always
return 0, we can remove the redundant return value and void it.  Moreover
remove the unused gfp_mask.

Link: https://lkml.kernel.org/r/609c30e5274ba15d8b90c872fd0d8ac437a9b2bb.1610071401.git.baolin.wang@linux.alibaba.comSigned-off-by: NBaolin Wang <baolin.wang@linux.alibaba.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We want to allow submounts for the same fuse_conn, but with different
superblocks so that each of the submounts has its own device ID.  To do
so, we need to split all mount-specific information off of fuse_conn
into a new fuse_mount structure, so that multiple mounts can share a
single fuse_conn.

We need to take care only to perform connection-level actions once (i.e.
when the fuse_conn and thus the first fuse_mount are established, or
when the last fuse_mount and thus the fuse_conn are destroyed).  For
example, fuse_sb_destroy() must invoke fuse_send_destroy() until the
last superblock is released.

To do so, we keep track of which fuse_mount is the root mount and
perform all fuse_conn-level actions only when this fuse_mount is
involved.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

With the last commit, all functions that handle some existing fuse_req
no longer need to be given the associated fuse_conn, because they can
get it from the fuse_req object.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Every fuse_req belongs to a fuse_conn.  Right now, we always know which
fuse_conn that is based on the respective device, but we want to allow
multiple (sub)mounts per single connection, and then the corresponding
filesystem is not going to be so trivial to obtain.

Storing a pointer to the associated fuse_conn in every fuse_req will
allow us to trivially find any request's superblock (and thus
filesystem) even then.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

After unlock_request() pages from the ap->pages[] array may be put (e.g. by
aborting the connection) and the pages can be freed.

Prevent use after free by grabbing a reference to the page before calling
unlock_request().

The original patch was created by Pradeep P V K.
Reported-by: NPradeep P V K <ppvk@codeaurora.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

They're the same function, and for the purpose of all callers they are
equivalent to lru_cache_add().

[akpm@linux-foundation.org: fix it for local_lock changes]
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: NRik van Riel <riel@surriel.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Link: http://lkml.kernel.org/r/20200520232525.798933-5-hannes@cmpxchg.orgSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

And replace the arcane return value convention with a simple bool
where true means success and false means failure.

[AV: braino fix folded in]
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

page_count() is unstable.  Unless there has been an RCU grace period
between when the page was removed from the page cache and now, a
speculative reference may exist from the page cache.
Reported-by: NMatthew Wilcox <willy@infradead.org>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

When PageWaiters was added, updating this check was missed.
Reported-by: NNikolaus Rath <Nikolaus@rath.org>
Reported-by: NHugh Dickins <hughd@google.com>
Fixes: 62906027 ("mm: add PageWaiters indicating tasks are waiting for a page bit")
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Instead of custom page dumping, use the standard helper.
Reported-by: NMatthew Wilcox <willy@infradead.org>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Several references got broken due to txt to ReST conversion.

Several of them can be automatically fixed with:

	scripts/documentation-file-ref-check --fix

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org> # hwtracing/coresight/Kconfig
Reviewed-by: Paul E. McKenney <paulmck@kernel.org> # memory-barrier.txt
Acked-by: Alex Shi <alex.shi@linux.alibaba.com> # translations/zh_CN
Acked-by: Federico Vaga <federico.vaga@vaga.pv.it> # translations/it_IT
Acked-by: Marc Zyngier <maz@kernel.org> # kvm/arm64
Signed-off-by: NMauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/6f919ddb83a33b5f2a63b6b5f0575737bb2b36aa.1586881715.git.mchehab+huawei@kernel.orgSigned-off-by: NJonathan Corbet <corbet@lwn.net>

Fixes: 04ec5af0 "fuse: export fuse_end_request()"
Signed-off-by: NKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

commit 96354535 ("fuse: reduce allocation size for splice_write")
changed size of bufs array, so BUG_ON which checks the index of the array
shold also be fixed.

[SzM: turn BUG_ON into WARN_ON]

Fixes: 96354535 ("fuse: reduce allocation size for splice_write")
Signed-off-by: NVasily Averin <vvs@virtuozzo.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Normal, synchronous requests will have their args allocated on the stack.
After the FR_FINISHED bit is set by receiving the reply from the userspace
fuse server, the originating task may return and reuse the stack frame,
resulting in an Oops if the args structure is dereferenced.

