dlm_request_all_locks() should deal with the status sent from target node
if DLM_LOCK_REQUEST_MSG is sent successfully, or recovery master will fall
into endless loop, waiting for other nodes to send locks and
DLM_RECO_DATA_DONE_MSG to me.

        NodeA                                  NodeB
                                     selected as recovery master
                                     dlm_remaster_locks()
                                     ->dlm_request_all_locks()
                                     send DLM_LOCK_REQUEST_MSG to nodeA

It happened that NodeA cannot alloc memory when it processes this
message.  dlm_request_all_locks_handler() do not queue
dlm_request_all_locks_worker and returns -ENOMEM.  It will never send
locks and DLM_RECO_DATA_DONE_MSG to NodeB.

                                    NodeB do not deal with the status
                                    sent from nodeA, and will fall in
                                    endless loop waiting for the
                                    recovery state of NodeA to be
                                    changed.
Signed-off-by: Njoyce <xuejiufei@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Jeff Liu <jeff.liu@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Though ocfs2 uses inode->i_mutex to protect i_size, there are both
i_size_read/write() and direct accesses.  Clean up all direct access to
eliminate confusion.
Signed-off-by: NJunxiao Bi <junxiao.bi@oracle.com>
Cc: Jie Liu <jeff.liu@oracle.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The issue scenario is as following:

When fallocating a very large disk space for a small file,
__ocfs2_extend_allocation attempts to get a very large transaction.  For
some journal sizes, there may be not enough room for this transaction,
and the fallocate will fail.

The patch below extends & restarts the transaction as necessary while
allocating space, and should work with even the smallest journal.  This
patch refers ext4 resize.

Test:
# mkfs.ocfs2 -b 4K -C 32K -T datafiles /dev/sdc
...(jounral size is 32M)
# mount.ocfs2 /dev/sdc /mnt/ocfs2/
# touch /mnt/ocfs2/1.log
# fallocate -o 0 -l 400G /mnt/ocfs2/1.log
fallocate: /mnt/ocfs2/1.log: fallocate failed: Cannot allocate memory
# tail -f /var/log/messages
[ 7372.278591] JBD: fallocate wants too many credits (2051 > 2048)
[ 7372.278597] (fallocate,6438,0):__ocfs2_extend_allocation:709 ERROR: status = -12
[ 7372.278603] (fallocate,6438,0):ocfs2_allocate_unwritten_extents:1504 ERROR: status = -12
[ 7372.278607] (fallocate,6438,0):__ocfs2_change_file_space:1955 ERROR: status = -12
^C
With this patch, the test works well.
Signed-off-by: NYounger Liu <younger.liu@huawei.com>
Cc: Jie Liu <jeff.liu@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When I moved the RCU walk termination into unlazy_walk(), I didn't copy
quite all of it: for the successful RCU termination we properly add the
necessary reference counts to our temporary copy of the root path, but
for the failure case we need to make sure that any temporary root path
information is cleared out (since it does _not_ have the proper
reference counts from the RCU lookup).

We could clean up this mess by just always dropping the temporary root
information, but Al points out that that would mean that a single lookup
through symlinks could see multiple different root entries if it races
with another thread doing chroot.  Not that I think we should really
care (we had that before too, back before we had a copy of the root path
in the nameidata).

Al says he has a cunning plan.  In the meantime, this is the minimal fix
for the problem, even if it's not all that pretty.
Reported-by: NMace Moneta <moneta.mace@gmail.com>
Acked-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Separate "check if we need to retry" from "unlock if we are done and
had seq_writelock"; that allows to use these guys in d_walk(), where
we need to recheck every time we ascend back to parent, but do *not*
want to unlock until the very end.  Lift rcu_read_lock/rcu_read_unlock
out into callers.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Not using the return value can in the generic case be racy, so it's
in general good practice to check the return value instead.

