Should clear the next pointer of the TX if we are sure that the
next TX (say NXT) will be submitted to the channel too. Overwise,
we break the chain of descriptors, because we lose the information
about the next descriptor to run. So next time, when invoke
async_tx_run_dependencies() with TX, it's TX->next will be NULL, and
NXT will be never submitted.

Cc: <stable@kernel.org>		[2.6.26]
Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Ilya Yanok <yanok@emcraft.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Found-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx: (24 commits)
  I/OAT: I/OAT version 3.0 support
  I/OAT: tcp_dma_copybreak default value dependent on I/OAT version
  I/OAT: Add watchdog/reset functionality to ioatdma
  iop_adma: cleanup iop_chan_xor_slot_count
  iop_adma: document how to calculate the minimum descriptor pool size
  iop_adma: directly reclaim descriptors on allocation failure
  async_tx: make async_tx_test_ack a boolean routine
  async_tx: remove depend_tx from async_tx_sync_epilog
  async_tx: export async_tx_quiesce
  async_tx: fix handling of the "out of descriptor" condition in async_xor
  async_tx: ensure the xor destination buffer remains dma-mapped
  async_tx: list_for_each_entry_rcu() cleanup
  dmaengine: Driver for the Synopsys DesignWare DMA controller
  dmaengine: Add slave DMA interface
  dmaengine: add DMA_COMPL_SKIP_{SRC,DEST}_UNMAP flags to control dma unmap
  dmaengine: Add dma_client parameter to device_alloc_chan_resources
  dmatest: Simple DMA memcpy test client
  dmaengine: DMA engine driver for Marvell XOR engine
  iop-adma: fix platform driver hotplug/coldplug
  dmaengine: track the number of clients using a channel
  ...

Fixed up conflict in drivers/dca/dca-sysfs.c manually

All callers of async_tx_sync_epilog have called async_tx_quiesce on the
depend_tx, so async_tx_sync_epilog need only call the callback to
complete the operation.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Replace open coded "wait and acknowledge" instances with async_tx_quiesce.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Ensure forward progress is made when a dmaengine driver is unable to
allocate an xor descriptor by breaking the dependency chain with
async_tx_quisce() and issue any pending descriptors.

Tested with iop-adma by setting device->max_xor = 2 to force multiple
calls to device_prep_dma_xor for each call to async_xor and limiting the
descriptor slot pool to 5.  Discovered that the minimum descriptor pool
size for iop-adma is 2 * iop_chan_xor_slot_cnt(device->max_xor) + 1.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

When the number of source buffers for an xor operation exceeds the hardware
channel maximum async_xor creates a chain of dependent operations.  The result
of one operation is reused as an input to the next to continue the xor
calculation.  The destination buffer should remain mapped for the duration of
the entire chain.  To provide this guarantee the code must no longer be allowed
to fallback to the synchronous path as this will preclude the buffer from being
unmapped, i.e. the dma-driver will potentially miss the descriptor with
!DMA_COMPL_SKIP_DEST_UNMAP.

Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

In the rcu update side, don't use list_for_each_entry_rcu().

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

commit 636bdeaa 'dmaengine: ack to flags: make use of the unused bits in
the 'ack' field' missed an ->ack conversion in
crypto/async_tx/async_memset.c

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Move rcu-protected lists from list.h into a new header file rculist.h.

This is done because list are a very used primitive structure all over the
kernel and it's currently impossible to include other header files in this
list.h without creating some circular dependencies.

For example, list.h implements rcu-protected list and uses rcu_dereference()
without including rcupdate.h.  It actually compiles because users of
rcu_dereference() are macros.  Others RCU functions could be used too but
aren't probably because of this.

Therefore this patch creates rculist.h which includes rcupdates without to
many changes/troubles.

Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Josh Triplett <josh@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>