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892 commits

Author SHA1 Message Date
Jeff Layton
4ad9a344be nfsd4: fix v4 state shutdown error paths
If someone tries to shut down the laundry_wq while it isn't up it'll
cause an oops.

This can happen because write_ports can create a nfsd_svc before we
really start the nfs server, and we may fail before the server is ever
started.

Also make sure state is shutdown on error paths in nfsd_svc().

Use a common global nfsd_up flag instead of nfs4_init, and create common
helper functions for nfsd start/shutdown, as there will be other work
that we want done only when we the number of nfsd threads transitions
between zero and nonzero.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
2010-07-23 08:51:22 -04:00
J. Bruce Fields
55b13354d7 nfsd: remove unused assignment from nfsd_link
Trivial cleanup, since "dest" is never used.

Reported-by: Anshul Madan <Anshul.Madan@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
2010-07-23 08:50:39 -04:00
Chuck Lever
43a9aa64a2 NFSD: Fill in WCC data for REMOVE, RMDIR, MKNOD, and MKDIR
Some well-known NFSv3 clients drop their directory entry caches when
they receive replies with no WCC data.  Without this data, they
employ extra READ, LOOKUP, and GETATTR requests to ensure their
directory entry caches are up to date, causing performance to suffer
needlessly.

In order to return WCC data, our server has to have both the pre-op
and the post-op attribute data on hand when a reply is XDR encoded.
The pre-op data is filled in when the incoming fh is locked, and the
post-op data is filled in when the fh is unlocked.

Unfortunately, for REMOVE, RMDIR, MKNOD, and MKDIR, the directory fh
is not unlocked until well after the reply has been XDR encoded.  This
means that encode_wcc_data() does not have wcc_data for the parent
directory, so none is returned to the client after these operations
complete.

By unlocking the parent directory fh immediately after the internal
operations for each NFS procedure is complete, the post-op data is
filled in before XDR encoding starts, so it can be returned to the
client properly.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-07-07 17:12:32 -04:00
J. Bruce Fields
6a85d6c769 nfsd4: comment nitpick
Reported-by: "Madan, Anshul" <Anshul.Madan@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-07-06 12:40:22 -04:00
J. Bruce Fields
cba9ba4b90 nfsd4: fix delegation recall race use-after-free
When the rarely-used callback-connection-changing setclientid occurs
simultaneously with a delegation recall, we rerun the recall by
requeueing it on a workqueue.  But we also need to take a reference on
the delegation in that case, since the delegation held by the rpc itself
will be released by the rpc_release callback.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-06-24 12:24:55 -04:00
J. Bruce Fields
ac94bf5825 nfsd4: fix deleg leak on callback error
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-06-24 12:24:53 -04:00
J. Bruce Fields
ec8acac84a nfsd4: remove some debugging code
This is overkill.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-06-22 22:29:03 -04:00
Benny Halevy
9303bbd3de nfsd: nfs4callback encode_stateid helper function
To be used also for the pnfs cb_layoutrecall callback

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfsd4: fix cb_recall encoding]
    "nfsd: nfs4callback encode_stateid helper function" forgot to reserve
    more space after return from the new helper.
Reported-by: Michael Groshans <groshans@citi.umich.edu>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-06-22 17:19:51 -04:00
J. Bruce Fields
4731030d58 nfsd4: translate memory errors to delay, not serverfault
If the server is out of memory is better for clients to back off and
retry than to just error out.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-06-22 17:19:36 -04:00
J. Bruce Fields
76407f76e0 nfsd4; fix session reference count leak
Note the session has to be put() here regardless of what happens to the
client.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-06-22 17:19:28 -04:00
J. Bruce Fields
68a4b48ce6 nfsd4: don't bother storing callback reply tag
We don't use this, and probably never will.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-31 12:43:59 -04:00
J. Bruce Fields
24a0111e40 nfsd4: fix use of op_share_access
NFSv4.1 adds additional flags to the share_access argument of the open
call.  These flags need to be masked out in some of the existing code,
but current code does that inconsistently.

Tested-by: Michael Groshans <groshans@citi.umich.edu>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-31 12:43:55 -04:00
J. Bruce Fields
172c85dd57 nfsd4: treat more recall errors as failures
If a recall fails for some unexpected reason, instead of ignoring it and
treating it like a success, it's safer to treat it as a failure,
preventing further delgation grants and returning CB_PATH_DOWN.

Also put put switches in a (two me) more logical order, with normal case
first.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-31 12:43:53 -04:00
J. Bruce Fields
378b7d37f9 nfsd4: remove extra put() on callback errors
Since rpc_call_async() guarantees that the release method will be called
even on failure, this put is wrong.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-31 12:43:51 -04:00
Alexey Dobriyan
4be929be34 kernel-wide: replace USHORT_MAX, SHORT_MAX and SHORT_MIN with USHRT_MAX, SHRT_MAX and SHRT_MIN
- C99 knows about USHRT_MAX/SHRT_MAX/SHRT_MIN, not
  USHORT_MAX/SHORT_MAX/SHORT_MIN.

