19 Oct, 2011
4 commits
-
request_queue is refcounted but actually depdends on lifetime
management from the queue owner - on blk_cleanup_queue(), block layer
expects that there's no request passing through request_queue and no
new one will.This is fundamentally broken. The queue owner (e.g. SCSI layer)
doesn't have a way to know whether there are other active users before
calling blk_cleanup_queue() and other users (e.g. bsg) don't have any
guarantee that the queue is and would stay valid while it's holding a
reference.With delay added in blk_queue_bio() before queue_lock is grabbed, the
following oops can be easily triggered when a device is removed with
in-flight IOs.sd 0:0:1:0: [sdb] Stopping disk
ata1.01: disabled
general protection fault: 0000 [#1] PREEMPT SMP
CPU 2
Modules linked in:Pid: 648, comm: test_rawio Not tainted 3.1.0-rc3-work+ #56 Bochs Bochs
RIP: 0010:[] [] elv_rqhash_find+0x61/0x100
...
Process test_rawio (pid: 648, threadinfo ffff880019efa000, task ffff880019ef8a80)
...
Call Trace:
[] elv_merge+0x84/0xe0
[] blk_queue_bio+0xf4/0x400
[] generic_make_request+0xca/0x100
[] submit_bio+0x74/0x100
[] dio_bio_submit+0xbc/0xc0
[] __blockdev_direct_IO+0x92e/0xb40
[] blkdev_direct_IO+0x57/0x60
[] generic_file_aio_read+0x6d5/0x760
[] do_sync_read+0xda/0x120
[] vfs_read+0xc5/0x180
[] sys_pread64+0x9a/0xb0
[] system_call_fastpath+0x16/0x1bThis happens because blk_queue_cleanup() destroys the queue and
elevator whether IOs are in progress or not and DEAD tests are
sprinkled in the request processing path without proper
synchronization.Similar problem exists for blk-throtl. On queue cleanup, blk-throtl
is shutdown whether it has requests in it or not. Depending on
timing, it either oopses or throttled bios are lost putting tasks
which are waiting for bio completion into eternal D state.The way it should work is having the usual clear distinction between
shutdown and release. Shutdown drains all currently pending requests,
marks the queue dead, and performs partial teardown of the now
unnecessary part of the queue. Even after shutdown is complete,
reference holders are still allowed to issue requests to the queue
although they will be immmediately failed. The rest of teardown
happens on release.This patch makes the following changes to make blk_queue_cleanup()
behave as proper shutdown.* QUEUE_FLAG_DEAD is now set while holding both q->exit_mutex and
queue_lock.* Unsynchronized DEAD check in generic_make_request_checks() removed.
This couldn't make any meaningful difference as the queue could die
after the check.* blk_drain_queue() updated such that it can drain all requests and is
now called during cleanup.* blk_throtl updated such that it checks DEAD on grabbing queue_lock,
drains all throttled bios during cleanup and free td when queue is
released.Signed-off-by: Tejun Heo
Cc: Vivek Goyal
Signed-off-by: Jens Axboe -
blk_throtl_bio() and throtl_get_tg() have rather unusual interface.
* throtl_get_tg() returns pointer to a valid tg or ERR_PTR(-ENODEV),
and drops queue_lock in the latter case. Different locking context
depending on return value is error-prone and DEAD state is scheduled
to be protected by queue_lock anyway. Move DEAD check inside
queue_lock and return valid tg or NULL.* blk_throtl_bio() indicates return status both with its return value
and in/out param **@bio. The former is used to indicate whether
queue is found to be dead during throtl processing. The latter
whether the bio is throttled.There's no point in returning DEAD check result from
blk_throtl_bio(). The queue can die after blk_throtl_bio() is
finished but before make_request_fn() grabs queue lock.Make it take *@bio instead and return boolean result indicating
whether the request is throttled or not.This patch doesn't cause any visible functional difference.
