Commit Graph

143 Commits

Author SHA1 Message Date
Yan, Zheng ca665e0282 mds: check cap ID when handling cap export message
handle following sequence of events:
- mds0 exports an inode to mds1. client receives the cap import
  message from mds1. caps from mds0 are removed while handling
  the cap import message.
- mds1 exports an inode to mds0. client receives the cap export
  message from mds1. handle_cap_export() adds placeholder caps
  for mds0
- client receives the first cap export message (for exporting
  inode from mds0 to mds1)

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-06-06 09:29:55 +08:00
Yan, Zheng 2cd698be9a ceph: handle cap import atomically
cap import messages are processed by both handle_cap_import() and
handle_cap_grant(). These two functions are not executed in the same
atomic context, so they can races with cap release.

The fix is make handle_cap_import() not release the i_ceph_lock when
it returns. Let handle_cap_grant() release the lock after it finishes
its job.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-06-06 09:29:53 +08:00
Yan, Zheng d9df278350 ceph: pre-allocate ceph_cap struct for ceph_add_cap()
So that ceph_add_cap() can be used while i_ceph_lock is locked.
This simplifies the code that handle cap import/export.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-06-06 09:29:53 +08:00
Yan, Zheng f98a128a55 ceph: update inode fields according to issued caps
Cap message and request reply from non-auth MDS may carry stale
information (corresponding locks are in LOCK states) even they
have the newest inode version. So client should update inode fields
according to issued caps.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-06-06 09:29:52 +08:00
Yan, Zheng c6bcda6f52 ceph: queue vmtruncate if necessary when handing cap grant/revoke
cap grant/revoke message from non-auth MDS can update inode's size
and truncate_seq/truncate_size. (the message arrives before auth
MDS's cap trunc message)

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-06-06 09:29:51 +08:00
Yan, Zheng fd7b95cd1b ceph: avoid releasing caps that are being used
To avoid releasing caps that are being used, encode_inode_release()
should send implemented caps to MDS.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2014-04-28 12:55:01 -07:00
Yan, Zheng d9ffc4f770 ceph: set mds_wanted when MDS reply changes a cap to auth cap
When adjusting caps client wants, MDS does not record caps that are
not allowed. For non-auth MDS, it does not record WR caps. So when
a MDS reply changes a non-auth cap to auth cap, client needs to set
cap's mds_wanted according to the reply.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-04-04 21:07:12 -07:00
Yan, Zheng a255060451 ceph: make sure write caps are registered with auth MDS
Only auth MDS can issue write caps to clients, so don't consider
write caps registered with non-auth MDS as valid.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-04-04 21:07:05 -07:00
Yan, Zheng 11df2dfb61 ceph: add imported caps when handling cap export message
Version 3 cap export message includes information about the imported
caps. It allows us to add the imported caps if the corresponding cap
import message still hasn't been received.

This allow us to handle situation that the importer MDS crashes and
the cap import message is missing.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-01-21 16:30:31 +08:00
Yan, Zheng 4ee6a914ed ceph: remove exported caps when handling cap import message
Version 3 cap import message includes the ID of the exported
caps. It allow us to remove the exported caps if we still haven't
received the corresponding cap export message.

We remove the exported caps because they are stale, keeping them
can compromise consistence.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-01-21 16:30:28 +08:00
Yan, Zheng 9215aeea62 ceph: check inode caps in ceph_d_revalidate
Some inodes in readdir reply may have no caps. Getattr mds request
for these inodes can return -ESTALE. The fix is consider dentry that
links to inode with no caps as invalid. Invalid dentry causes a
lookup request to send to the mds, the MDS will send caps back.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-01-21 13:29:33 +08:00
Yan, Zheng 9563f88c1f ceph: fix cache revoke race
handle following sequence of events:

- non-auth MDS revokes Fc cap. queue invalidate work
- auth MDS issues Fc cap through request reply. i_rdcache_gen gets
  increased.
- invalidate work runs. it finds i_rdcache_revoking != i_rdcache_gen,
  so it does nothing.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-01-21 13:29:32 +08:00
Yan, Zheng d1b87809fb ceph: use ceph_seq_cmp() to compare migrate_seq
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-01-21 13:29:32 +08:00
Yan, Zheng 4fe59789ad ceph: handle cap export race in try_flush_caps()
auth cap may change after releasing the i_ceph_lock

