linux-stable.git/block/blk-sysfs.c, branch linux-3.10.y

block: avoid using uninitialized value in from queue_var_store

2013-04-03T19:53:57+00:00

As found by gcc-4.8, the QUEUE_SYSFS_BIT_FNS macro creates functions
that use a value generated by queue_var_store independent of whether
that value was set or not.

block/blk-sysfs.c: In function 'queue_store_nonrot':
block/blk-sysfs.c:244:385: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]

Unlike most other such warnings, this one is not a false positive,
writing any non-number string into the sysfs files indeed has
an undefined result, rather than returning an error.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Jens Axboe

block: RCU free request_queue

2013-01-09T16:05:13+00:00

RCU free request_queue so that blkcg_gq->q can be dereferenced under
RCU lock.  This will be used to implement hierarchical stats.

Signed-off-by: Tejun Heo 
Acked-by: Vivek Goyal

block: Rename queue dead flag

2012-12-06T13:30:58+00:00

QUEUE_FLAG_DEAD is used to indicate that queuing new requests must
stop. After this flag has been set queue draining starts. However,
during the queue draining phase it is still safe to invoke the
queue's request_fn, so QUEUE_FLAG_DYING is a better name for this
flag.

This patch has been generated by running the following command
over the kernel source tree:

git grep -lEw 'blk_queue_dead|QUEUE_FLAG_DEAD' |
    xargs sed -i.tmp -e 's/blk_queue_dead/blk_queue_dying/g'      \
        -e 's/QUEUE_FLAG_DEAD/QUEUE_FLAG_DYING/g';                \
sed -i.tmp -e "s/QUEUE_FLAG_DYING$(printf \\t)*5/QUEUE_FLAG_DYING$(printf \\t)5/g" \
    include/linux/blkdev.h;                                       \
sed -i.tmp -e 's/ DEAD/ DYING/g' -e 's/dead queue/a dying queue/' \
    -e 's/Dead queue/A dying queue/' block/blk-core.c

Signed-off-by: Bart Van Assche 
Acked-by: Tejun Heo 
Cc: James Bottomley 
Cc: Mike Christie 
Cc: Jens Axboe 
Cc: Chanho Min 
Signed-off-by: Jens Axboe

block: lift the initial queue bypass mode on blk_register_queue() instead of blk_init_allocated_queue()

2012-09-21T13:32:57+00:00

b82d4b197c ("blkcg: make request_queue bypassing on allocation") made
request_queues bypassed on allocation to avoid switching on and off
bypass mode on a queue being initialized.  Some drivers allocate and
then destroy a lot of queues without fully initializing them and
incurring bypass latency overhead on each of them could add upto
significant overhead.

Unfortunately, blk_init_allocated_queue() is never used by queues of
bio-based drivers, which means that all bio-based driver queues are in
bypass mode even after initialization and registration complete
successfully.

Due to the limited way request_queues are used by bio drivers, this
problem is hidden pretty well but it shows up when blk-throttle is
used in combination with a bio-based driver.  Trying to configure
(echoing to cgroupfs file) blk-throttle for a bio-based driver hangs
indefinitely in blkg_conf_prep() waiting for bypass mode to end.

This patch moves the initial blk_queue_bypass_end() call from
blk_init_allocated_queue() to blk_register_queue() which is called for
any userland-visible queues regardless of its type.

I believe this is correct because I don't think there is any block
driver which needs or wants working elevator and blk-cgroup on a queue
which isn't visible to userland.  If there are such users, we need a
different solution.

Signed-off-by: Tejun Heo 
Reported-by: Joseph Glanville 
Cc: stable@vger.kernel.org
Acked-by: Vivek Goyal 
Signed-off-by: Jens Axboe

block: Implement support for WRITE SAME

2012-09-20T12:31:45+00:00

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 
Acked-by: Mike Snitzer 
Signed-off-by: Jens Axboe

block: reject invalid queue attribute values

2012-09-09T08:39:18+00:00

Instead of using simple_strtoul which "converts" invalid numbers to 0,
use strict_strtoul and perform error checking to ensure that userspace
passes us a valid unsigned long. This addresses problems with functions
such as writev, which might want to write a trailing newline -- the
newline should rightfully be rejected, but the value preceeding it
should be preserved.

Fixes BZ#46981.

Signed-off-by: Dave Reisner 
Signed-off-by: Jens Axboe

blkcg: implement per-blkg request allocation

2012-06-26T22:42:49+00:00

Currently, request_queue has one request_list to allocate requests
from regardless of blkcg of the IO being issued.  When the unified
request pool is used up, cfq proportional IO limits become meaningless
- whoever grabs the next request being freed wins the race regardless
of the configured weights.