Signed-off-by: Tejun Heo
Cc: Vivek Goyal
Signed-off-by: Jens Axboe -
Reorganize queue draining related code in preparation of queue exit
changes.* Factor out actual draining from elv_quiesce_start() to
blk_drain_queue().* Make elv_quiesce_start/end() responsible for their own locking.
* Replace open-coded ELVSWITCH clearing in elevator_switch() with
elv_quiesce_end().This patch doesn't cause any visible functional difference.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
blk_throtl interface is block internal and there's no reason to have
them in linux/blkdev.h. Move them to block/blk.h.This patch doesn't introduce any functional change.
Signed-off-by: Tejun Heo
Cc: Vivek Goyal
Signed-off-by: Jens Axboe
16 Aug, 2011
1 commit
-
Commit ae1b1539622fb46e51b4d13b3f9e5f4c713f86ae, block: reimplement
FLUSH/FUA to support merge, introduced a performance regression when
running any sort of fsyncing workload using dm-multipath and certain
storage (in our case, an HP EVA). The test I ran was fs_mark, and it
dropped from ~800 files/sec on ext4 to ~100 files/sec. It turns out
that dm-multipath always advertised flush+fua support, and passed
commands on down the stack, where those flags used to get stripped off.
The above commit changed that behavior:static inline struct request *__elv_next_request(struct request_queue *q)
{
struct request *rq;while (1) {
- while (!list_empty(&q->queue_head)) {
+ if (!list_empty(&q->queue_head)) {
rq = list_entry_rq(q->queue_head.next);
- if (!(rq->cmd_flags & (REQ_FLUSH | REQ_FUA)) ||
- (rq->cmd_flags & REQ_FLUSH_SEQ))
- return rq;
- rq = blk_do_flush(q, rq);
- if (rq)
- return rq;
+ return rq;
}Note that previously, a command would come in here, have
REQ_FLUSH|REQ_FUA set, and then get handed off to blk_do_flush:struct request *blk_do_flush(struct request_queue *q, struct request *rq)
{
unsigned int fflags = q->flush_flags; /* may change, cache it */
bool has_flush = fflags & REQ_FLUSH, has_fua = fflags & REQ_FUA;
bool do_preflush = has_flush && (rq->cmd_flags & REQ_FLUSH);
bool do_postflush = has_flush && !has_fua && (rq->cmd_flags &
REQ_FUA);
unsigned skip = 0;
...
if (blk_rq_sectors(rq) && !do_preflush && !do_postflush) {
rq->cmd_flags &= ~REQ_FLUSH;
if (!has_fua)
rq->cmd_flags &= ~REQ_FUA;
return rq;
}So, the flush machinery was bypassed in such cases (q->flush_flags == 0
&& rq->cmd_flags & (REQ_FLUSH|REQ_FUA)).Now, however, we don't get into the flush machinery at all. Instead,
__elv_next_request just hands a request with flush and fua bits set to
the scsi_request_fn, even if the underlying request_queue does not
support flush or fua.The agreed upon approach is to fix the flush machinery to allow
stacking. While this isn't used in practice (since there is only one
request-based dm target, and that target will now reflect the flush
flags of the underlying device), it does future-proof the solution, and
make it function as designed.In order to make this work, I had to add a field to the struct request,
inside the flush structure (to store the original req->end_io). Shaohua
had suggested overloading the union with rb_node and completion_data,
but the completion data is used by device mapper and can also be used by
other drivers. So, I didn't see a way around the additional field.I tested this patch on an HP EVA with both ext4 and xfs, and it recovers
the lost performance. Comments and other testers, as always, are
appreciated.Cheers,
JeffSigned-off-by: Jeff Moyer
Acked-by: Tejun Heo
Signed-off-by: Jens Axboe
21 May, 2011
2 commits
-
This patch merges in a fix that missed 2.6.39 final.
Conflicts:
block/blk.h -
Since for-2.6.40/core was forked off the 2.6.39 devel tree, we've
had churn in the core area that makes it difficult to handle
patches for eg cfq or blk-throttle. Instead of requiring that they
be based in older versions with bugs that have been fixed later
in the rc cycle, merge in 2.6.39 final.Also fixes up conflicts in the below files.