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2014-01-21 13:29:32 +08:00
J. Bruce Fields fc12c80aa5 ceph: trivial comment fix
"disconnected" is too easily confused with "DCACHE_DISCONNECTED".  I
think "unhashed" is the more precise term here.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2014-01-16 16:03:50 -08:00
Guangliang Zhao 7221fe4c2e ceph: add acl for cephfs
Signed-off-by: Guangliang Zhao <lucienchao@gmail.com>
Reviewed-by: Li Wang <li.wang@ubuntykylin.com>
Reviewed-by: Zheng Yan <zheng.z.yan@intel.com>
2013-12-31 20:32:01 +02:00
Yan, Zheng 99a9c273b9 ceph: handle race between cap reconnect and cap release
When a cap get released while composing the cap reconnect message.
We should skip queuing the release message if the cap hasn't been
added to the cap reconnect message.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-11-23 11:01:02 -08:00
Yan, Zheng a096b09aee ceph: queue cap release in __ceph_remove_cap()
call __queue_cap_release() in __ceph_remove_cap(), this avoids
acquiring s_cap_lock twice.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-11-23 11:00:59 -08:00
Yan, Zheng a8d436f015 ceph: use d_invalidate() to invalidate aliases
d_invalidate() is the standard VFS method to invalidate dentry.
compare to d_delete(), it also try shrinking children dentries.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-09-06 12:55:29 -07:00
Milosz Tanski 99ccbd229c ceph: use fscache as a local presisent cache
Adding support for fscache to the Ceph filesystem. This would bring it to on
par with some of the other network filesystems in Linux (like NFS, AFS, etc...)

In order to mount the filesystem with fscache the 'fsc' mount option must be
passed.

Signed-off-by: Milosz Tanski <milosz@adfin.com>
Signed-off-by: Sage Weil <sage@inktank.com>
2013-09-06 16:50:11 +00:00
Li Wang e907574323 ceph: remove useless variable revoked_rdcache
Cleanup in handle_cap_grant().

Signed-off-by: Li Wang <liwang@ubuntukylin.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-08-27 12:28:44 -07:00
Yan, Zheng 3871cbb9a4 ceph: fix request max size
ceph_check_caps() requests new max size only when there is Fw cap.
If we call check_max_size() while there is no Fw cap. It updates
i_wanted_max_size and calls ceph_check_caps(), but ceph_check_caps()
does nothing. Later when Fw cap is issued, we call check_max_size()
again. But i_wanted_max_size is equal to 'endoff' at this time, so
check_max_size() doesn't call ceph_check_caps() and we end up with
waiting for the new max size forever.

The fix is duplicate ceph_check_caps()'s "request max size" code in
check_max_size(), and make try_get_cap_refs() wait for the Fw cap
before retry requesting new max size.

This patch also removes the "endoff > (inode->i_size << 1)" check
in check_max_size(). It's useless because there is no corresponding
logic in ceph_check_caps().

Reviewed-by: Sage Weil <sage@inktank.com>
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2013-08-15 11:12:11 -07:00
Yan, Zheng b0d7c22310 ceph: introduce i_truncate_mutex
I encountered below deadlock when running fsstress

wmtruncate work      truncate                 MDS
---------------  ------------------  --------------------------
                   lock i_mutex
                                      <- truncate file
lock i_mutex (blocked)
                                      <- revoking Fcb (filelock to MIX)
                   send request ->
                                         handle request (xlock filelock)

At the initial time, there are some dirty pages in the page cache.
When the kclient receives the truncate message, it reduces inode size
and creates some 'out of i_size' dirty pages. wmtruncate work can't
truncate these dirty pages because it's blocked by the i_mutex. Later
when the kclient receives the cap message that revokes Fcb caps, It
can't flush all dirty pages because writepages() only flushes dirty
pages within the inode size.

