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Adrian Hunter f281fb5fe5 block: prevent merges of discard and write requests 
Add logic to prevent two I/O requests being merged if
only one of them is a discard.  Ditto secure discard.

Without this fix, it is possible for write requests
to transform into discard requests.  For example:

  Submit bio 1 to discard 8 sectors from sector n
  Submit bio 2 to write 8 sectors from sector n + 16
  Submit bio 3 to write 8 sectors from sector n + 8

Bio 1 becomes request 1.  Bio 2 becomes request 2.
Bio 3 is merged with request 2, and then subsequently
request 2 is merged with request 1 resulting in just
one I/O request which discards all 24 sectors.

Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>

(Moved the checks above the position checks /Jens)

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
 		2010-09-25 12:42:55 +02:00
..
Kconfig blk-cgroup: config options re-arrangement 2010-04-26 19:27:56 +02:00
Kconfig.iosched blk-cgroup: config options re-arrangement 2010-04-26 19:27:56 +02:00
Makefile blkdev: move blkdev_issue helper functions to separate file 2010-04-28 19:47:36 +02:00
blk-barrier.c block: set up rq->rq_disk properly for flush requests 2010-08-07 18:52:41 +02:00
blk-cgroup.c blkio: Fix return code for mkdir calls 2010-08-23 10:56:30 +02:00
blk-cgroup.h blk-cgroup: config options re-arrangement 2010-04-26 19:27:56 +02:00
blk-core.c BLOCK: fix bio.bi_rw handling 2010-08-23 12:33:10 +02:00
blk-exec.c block: remove wrappers for request type/flags 2010-08-07 18:17:56 +02:00
blk-integrity.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
blk-ioc.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
blk-iopoll.c tree-wide: fix assorted typos all over the place 2009-12-04 15:39:55 +01:00
blk-lib.c block: add secure discard 2010-08-12 08:43:30 -07:00
blk-map.c block: fix blk_rq_map_kern bio direction flag 2010-09-21 11:49:17 +02:00
blk-merge.c block: prevent merges of discard and write requests 2010-09-25 12:42:55 +02:00
blk-settings.c block: implement an unprep function corresponding directly to prep 2010-08-07 18:23:47 +02:00
blk-softirq.c generic-ipi: remove CSD_FLAG_WAIT 2009-02-25 14:13:44 +01:00
blk-sysfs.c block: put dev->kobj in blk_register_queue fail path 2010-08-23 12:30:29 +02:00
blk-tag.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
blk-timeout.c block: ensure jiffies wrap is handled correctly in blk_rq_timed_out_timer 2010-04-21 17:42:08 +02:00
blk.h block: Range check cpu in blk_cpu_to_group 2010-09-10 09:03:21 +02:00
bsg.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
cfq-iosched.c cfq-iosched: fix a kernel OOPs when usb key is inserted 2010-09-21 11:49:17 +02:00
cfq.h cfq: fix recursive call in cfq_blkiocg_update_completion_stats() 2010-06-21 09:10:55 +02:00
compat_ioctl.c block: add secure discard 2010-08-12 08:43:30 -07:00
deadline-iosched.c block: convert to pos and nr_sectors accessors 2009-05-11 09:50:54 +02:00
elevator.c block: add function call to switch the IO scheduler from a driver 2010-08-23 13:52:19 +02:00
genhd.c block: remove all rcu head initializations 2010-05-21 20:01:02 +02:00
ioctl.c block: add secure discard 2010-08-12 08:43:30 -07:00
noop-iosched.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
scsi_ioctl.c block/scsi_ioctl.c: quiet sparse noise 2009-11-04 09:10:33 +01:00