Fix by setting a flag in the request itself upon initializing, indicating
whether it has an asynchronous ->end() callback.
Reported-by: NKyle Sanderson <kyle.leet@gmail.com>
Reported-by: NMichael Stapelberg <michael+lkml@stapelberg.ch>
Fixes: 2b319d1f ("fuse: don't dereference req->args on finished request")
Cc: <stable@vger.kernel.org> # v5.4
Tested-by: NMichael Stapelberg <michael+lkml@stapelberg.ch>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Fix the iteration end check in fuse_dev_splice_write().  The iterator
position can only be compared with == or != since wrappage may be involved.

Fixes: 8cefc107 ("pipe: Use head and tail pointers for the ring, not cursor and length")
Reported-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Split pipe->ring_size into two numbers:

 (1) pipe->ring_size - indicates the hard size of the pipe ring.

 (2) pipe->max_usage - indicates the maximum number of pipe ring slots that
     userspace orchestrated events can fill.

This allows for a pipe that is both writable by the general kernel
notification facility and by userspace, allowing plenty of ring space for
notifications to be added whilst preventing userspace from being able to
pin too much unswappable kernel space.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Convert pipes to use head and tail pointers for the buffer ring rather than
pointer and length as the latter requires two atomic ops to update (or a
combined op) whereas the former only requires one.

 (1) The head pointer is the point at which production occurs and points to
     the slot in which the next buffer will be placed.  This is equivalent
     to pipe->curbuf + pipe->nrbufs.

     The head pointer belongs to the write-side.

 (2) The tail pointer is the point at which consumption occurs.  It points
     to the next slot to be consumed.  This is equivalent to pipe->curbuf.

     The tail pointer belongs to the read-side.

 (3) head and tail are allowed to run to UINT_MAX and wrap naturally.  They
     are only masked off when the array is being accessed, e.g.:

	pipe->bufs[head & mask]

     This means that it is not necessary to have a dead slot in the ring as
     head == tail isn't ambiguous.

 (4) The ring is empty if "head == tail".

     A helper, pipe_empty(), is provided for this.

 (5) The occupancy of the ring is "head - tail".

     A helper, pipe_occupancy(), is provided for this.

 (6) The number of free slots in the ring is "pipe->ring_size - occupancy".

     A helper, pipe_space_for_user() is provided to indicate how many slots
     userspace may use.

 (7) The ring is full if "head - tail >= pipe->ring_size".

     A helper, pipe_full(), is provided for this.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

The .ioctl and .compat_ioctl file operations have the same prototype so
they can both point to the same function, which works great almost all
the time when all the commands are compatible.

One exception is the s390 architecture, where a compat pointer is only
31 bit wide, and converting it into a 64-bit pointer requires calling
compat_ptr(). Most drivers here will never run in s390, but since we now
have a generic helper for it, it's easy enough to use it consistently.

I double-checked all these drivers to ensure that all ioctl arguments
are used as pointers or are ignored, but are not interpreted as integer
values.
Acked-by: NJason Gunthorpe <jgg@mellanox.com>
Acked-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: NMauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: NDavid Sterba <dsterba@suse.com>
Acked-by: NDarren Hart (VMware) <dvhart@infradead.org>
Acked-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: NBjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>

Move the check for async request after check for the request being already
finished and done with.

Reported-by: syzbot+ae0bb7aae3de6b4594e2@syzkaller.appspotmail.com
Fixes: d4993774 ("fuse: stop copying args to fuse_req")
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Fix sparse warning:

fs/fuse/dev.c:468:6: warning: symbol 'fuse_args_to_req' was not declared. Should it be static?
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Fixes: 68583165 ("fuse: add pages to fuse_args")
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

This function has been made static, which now causes a compile-time
warning:

WARNING: "fuse_put_request" [vmlinux] is a static EXPORT_SYMBOL_GPL

Remove the unneeded export.