When the MDS handles the 'truncate' request from kclient, it waits
for the filelock to become stable. But the filelock is stuck in
unstable state because it can't finish revoking kclient's Fcb caps.

The truncate pagecache locking has already caused lots of trouble
for use. I think it's time simplify it by introducing a new mutex.
We use the new mutex to prevent concurrent truncate_inode_pages().
There is no need to worry about race between buffered write and
truncate_inode_pages(), because our "get caps" mechanism prevents
them from concurrent execution.

Reviewed-by: Sage Weil <sage@inktank.com>
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2013-08-15 11:12:06 -07:00
Yan, Zheng ca20c99191 ceph: trim deleted inode
The MDS uses caps message to notify clients about deleted inode.
when receiving a such message, invalidate any alias of the inode.
This makes the kernel release the inode ASAP.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-08-09 17:55:10 -07:00
Yan, Zheng 6ee6b95373 ceph: fix race between cap issue and revoke
If we receive new caps from the auth MDS and the non-auth MDS is
revoking the newly issued caps, we should release the caps from
the non-auth MDS. The scenario is filelock's state changes from
SYNC to LOCK. Non-auth MDS revokes Fc cap, the client gets Fc cap
from the auth MDS at the same time.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-07-03 15:32:57 -07:00
Yan, Zheng b1530f5704 ceph: fix cap revoke race
If caps are been revoking by the auth MDS, don't consider them as
issued even they are still issued by non-auth MDS. The non-auth
MDS should also be revoking/exporting these caps, the client just
hasn't received the cap revoke/export message.

The race I encountered is: When caps are exporting to new MDS, the
client receives cap import message and cap revoke message from the
new MDS, then receives cap export message from the old MDS. When
the client receives cap revoke message from the new MDS, the revoking
caps are still issued by the old MDS, so the client does nothing.
Later when the cap export message is received, the client removes
the caps issued by the old MDS. (Another way to fix the race is
calling ceph_check_caps() in handle_cap_export())

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-07-03 15:32:57 -07:00
Yan, Zheng b415bf4f9f ceph: fix pending vmtruncate race
The locking order for pending vmtruncate is wrong, it can lead to
following race:

        write                  wmtruncate work
------------------------    ----------------------
lock i_mutex
check i_truncate_pending   check i_truncate_pending
truncate_inode_pages()     lock i_mutex (blocked)
copy data to page cache
unlock i_mutex
                           truncate_inode_pages()

The fix is take i_mutex before calling __ceph_do_pending_vmtruncate()

Fixes: http://tracker.ceph.com/issues/5453
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-07-03 15:32:56 -07:00
majianpeng 93faca6ef4 ceph: Reconstruct the func ceph_reserve_caps.
Drop ignored return value.  Fix allocation failure case to not leak.

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-07-03 15:32:54 -07:00
Yan, Zheng 005c46970e ceph: move inode to proper flushing list when auth MDS changes
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-07-03 15:32:50 -07:00
Yan, Zheng b8c2f3ae2d ceph: check migrate seq before changing auth cap
We may receive old request reply from the exporter MDS after receiving
the importer MDS' cap import message.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-07-03 15:32:48 -07:00
Yan, Zheng bb137f84d1 ceph: fix cap release race
ceph_encode_inode_release() can race with ceph_open() and release
caps wanted by open files. So it should call __ceph_caps_wanted()
to get the wanted caps.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-07-03 15:32:46 -07:00
Yan, Zheng 37505d5768 ceph: take i_mutex before getting Fw cap
There is deadlock as illustrated bellow. The fix is taking i_mutex
before getting Fw cap reference.

      write                    truncate                 MDS
---------------------     --------------------      --------------
get Fw cap
                          lock i_mutex
lock i_mutex (blocked)
                          request setattr.size  ->
                                                <-   revoke Fw cap

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-05-01 21:18:53 -07:00
Yan, Zheng 2f276c5111 ceph: use i_release_count to indicate dir's completeness
Current ceph code tracks directory's completeness in two places.
ceph_readdir() checks i_release_count to decide if it can set the
I_COMPLETE flag in i_ceph_flags. All other places check the I_COMPLETE
flag. This indirection introduces locking complexity.