- Make SHRT_MIN of type s16, not int, for consistency.

[akpm@linux-foundation.org: fix drivers/dma/timb_dma.c]
[akpm@linux-foundation.org: fix security/keys/keyring.c]
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-05-25 08:07:02 -07:00
Christoph Hellwig
8018ab0574 sanitize vfs_fsync calling conventions
Now that the last user passing a NULL file pointer is gone we can remove
the redundant dentry argument and associated hacks inside vfs_fsynmc_range.

The next step will be removig the dentry argument from ->fsync, but given
the luck with the last round of method prototype changes I'd rather
defer this until after the main merge window.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-05-21 18:31:21 -04:00
Christoph Hellwig
e970a573ce nfsd: open a file descriptor for fsync in nfs4 recovery
Instead of just looking up a path use do_filp_open to get us a file
structure for the nfs4 recovery directory.  This allows us to get
rid of the last non-standard vfs_fsync caller with a NULL file
pointer.

[AV: should be using fput(), not filp_close()]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-05-21 18:31:21 -04:00
J. Bruce Fields
e4e83ea47b Revert "nfsd4: distinguish expired from stale stateids"
This reverts commit 78155ed75f.

We're depending here on the boot time that we use to generate the
stateid being monotonic, but get_seconds() is not necessarily.

We still depend at least on boot_time being different every time, but
that is a safer bet.

We have a few reports of errors that might be explained by this problem,
though we haven't been able to confirm any of them.

But the minor gain of distinguishing expired from stale errors seems not
worth the risk.

Conflicts:

	fs/nfsd/nfs4state.c

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-18 19:03:50 -04:00
Pavel Emelyanov
47cee541a4 nfsd: safer initialization order in find_file()
The alloc_init_file() first adds a file to the hash and then
initializes its fi_inode, fi_id and fi_had_conflict.

The uninitialized fi_inode could thus be erroneously checked by
the find_file(), so move the hash insertion lower.

The client_mutex should prevent this race in practice; however, we
eventually hope to make less use of the client_mutex, so the ordering
here is an accident waiting to happen.

I didn't find whether the same can be true for two other fields,
but the common sense tells me it's better to initialize an object
before putting it into a global hash table :)

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-18 12:05:20 -04:00
J. Bruce Fields
b7299f4439 nfs4: minor callback code simplification, comment
Note the position in the version array doesn't have to match the actual
rpc version number--to me it seems clearer to maintain the distinction.

Also document choice of rpc callback version number, as discussed in
e.g. http://www.ietf.org/mail-archive/web/nfsv4/current/msg07985.html
and followups.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-18 11:51:38 -04:00
Pavel Emelyanov
15ddb4aec5 NFSD: don't report compiled-out versions as present
The /proc/fs/nfsd/versions file calls nfsd_vers() to check whether
the particular nfsd version is present/available. The problem is
that once I turn off e.g. NFSD-V4 this call returns -1 which is
true from the callers POV which is wrong.

The proposal is to report false in that case.

The bug has existed since 6658d3a7bb "[PATCH] knfsd: remove
nfsd_versbits as intermediate storage for desired versions".

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: stable@kernel.org
Acked-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-14 18:46:14 -04:00
J. Bruce Fields
4dc6ec00f6 nfsd4: implement reclaim_complete
This is a mandatory operation.  Also, here (not in open) is where we
should be committing the reboot recovery information.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-13 12:03:11 -04:00
Benny Halevy
ab707e1565 nfsd4: nfsd4_destroy_session must set callback client under the state lock
nfsd4_set_callback_client must be called under the state lock to atomically
set or unset the callback client and shutting down the previous one.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-13 11:59:11 -04:00
Benny Halevy
d76829889a nfsd4: keep a reference count on client while in use
Get a refcount on the client on SEQUENCE,
Release the refcount and renew the client when all respective compounds completed.
Do not expire the client by the laundromat while in use.
If the client was expired via another path, free it when the compounds
complete and the refcount reaches 0.

Note that unhash_client_locked must call list_del_init on cl_lru as
it may be called twice for the same client (once from nfs4_laundromat
and then from expire_client)

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-13 11:58:54 -04:00
Benny Halevy
07cd4909a6 nfsd4: mark_client_expired
Mark the client as expired under the client_lock so it won't be renewed
when an nfsv4.1 session is done, after it was explicitly expired
during processing of the compound.

