Commit Graph

57 Commits

Author SHA1 Message Date
Paolo Bonzini c8164d8931 scatterlist: introduce sg_unmark_end
This is useful in places that recycle the same scatterlist multiple
times, and do not want to incur the cost of sg_init_table every
time in hot paths.

Acked-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2013-03-20 15:43:04 +10:30
Martin K. Petersen 4363ac7c13 block: Implement support for WRITE SAME
The WRITE SAME command supported on some SCSI devices allows the same
block to be efficiently replicated throughout a block range. Only a
single logical block is transferred from the host and the storage device
writes the same data to all blocks described by the I/O.

This patch implements support for WRITE SAME in the block layer. The
blkdev_issue_write_same() function can be used by filesystems and block
drivers to replicate a buffer across a block range. This can be used to
efficiently initialize software RAID devices, etc.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-09-20 14:31:45 +02:00
Martin K. Petersen f31dc1cd49 block: Consolidate command flag and queue limit checks for merges
- blk_check_merge_flags() verifies that cmd_flags / bi_rw are
   compatible. This function is called for both req-req and req-bio
   merging.

 - blk_rq_get_max_sectors() and blk_queue_get_max_sectors() can be used
   to query the maximum sector count for a given request or queue. The
   calls will return the right value from the queue limits given the
   type of command (RW, discard, write same, etc.)

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-09-20 14:31:41 +02:00
Martin K. Petersen e2a60da74f block: Clean up special command handling logic
Remove special-casing of non-rw fs style requests (discard). The nomerge
flags are consolidated in blk_types.h, and rq_mergeable() and
bio_mergeable() have been modified to use them.

bio_is_rw() is used in place of bio_has_data() a few places. This is
done to to distinguish true reads and writes from other fs type requests
that carry a payload (e.g. write same).

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-09-20 14:31:38 +02:00
Asias He 85b9f66a41 block: Add blk_bio_map_sg() helper
Add a helper to map a bio to a scatterlist, modelled after
blk_rq_map_sg.

This helper is useful for any driver that wants to create
a scatterlist from its ->make_request_fn method.

Changes in v2:
 - Use __blk_segment_map_sg to avoid duplicated code
 - Add cocbook style function comment

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-08-02 23:42:04 +02:00
Asias He 963ab9e5da block: Introduce __blk_segment_map_sg() helper
Split the mapping code in blk_rq_map_sg() to a helper
__blk_segment_map_sg(), so that other mapping function, e.g.
blk_bio_map_sg(), can share the code.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Suggested-by: Jens Axboe <axboe@kernel.dk>
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-08-02 23:42:03 +02:00
Tejun Heo 050c8ea80e block: separate out blk_rq_merge_ok() and blk_try_merge() from elevator functions
blk_rq_merge_ok() is the elevator-neutral part of merge eligibility
test.  blk_try_merge() determines merge direction and expects the
caller to have tested elv_rq_merge_ok() previously.

elv_rq_merge_ok() now wraps blk_rq_merge_ok() and then calls
elv_iosched_allow_merge().  elv_try_merge() is removed and the two
callers are updated to call elv_rq_merge_ok() explicitly followed by
blk_try_merge().  While at it, make rq_merge_ok() functions return
bool.

This is to prepare for plug merge update and doesn't introduce any
behavior change.

This is based on Jens' patch to skip elevator_allow_merge_fn() from
plug merge.

Signed-off-by: Tejun Heo <tj@kernel.org>
LKML-Reference: <4F16F3CA.90904@kernel.dk>
Original-patch-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-02-08 09:19:38 +01:00
Jens Axboe 5e84ea3a9c block: attempt to merge with existing requests on plug flush
One of the disadvantages of on-stack plugging is that we potentially
lose out on merging since all pending IO isn't always visible to
everybody. When we flush the on-stack plugs, right now we don't do
any checks to see if potential merge candidates could be utilized.

Correct this by adding a new insert variant, ELEVATOR_INSERT_SORT_MERGE.
It works just ELEVATOR_INSERT_SORT, but first checks whether we can
merge with an existing request before doing the insertion (if we fail
merging).

This fixes a regression with multiple processes issuing IO that
can be merged.