This patch adds a new variable i_complete_count to ceph_inode_info.
Set i_release_count's value to it when marking a directory complete.
By comparing the two variables, we know if a directory is complete

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
2013-05-01 21:17:07 -07:00
Yan, Zheng a8673d61ad ceph: use I_COMPLETE inode flag instead of D_COMPLETE flag
commit c6ffe10015 moved the flag that tracks if the dcache contents
for a directory are complete to dentry. The problem is there are
lots of places that use ceph_dir_{set,clear,test}_complete() while
holding i_ceph_lock. but ceph_dir_{set,clear,test}_complete() may
sleep because they call dput().

This patch basically reverts that commit. For ceph_d_prune(), it's
called with both the dentry to prune and the parent dentry are
locked. So it's safe to access the parent dentry's d_inode and
clear I_COMPLETE flag.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Greg Farnum <greg@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-05-01 21:14:33 -07:00
Yan, Zheng 964266cce9 ceph: set mds_want according to cap import message
MDS ignores cap update message if migrate_seq mismatch, so when
receiving a cap import message with higher migrate_seq, set mds_want
according to the cap import message.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Greg Farnum <greg@inktank.com>
2013-05-01 21:14:32 -07:00
Yan, Zheng d40ee0dcc1 ceph: queue cap release when trimming cap
So the client will later send cap release message to MDS

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Greg Farnum <greg@inktank.com>
2013-05-01 21:14:31 -07:00
Linus Torvalds 1cf0209c43 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client
Pull Ceph updates from Sage Weil:
 "A few groups of patches here.  Alex has been hard at work improving
  the RBD code, layout groundwork for understanding the new formats and
  doing layering.  Most of the infrastructure is now in place for the
  final bits that will come with the next window.

  There are a few changes to the data layout.  Jim Schutt's patch fixes
  some non-ideal CRUSH behavior, and a set of patches from me updates
  the client to speak a newer version of the protocol and implement an
  improved hashing strategy across storage nodes (when the server side
  supports it too).

  A pair of patches from Sam Lang fix the atomicity of open+create
  operations.  Several patches from Yan, Zheng fix various mds/client
  issues that turned up during multi-mds torture tests.

  A final set of patches expose file layouts via virtual xattrs, and
  allow the policies to be set on directories via xattrs as well
  (avoiding the awkward ioctl interface and providing a consistent
  interface for both kernel mount and ceph-fuse users)."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: (143 commits)
  libceph: add support for HASHPSPOOL pool flag
  libceph: update osd request/reply encoding
  libceph: calculate placement based on the internal data types
  ceph: update support for PGID64, PGPOOL3, OSDENC protocol features
  ceph: update "ceph_features.h"
  libceph: decode into cpu-native ceph_pg type
  libceph: rename ceph_pg -> ceph_pg_v1
  rbd: pass length, not op for osd completions
  rbd: move rbd_osd_trivial_callback()
  libceph: use a do..while loop in con_work()
  libceph: use a flag to indicate a fault has occurred
  libceph: separate non-locked fault handling
  libceph: encapsulate connection backoff
  libceph: eliminate sparse warnings
  ceph: eliminate sparse warnings in fs code
  rbd: eliminate sparse warnings
  libceph: define connection flag helpers
  rbd: normalize dout() calls
  rbd: barriers are hard
  rbd: ignore zero-length requests
  ...
2013-02-28 17:43:09 -08:00
Eric W. Biederman bd2bae6a66 ceph: Convert kuids and kgids before printing them.
Before printing kuid and kgids values convert them into
the initial user namespace.

Cc: Sage Weil <sage@inktank.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-02-12 03:19:27 -08:00
Eric W. Biederman 05cb11c17e ceph: Translate between uid and gids in cap messages and kuids and kgids
- Make the uid and gid arguments of send_cap_msg() used to compose
  ceph_mds_caps messages of type kuid_t and kgid_t.

- Pass inode->i_uid and inode->i_gid in __send_cap to send_cap_msg()
  through variables of type kuid_t and kgid_t.

