nfsd: eliminate one of the DRC cache searches

The most common case is to do a search of the cache, followed by an
insert. In the case where we have to allocate an entry off the slab,
then we end up having to redo the search, which is wasteful.

Better optimize the code for the common case by eliminating the initial
search of the cache and always preallocating an entry. In the case of a
cache hit, we'll end up just freeing that entry but that's preferable to
an extra search.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd: break out comparator into separate function

Break out the function that compares the rqstp and checksum against a
reply cache entry. While we're at it, track the efficacy of the checksum
over the NFS data by tracking the cases where we would have incorrectly
matched a DRC entry if we had not tracked it or the length.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd: track memory utilization by the DRC

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd: add new reply_cache_stats file in nfsdfs

For presenting statistics relating to duplicate reply cache.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd: keep stats on worst hash balancing seen so far

The typical case with the DRC is a cache miss, so if we keep track of
the max number of entries that we've ever walked over in a search, then
we should have a reasonable estimate of the longest hash chain that
we've ever seen.

With that, we'll also keep track of the total size of the cache when we
see the longest chain. In the case of a tie, we prefer to track the
smallest total cache size in order to properly gauge the worst-case
ratio of max vs. avg chain length.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd: scale up the number of DRC hash buckets with cache size

We've now increased the size of the duplicate reply cache by quite a
bit, but the number of hash buckets has not changed. So, we've gone from
an average hash chain length of 16 in the old code to 4096 when the
cache is its largest. Change the code to scale out the number of buckets
with the max size of the cache.

At the same time, we also need to fix the hash function since the
existing one isn't really suitable when there are more than 256 buckets.
Move instead to use the stock hash_32 function for this. Testing on a
machine that had 2048 buckets showed that this gave a smaller
longest:average ratio than the existing hash function:

The formula here is longest hash bucket searched divided by average
number of entries per bucket at the time that we saw that longest
bucket:

    old hash: 68/(39258/2048) == 3.547404
    hash_32:  45/(33773/2048) == 2.728807

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: remove BUG_ON

This BUG_ON just crashes the thread a little earlier than it would
otherwise--it doesn't seem useful.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: handle seqid-mutating open errors from xdr decoding

If a client sets an owner (or group_owner or acl) attribute on open for
create, and the mapping of that owner to an id fails, then we return
BAD_OWNER.  But BAD_OWNER is a seqid-mutating error, so we can't
shortcut the open processing that case: we have to at least look up the
owner so we can find the seqid to bump.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: fix race on client shutdown

Dropping the session's reference count after the client's means we leave
a window where the session's se_client pointer is NULL.  An xpt_user
callback that encounters such a session may then crash:

