Before a page get locked, someone else can write data to the page
and increase the i_size. So we should re-check the i_size after
pages are locked.

Signed-off-by: Yan, Zheng <zyan@redhat.com>

GFP_NOFS memory allocation is required for page writeback path.
But there is no need to use GFP_NOFS in syscall path and readpage
path

Signed-off-by: Yan, Zheng <zyan@redhat.com>

Signed-off-by: Yan, Zheng <zyan@redhat.com>

In most cases that snap context is needed, we are holding
reference of CEPH_CAP_FILE_WR. So we can set ceph inode's
i_head_snapc when getting the CEPH_CAP_FILE_WR reference,
and make codes get snap context from i_head_snapc. This makes
the code simpler.

Another benefit of this change is that we can handle snap
notification more elegantly. Especially when snap context
is updated while someone else is doing write. The old queue
cap_snap code may set cap_snap's context to ether the old
context or the new snap context, depending on if i_head_snapc
is set. The new queue capp_snap code always set cap_snap's
context to the old snap context.

Signed-off-by: Yan, Zheng <zyan@redhat.com>

Cached_context in ceph_snap_realm is directly accessed by
uninline_data() and get_pool_perm(). This is racy in theory.
both uninline_data() and get_pool_perm() do not modify existing
object, they only create new object. So we can pass the empty
snap context to them.  Unlike cached_context in ceph_snap_realm,
we do not need to protect the empty snap context.

Signed-off-by: Yan, Zheng <zyan@redhat.com>

Signed-off-by: Yan, Zheng <zyan@redhat.com>

Signed-off-by: Yan, Zheng <zyan@redhat.com>
Reviewed-by: Alex Elder <elder@linaro.org>

Pull Ceph updates from Sage Weil:
 "This time around we have a collection of CephFS fixes from Zheng
  around MDS failure handling and snapshots, support for a new CRUSH
  straw2 algorithm (to sync up with userspace) and several RBD cleanups
  and fixes from Ilya, an error path leak fix from Taesoo, and then an
  assorted collection of cleanups from others"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: (28 commits)
  rbd: rbd_wq comment is obsolete
  libceph: announce support for straw2 buckets
  crush: straw2 bucket type with an efficient 64-bit crush_ln()
  crush: ensuring at most num-rep osds are selected
  crush: drop unnecessary include from mapper.c
  ceph: fix uninline data function
  ceph: rename snapshot support
  ceph: fix null pointer dereference in send_mds_reconnect()
  ceph: hold on to exclusive caps on complete directories
  libceph: simplify our debugfs attr macro
  ceph: show non-default options only
  libceph: expose client options through debugfs
  libceph, ceph: split ceph_show_options()
  rbd: mark block queue as non-rotational
  libceph: don't overwrite specific con error msgs
  ceph: cleanup unsafe requests when reconnecting is denied
  ceph: don't zero i_wrbuffer_ref when reconnecting is denied
  ceph: don't mark dirty caps when there is no auth cap
  ceph: keep i_snap_realm while there are writers
  libceph: osdmap.h: Add missing format newlines
  ...

For CEPH_OSD_CMPXATTR_MODE_U64, OSD expects the u64 to be encoded
as string in object's xattr.

Signed-off-by: Yan, Zheng <zyan@redhat.com>

When ceph_update_writeable_page fails (including -EAGAIN), it
unlocks (w/ unlock_page) the page but does not 'release'
(w/ page_cache_release) properly.

Upon error, properly set *pagep to NULL, indicating an error.

Signed-off-by: Taesoo Kim <tsgatesv@gmail.com>
Signed-off-by: Yan, Zheng <zyan@redhat.com>