- Modify struct ceph_cap_snap to store uids and gids in types kuid_t
  and kgid_t.  This allows capturing inode->i_uid and inode->i_gid in
  ceph_queue_cap_snap() without loss and pssing them to
  __ceph_flush_snaps() where they are removed from struct
  ceph_cap_snap and passed to send_cap_msg().

- In handle_cap_grant translate uid and gids in the initial user
  namespace stored in struct ceph_mds_cap into kuids and kgids
  before setting inode->i_uid and inode->i_gid.

Cc: Sage Weil <sage@inktank.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-02-12 03:19:24 -08:00
Yan, Zheng 390306c38d ceph: check mds_wanted for imported cap
The MDS may have incorrect wanted caps after importing caps. So the
client should check the value mds has and send cap update if necessary.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-01-17 12:42:38 -06:00
Yan, Zheng 66f58691c5 ceph: allocate cap_release message when receiving cap import
When client wants to release an imported cap, it's possible there
is no reserved cap_release message in corresponding mds session.
so __queue_cap_release causes kernel panic.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-01-17 12:42:38 -06:00
Yan, Zheng 395c312b9c ceph: allow revoking duplicated caps issued by non-auth MDS
Allow revoking duplicated caps issued by non-auth MDS if these caps
are also issued by auth MDS.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-01-17 12:42:38 -06:00
Yan, Zheng 8a92a119b2 ceph: move dirty inode to migrating list when clearing auth caps
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
2013-01-17 12:42:37 -06:00
Yan, Zheng 0e5e1774a9 ceph: call handle_cap_grant() for cap import message
If client sends cap message that requests new max size during
exporting caps, the exporting MDS will drop the message quietly.
So the client may wait for the reply that updates the max size
forever. call handle_cap_grant() for cap import message can
avoid this issue.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Sage Weil <sage@inktank.com>
2012-12-13 08:13:08 -06:00
Yan, Zheng 0685235ffd ceph: Don't add dirty inode to dirty list if caps is in migration
Add dirty inode to cap_dirty_migrating list instead, this can avoid
ceph_flush_dirty_caps() entering infinite loop.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Sage Weil <sage@inktank.com>
2012-12-13 08:13:08 -06:00
Yan, Zheng 5e62ad3015 ceph: Don't update i_max_size when handling non-auth cap
The cap from non-auth mds doesn't have a meaningful max_size value.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Sage Weil <sage@inktank.com>
2012-12-13 08:13:07 -06:00
Yan, Zheng 4d1d0534f5 ceph: Hold caps_list_lock when adjusting caps_{use, total}_count
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Sage Weil <sage@inktank.com>
2012-11-04 03:08:24 -08:00
Wei Yongjun b905a7f8b7 ceph: convert to use le32_add_cpu()
Convert cpu_to_le32(le32_to_cpu(E1) + E2) to use le32_add_cpu().

dpatch engine is used to auto generate this patch.
(https://github.com/weiyj/dpatch)

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Sage Weil <sage@inktank.com>
2012-10-01 14:30:54 -05:00
Linus Torvalds 6c073a7ee2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client:
  rbd: fix safety of rbd_put_client()
  rbd: fix a memory leak in rbd_get_client()
  ceph: create a new session lock to avoid lock inversion
  ceph: fix length validation in parse_reply_info()
  ceph: initialize client debugfs outside of monc->mutex
  ceph: change "ceph.layout" xattr to be "ceph.file.layout"
2012-02-02 15:47:33 -08:00
Alex Elder d8fb02abdc ceph: create a new session lock to avoid lock inversion
Lockdep was reporting a possible circular lock dependency in
dentry_lease_is_valid().  That function needs to sample the
session's s_cap_gen and and s_cap_ttl fields coherently, but needs
to do so while holding a dentry lock.  The s_cap_lock field was
being used to protect the two fields, but that can't be taken while
holding a lock on a dentry within the session.

In most cases, the s_cap_gen and s_cap_ttl fields only get operated
on separately.  But in three cases they need to be updated together.
Implement a new lock to protect the spots updating both fields
atomically is required.

Signed-off-by: Alex Elder <elder@dreamhost.com>
Reviewed-by: Sage Weil <sage@newdream.net>
2012-02-02 12:49:19 -08:00