[  303.956011] BUG: unable to handle kernel NULL pointer dereference at 0000000000000318
[  303.959061] IP: [<ffffffff81481a8e>] _raw_spin_lock+0x1e/0x40
[  303.959061] PGD 37811067 PUD 3d498067 PMD 0
[  303.959061] Oops: 0002 [#8] PREEMPT SMP
[  303.959061] Modules linked in: md5 nfsd auth_rpcgss nfs_acl snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_page_alloc microcode psmouse snd_timer serio_raw pcspkr evdev snd soundcore i2c_piix4 i2c_core intel_agp intel_gtt processor button nfs lockd sunrpc fscache ata_generic pata_acpi ata_piix uhci_hcd libata btrfs usbcore usb_common crc32c scsi_mod libcrc32c zlib_deflate floppy virtio_balloon virtio_net virtio_pci virtio_blk virtio_ring virtio
[  303.959061] CPU 0
[  303.959061] Pid: 264, comm: nfsd Tainted: G      D      3.8.0-ARCH+ #156 Bochs Bochs
[  303.959061] RIP: 0010:[<ffffffff81481a8e>]  [<ffffffff81481a8e>] _raw_spin_lock+0x1e/0x40
[  303.959061] RSP: 0018:ffff880037877dd8  EFLAGS: 00010202
[  303.959061] RAX: 0000000000000100 RBX: ffff880037a2b698 RCX: ffff88003d879278
[  303.959061] RDX: ffff88003d879278 RSI: dead000000100100 RDI: 0000000000000318
[  303.959061] RBP: ffff880037877dd8 R08: ffff88003c5a0f00 R09: 0000000000000002
[  303.959061] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
[  303.959061] R13: 0000000000000318 R14: ffff880037a2b680 R15: ffff88003c1cbe00
[  303.959061] FS:  0000000000000000(0000) GS:ffff88003fc00000(0000) knlGS:0000000000000000
[  303.959061] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[  303.959061] CR2: 0000000000000318 CR3: 000000003d49c000 CR4: 00000000000006f0
[  303.959061] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  303.959061] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[  303.959061] Process nfsd (pid: 264, threadinfo ffff880037876000, task ffff88003c1fd0a0)
[  303.959061] Stack:
[  303.959061]  ffff880037877e08 ffffffffa03772ec ffff88003d879000 ffff88003d879278
[  303.959061]  ffff88003d879080 0000000000000000 ffff880037877e38 ffffffffa0222a1f
[  303.959061]  0000000000107ac0 ffff88003c22e000 ffff88003d879000 ffff88003c1cbe00
[  303.959061] Call Trace:
[  303.959061]  [<ffffffffa03772ec>] nfsd4_conn_lost+0x3c/0xa0 [nfsd]
[  303.959061]  [<ffffffffa0222a1f>] svc_delete_xprt+0x10f/0x180 [sunrpc]
[  303.959061]  [<ffffffffa0223d96>] svc_recv+0xe6/0x580 [sunrpc]
[  303.959061]  [<ffffffffa03587c5>] nfsd+0xb5/0x140 [nfsd]
[  303.959061]  [<ffffffffa0358710>] ? nfsd_destroy+0x90/0x90 [nfsd]
[  303.959061]  [<ffffffff8107ae00>] kthread+0xc0/0xd0
[  303.959061]  [<ffffffff81010000>] ? perf_trace_xen_mmu_set_pte_at+0x50/0x100
[  303.959061]  [<ffffffff8107ad40>] ? kthread_freezable_should_stop+0x70/0x70
[  303.959061]  [<ffffffff814898ec>] ret_from_fork+0x7c/0xb0
[  303.959061]  [<ffffffff8107ad40>] ? kthread_freezable_should_stop+0x70/0x70
[  303.959061] Code: ff ff 5d c3 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 55 65 48 8b 04 25 f0 c6 00 00 48 89 e5 83 80 44 e0 ff ff 01 b8 00 01 00 00 <3e> 66 0f c1 07 0f b6 d4 38 c2 74 0f 66 0f 1f 44 00 00 f3 90 0f
[  303.959061] RIP  [<ffffffff81481a8e>] _raw_spin_lock+0x1e/0x40
[  303.959061]  RSP <ffff880037877dd8>
[  303.959061] CR2: 0000000000000318
[  304.001218] ---[ end trace 2d809cd4a7931f5a ]---
[  304.001903] note: nfsd[264] exited with preempt_count 2

Reported-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: fix use-after-free of 4.1 client on connection loss

Once we drop the lock here there's nothing keeping the client around:
the only lock still held is the xpt_lock on this socket, but this socket
no longer has any connection with the client so there's no way for other
code to know we're still using the client.

The solution is simple: all nfsd4_probe_callback does is set a few
variables and queue some work, so there's no reason we can't just keep
it under the lock.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd: remove unused macro in nfsv4

lk_rflags is never used anywhere, and rflags is not defined in struct
nfsd4_lock.

Signed-off-by: Yanchuan Nian <ycnian@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd: fix bug on nfs4 stateid deallocation

NFS4_OO_PURGE_CLOSE is not handled properly. To avoid memory leak, nfs4
stateid which is pointed by oo_last_closed_stid is freed in nfsd4_close(),
but NFS4_OO_PURGE_CLOSE isn't cleared meanwhile. So the stateid released in
THIS close procedure may be freed immediately in the coming encoding function.
Sorry that Signed-off-by was forgotten in last version.

Signed-off-by: Yanchuan Nian <ycnian@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: warn on odd create_session state

This should never happen.

(Note: the comparable case in setclientid_confirm *can* happen, since
updating a client record can result in both confirmed and unconfirmed
records with the same clientid.)

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: STALE_STATEID cleanup

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: remove some dprintk's

E.g. printk's that just report the return value from an op are
uninteresting as we already do that in the main proc_compound loop.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: destroy_clientid simplification

I'm not sure what the check for clientid expiry was meant to do here.

The check for a matching session is redundant given the previous check
for state: a client without state is, in particular, a client without
sessions.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: clientid lookup cleanup

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: fix destroy_session race

destroy_session uses the session and client without continuously holding
any reference or locks.

Put the whole thing under the state lock for now.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: simplify bind_conn_to_session locking

The locking here is very fiddly, and there's no reason for us to be
setting cstate->session, since this is the only op in the compound.
Let's just take the state lock and drop the reference counting.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
nfsd4: don't destroy in-use clients

When a setclientid_confirm or create_session confirms a client after a
client reboot, it also destroys any previous state held by that client.

The shutdown of that previous state must be careful not to free the
client out from under threads processing other requests that refer to
the client.

This is a particular problem in the NFSv4.1 case when we hold a
reference to a session (hence a client) throughout compound processing.

The server attempts to handle this by unhashing the client at the time
it's destroyed, then delaying the final free to the end.  But this still
leaves some races in the current code.

I believe it's simpler just to fail the attempt to destroy the client by
returning NFS4ERR_DELAY.  This is a case that should never happen
anyway.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>