Christoph had requested that the stats related code (in
CONFIG_CIFS_STATS2) be moved into helpers to make code flow more
readable. This patch should help. For example the following
section from transport.c
spin_unlock(&GlobalMid_Lock);
atomic_inc(&ses->server->num_waiters);
wait_event(ses->server->request_q,
atomic_read(&ses->server->inFlight)
< cifs_max_pending);
atomic_dec(&ses->server->num_waiters);
spin_lock(&GlobalMid_Lock);
becomes simpler (with the patch below):
spin_unlock(&GlobalMid_Lock);
cifs_num_waiters_inc(server);
wait_event(server->request_q,
atomic_read(&server->inFlight)
< cifs_max_pending);
cifs_num_waiters_dec(server);
spin_lock(&GlobalMid_Lock);
Reviewed-by: Jeff Layton <jlayton@redhat.com>
CC: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
if we failed on getting mid entry in cifs_call_async.
Cc: stable@kernel.org
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Minor revision to the last version of this patch -- the only difference
is the fix to the cFYI statement in cifs_reconnect.
Holding the spinlock while we call this function means that it can't
sleep, which really limits what it can do. Taking it out from under
the spinlock also means less contention for this global lock.
Change the semantics such that the Global_MidLock is not held when
the callback is called. To do this requires that we take extra care
not to have sync_mid_result remove the mid from the list when the
mid is in a state where that has already happened. This prevents
list corruption when the mid is sitting on a private list for
reconnect or when cifsd is coming down.
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
The current code always ignores the max_pending limit. Have it instead
only optionally ignore the pending limit. For CIFSSMBEcho, we need to
ignore it to make sure they always can go out. For async reads, writes
and potentially other calls, we need to respect it.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
We'll need this for async writes, so convert the call to take a kvec
array. CIFSSMBEcho is changed to put a kvec on the stack and pass
in the SMB buffer using that.
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Further consolidate the SendReceive code by moving the checks run over
the packet into a separate function that all the SendReceive variants
can call.
We can also eliminate the check for a receive_len that's too big or too
small. cifs_demultiplex_thread already checks that and disconnects the
socket if that occurs, while setting the midStatus to MALFORMED. It'll
never call this code if that's the case.
Finally do a little cleanup. Use "goto out" on errors so that the flow
of code in the normal case is more evident. Also switch the logErr
variable in map_smb_to_linux_error to a bool.
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
This is the same patch as originally posted, just with some merge
conflicts fixed up...
Currently, the ByteCount is usually converted to host-endian on receive.
This is confusing however, as we need to keep two sets of routines for
accessing it, and keep track of when to use each routine. Munging
received packets like this also limits when the signature can be
calulated.
Simplify the code by keeping the received ByteCount in little-endian
format. This allows us to eliminate a set of routines for accessing it
and we can now drop the *_le suffixes from the accessor functions since
that's now implied.
While we're at it, switch all of the places that read the ByteCount
directly to use the get_bcc inline which should also clean up some
unaligned accesses.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
There is one big endian field in the cifs protocol, the RFC1001
length, which cifs code (unlike in the smb2 code) had been handling as
u32 until the last possible moment, when it was converted to be32 (its
native form) before sending on the wire. To remove the last sparse
endian warning, and to make this consistent with the smb2
implementation (which always treats the fields in their
native size and endianness), convert all uses of smb_buf_length to
be32.
This version incorporates Christoph's comment about
using be32_add_cpu, and fixes a typo in the second
version of the patch.
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Slight revision to this patch...use min_t() instead of conditional
assignment. Also, remove the FIXME comment and replace it with the
explanation that Steve gave earlier.
After receiving a packet, we currently check the header. If it's no
good, then we toss it out and continue the loop, leaving the caller
waiting on that response.
In cases where the packet has length inconsistencies, but the MID is
valid, this leads to unneeded delays. That's especially problematic now
that the client waits indefinitely for responses.