Thanks to Shaohua Li <shaohua.li@intel.com> for testing and fixing
an accounting bug.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2011-03-21 10:14:27 +01:00
Linus Torvalds 275220f0fc Merge branch 'for-2.6.38/core' of git://git.kernel.dk/linux-2.6-block
* 'for-2.6.38/core' of git://git.kernel.dk/linux-2.6-block: (43 commits)
  block: ensure that completion error gets properly traced
  blktrace: add missing probe argument to block_bio_complete
  block cfq: don't use atomic_t for cfq_group
  block cfq: don't use atomic_t for cfq_queue
  block: trace event block fix unassigned field
  block: add internal hd part table references
  block: fix accounting bug on cross partition merges
  kref: add kref_test_and_get
  bio-integrity: mark kintegrityd_wq highpri and CPU intensive
  block: make kblockd_workqueue smarter
  Revert "sd: implement sd_check_events()"
  block: Clean up exit_io_context() source code.
  Fix compile warnings due to missing removal of a 'ret' variable
  fs/block: type signature of major_to_index(int) to major_to_index(unsigned)
  block: convert !IS_ERR(p) && p to !IS_ERR_NOR_NULL(p)
  cfq-iosched: don't check cfqg in choose_service_tree()
  fs/splice: Pull buf->ops->confirm() from splice_from_pipe actors
  cdrom: export cdrom_check_events()
  sd: implement sd_check_events()
  sr: implement sr_check_events()
  ...
2011-01-13 10:45:01 -08:00
Jens Axboe 6c23a9681c block: add internal hd part table references
We can't use krefs since it's apparently restricted to very basic
reference counting.

This reverts commit e4a683c8.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2011-01-07 08:43:37 +01:00
Jerome Marchand 09e099d4ba block: fix accounting bug on cross partition merges
/proc/diskstats would display a strange output as follows.

$ cat /proc/diskstats |grep sda
   8       0 sda 90524 7579 102154 20464 0 0 0 0 0 14096 20089
   8       1 sda1 19085 1352 21841 4209 0 0 0 0 4294967064 15689 4293424691
                                                ~~~~~~~~~~
   8       2 sda2 71252 3624 74891 15950 0 0 0 0 232 23995 1562390
   8       3 sda3 54 487 2188 92 0 0 0 0 0 88 92
   8       4 sda4 4 0 8 0 0 0 0 0 0 0 0
   8       5 sda5 81 2027 2130 138 0 0 0 0 0 87 137

Its reason is the wrong way of accounting hd_struct->in_flight. When a bio is
merged into a request belongs to different partition by ELEVATOR_FRONT_MERGE.

The detailed root cause is as follows.

Assuming that there are two partition, sda1 and sda2.

1. A request for sda2 is in request_queue. Hence sda1's hd_struct->in_flight
   is 0 and sda2's one is 1.

        | hd_struct->in_flight
   ---------------------------
   sda1 |          0
   sda2 |          1
   ---------------------------

2. A bio belongs to sda1 is issued and is merged into the request mentioned on
   step1 by ELEVATOR_BACK_MERGE. The first sector of the request is changed
   from sda2 region to sda1 region. However the two partition's
   hd_struct->in_flight are not changed.

        | hd_struct->in_flight
   ---------------------------
   sda1 |          0
   sda2 |          1
   ---------------------------

3. The request is finished and blk_account_io_done() is called. In this case,
   sda2's hd_struct->in_flight, not a sda1's one, is decremented.

        | hd_struct->in_flight
   ---------------------------
   sda1 |         -1
   sda2 |          1
   ---------------------------

The patch fixes the problem by caching the partition lookup
inside the request structure, hence making sure that the increment
and decrement will always happen on the same partition struct. This
also speeds up IO with accounting enabled, since it cuts down on
the number of lookups we have to do.

Also add a refcount to struct hd_struct to keep the partition in
memory as long as users exist. We use kref_test_and_get() to ensure
we don't add a reference to a partition which is going away.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2011-01-05 16:57:38 +01:00
Martin K. Petersen e692cb668f block: Deprecate QUEUE_FLAG_CLUSTER and use queue_limits instead
When stacking devices, a request_queue is not always available. This
forced us to have a no_cluster flag in the queue_limits that could be
used as a carrier until the request_queue had been set up for a
metadevice.

There were several problems with that approach. First of all it was up
to the stacking device to remember to set queue flag after stacking had
completed. Also, the queue flag and the queue limits had to be kept in
sync at all times. We got that wrong, which could lead to us issuing
commands that went beyond the max scatterlist limit set by the driver.

The proper fix is to avoid having two flags for tracking the same thing.
We deprecate QUEUE_FLAG_CLUSTER and use the queue limit directly in the
block layer merging functions. The queue_limit 'no_cluster' is turned
into 'cluster' to avoid double negatives and to ease stacking.
Clustering defaults to being enabled as before. The queue flag logic is
removed from the stacking function, and explicitly setting the cluster
flag is no longer necessary in DM and MD.

