block: add REQ_URGENT to request flags

This patch adds a new flag to be used in cmd_flags field of struct request
for marking request as urgent.
Urgent request is the one that should be given priority currently handled
(regular) request by the device driver. The decision of a request urgency
is taken by the scheduler.

Change-Id: Ic20470987ef23410f1d0324f96f00578f7df8717
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: add a flag to identify PM request

Add a flag REQ_PM to identify the request is PM related, such requests
will not change the device request queue's runtime status. It is
intended to be used in driver's runtime PM callback, so that driver can
perform some IO to the device there with the queue's runtime status
unaffected. e.g. in SCSI disk's runtime suspend callback, the disk will
be put into stopped power state, and this require sending a command to
the device. Such command processing should not change the disk's runtime
status.

Change-Id: I522bbee6cc911cefeefba50517ebc283e2838918
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Git-commit: 66311274691ec65972cad3626057fa8d00c146d8
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[sthumma@codeaurora.org: resolve trival merge conflicts]
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>
mm: pass readahead info down to the i/o scheduler

Some i/o schedulers (i.e. row-iosched, cfq-iosched) deploy an idling
algorithm in order to be better synced with the readahead algorithm.
Idling is a prediction algorithm for incoming read requests.

In this patch we mark pages which are part of a readahead window, by
setting a newly introduced flag. With this flag, the i/o scheduler can
identify a request which is associated with a readahead page. This
enables the i/o scheduler's idling mechanism to be en-sync with the
readahead mechanism and, in turn, can increase read throughput.

Change-Id: I0654f23315b6d19d71bcc9cc029c6b281a44b196
Signed-off-by: Lee Susman <lsusman@codeaurora.org>