Do not renew a client mark as expired (in particular, it is not
on the lru list anymore)

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-13 11:47:22 -04:00
Benny Halevy
46583e2597 nfsd4: introduce nfs4_client.cl_refcount
Currently just initialize the cl_refcount to 1
and decrement in expire_client(), conditionally freeing the
client when the refcount reaches 0.

To be used later by nfsv4.1 compounds to keep the client from
timing out while in use.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-13 11:47:03 -04:00
Benny Halevy
84d38ac9ab nfsd4: refactor expire_client
Separate out unhashing of the client and session.
To be used later by the laundromat.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-11 21:02:02 -04:00
Benny Halevy
36acb66bda nfsd4: extend the client_lock to cover cl_lru
To be used later on to hold a reference count on the client while in use by a
nfsv4.1 compound.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-11 21:02:02 -04:00
Benny Halevy
328efbab0f nfsd4: use list_move in move_to_confirmed
rather than list_del_init, list_add

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-11 21:02:01 -04:00
Benny Halevy
be1fdf6c43 nfsd4: fold release_session into expire_client
and grab the client lock once for all the client's sessions.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-11 21:02:01 -04:00
Benny Halevy
9089f1b478 nfsd4: rename sessionid_lock to client_lock
In preparation to share the lock's scope to both client
and session hash tables.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-11 21:02:01 -04:00
J. Bruce Fields
5d4cec2f2f nfsd4: fix bare destroy_session null dereference
It's legal to send a DESTROY_SESSION outside any session (as the only
operation in a compound), in which case cstate->session will be NULL;
check for that case.

While we're at it, move these checks into a separate helper function.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-07 19:08:47 -04:00
J. Bruce Fields
5306293c9c Merge commit 'v2.6.34-rc6'
Conflicts:
	fs/nfsd/nfs4callback.c
2010-05-04 11:29:05 -04:00
Benny Halevy
dbd65a7e44 nfsd4: use local variable in nfs4svc_encode_compoundres
'cs' is already computed, re-use it.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-05-04 10:10:36 -04:00
J. Bruce Fields
26c0c75e69 nfsd4: fix unlikely race in session replay case
In the replay case, the

	renew_client(session->se_client);

happens after we've droppped the sessionid_lock, and without holding a
reference on the session; so there's nothing preventing the session
being freed before we get here.

Thanks to Benny Halevy for catching a bug in an earlier version of this
patch.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Acked-by: Benny Halevy <bhalevy@panasas.com>
2010-05-03 08:32:31 -04:00
Neil Brown
2bc3c1179c nfsd4: bug in read_buf
When read_buf is called to move over to the next page in the pagelist
of an NFSv4 request, it sets argp->end to essentially a random
number, certainly not an address within the page which argp->p now
points to.  So subsequent calls to READ_BUF will think there is much
more than a page of spare space (the cast to u32 ensures an unsigned
comparison) so we can expect to fall off the end of the second
page.

We never encountered thsi in testing because typically the only
operations which use more than two pages are write-like operations,
which have their own decoding logic.  Something like a getattr after a
write may cross a page boundary, but it would be very unusual for it to
cross another boundary after that.

Cc: stable@kernel.org
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-26 15:39:08 -04:00
Dan Carpenter
d03859a4ac nfsd: potential ERR_PTR dereference on exp_export() error paths.
We "goto finish" from several places where "exp" is an ERR_PTR.  Also I
changed the check for "fsid_key" so that it was consistent with the check
I added.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-22 12:03:02 -04:00
J. Bruce Fields
5771635592 nfsd4: complete enforcement of 4.1 op ordering
Enforce the rules about compound op ordering.

Motivated by implementing RECLAIM_COMPLETE, for which the client is
implicit in the current session, so it is important to ensure a
succesful SEQUENCE proceeds the RECLAIM_COMPLETE.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-22 11:35:14 -04:00
J. Bruce Fields
4b21d0defc nfsd4: allow 4.0 clients to change callback path
The rfc allows a client to change the callback parameters, but we didn't
previously implement it.

Teach the callbacks to rerun themselves (by placing themselves on a
workqueue) when they recognize that their rpc task has been killed and
that the callback connection has changed.

Then we can change the callback connection by setting up a new rpc
client, modifying the nfs4 client to point at it, waiting for any work
in progress to complete, and then shutting down the old client.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-22 11:34:02 -04:00
J. Bruce Fields
2bf23875f5 nfsd4: rearrange cb data structures
Mainly I just want to separate the arguments used for setting up the tcp
client from the rest.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-22 11:34:02 -04:00
J. Bruce Fields
b12a05cbdf nfsd4: cl_count is unused
Now that the shutdown sequence guarantees callbacks are shut down before
the client is destroyed, we no longer have a use for cl_count.

We'll probably reinstate a reference count on the client some day, but
it will be held by users other than callbacks.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-22 11:34:02 -04:00
J. Bruce Fields
b5a1a81e5c nfsd4: don't sleep in lease-break callback
The NFSv4 server's fl_break callback can sleep (dropping the BKL), in
order to allocate a new rpc task to send a recall to the client.