Reported-by: Ed Lin <ed.lin@promise.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-12-17 08:35:53 +01:00
Jens Axboe f253b86b4a Revert "block: fix accounting bug on cross partition merges"
This reverts commit 7681bfeecc.

Conflicts:

	include/linux/genhd.h

It has numerous issues with the cleanup path and non-elevator
devices. Revert it for now so we can come up with a clean
version without rushing things.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-10-24 22:06:02 +02:00
Linus Torvalds e9dd2b6837 Merge branch 'for-2.6.37/core' of git://git.kernel.dk/linux-2.6-block
* 'for-2.6.37/core' of git://git.kernel.dk/linux-2.6-block: (39 commits)
  cfq-iosched: Fix a gcc 4.5 warning and put some comments
  block: Turn bvec_k{un,}map_irq() into static inline functions
  block: fix accounting bug on cross partition merges
  block: Make the integrity mapped property a bio flag
  block: Fix double free in blk_integrity_unregister
  block: Ensure physical block size is unsigned int
  blkio-throttle: Fix possible multiplication overflow in iops calculations
  blkio-throttle: limit max iops value to UINT_MAX
  blkio-throttle: There is no need to convert jiffies to milli seconds
  blkio-throttle: Fix link failure failure on i386
  blkio: Recalculate the throttled bio dispatch time upon throttle limit change
  blkio: Add root group to td->tg_list
  blkio: deletion of a cgroup was causes oops
  blkio: Do not export throttle files if CONFIG_BLK_DEV_THROTTLING=n
  block: set the bounce_pfn to the actual DMA limit rather than to max memory
  block: revert bad fix for memory hotplug causing bounces
  Fix compile error in blk-exec.c for !CONFIG_DETECT_HUNG_TASK
  block: set the bounce_pfn to the actual DMA limit rather than to max memory
  block: Prevent hang_check firing during long I/O
  cfq: improve fsync performance for small files
  ...

Fix up trivial conflicts due to __rcu sparse annotation in include/linux/genhd.h
2010-10-22 17:00:32 -07:00
Yasuaki Ishimatsu 7681bfeecc block: fix accounting bug on cross partition merges
/proc/diskstats would display a strange output as follows.

$ cat /proc/diskstats |grep sda
   8       0 sda 90524 7579 102154 20464 0 0 0 0 0 14096 20089
   8       1 sda1 19085 1352 21841 4209 0 0 0 0 4294967064 15689 4293424691
                                                ~~~~~~~~~~
   8       2 sda2 71252 3624 74891 15950 0 0 0 0 232 23995 1562390
   8       3 sda3 54 487 2188 92 0 0 0 0 0 88 92
   8       4 sda4 4 0 8 0 0 0 0 0 0 0 0
   8       5 sda5 81 2027 2130 138 0 0 0 0 0 87 137

Its reason is the wrong way of accounting hd_struct->in_flight. When a bio is
merged into a request belongs to different partition by ELEVATOR_FRONT_MERGE.

The detailed root cause is as follows.

Assuming that there are two partition, sda1 and sda2.

1. A request for sda2 is in request_queue. Hence sda1's hd_struct->in_flight
   is 0 and sda2's one is 1.

        | hd_struct->in_flight
   ---------------------------
   sda1 |          0
   sda2 |          1
   ---------------------------

2. A bio belongs to sda1 is issued and is merged into the request mentioned on
   step1 by ELEVATOR_BACK_MERGE. The first sector of the request is changed
   from sda2 region to sda1 region. However the two partition's
   hd_struct->in_flight are not changed.

        | hd_struct->in_flight
   ---------------------------
   sda1 |          0
   sda2 |          1
   ---------------------------

3. The request is finished and blk_account_io_done() is called. In this case,
   sda2's hd_struct->in_flight, not a sda1's one, is decremented.

        | hd_struct->in_flight
   ---------------------------
   sda1 |         -1
   sda2 |          1
   ---------------------------

The patch fixes the problem by caching the partition lookup
inside the request structure, hence making sure that the increment
and decrement will always happen on the same partition struct. This
also speeds up IO with accounting enabled, since it cuts down on
the number of lookups we have to do.

When reloading partition tables, quiesce IO to ensure that no
request references to the partition struct exists. When it is safe
to free the partition table, the IO for that device is restarted
again.

Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-10-19 09:07:02 +02:00
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
Martin K. Petersen 13f05c8d8e block/scsi: Provide a limit on the number of integrity segments
Some controllers have a hardware limit on the number of protection
information scatter-gather list segments they can handle.

Introduce a max_integrity_segments limit in the block layer and provide
a new scsi_host_template setting that allows HBA drivers to provide a
value suitable for the hardware.