This also resolved the warning caused on ARM and other architectures:

  fs/direct-io.c: In function 'sb_init_dio_done_wq':
  fs/direct-io.c:557:2: warning: value computed is not used [-Wunused-value]
Signed-off-by: NOlof Johansson <olof@lixom.net>
Reviewed-by: NJan Kara <jack@suse.cz>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: H Peter Anvin <hpa@zytor.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When running the AIM7's short workload, Linus' lockref patch eliminated
most of the spinlock contention. However, there were still some left:

     8.46%     reaim  [kernel.kallsyms]     [k] _raw_spin_lock
                 |--42.21%-- d_path
                 |          proc_pid_readlink
                 |          SyS_readlinkat
                 |          SyS_readlink
                 |          system_call
                 |          __GI___readlink
                 |
                 |--40.97%-- sys_getcwd
                 |          system_call
                 |          __getcwd

The big one here is the rename_lock (seqlock) contention in d_path()
and the getcwd system call. This patch will eliminate the need to take
the rename_lock while translating dentries into the full pathnames.

The need to take the rename_lock is to make sure that no rename
operation can be ongoing while the translation is in progress. However,
only one thread can take the rename_lock thus blocking all the other
threads that need it even though the translation process won't make
any change to the dentries.

This patch will replace the writer's write_seqlock/write_sequnlock
sequence of the rename_lock of the callers of the prepend_path() and
__dentry_path() functions with the reader's read_seqbegin/read_seqretry
sequence within these 2 functions. As a result, the code will have to
retry if one or more rename operations had been performed. In addition,
RCU read lock will be taken during the translation process to make sure
that no dentries will go away. To prevent live-lock from happening,
the code will switch back to take the rename_lock if read_seqretry()
fails for three times.

To further reduce spinlock contention, this patch does not take the
dentry's d_lock when copying the filename from the dentries. Instead,
it treats the name pointer and length as unreliable and just copy
the string byte-by-byte over until it hits a null byte or the end of
string as specified by the length. This should avoid stepping into
invalid memory address. The error cases are left to be handled by
the sequence number check.

The following code re-factoring are also made:
1. Move prepend('/') into prepend_name() to remove one conditional
   check.
2. Move the global root check in prepend_path() back to the top of
   the while loop.

With this patch, the _raw_spin_lock will now account for only 1.2%
of the total CPU cycles for the short workload. This patch also has
the effect of reducing the effect of running perf on its profile
since the perf command itself can be a heavy user of the d_path()
function depending on the complexity of the workload.

When taking the perf profile of the high-systime workload, the amount
of spinlock contention contributed by running perf without this patch
was about 16%. With this patch, the spinlock contention caused by
the running of perf will go away and we will have a more accurate
perf profile.
Signed-off-by: NWaiman Long <Waiman.Long@hp.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

When reconnecting to automounts at startup an autofs ioctl is used
to find the device and inode of existing mounts so they can be used
to open a file descriptor of possibly covered mounts.

At this time the the caller might not yet "own" the mount so it can
trigger calling ->d_automount(). This causes automount to hang when
trying to reconnect to direct or offset mount types.

Consequently kern_path() can't be used but kern_path_mountpoint() can be.
Signed-off-by: NIan Kent <raven@themaw.net>
Cc: Jeff Layton <jlayton@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

This is the fix that the last two commits indirectly led up to - making
sure that we don't call dput() in a bad context on the dentries we've
looked up in RCU mode after the sequence count validation fails.

This basically expands d_rcu_to_refcount() into the callers, and then
fixes the callers to delay the dput() in the failure case until _after_
we've dropped all locks and are no longer in an RCU-locked region.

The case of 'complete_walk()' was trivial, since its failure case did
the unlock_rcu_walk() directly after the call to d_rcu_to_refcount(),
and as such that is just a pure expansion of the function with a trivial
movement of the resulting dput() to after 'unlock_rcu_walk()'.