Instead, don't immediately discard the packet if checkSMB fails. Try to
find a matching mid_q_entry, mark it as having a malformed response and
issue the callback.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
cifs_sign_smb only generates a signature if the correct Flags2 bit is
set. Make sure that it gets set correctly if we're sending an async
call.
This patch fixes:
https://bugzilla.kernel.org/show_bug.cgi?id=28142
Reported-and-Tested-by: JG <jg@cms.ac>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
If we kill the process while it's sending on a socket then the
kernel_sendmsg will return -EINTR. This is normal. No need to spam the
ring buffer with this info.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Use the new send_nt_cancel function to send an NT_CANCEL when the
process is delivered a fatal signal. This is a "best effort" enterprise
however, so don't bother to check the return code. There's nothing we
can reasonably do if it fails anyway.
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Currently, when a request is cancelled via signal, we delete the mid
immediately. If the request was already transmitted however, the client
is still likely to receive a response. When it does, it won't recognize
it however and will pop a printk.
It's also a little dangerous to just delete the mid entry like this. We
may end up reusing that mid. If we do then we could potentially get the
response from the first request confused with the later one.
Prevent the reuse of mids by marking them as cancelled and keeping them
on the pending_mid_q list. If the reply comes in, we'll delete it from
the list then. If it never comes, then we'll delete it at reconnect
or when cifsd comes down.
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
It's possible that when we access the ByteCount that the alignment
will be off. Most CPUs deal with that transparently, but there's
usually some performance impact. Some CPUs raise an exception on
unaligned accesses.
Fix this by accessing the byte count using the get_unaligned and
put_unaligned inlined functions. While we're at it, fix the types
of some of the variables that end up getting returns from these
functions.
Acked-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
The NT_CANCEL command looks just like the original command, except for a
few small differences. The send_nt_cancel function however currently takes
a tcon, which we don't have in SendReceive and SendReceive2.
Instead of "respinning" the entire header for an NT_CANCEL, just mangle
the existing header by replacing just the fields we need. This means we
don't need a tcon and allows us to call it from other places.
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Since we don't time out individual requests anymore, remove the code
that we used to use for setting timeouts on different requests.
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Add a function that will send a request, and set up the mid for an
async reply.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
In order to incorporate async requests, we need to allow for a more
general way to do things on receive, rather than just waking up a
process.
Turn the task pointer in the mid_q_entry into a callback function and a
generic data pointer. When a response comes in, or the socket is
reconnected, cifsd can call the callback function in order to wake up
the process.
The default is to just wake up the current process which should mean no
change in behavior for existing code.
Also, clean up the locking in cifs_reconnect. There doesn't seem to be
any need to hold both the srv_mutex and GlobalMid_Lock when walking the
list of mids.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Make it use a switch statement based on the value of the midStatus. If
the resp_buf is set, then MID_RESPONSE_RECEIVED is too.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
We only want to force a reconnect to the server under very limited and
specific circumstances. Now that we have processes waiting indefinitely
for responses, we shouldn't reach this point unless a reconnect is
already in process. Thus, there's no reason to re-mark the server for
reconnect here.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
The client should not be timing out on individual SMB requests. Too much
of the state between client and server is tied to the state of the
socket. If we time out requests and issue spurious disconnects then that
comprimises data integrity.
Instead of doing this complicated dance where we try to decide how long
to wait for a response for particular requests, have the client instead
wait indefinitely for a response. Also, use a TASK_KILLABLE sleep here
so that fatal signals will break out of this waiting.