Add support for honoring the integrity segment limit when merging both
bios and requests.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@carl.home.kernel.dk>
2010-09-10 20:50:10 +02:00
Andi Kleen 2c8919dee6 gcc-4.6: block: fix unused but set variables in blk-merge
Just some dead code.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-08-07 18:23:10 +02:00
Christoph Hellwig 7b6d91daee block: unify flags for struct bio and struct request
Remove the current bio flags and reuse the request flags for the bio, too.
This allows to more easily trace the type of I/O from the filesystem
down to the block driver.  There were two flags in the bio that were
missing in the requests:  BIO_RW_UNPLUG and BIO_RW_AHEAD.  Also I've
renamed two request flags that had a superflous RW in them.

Note that the flags are in bio.h despite having the REQ_ name - as
blkdev.h includes bio.h that is the only way to go for now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-08-07 18:20:39 +02:00
Christoph Hellwig 33659ebbae block: remove wrappers for request type/flags
Remove all the trivial wrappers for the cmd_type and cmd_flags fields in
struct requests.  This allows much easier grepping for different request
types instead of unwinding through macros.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-08-07 18:17:56 +02:00
Martin K. Petersen 8a78362c4e block: Consolidate phys_segment and hw_segment limits
Except for SCSI no device drivers distinguish between physical and
hardware segment limits.  Consolidate the two into a single segment
limit.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-02-26 13:58:08 +01:00
Nikanth Karthikesan 316d315bff block: Seperate read and write statistics of in_flight requests v2
Commit a9327cac44 added seperate read
and write statistics of in_flight requests. And exported the number
of read and write requests in progress seperately through sysfs.

But  Corrado Zoccolo <czoccolo@gmail.com> reported getting strange
output from "iostat -kx 2". Global values for service time and
utilization were garbage. For interval values, utilization was always
100%, and service time is higher than normal.

So this was reverted by commit 0f78ab9899

The problem was in part_round_stats_single(), I missed the following:
        if (now == part->stamp)
                return;

-       if (part->in_flight) {
+       if (part_in_flight(part)) {
                __part_stat_add(cpu, part, time_in_queue,
                                part_in_flight(part) * (now - part->stamp));
                __part_stat_add(cpu, part, io_ticks, (now - part->stamp));

With this chunk included, the reported regression gets fixed.

Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>

--
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-06 20:16:55 +02:00
Jens Axboe 0f78ab9899 Revert "Seperate read and write statistics of in_flight requests"
This reverts commit a9327cac44.

Corrado Zoccolo <czoccolo@gmail.com> reports:

"with 2.6.32-rc1 I started getting the following strange output from
"iostat -kx 2":
Linux 2.6.31bisect (et2) 	04/10/2009 	_i686_	(2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
          10,70    0,00    3,16   15,75    0,00   70,38

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda              18,22     0,00    0,67    0,01    14,77     0,02
43,94     0,01   10,53 39043915,03 2629219,87
sdb              60,89     9,68   50,79    3,04  1724,43    50,52
65,95     0,70   13,06 488437,47 2629219,87

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           2,72    0,00    0,74    0,00    0,00   96,53

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00
sdb               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           6,68    0,00    0,99    0,00    0,00   92,33

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00
sdb               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           4,40    0,00    0,73    1,47    0,00   93,40

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00
sdb               0,00     4,00    0,00    3,00     0,00    28,00
18,67     0,06   19,50 333,33 100,00

Global values for service time and utilization are garbage. For
interval values, utilization is always 100%, and service time is
higher than normal.

I bisected it down to:
[a9327cac44] Seperate read and write
statistics of in_flight requests
and verified that reverting just that commit indeed solves the issue
on 2.6.32-rc1."

So until this is debugged, revert the bad commit.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-04 21:04:38 +02:00
Nikanth Karthikesan a9327cac44 Seperate read and write statistics of in_flight requests
Currently, there is a single in_flight counter measuring the number of
requests in the request_queue. But some monitoring tools would like to
know how many read requests and write requests are in progress. Split the
current in_flight counter into two seperate counters for read and write.

This information is exported as a sysfs attribute, as changing the
currently available stat files would break the existing tools.

Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-09-14 08:24:52 +02:00
Tejun Heo da6c5c720c scsi,block: update SCSI to handle mixed merge failures
Update scsi_io_completion() such that it only fails requests till the
next error boundary and retry the leftover.  This enables block layer
to merge requests with different failfast settings and still behave
correctly on errors.  Allow merge of requests of different failfast
settings.