In contrast, the unlazy_walk() case was much more complicated, because
not only does convert two different dentries from RCU to be reference
counted, but it used to not call unlock_rcu_walk() at all, and instead
just returned an error and let the caller clean everything up in
"terminate_walk()".

Happily, one of the dentries in question (called "parent" inside
unlazy_walk()) is the dentry of "nd->path", which terminate_walk() wants
a refcount to anyway for the non-RCU case.

So what the new and improved unlazy_walk() does is to first turn that
dentry into a refcounted one, and once that is set up, the error cases
can continue to use the terminate_walk() helper for cleanup, but for the
non-RCU case.  Which makes it possible to drop out of RCU mode if we
actually hit the sequence number failure case.
Acked-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

... and move the extern from linux/namei.h to fs/internal.h,
along with that of vfs_path_lookup().
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

... and massage it a bit to reduce nesting
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

This simplifies the RCU to refcounting code in particular.

I was originally intending to leave this for later, but walking through
all the dput() logic (see previous commit), I realized that the dput()
"might_sleep()" check was misleadingly weak.  And I removed it as
misleading, both for performance profiling and for debugging.

However, the might_sleep() debugging case is actually true: the final
dput() can indeed sleep, if the inode of the dentry that you are
releasing ends up sleeping at iput time (see dentry_iput()).  So the
problem with the might_sleep() in dput() wasn't that it wasn't true, it
was that it wasn't actually testing and triggering on the interesting
case.

In particular, just about *any* dput() can indeed sleep, if you happen
to race with another thread deleting the file in question, and you then
lose the race to the be the last dput() for that file.  But because it's
a very rare race, the debugging code would never trigger it in practice.

Why is this problematic? The new d_rcu_to_refcount() (see commit
15570086: "vfs: reimplement d_rcu_to_refcount() using
lockref_get_or_lock()") does a dput() for the failure case, and it does
it under the RCU lock.  So potentially sleeping really is a bug.

But there's no way I'm going to fix this with the previous complicated
"lockref_get_or_lock()" interface.  And rather than revert to the old
and crufty nested dentry locking code (which did get this right by
delaying the reference count updates until they were verified to be
safe), let's make forward progress.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This is me being a bit OCD after all the dentry optimization work this
merge window: profiles end up showing 'dput()' as a rather expensive
operation, and there were two unrelated bad reasons for that.

The first reason was reading d_lockref.count for debugging purposes,
which touches the lockref cacheline (for reads) before really need to.
More importantly, the debugging test in question is _wrong_, and has
hidden bugs.  It's true that we can only sleep when the count goes down
to zero, but the test as-is hides the much more subtle bug that happens
if we race with somebody else deleting the file.

Anyway we _will_ touch that cacheline, but let's do it for a write and
in the right routine (ie in "lockref_put_or_lock()") which annotates the
costs better.  So remove the misleading debug code.

The other was an unnecessary access to the cacheline that contains the
d_lru list, just to check whether we already were on the LRU list or
not.  This is exactly what we have d_flags for, so that we can avoid
touching extra cache lines for the common case.  So just add another bit
for "is this dentry on the LRU".

Finally, mark the tests properly likely/unlikely, so that the common
fast-paths are dense in the instruction stream.

This makes the profiles look much saner.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

On some filesystems it's impossible even with fs corruption, but we'd
better not rely on that, what with memcpy() into on-stack array we
are doing there.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

No dentry can get to directory modification methods without
having passed either ->lookup() or ->atomic_open(); if name is
rejected by those two (or by ->d_hash()) with an error, it won't
be seen by anything else.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Commit 97431204 introduced a regression
that causes SECINFO_NO_NAME to fail without sending an RPC if:

 1) the nfs_client's rpc_client is using krb5i/p (now tried by default)
 2) the current user doesn't have valid kerberos credentials

This situation is quite common - as of now a sec=sys mount would use
krb5i for the nfs_client's rpc_client and a user would hardly be faulted
for not having run kinit.

The solution is to use the machine cred when trying to use an integrity
protected auth flavor for SECINFO_NO_NAME.

