skb_can_coalesce() allows coalescing neighboring slab objects into
a single frag:

  return page == skb_frag_page(frag) &&
         off == frag->page_offset + skb_frag_size(frag);

ceph_tcp_sendpage() can be handed slab pages.  One example of this is
XFS: it passes down sector sized slab objects for its metadata I/O.  If
the kernel client is co-located on the OSD node, the skb may go through
loopback and pop on the receive side with the exact same set of frags.
When tcp_recvmsg() attempts to copy out such a frag, hardened usercopy
complains because the size exceeds the object's allocated size:

  usercopy: kernel memory exposure attempt detected from ffff9ba917f20a00 (kmalloc-512) (1024 bytes)

Although skb_can_coalesce() could be taught to return false if the
resulting frag would cross a slab object boundary, we already have
a fallback for non-refcounted pages.  Utilize it for slab pages too.

Cc: stable@vger.kernel.org # 4.8+
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Pull AFS updates from Al Viro:
 "AFS series, with some iov_iter bits included"

* 'work.afs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (26 commits)
  missing bits of "iov_iter: Separate type from direction and use accessor functions"
  afs: Probe multiple fileservers simultaneously
  afs: Fix callback handling
  afs: Eliminate the address pointer from the address list cursor
  afs: Allow dumping of server cursor on operation failure
  afs: Implement YFS support in the fs client
  afs: Expand data structure fields to support YFS
  afs: Get the target vnode in afs_rmdir() and get a callback on it
  afs: Calc callback expiry in op reply delivery
  afs: Fix FS.FetchStatus delivery from updating wrong vnode
  afs: Implement the YFS cache manager service
  afs: Remove callback details from afs_callback_break struct
  afs: Commit the status on a new file/dir/symlink
  afs: Increase to 64-bit volume ID and 96-bit vnode ID for YFS
  afs: Don't invoke the server to read data beyond EOF
  afs: Add a couple of tracepoints to log I/O errors
  afs: Handle EIO from delivery function
  afs: Fix TTL on VL server and address lists
  afs: Implement VL server rotation
  afs: Improve FS server rotation error handling
  ...

Pull ceph updates from Ilya Dryomov:
 "The highlights are:

   - a series that fixes some old memory allocation issues in libceph
     (myself). We no longer allocate memory in places where allocation
     failures cannot be handled and BUG when the allocation fails.

   - support for copy_file_range() syscall (Luis Henriques). If size and
     alignment conditions are met, it leverages RADOS copy-from
     operation. Otherwise, a local copy is performed.

   - a patch that reduces memory requirement of ceph_sync_read() from
     the size of the entire read to the size of one object (Zheng Yan).

   - fallocate() syscall is now restricted to FALLOC_FL_PUNCH_HOLE (Luis
     Henriques)"

* tag 'ceph-for-4.20-rc1' of git://github.com/ceph/ceph-client: (25 commits)
  ceph: new mount option to disable usage of copy-from op
  ceph: support copy_file_range file operation
  libceph: support the RADOS copy-from operation
  ceph: add non-blocking parameter to ceph_try_get_caps()
  libceph: check reply num_data_items in setup_request_data()
  libceph: preallocate message data items
  libceph, rbd, ceph: move ceph_osdc_alloc_messages() calls
  libceph: introduce alloc_watch_request()
  libceph: assign cookies in linger_submit()
  libceph: enable fallback to ceph_msg_new() in ceph_msgpool_get()
  ceph: num_ops is off by one in ceph_aio_retry_work()
  libceph: no need to call osd_req_opcode_valid() in osd_req_encode_op()
  ceph: set timeout conditionally in __cap_delay_requeue
  libceph: don't consume a ref on pagelist in ceph_msg_data_add_pagelist()
  libceph: introduce ceph_pagelist_alloc()
  libceph: osd_req_op_cls_init() doesn't need to take opcode
  libceph: bump CEPH_MSG_MAX_DATA_LEN
  ceph: only allow punch hole mode in fallocate
  ceph: refactor ceph_sync_read()
  ceph: check if LOOKUPNAME request was aborted when filling trace
  ...

In the iov_iter struct, separate the iterator type from the iterator
direction and use accessor functions to access them in most places.

Convert a bunch of places to use switch-statements to access them rather
then chains of bitwise-AND statements.  This makes it easier to add further
iterator types.  Also, this can be more efficient as to implement a switch
of small contiguous integers, the compiler can use ~50% fewer compare
instructions than it has to use bitwise-and instructions.

Further, cease passing the iterator type into the iterator setup function.
The iterator function can set that itself.  Only the direction is required.

Signed-off-by: David Howells <dhowells@redhat.com>

Add support for performing remote object copies using the 'copy-from'
operation.

[ Add COPY_FROM to get_num_data_items(). ]

Signed-off-by: Luis Henriques <lhenriques@suse.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

setup_request_data() adds message data items to both request and reply
messages, but only checks request num_data_items before proceeding with
the loop.  This is wrong because if an op doesn't have any request data
items but has a reply data item (e.g. read), a duplicate data item gets
added to the message on every resend attempt.

This went unnoticed for years but now that message data items are
preallocated, it promptly crashes in ceph_msg_data_add().  Amend the
signature to make it clear that setup_request_data() operates on both
request and reply messages.  Also, remove data_len assert -- we have
another one in prepare_write_message().

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Currently message data items are allocated with ceph_msg_data_create()
in setup_request_data() inside send_request().  send_request() has never
been allowed to fail, so each allocation is followed by a BUG_ON:

  data = ceph_msg_data_create(...);
  BUG_ON(!data);

It's been this way since support for multiple message data items was
added in commit 6644ed7b7e04 ("libceph: make message data be a pointer")
in 3.10.

There is no reason to delay the allocation of message data items until
the last possible moment and we certainly don't need a linked list of
them as they are only ever appended to the end and never erased.  Make
ceph_msg_new2() take max_data_items and adapt the rest of the code.

Reported-by: Jerry Lee <leisurelysw24@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

The current requirement is that ceph_osdc_alloc_messages() should be
called after oid and oloc are known.  In preparation for preallocating
message data items, move ceph_osdc_alloc_messages() further down, so
that it is called when OSD op codes are known.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

ceph_osdc_alloc_messages() call will be moved out of
alloc_linger_request() in the next commit, which means that
ceph_osdc_watch() will need to call ceph_osdc_alloc_messages()
twice.  Add a helper for that.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

Register lingers directly in linger_submit().  This avoids allocating
memory for notify pagelist while holding osdc->lock and simplifies both
callers of linger_submit().

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>