As SCSI is currently the only subsystem which follows failfast status,
there's no need to worry about other block drivers for now.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Niel Lambrechts <niel.lambrechts@gmail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-09-11 14:33:30 +02:00
Tejun Heo 80a761fd33 block: implement mixed merge of different failfast requests
Failfast has characteristics from other attributes.  When issuing,
executing and successuflly completing requests, failfast doesn't make
any difference.  It only affects how a request is handled on failure.
Allowing requests with different failfast settings to be merged cause
normal IOs to fail prematurely while not allowing has performance
penalties as failfast is used for read aheads which are likely to be
located near in-flight or to-be-issued normal IOs.

This patch introduces the concept of 'mixed merge'.  A request is a
mixed merge if it is merge of segments which require different
handling on failure.  Currently the only mixable attributes are
failfast ones (or lack thereof).

When a bio with different failfast settings is added to an existing
request or requests of different failfast settings are merged, the
merged request is marked mixed.  Each bio carries failfast settings
and the request always tracks failfast state of the first bio.  When
the request fails, blk_rq_err_bytes() can be used to determine how
many bytes can be safely failed without crossing into an area which
requires further retrials.

This allows request merging regardless of failfast settings while
keeping the failure handling correct.

This patch only implements mixed merge but doesn't enable it.  The
next one will update SCSI to make use of mixed merge.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Niel Lambrechts <niel.lambrechts@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-09-11 14:33:30 +02:00
Tejun Heo ab0fd1debe block: don't merge requests of different failfast settings
Block layer used to merge requests and bios with different failfast
settings.  This caused regular IOs to fail prematurely when they were
merged into failfast requests for readahead.

Niel Lambrechts could trigger the problem semi-reliably on ext4 when
resuming from STR.  ext4 uses readahead when reading inodes and
combined with the deterministic extra SATA PHY exception cycle during
resume on the specific configuration, non-readahead inode read would
fail causing ext4 errors.  Please read the following thread for
details.

  http://lkml.org/lkml/2009/5/23/21

This patch makes block layer reject merging if the failfast settings
don't match.  This is correct but likely to lower IO performance by
preventing regular IOs from mingling into surrounding readahead
requests.  Changes to allow such mixed merges and handle errors
correctly will be added later.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Niel Lambrechts <niel.lambrechts@gmail.com>
Cc: Theodore Tso <tytso@mit.edu>
Signed-off-by: Jens Axboe <axboe@carl.(none)>
2009-07-03 21:06:45 +02:00
Martin K. Petersen ae03bf639a block: Use accessor functions for queue limits
Convert all external users of queue limits to using wrapper functions
instead of poking the request queue variables directly.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-05-22 23:22:54 +02:00
Tejun Heo a2dec7b363 block: hide request sector and data_len
Block low level drivers for some reason have been pretty good at
abusing block layer API.  Especially struct request's fields tend to
get violated in all possible ways.  Make it clear that low level
drivers MUST NOT access or manipulate rq->sector and rq->data_len
directly by prefixing them with double underscores.

This change is also necessary to break build of out-of-tree codes
which assume the previous block API where internal fields can be
manipulated and rq->data_len carries residual count on completion.

[ Impact: hide internal fields, block API change ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-05-11 09:50:55 +02:00
Tejun Heo 2e46e8b27a block: drop request->hard_* and *nr_sectors
struct request has had a few different ways to represent some
properties of a request.  ->hard_* represent block layer's view of the
request progress (completion cursor) and the ones without the prefix
are supposed to represent the issue cursor and allowed to be updated
as necessary by the low level drivers.  The thing is that as block
layer supports partial completion, the two cursors really aren't
necessary and only cause confusion.  In addition, manual management of
request detail from low level drivers is cumbersome and error-prone at
the very least.

Another interesting duplicate fields are rq->[hard_]nr_sectors and
rq->{hard_cur|current}_nr_sectors against rq->data_len and
rq->bio->bi_size.  This is more convoluted than the hard_ case.

rq->[hard_]nr_sectors are initialized for requests with bio but
blk_rq_bytes() uses it only for !pc requests.  rq->data_len is
initialized for all request but blk_rq_bytes() uses it only for pc
requests.  This causes good amount of confusion throughout block layer
and its drivers and determining the request length has been a bit of
black magic which may or may not work depending on circumstances and
what the specific LLD is actually doing.

rq->{hard_cur|current}_nr_sectors represent the number of sectors in
the contiguous data area at the front.  This is mainly used by drivers
which transfers data by walking request segment-by-segment.  This
value always equals rq->bio->bi_size >> 9.  However, data length for
pc requests may not be multiple of 512 bytes and using this field
becomes a bit confusing.