Fixes: 66abc359 ("fuse: unexport request ops")
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

As of now fuse_dev_alloc() both allocates a fuse device and installs it in
fuse_conn list.  fuse_dev_alloc() can fail if fuse_device allocation fails.

virtio-fs needs to initialize multiple fuse devices (one per virtio queue).
It initializes one fuse device as part of call to fuse_fill_super_common()
and rest of the devices are allocated and installed after that.

But, we can't afford to fail after calling fuse_fill_super_common() as we
don't have a way to undo all the actions done by fuse_fill_super_common().
So to avoid failures after the call to fuse_fill_super_common(),
pre-allocate all fuse devices early and install them into fuse connection
later.

This patch provides two separate helpers for fuse device allocation and
fuse device installation in fuse_conn.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

The /dev/fuse device uses fiq->waitq and fasync to signal that requests are
available.  These mechanisms do not apply to virtio-fs.  This patch
introduces callbacks so alternative behavior can be used.

Note that queue_interrupt() changes along these lines:

  spin_lock(&fiq->waitq.lock);
  wake_up_locked(&fiq->waitq);
+ kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
  spin_unlock(&fiq->waitq.lock);
- kill_fasync(&fiq->fasync, SIGIO, POLL_IN);

Since queue_request() and queue_forget() also call kill_fasync() inside
the spinlock this should be safe.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

File systems like virtio-fs need to do not have to play directly with
forget list data structures. There is a helper function use that instead.

Rename dequeue_forget() to fuse_dequeue_forget() and export it so that
stacked filesystems can use it.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

virtio-fs will need unique IDs for FORGET requests from outside
fs/fuse/dev.c.  Make the symbol visible.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

virtio-fs will need to query the length of fuse_arg lists.  Make the symbol
visible.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

virtio-fs will need to complete requests from outside fs/fuse/dev.c.  Make
the symbol visible.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

The page array pointers are also duplicated across fuse_args_pages and
fuse_req.  Get rid of the fuse_req ones.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

No need to duplicate the argument arrays in fuse_req, so just dereference
req->args instead of copying to the fuse_req internal ones.

This allows further cleanup of the fuse_req structure.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Page arrays are not allocated together with the request anymore.  Get rid
of the dead code
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

All requests are now sent with one of the fuse_simple_... helpers.  Get rid
of the old api from the fuse internal header.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Rename fuse_request_send_notify_reply() to fuse_simple_notify_reply() and
convert to passing fuse_args instead of fuse_req.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Derive fuse_writepage_args from fuse_io_args.

Sending the request is tricky since it was done with fi->lock held, hence
we must either use atomic allocation or release the lock.  Both are
possible so try atomic first and if it fails, release the lock and do the
regular allocation with GFP_NOFS and __GFP_NOFAIL.  Both flags are
necessary for correct operation.

Move the page realloc function from dev.c to file.c and convert to using
fuse_writepage_args.

The last caller of fuse_write_fill() is gone, so get rid of it.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Create a helper named fuse_simple_background() that is similar to
fuse_simple_request().  Unlike the latter, it returns immediately and calls
the supplied 'end' callback when the reply is received.

The supplied 'args' pointer is stored in 'fuse_req' which allows the
callback to interpret the output arguments decoded from the reply.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

fuse_simple_request() is converted to return length of last (instead of
single) out arg, since FUSE_IOCTL_OUT has two out args, the second of which
is variable length.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

fuse_req_pages_alloc() is moved to file.c, since its internal use by the
device code will eventually be removed.

Rename to fuse_pages_alloc() to signify that it's not only usable for
fuse_req page array.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Derive fuse_args_pages from fuse_args. This is used to handle requests
which use pages for input or output.  The related flags are added to
fuse_args.

New FR_ALLOC_PAGES flags is added to indicate whether the page arrays in
fuse_req need to be freed by fuse_put_request() or not.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

In some cases it makes no sense to set pid/uid/gid fields in the request
header.  Allow fuse_simple_background() to omit these.  This is only
required in the "force" case, so for now just WARN if set otherwise.

Fold fuse_get_req_nofail_nopages() into its only caller.  Comment is
obsolete anyway.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Move this function to the readdir.c where its only caller resides.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

This will be used by fuse_force_forget().

We can expand fuse_request_send() into fuse_simple_request().  The
FR_WAITING bit has already been set, no need to check.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>