This can be easily demonstrated by creating a blkio cgroup w/ very low
weight, put a program which can issue a lot of random direct IOs there
and running a sequential IO from a different cgroup.  As soon as the
request pool is used up, the sequential IO bandwidth crashes.

This patch implements per-blkg request_list.  Each blkg has its own
request_list and any IO allocates its request from the matching blkg
making blkcgs completely isolated in terms of request allocation.

* Root blkcg uses the request_list embedded in each request_queue,
  which was renamed to @q->root_rl from @q->rq.  While making blkcg rl
  handling a bit harier, this enables avoiding most overhead for root
  blkcg.

* Queue fullness is properly per request_list but bdi isn't blkcg
  aware yet, so congestion state currently just follows the root
  blkcg.  As writeback isn't aware of blkcg yet, this works okay for
  async congestion but readahead may get the wrong signals.  It's
  better than blkcg completely collapsing with shared request_list but
  needs to be improved with future changes.

* After this change, each block cgroup gets a full request pool making
  resource consumption of each cgroup higher.  This makes allowing
  non-root users to create cgroups less desirable; however, note that
  allowing non-root users to directly manage cgroups is already
  severely broken regardless of this patch - each block cgroup
  consumes kernel memory and skews IO weight (IO weights are not
  hierarchical).

v2: queue-sysfs.txt updated and patch description udpated as suggested
    by Vivek.

v3: blk_get_rl() wasn't checking error return from
    blkg_lookup_create() and may cause oops on lookup failure.  Fix it
    by falling back to root_rl on blkg lookup failures.  This problem
    was spotted by Rakesh Iyer .

v4: Updated to accomodate 458f27a982 "block: Avoid missed wakeup in
    request waitqueue".  blk_drain_queue() now wakes up waiters on all
    blkg->rl on the target queue.

Signed-off-by: Tejun Heo 
Acked-by: Vivek Goyal 
Cc: Wu Fengguang 
Signed-off-by: Jens Axboe

block: prepare for multiple request_lists

2012-06-25T09:53:52+00:00

Request allocation is about to be made per-blkg meaning that there'll
be multiple request lists.

* Make queue full state per request_list.  blk_*queue_full() functions
  are renamed to blk_*rl_full() and takes @rl instead of @q.

* Rename blk_init_free_list() to blk_init_rl() and make it take @rl
  instead of @q.  Also add @gfp_mask parameter.

* Add blk_exit_rl() instead of destroying rl directly from
  blk_release_queue().

* Add request_list->q and make request alloc/free functions -
  blk_free_request(), [__]freed_request(), __get_request() - take @rl
  instead of @q.

This patch doesn't introduce any functional difference.

Signed-off-by: Tejun Heo 
Acked-by: Vivek Goyal 
Signed-off-by: Jens Axboe

blkcg: unify blkg's for blkcg policies

2012-03-06T20:27:23+00:00

Currently, blkg is per cgroup-queue-policy combination.  This is
unnatural and leads to various convolutions in partially used
duplicate fields in blkg, config / stat access, and general management
of blkgs.

This patch make blkg's per cgroup-queue and let them serve all
policies.  blkgs are now created and destroyed by blkcg core proper.
This will allow further consolidation of common management logic into
blkcg core and API with better defined semantics and layering.

As a transitional step to untangle blkg management, elvswitch and
policy [de]registration, all blkgs except the root blkg are being shot
down during elvswitch and bypass.  This patch adds blkg_root_update()
to update root blkg in place on policy change.  This is hacky and racy
but should be good enough as interim step until we get locking
simplified and switch over to proper in-place update for all blkgs.

-v2: Root blkgs need to be updated on elvswitch too and blkg_alloc()
     comment wasn't updated according to the function change.  Fixed.
     Both pointed out by Vivek.

-v3: v2 updated blkg_destroy_all() to invoke update_root_blkg_pd() for
     all policies.  This freed root pd during elvswitch before the
     last queue finished exiting and led to oops.  Directly invoke
     update_root_blkg_pd() only on BLKIO_POLICY_PROP from
     cfq_exit_queue().  This also is closer to what will be done with
     proper in-place blkg update.  Reported by Vivek.

Signed-off-by: Tejun Heo 
Cc: Vivek Goyal 
Signed-off-by: Jens Axboe

blkcg: add blkcg_{init|drain|exit}_queue()

2012-03-06T20:27:23+00:00

Currently block core calls directly into blk-throttle for init, drain
and exit.  This patch adds blkcg_{init|drain|exit}_queue() which wraps
the blk-throttle functions.  This is to give more control and
visiblity to blkcg core layer for proper layering.  Further patches
will add logic common to blkcg policies to the functions.

While at it, collapse blk_throtl_release() into blk_throtl_exit().
There's no reason to keep them separate.

Signed-off-by: Tejun Heo 
Cc: Vivek Goyal 
Signed-off-by: Jens Axboe