In general, having multiple fields to represent the same property
leads only to confusion and subtle bugs.  With recent block low level
driver cleanups, no driver is accessing or manipulating these
duplicate fields directly.  Drop all the duplicates.  Now rq->sector
means the current sector, rq->data_len the current total length and
rq->bio->bi_size the current segment length.  Everything else is
defined in terms of these three and available only through accessors.

* blk_recalc_rq_sectors() is collapsed into blk_update_request() and
  now handles pc and fs requests equally other than rq->sector update.
  This means that now pc requests can use partial completion too (no
  in-kernel user yet tho).

* bio_cur_sectors() is replaced with bio_cur_bytes() as block layer
  now uses byte count as the primary data length.

* blk_rq_pos() is now guranteed to be always correct.  In-block users
  converted.

* blk_rq_bytes() is now guaranteed to be always valid as is
  blk_rq_sectors().  In-block users converted.

* blk_rq_sectors() is now guaranteed to equal blk_rq_bytes() >> 9.
  More convenient one is used.

* blk_rq_bytes() and blk_rq_cur_bytes() are now inlined and take const
  pointer to request.

[ Impact: API cleanup, single way to represent one property of a request ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-05-11 09:50:54 +02:00
Tejun Heo 83096ebf12 block: convert to pos and nr_sectors accessors
With recent cleanups, there is no place where low level driver
directly manipulates request fields.  This means that the 'hard'
request fields always equal the !hard fields.  Convert all
rq->sectors, nr_sectors and current_nr_sectors references to
accessors.

While at it, drop superflous blk_rq_pos() < 0 test in swim.c.

[ Impact: use pos and nr_sectors accessors ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Tested-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Tested-by: Adrian McMenamin <adrian@mcmen.demon.co.uk>
Acked-by: Adrian McMenamin <adrian@mcmen.demon.co.uk>
Acked-by: Mike Miller <mike.miller@hp.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Borislav Petkov <petkovbb@googlemail.com>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Eric Moore <Eric.Moore@lsi.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Pete Zaitcev <zaitcev@redhat.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Paul Clements <paul.clements@steeleye.com>
Cc: Tim Waugh <tim@cyberelk.net>
Cc: Jeff Garzik <jgarzik@pobox.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Alex Dubov <oakad@yahoo.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Dario Ballabio <ballabio_dario@emc.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: unsik Kim <donari75@gmail.com>
Cc: Laurent Vivier <Laurent@lvivier.info>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-05-11 09:50:54 +02:00
Jerome Marchand 42dad7647a block: simplify I/O stat accounting
This simplifies I/O stat accounting switching code and separates it
completely from I/O scheduler switch code.

Requests are accounted according to the state of their request queue
at the time of the request allocation. There is no need anymore to
flush the request queue when switching I/O accounting state.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-24 08:54:21 +02:00
Jerome Marchand 26308eab69 block: fix inconsistency in I/O stat accounting code
This forces in_flight to be zero when turning off or on the I/O stat
accounting and stops updating I/O stats in attempt_merge() when
accounting is turned off.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-07 08:12:38 +02:00
Boaz Harrosh 1cd96c242a block: WARN in __blk_put_request() for potential bio leak
Put a WARN_ON in __blk_put_request if it is about to
leak bio(s). This is a serious bug that can happen in error
handling code paths.

For this to work I have fixed a couple of places in block/ where
request->bio != NULL ownership was not honored. And a small cleanup
at sg_io() while at it.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-03-26 11:01:23 +01:00
Jens Axboe 59247eaea5 block: fix missing bio back/front segment size setting in blk_recount_segments()
Commit 1e42807918 introduced a bug where we
don't get front/back segment sizes in the bio in blk_recount_segments().
Fix this by tracking the back bio as well as the front bio in
__blk_recalc_rq_segments(), this also cleans up the interface by getting
rid of the segment size pointer passing.

Tested-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-03-06 08:55:24 +01:00
Jens Axboe 1e42807918 block: reduce stack footprint of blk_recount_segments()
blk_recalc_rq_segments() requires a request structure passed in, which
we don't have from blk_recount_segments(). So the latter allocates one on
the stack, using > 400 bytes of stack for that. This can cause us to spill
over one page of stack from ext4 at least:

 0)     4560     400   blk_recount_segments+0x43/0x62
 1)     4160      32   bio_phys_segments+0x1c/0x24
 2)     4128      32   blk_rq_bio_prep+0x2a/0xf9
 3)     4096      32   init_request_from_bio+0xf9/0xfe
 4)     4064     112   __make_request+0x33c/0x3f6
 5)     3952     144   generic_make_request+0x2d1/0x321
 6)     3808      64   submit_bio+0xb9/0xc3
 7)     3744      48   submit_bh+0xea/0x10e
 8)     3696     368   ext4_mb_init_cache+0x257/0xa6a [ext4]
 9)     3328     288   ext4_mb_regular_allocator+0x421/0xcd9 [ext4]
10)     3040     160   ext4_mb_new_blocks+0x211/0x4b4 [ext4]
11)     2880     336   ext4_ext_get_blocks+0xb61/0xd45 [ext4]
12)     2544      96   ext4_get_blocks_wrap+0xf2/0x200 [ext4]
13)     2448      80   ext4_da_get_block_write+0x6e/0x16b [ext4]
14)     2368     352   mpage_da_map_blocks+0x7e/0x4b3 [ext4]
15)     2016     352   ext4_da_writepages+0x2ce/0x43c [ext4]
16)     1664      32   do_writepages+0x2d/0x3c
17)     1632     144   __writeback_single_inode+0x162/0x2cd
18)     1488      96   generic_sync_sb_inodes+0x1e3/0x32b
19)     1392      16   sync_sb_inodes+0xe/0x10
20)     1376      48   writeback_inodes+0x69/0xb3
21)     1328     208   balance_dirty_pages_ratelimited_nr+0x187/0x2f9
22)     1120     224   generic_file_buffered_write+0x1d4/0x2c4
23)      896     176   __generic_file_aio_write_nolock+0x35f/0x393
24)      720      80   generic_file_aio_write+0x6c/0xc8
25)      640      80   ext4_file_write+0xa9/0x137 [ext4]
26)      560     320   do_sync_write+0xf0/0x137
27)      240      48   vfs_write+0xb3/0x13c
28)      192      64   sys_write+0x4c/0x74
29)      128     128   system_call_fastpath+0x16/0x1b

Split the segment counting out into a __blk_recalc_rq_segments() helper
to avoid allocating an onstack request just for checking the physical
segment count.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-02-26 10:45:48 +01:00
FUJITA Tomonori 43381785a5 block: remove unused ll_new_mergeable()
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-11-06 08:41:55 +01:00
FUJITA Tomonori 8677142710 block: fix nr_phys_segments miscalculation bug
This fixes the bug reported by Nikanth Karthikesan <knikanth@suse.de>:

http://lkml.org/lkml/2008/10/2/203

The root cause of the bug is that blk_phys_contig_segment
miscalculates q->max_segment_size.

blk_phys_contig_segment checks:

req->biotail->bi_size + next_req->bio->bi_size > q->max_segment_size

But blk_recalc_rq_segments might expect that req->biotail and the
previous bio in the req are supposed be merged into one
segment. blk_recalc_rq_segments might also expect that next_req->bio
and the next bio in the next_req are supposed be merged into one
segment. In such case, we merge two requests that can't be merged
here. Later, blk_rq_map_sg gives more segments than it should.

We need to keep track of segment size in blk_recalc_rq_segments and
use it to see if two requests can be merged. This patch implements it
in the similar way that we used to do for hw merging (virtual
merging).

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-17 08:46:56 +02:00
Jens Axboe ab780f1ece block: inherit CPU completion on bio->rq and rq->rq merges
Somewhat incomplete, as we do allow merges of requests and bios
that have different completion CPUs given. This is done on the
assumption that a larger IO is still more beneficial than CPU
locality.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:09 +02:00
Tejun Heo 074a7aca7a block: move stats from disk to part0
Move stats related fields - stamp, in_flight, dkstats - from disk to
part0 and unify stat handling such that...

* part_stat_*() now updates part0 together if the specified partition
  is not part0.  ie. part_stat_*() are now essentially all_stat_*().

* {disk|all}_stat_*() are gone.

* part_round_stats() is updated similary.  It handles part0 stats
  automatically and disk_round_stats() is killed.

* part_{inc|dec}_in_fligh() is implemented which automatically updates
  part0 stats for parts other than part0.

* disk_map_sector_rcu() is updated to return part0 if no part matches.
  Combined with the above changes, this makes NULL special case
  handling in callers unnecessary.

* Separate stats show code paths for disk are collapsed into part
  stats show code paths.

* Rename disk_stat_lock/unlock() to part_stat_lock/unlock()

While at it, reposition stat handling macros a bit and add missing
parentheses around macro parameters.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:08 +02:00
Tejun Heo c995905916 block: fix diskstats access
There are two variants of stat functions - ones prefixed with double
underbars which don't care about preemption and ones without which
disable preemption before manipulating per-cpu counters.  It's unclear
whether the underbarred ones assume that preemtion is disabled on
entry as some callers don't do that.