Later patches will add support for detecting dead peers and forcing
reconnects based on that.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
In later patches, we're going to need to have finer-grained control
over the addition and removal of these structs from the pending_mid_q
and we'll need to be able to call the destructor while holding the
spinlock. Move the locked sections out of both routines and into
the callers. Fix up current callers of DeleteMidQEntry to call a new
routine that dequeues the entry and then destroys it.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
It's an atomic_t and the code accesses the "counter" field in it directly
instead of using atomic_read(). It also is sometimes accessed under a
spinlock and sometimes not. Move it out of the spinlock since we don't need
belt-and-suspenders for something that's just informational.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
The cifsSesInfo pointer is only used to get at the server.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Make connect logic more ip-protocol independent and move RFC1001 stuff into
a separate function. Also replace union addr in TCP_Server_Info structure
with sockaddr_storage.
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-and-Tested-by: Jeff Layton <jlayton@samba.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Start calculating auth response within a session. Move/Add pertinet
data structures like session key, server challenge and ntlmv2_hash in
a session structure. We should do the calculations within a session
before copying session key and response over to server data
structures because a session setup can fail.
Only after a very first smb session succeeds, it copy/make its
session key, session key of smb connection. This key stays with
the smb connection throughout its life.
sequence_number within server is set to 0x2.
The authentication Message Authentication Key (mak) which consists
of session key followed by client response within structure session_key
is now dynamic. Every authentication type allocates the key + response
sized memory within its session structure and later either assigns or
frees it once the client response is sent and if session's session key
becomes connetion's session key.
ntlm/ntlmi authentication functions are rearranged. A function
named setup_ntlm_resp(), similar to setup_ntlmv2_resp(), replaces
function cifs_calculate_session_key().
size of CIFS_SESS_KEY_SIZE is changed to 16, to reflect the byte size
of the key it holds.
Reviewed-by: Jeff Layton <jlayton@samba.org>
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Change name of variable mac_key to session key.
The reason mac_key was changed to session key is, this structure does not
hold message authentication code, it holds the session key (for ntlmv2,
ntlmv1 etc.). mac is generated as a signature in cifs_calc* functions.
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
This reverts commit 9fbc590860.
The change to kernel crypto and fixes to ntlvm2 and ntlmssp
series, introduced a regression. Deferring this patch series
to 2.6.37 after Shirish fixes it.
Signed-off-by: Steve French <sfrench@us.ibm.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
CC: Shirish Pargaonkar <shirishp@us.ibm.com>
Make ntlmv2 as an authentication mechanism within ntlmssp
instead of ntlmv1.
Parse type 2 response in ntlmssp negotiation to pluck
AV pairs and use them to calculate ntlmv2 response token.
Also, assign domain name from the sever response in type 2
packet of ntlmssp and use that (netbios) domain name in
calculation of response.
Enable cifs/smb signing using rc4 and md5.
Changed name of the structure mac_key to session_key to reflect
the type of key it holds.
Use kernel crypto_shash_* APIs instead of the equivalent cifs functions.
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Neaten cERROR and cFYI macros, reduce text space
~2.5K
Convert '__FILE__ ": " fmt' to '"%s: " fmt', __FILE__' to save text space
Surround macros with do {} while
Add parentheses to macros
Make statement expression macro from macro with assign
Remove now unnecessary parentheses from cFYI and cERROR uses
defconfig with CIFS support old
$ size fs/cifs/built-in.o
text data bss dec hex filename
156012 1760 148 157920 268e0 fs/cifs/built-in.o
defconfig with CIFS support old
$ size fs/cifs/built-in.o
text data bss dec hex filename
153508 1760 148 155416 25f18 fs/cifs/built-in.o
allyesconfig old:
$ size fs/cifs/built-in.o
text data bss dec hex filename
309138 3864 74824 387826 5eaf2 fs/cifs/built-in.o
allyesconfig new
$ size fs/cifs/built-in.o
text data bss dec hex filename
305655 3864 74824 384343 5dd57 fs/cifs/built-in.o
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
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>
This is the fourth respin of the patch to convert oplock breaks to
use the slow_work facility.
A customer of ours was testing a backport of one of the earlier
patchsets, and hit a "Busy inodes after umount..." problem. An oplock
break job had raced with a umount, and the superblock got torn down and
its memory reused. When the oplock break job tried to dereference the
inode->i_sb, the kernel oopsed.