Older servers may not support using the machine cred or an integrity
protected auth flavor for SECINFO_NO_NAME in every circumstance, so we fall
back to using the user's cred and the filesystem's auth flavor in this case.

We run into another problem when running against linux nfs servers -
they return NFS4ERR_WRONGSEC when using integrity auth flavor (unless the
mount is also that flavor) even though that is not a valid error for
SECINFO*.  Even though it's against spec, handle WRONGSEC errors on
SECINFO_NO_NAME by falling back to using the user cred and the
filesystem's auth flavor.
Signed-off-by: NWeston Andros Adamson <dros@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Also don't worry about obsolete mount flags...
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

In cases where the parent super block was not mounted with a 'sec=' line,
allow autonegotiation of security for the submounts.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Ensure that nfs4_proc_lookup_common respects the NFS_MOUNT_SECFLAVOUR
flag.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

NFSv4 security auto-negotiation has been broken since
commit 4580a92d (NFS:
Use server-recommended security flavor by default (NFSv3))
because nfs4_try_mount() will automatically select AUTH_SYS
if it sees no auth flavours.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Cc: Chuck Lever <chuck.lever@oracle.com>

Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

What is the point of having a 'auth_flavor_len' field, if it is
always set to 1, and can't be used to determine if the user has
selected an auth flavour?
This cleanup goes back to using auth_flavor_len for its original
intended purpose, and gets rid of the ad-hoc replacements.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

We have to implement ->release() and trigger writeback from it.
Otherwise we might lose dirty pages at munmap().
Signed-off-by: NRichard Weinberger <richard@nod.at>

d_invalidate() is the standard VFS method to invalidate dentry.
compare to d_delete(), it also try shrinking children dentries.
Signed-off-by: NYan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: NSage Weil <sage@inktank.com>

commit 6f60f889 (ceph: fix freeing inode vs removing session caps race)
introduced ceph_lookup_inode(). But there is already a ceph_find_inode()
which provides similar function. So remove ceph_lookup_inode(), use
ceph_find_inode() instead.
Signed-off-by: NYan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: NAlex Elder <alex.elder@linary.org>
Reviewed-by: NSage Weil <sage@inktank.com>

Commit 4edaa308 "NFS: Use "krb5i" to establish NFSv4 state whenever possible"
uses the nfs_client cl_rpcclient for all state management operations, and
will use krb5i or auth_sys with no regard to the mount command authflavor
choice.

The MDS, as any NFSv4.1 mount point, uses the nfs_server rpc client for all
non-state management operations with a different nfs_server for each fsid
encountered traversing the mount point, each with a potentially different
auth flavor.

pNFS data servers are not mounted in the normal sense as there is no associated
nfs_server structure. Data servers can also export multiple fsids, each with
a potentially different auth flavor.

Data servers need to use the same authflavor as the MDS server rpc client for
non-state management operations. Populate a list of rpc clients with the MDS
server rpc client auth flavor for the DS to use.
Signed-off-by: NAndy Adamson <andros@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

The linux-next build bot found a three of warnings, this addresses all of them.

 * non-ANSI function declaration of function 'ceph_fscache_register' and
   'ceph_fscache_unregister'
 * symbol 'ceph_cache_netfs' was not declared, now it's extern in the header.
 * warning: "pr_fmt" redefined
Signed-off-by: NMilosz Tanski <milosz@adfin.com>

Previously we would always try to enqueue work even if the filesystem is not
mounted with fscache enabled (or the file has no cookie). In the case of the
filesystem mouned nofsc (but with fscache compiled in) this would lead to a
crash.
Signed-off-by: NMilosz Tanski <milosz@adfin.com>

Previous patch that allowed us to cleanup most of the issues with pages marked
as private_2 when calling ceph_readpages. However, there seams to be a case in
the error case clean up in start read that still trigers this from time to
time. I've only seen this one a couple times.