This patch unifies diskstats access by implementing disk_stat_lock()
and disk_stat_unlock() which take care of both RCU (for partition
access) and preemption (for per-cpu counter access).  diskstats access
should always be enclosed between the two functions.  As such, there's
no need for the versions which disables preemption.  They're removed
and double underbars ones are renamed to drop the underbars.  As an
extra argument is added, there's no danger of using the old version
unconverted.

disk_stat_lock() uses get_cpu() and returns the cpu index and all
diskstat functions which access per-cpu counters now has @cpu
argument to help RT.

This change adds RCU or preemption operations at some places but also
collapses several preemption ops into one at others.  Overall, the
performance difference should be negligible as all involved ops are
very lightweight per-cpu ones.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:06 +02:00
Tejun Heo e71bf0d0ee block: fix disk->part[] dereferencing race
disk->part[] is protected by its matching bdev's lock.  However,
non-critical accesses like collecting stats and printing out sysfs and
proc information used to be performed without any locking.  As
partitions can come and go dynamically, partitions can go away
underneath those non-critical accesses.  As some of those accesses are
writes, this theoretically can lead to silent corruption.

This patch fixes the race by using RCU for the partition array and dev
reference counter to hold partitions.

* Rename disk->part[] to disk->__part[] to make sure no one outside
  genhd layer proper accesses it directly.

* Use RCU for disk->__part[] dereferencing.

* Implement disk_{get|put}_part() which can be used to get and put
  partitions from gendisk respectively.

* Iterators are implemented to help iterate through all partitions
  safely.

* Functions which require RCU readlock are marked with _rcu suffix.

* Use disk_put_part() in __blkdev_put() instead of directly putting
  the contained kobject.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:06 +02:00
Tejun Heo 310a2c1012 block: misc updates
This patch makes the following misc updates in preparation for
disk->part dereference fix and extended block devt support.

* implment part_to_disk()

* fix comment about gendisk->part indexing

* rename get_part() to disk_map_sector()

* don't use n which is always zero while printing disk information in
  diskstats_show()

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:04 +02:00
Mikulas Patocka 5df97b91b5 drop vmerge accounting
Remove hw_segments field from struct bio and struct request. Without virtual
merge accounting they have no purpose.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:03 +02:00
Mikulas Patocka b8b3e16cfe block: drop virtual merging accounting
Remove virtual merge accounting.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:03 +02:00
David Woodhouse e17fc0a1cc Allow elevators to sort/merge discard requests
But blkdev_issue_discard() still emits requests which are interpreted as
soft barriers, because naïve callers might otherwise issue subsequent
writes to those same sectors, which might cross on the queue (if they're
reallocated quickly enough).

Callers still _can_ issue non-barrier discard requests, but they have to
take care of queue ordering for themselves.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:02 +02:00
Martin K. Petersen 7ba1ba12ee block: Block layer data integrity support
Some block devices support verifying the integrity of requests by way
of checksums or other protection information that is submitted along
with the I/O.

This patch implements support for generating and verifying integrity
metadata, as well as correctly merging, splitting and cloning bios and
requests that have this extra information attached.

See Documentation/block/data-integrity.txt for more information.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-07-03 13:21:13 +02:00
Jens Axboe 2cdf79cafb block: get rid of likely/unlikely predictions in merge logic
They tend to depend a lot on the workload, so not a clear-cut
likely or unlikely fit.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-05-07 09:33:55 +02:00
Nick Piggin 75ad23bc0f block: make queue flags non-atomic
We can save some atomic ops in the IO path, if we clearly define
the rules of how to modify the queue flags.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-04-29 14:48:33 +02:00
FUJITA Tomonori f18573abcc block: move the padding adjustment to blk_rq_map_sg
blk_rq_map_user adjusts bi_size of the last bio. It breaks the rule
that req->data_len (the true data length) is equal to sum(bio). It
broke the scsi command completion code.

commit e97a294ef6 was introduced to fix
the above issue. However, the partial completion code doesn't work
with it. The commit is also a layer violation (scsi mid-layer should
not know about the block layer's padding).

This patch moves the padding adjustment to blk_rq_map_sg (suggested by
James). The padding works like the drain buffer. This patch breaks the
rule that req->data_len is equal to sum(sg), however, the drain buffer
already broke it. So this patch just restores the rule that
req->data_len is equal to sub(bio) without breaking anything new.

Now when a low level driver needs padding, blk_rq_map_user and
blk_rq_map_user_iov guarantee there's enough room for padding.
blk_rq_map_sg can safely extend the last entry of a scatter list.

blk_rq_map_sg must extend the last entry of a scatter list only for a
request that got through bio_copy_user_iov. This patches introduces
new REQ_COPY_USER flag.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-04-21 09:50:08 +02:00