This patchset has the oplock break job hold an inode and vfsmount
reference until the oplock break completes. With this, there should be
no need to take a tcon reference (the vfsmount implicitly holds one
already).
Currently, when an oplock break comes in there's a chance that the
oplock break job won't occur if the allocation of the oplock_q_entry
fails. There are also some rather nasty races in the allocation and
handling these structs.
Rather than allocating oplock queue entries when an oplock break comes
in, add a few extra fields to the cifsFileInfo struct. Get rid of the
dedicated cifs_oplock_thread as well and queue the oplock break job to
the slow_work thread pool.
This approach also has the advantage that the oplock break jobs can
potentially run in parallel rather than be serialized like they are
today.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Right now, the GlobalOplock_Q is protected by the GlobalMid_Lock. That
lock is also used for completely unrelated purposes (mostly for managing
the global mid queue). Give the list its own dedicated spinlock
(cifs_oplock_lock) and rename the list to cifs_oplock_list to
eliminate the camel-case.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
We have used approximately 15 second timeouts on nonblocking sends in the past, and
also 15 second SMB timeout (waiting for server responses, for most request types).
Now that we can do blocking tcp sends,
make blocking send timeout approximately the same (15 seconds).
Signed-off-by: Steve French <sfrench@us.ibm.com>
cifs: turn smb_send into a wrapper around smb_sendv
Rename smb_send2 to smb_sendv to make it consistent with kernel naming
conventions for functions that take a vector.
There's no need to have 2 functions to handle sending SMB calls. Turn
smb_send into a wrapper around smb_sendv. This also allows us to
properly mark the socket as needing to be reconnected when there's a
partial send from smb_send.
Also, in practice we always use the address and noblocksnd flag
that's attached to the TCP_Server_Info. There's no need to pass
them in as separate args to smb_sendv.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Remove an already-checked error condition in SendReceiveBlockingLock
Signed-off-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Streamline SendReceiveBlockingLock: Use "goto out:" in an error condition
Signed-off-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Streamline SendReceiveBlockingLock: Use "goto out:" in an error condition
Signed-off-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Slightly streamline SendReceive[2]
Remove an else branch by naming the error condition what it is
Signed-off-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>
This is no functional change, because in the "if" branch we do an early
"return 0;".
Signed-off-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Simplify allocate_mid() slightly: Remove some unnecessary "else" branches
Signed-off-by: Volker Lendecke <vl@samba.org>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
inbuf->smb_buf_length does not change in in wait_for_free_request() or in
allocate_mid(), so we can check it early.
Signed-off-by: Volker Lendecke <vl@samba.org>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
cifs: fix wait_for_response to time out sleeping processes correctly
The current scheme that CIFS uses to sleep and wait for a response is
not quite what we want. After sending a request, wait_for_response puts
the task to sleep with wait_event(). One of the conditions for
wait_event is a timeout (using time_after()).
The problem with this is that there is no guarantee that the process
will ever be woken back up. If the server stops sending data, then
cifs_demultiplex_thread will leave its response queue sleeping.
I think the only thing that saves us here is the fact that
cifs_dnotify_thread periodically (every 15s) wakes up sleeping processes
on all response_q's that have calls in flight. This makes for
unnecessary wakeups of some processes. It also means large variability
in the timeouts since they're all woken up at once.
Instead of this, put the tasks to sleep with wait_event_timeout. This
makes them wake up on their own if they time out. With this change,
cifs_dnotify_thread should no longer be needed.
I've been testing this in conjunction with some other patches that I'm
working on. It doesn't seem to affect performance at all with with heavy
I/O. Identical iozone -ac runs complete in almost exactly the same time
(<1% difference in times).
Thanks to Wasrshi Nimara for initially pointing this out. Wasrshi, it
would be nice to know whether this patch also helps your testcase.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Cc: Wasrshi Nimara <warshinimara@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