BUG: Bad page state in process petabucket  pfn:335b82
page:ffffea000cd6e080 count:0 mapcount:0 mapping:          (null) index:0x0
page flags: 0x200000000001000(private_2)
Call Trace:
 [<ffffffff81563442>] dump_stack+0x46/0x58
 [<ffffffff8112c7f7>] bad_page+0xc7/0x120
 [<ffffffff8112cd9e>] free_pages_prepare+0x10e/0x120
 [<ffffffff8112e580>] free_hot_cold_page+0x40/0x160
 [<ffffffff81132427>] __put_single_page+0x27/0x30
 [<ffffffff81132d95>] put_page+0x25/0x40
 [<ffffffffa02cb409>] ceph_readpages+0x2e9/0x6f0 [ceph]
 [<ffffffff811313cf>] __do_page_cache_readahead+0x1af/0x260
Signed-off-by: NMilosz Tanski <milosz@adfin.com>
Signed-off-by: NSage Weil <sage@inktank.com>

Previously ceph_readpage_to_fscache did not call if page was marked as cached
before calling fscache_write_page resulting in a BUG inside of fscache.

FS-Cache: Assertion failed
------------[ cut here ]------------
kernel BUG at fs/fscache/page.c:874!
invalid opcode: 0000 [#1] SMP
Call Trace:
 [<ffffffffa02e6566>] __ceph_readpage_to_fscache+0x66/0x80 [ceph]
 [<ffffffffa02caf84>] readpage_nounlock+0x124/0x210 [ceph]
 [<ffffffffa02cb08d>] ceph_readpage+0x1d/0x40 [ceph]
 [<ffffffff81126db6>] generic_file_aio_read+0x1f6/0x700
 [<ffffffffa02c6fcc>] ceph_aio_read+0x5fc/0xab0 [ceph]
Signed-off-by: NMilosz Tanski <milosz@adfin.com>
Signed-off-by: NSage Weil <sage@inktank.com>

In some cases the ceph readapages code code bails without filling all the pages
already marked by fscache. When we return back to readahead code this causes
a BUG.
Signed-off-by: NMilosz Tanski <milosz@adfin.com>

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: NMilosz Tanski <milosz@adfin.com>
Signed-off-by: NSage Weil <sage@inktank.com>

When coalescing requests into a single READ or WRITE RPC call, and there
is no file locking involved, we don't have to refuse coalescing for
requests where the lock owner information doesn't match.
Reported-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Currently the fscache code expect the netfs to call fscache_readpages_or_alloc
inside the aops readpages callback.  It marks all the pages in the list
provided by readahead with PG_private_2.  In the cases that the netfs fails to
read all the pages (which is legal) it ends up returning to the readahead and
triggering a BUG.  This happens because the page list still contains marked
pages.

This patch implements a simple fscache_readpages_cancel function that the netfs
should call before returning from readpages.  It will revoke the pages from the
underlying cache backend and unmark them.

The problem was originally worked out in the Ceph devel tree, but it also
occurs in CIFS.  It appears that NFS, AFS and 9P are okay as read_cache_pages()
will clean up the unprocessed pages in the case of an error.

This can be used to address the following oops:

[12410647.597278] BUG: Bad page state in process petabucket  pfn:3d504e
[12410647.597292] page:ffffea000f541380 count:0 mapcount:0 mapping:
	(null) index:0x0
[12410647.597298] page flags: 0x200000000001000(private_2)

...