As far as I can tell this doesn't cause any races in the current code,
but the analysis is difficult.  Also, the sleep here may complicate the
move away from the BKL.

So, just schedule some work to do the job for us instead.  The work will
later also prove useful for restarting a call after the callback
information is changed.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-22 11:34:01 -04:00
J. Bruce Fields
3c4ab2aaa9 nfsd4: indentation cleanup
Looks like a put-and-paste mistake.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-19 15:12:51 -04:00
J. Bruce Fields
408b79bcc3 nfsd4: consistent session flag setting
We should clear these flags on any new create_session, not just on the
first one.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-16 21:47:37 -04:00
J. Bruce Fields
9045b4b9f7 nfsd4: remove probe task's reference on client
Any null probe rpc will be synchronously destroyed by the
rpc_shutdown_client() in expire_client(), so the rpc task cannot outlast
the nfs4 client.  Therefore there's no need for that task to hold a
reference on the client.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-02 17:04:32 -04:00
J. Bruce Fields
3df796dbe9 nfsd4: remove dprintk
I haven't found this useful.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-02 17:04:31 -04:00
J. Bruce Fields
147efd0dd7 nfsd4: shutdown callbacks on expiry
Once we've expired the client, there's no further purpose to the
callbacks; go ahead and shut down the callback client rather than
waiting for the last reference to go.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-02 16:36:30 -04:00
J. Bruce Fields
227f98d98d nfsd4: preallocate nfs4_rpc_args
Instead of allocating this small structure, just include it in the
delegation.

The nfsd4_callback structure isn't really necessary yet, but we plan to
add to it all the information necessary to perform a callback.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-04-02 16:28:11 -04:00
Tejun Heo
5a0e3ad6af include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files.  percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed.  Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability.  As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

  http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
  only the necessary includes are there.  ie. if only gfp is used,
  gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
  blocks and try to put the new include such that its order conforms
  to its surrounding.  It's put in the include block which contains
  core kernel includes, in the same order that the rest are ordered -
  alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
  doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
  because the file doesn't have fitting include block), it prints out
  an error message indicating which .h file needs to be added to the
  file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
   over 4000 files, deleting around 700 includes and adding ~480 gfp.h
   and ~3000 slab.h inclusions.  The script emitted errors for ~400
   files.

2. Each error was manually checked.  Some didn't need the inclusion,
   some needed manual addition while adding it to implementation .h or
   embedding .c file was more appropriate for others.  This step added
   inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
   from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
   e.g. lib/decompress_*.c used malloc/free() wrappers around slab
   APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
   editing them as sprinkling gfp.h and slab.h inclusions around .h
   files could easily lead to inclusion dependency hell.  Most gfp.h
   inclusion directives were ignored as stuff from gfp.h was usually
   wildly available and often used in preprocessor macros.  Each
   slab.h inclusion directive was examined and added manually as
   necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
   were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
   distributed build env didn't work with gcov compiles) and a few
   more options had to be turned off depending on archs to make things
   build (like ipr on powerpc/64 which failed due to missing writeq).

   * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
   * powerpc and powerpc64 SMP allmodconfig
   * sparc and sparc64 SMP allmodconfig
   * ia64 SMP allmodconfig
   * s390 SMP allmodconfig
   * alpha SMP allmodconfig
   * um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
   a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-30 22:02:32 +09:00
Jeff Layton
91885258e8 nfsd: don't break lease while servicing a COMMIT
This is the second attempt to fix the problem whereby a COMMIT call
causes a lease break and triggers a possible deadlock.

The problem is that nfsd attempts to break a lease on a COMMIT call.
This triggers a delegation recall if the lease is held for a delegation.
If the client is the one holding the delegation and it's the same one on
which it's issuing the COMMIT, then it can't return that delegation
until the COMMIT is complete. But, nfsd won't complete the COMMIT until
the delegation is returned. The client and server are essentially
deadlocked until the state is marked bad (due to the client not
responding on the callback channel).

The first patch attempted to deal with this by eliminating the open of
the file altogether and simply had nfsd_commit pass a NULL file pointer
to the vfs_fsync_range. That would conflict with some work in progress
by Christoph Hellwig to clean up the fsync interface, so this patch
takes a different approach.

This declares a new NFSD_MAY_NOT_BREAK_LEASE access flag that indicates
to nfsd_open that it should not break any leases when opening the file,
and has nfsd_commit set that flag on the nfsd_open call.

For now, this patch leaves nfsd_commit opening the file with write
access since I'm not clear on what sort of access would be more
appropriate.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Cc: stable@kernel.org
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2010-03-22 15:37:53 -04:00