Conflicts:
drivers/block/paride/pcd.c
drivers/cdrom/viocd.c
drivers/ide/ide-cd.cSigned-off-by: Jens Axboe
19 May, 2011
1 commit
-
blk_cleanup_queue() calls elevator_exit() and after this, we can't
touch the elevator without oopsing. __elv_next_request() must check
for this state because in the refcounted queue model, we can still
call it after blk_cleanup_queue() has been called.This was reported as causing an oops attributable to scsi.
Signed-off-by: James Bottomley
Cc: stable@kernel.org
Signed-off-by: Jens Axboe
07 May, 2011
1 commit
-
In some drives, flush requests are non-queueable. When flush request is
running, normal read/write requests can't run. If block layer dispatches
such request, driver can't handle it and requeue it. Tejun suggested we
can hold the queue when flush is running. This can avoid unnecessary
requeue. Also this can improve performance. For example, we have
request flush1, write1, flush 2. flush1 is dispatched, then queue is
hold, write1 isn't inserted to queue. After flush1 is finished, flush2
will be dispatched. Since disk cache is already clean, flush2 will be
finished very soon, so looks like flush2 is folded to flush1.In my test, the queue holding completely solves a regression introduced by
commit 53d63e6b0dfb95882ec0219ba6bbd50cde423794:block: make the flush insertion use the tail of the dispatch list
It's not a preempt type request, in fact we have to insert it
behind requests that do specify INSERT_FRONT.which causes about 20% regression running a sysbench fileio
workload.Stable: 2.6.39 only
Cc: stable@kernel.org
Signed-off-by: Shaohua Li
Acked-by: Tejun Heo
Signed-off-by: Jens Axboe
19 Apr, 2011
1 commit
-
We are currently using this flag to check whether it's safe
to call into ->request_fn(). If it is set, we punt to kblockd.
But we get a lot of false positives and excessive punts to
kblockd, which hurts performance.The only real abuser of this infrastructure is SCSI. So export
the async queue run and convert SCSI over to use that. There's
room for improvement in that SCSI need not always use the async
call, but this fixes our performance issue and they can fix that
up in due time.Signed-off-by: Jens Axboe
18 Apr, 2011
1 commit
-
Instead of overloading __blk_run_queue to force an offload to kblockd
add a new blk_run_queue_async helper to do it explicitly. I've kept
the blk_queue_stopped check for now, but I suspect it's not needed
as the check we do when the workqueue items runs should be enough.Signed-off-by: Christoph Hellwig
Signed-off-by: Jens Axboe
31 Mar, 2011
1 commit
-
Fixes generated by 'codespell' and manually reviewed.
Signed-off-by: Lucas De Marchi
21 Mar, 2011
1 commit
-
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 for testing and fixing
an accounting bug.Signed-off-by: Jens Axboe
10 Mar, 2011
1 commit
-
Code has been converted over to the new explicit on-stack plugging,
and delay users have been converted to use the new API for that.
So lets kill off the old plugging along with aops->sync_page().Signed-off-by: Jens Axboe
25 Jan, 2011
2 commits
-
The current FLUSH/FUA support has evolved from the implementation
which had to perform queue draining. As such, sequencing is done
queue-wide one flush request after another. However, with the
draining requirement gone, there's no reason to keep the queue-wide
sequential approach.This patch reimplements FLUSH/FUA support such that each FLUSH/FUA
request is sequenced individually. The actual FLUSH execution is
double buffered and whenever a request wants to execute one for either
PRE or POSTFLUSH, it queues on the pending queue. Once certain
conditions are met, a flush request is issued and on its completion
all pending requests proceed to the next sequence.This allows arbitrary merging of different type of flushes. How they
are merged can be primarily controlled and tuned by adjusting the
above said 'conditions' used to determine when to issue the next
flush.This is inspired by Darrick's patches to merge multiple zero-data
flushes which helps workloads with highly concurrent fsync requests.* As flush requests are never put on the IO scheduler, request fields
used for flush share space with rq->rb_node. rq->completion_data is
moved out of the union. This increases the request size by one
pointer.As rq->elevator_private* are used only by the iosched too, it is
possible to reduce the request size further. However, to do that,
we need to modify request allocation path such that iosched data is
not allocated for flush requests.* FLUSH/FUA processing happens on insertion now instead of dispatch.