[12410647.597334] Call Trace:
[12410647.597345]  [<ffffffff815523f2>] dump_stack+0x19/0x1b
[12410647.597356]  [<ffffffff8111def7>] bad_page+0xc7/0x120
[12410647.597359]  [<ffffffff8111e49e>] free_pages_prepare+0x10e/0x120
[12410647.597361]  [<ffffffff8111fc80>] free_hot_cold_page+0x40/0x170
[12410647.597363]  [<ffffffff81123507>] __put_single_page+0x27/0x30
[12410647.597365]  [<ffffffff81123df5>] put_page+0x25/0x40
[12410647.597376]  [<ffffffffa02bdcf9>] ceph_readpages+0x2e9/0x6e0 [ceph]
[12410647.597379]  [<ffffffff81122a8f>] __do_page_cache_readahead+0x1af/0x260
[12410647.597382]  [<ffffffff81122ea1>] ra_submit+0x21/0x30
[12410647.597384]  [<ffffffff81118f64>] filemap_fault+0x254/0x490
[12410647.597387]  [<ffffffff8113a74f>] __do_fault+0x6f/0x4e0
[12410647.597391]  [<ffffffff810125bd>] ? __switch_to+0x16d/0x4a0
[12410647.597395]  [<ffffffff810865ba>] ? finish_task_switch+0x5a/0xc0
[12410647.597398]  [<ffffffff8113d856>] handle_pte_fault+0xf6/0x930
[12410647.597401]  [<ffffffff81008c33>] ? pte_mfn_to_pfn+0x93/0x110
[12410647.597403]  [<ffffffff81008cce>] ? xen_pmd_val+0xe/0x10
[12410647.597405]  [<ffffffff81005469>] ? __raw_callee_save_xen_pmd_val+0x11/0x1e
[12410647.597407]  [<ffffffff8113f361>] handle_mm_fault+0x251/0x370
[12410647.597411]  [<ffffffff812b0ac4>] ? call_rwsem_down_read_failed+0x14/0x30
[12410647.597414]  [<ffffffff8155bffa>] __do_page_fault+0x1aa/0x550
[12410647.597418]  [<ffffffff8108011d>] ? up_write+0x1d/0x20
[12410647.597422]  [<ffffffff8113141c>] ? vm_mmap_pgoff+0xbc/0xe0
[12410647.597425]  [<ffffffff81143bb8>] ? SyS_mmap_pgoff+0xd8/0x240
[12410647.597427]  [<ffffffff8155c3ae>] do_page_fault+0xe/0x10
[12410647.597431]  [<ffffffff81558818>] page_fault+0x28/0x30
Signed-off-by: NMilosz Tanski <milosz@adfin.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Implement the FS-Cache interface to check the consistency of a cache object in
CacheFiles.

Original-author: Hongyi Jia <jiayisuse@gmail.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
cc: Hongyi Jia <jiayisuse@gmail.com>
cc: Milosz Tanski <milosz@adfin.com>

Extend the fscache netfs API so that the netfs can ask as to whether a cache
object is up to date with respect to its corresponding netfs object:

	int fscache_check_consistency(struct fscache_cookie *cookie)

This will call back to the netfs to check whether the auxiliary data associated
with a cookie is correct.  It returns 0 if it is and -ESTALE if it isn't; it
may also return -ENOMEM and -ERESTARTSYS.

The backends now have to implement a mandatory operation pointer:

	int (*check_consistency)(struct fscache_object *object)

that corresponds to the above API call.  FS-Cache takes care of pinning the
object and the cookie in memory and managing this call with respect to the
object state.

Original-author: Hongyi Jia <jiayisuse@gmail.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
cc: Hongyi Jia <jiayisuse@gmail.com>
cc: Milosz Tanski <milosz@adfin.com>

If we're doing buffered writes, and there is no file locking involved,
then we don't have to worry about whether or not the lock owner information
is identical.
By relaxing this check, we ensure that fork()ed child processes can write
to a page without having to first sync dirty data that was written
by the parent to disk.
Reported-by: NQuentin Barnes <qbarnes@gmail.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Tested-by: NQuentin Barnes <qbarnes@gmail.com>

Drop a subtree when we find that it has moved or been delated.  This can be
done as long as there are no submounts under this location.

If the directory was moved and we come across the same directory in a
future lookup it will be reconnected by d_materialise_unique().
Signed-off-by: NAnand Avati <avati@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>