- Comments updated as per Vivek and Mike.
Signed-off-by: Tejun Heo
Cc: "Darrick J. Wong"
Cc: Shaohua Li
Cc: Christoph Hellwig
Cc: Vivek Goyal
Cc: Mike Snitzer
Signed-off-by: Jens Axboe -
rq == &q->flush_rq was used to determine whether a rq is part of a
flush sequence, which worked because all requests in a flush sequence
were sequenced using the single dedicated request. This is about to
change, so introduce REQ_FLUSH_SEQ flag to distinguish flush sequence
requests.This patch doesn't cause any behavior change.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe
25 Oct, 2010
1 commit
-
This reverts commit 7681bfeeccff5efa9eb29bf09249a3c400b15327.
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
23 Oct, 2010
2 commits
-
* 'for-2.6.37/barrier' of git://git.kernel.dk/linux-2.6-block: (46 commits)
xen-blkfront: disable barrier/flush write support
Added blk-lib.c and blk-barrier.c was renamed to blk-flush.c
block: remove BLKDEV_IFL_WAIT
aic7xxx_old: removed unused 'req' variable
block: remove the BH_Eopnotsupp flag
block: remove the BLKDEV_IFL_BARRIER flag
block: remove the WRITE_BARRIER flag
swap: do not send discards as barriers
fat: do not send discards as barriers
ext4: do not send discards as barriers
jbd2: replace barriers with explicit flush / FUA usage
jbd2: Modify ASYNC_COMMIT code to not rely on queue draining on barrier
jbd: replace barriers with explicit flush / FUA usage
nilfs2: replace barriers with explicit flush / FUA usage
reiserfs: replace barriers with explicit flush / FUA usage
gfs2: replace barriers with explicit flush / FUA usage
btrfs: replace barriers with explicit flush / FUA usage
xfs: replace barriers with explicit flush / FUA usage
block: pass gfp_mask and flags to sb_issue_discard
dm: convey that all flushes are processed as empty
... -
* '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
19 Oct, 2010
2 commits
-
Conflicts:
block/blk-core.c
drivers/block/loop.c
mm/swapfile.cSigned-off-by: Jens Axboe
-
/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 137Its 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
Cc: stable@kernel.org
Signed-off-by: Jens Axboe
11 Sep, 2010
1 commit
-
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
Signed-off-by: Jens Axboe
10 Sep, 2010
5 commits
-
Now that the backend conversion is complete, export sequenced
FLUSH/FUA capability through REQ_FLUSH/FUA flags. REQ_FLUSH means the
device cache should be flushed before executing the request. REQ_FUA
means that the data in the request should be on non-volatile media on
completion.Block layer will choose the correct way of implementing the semantics
and execute it. The request may be passed to the device directly if
the device can handle it; otherwise, it will be sequenced using one or
more proxy requests. Devices will never see REQ_FLUSH and/or FUA
which it doesn't support.Also, unlike the original REQ_HARDBARRIER, REQ_FLUSH/FUA requests are
never failed with -EOPNOTSUPP. If the underlying device doesn't
support FLUSH/FUA, the block layer simply make those noop. IOW, it no
longer distinguishes between writeback cache which doesn't support
cache flush and writethrough/no cache. Devices which have WB cache
w/o flush are very difficult to come by these days and there's nothing
much we can do anyway, so it doesn't make sense to require everyone to
implement -EOPNOTSUPP handling. This will simplify filesystems and
block drivers as they can drop -EOPNOTSUPP retry logic for barriers.* QUEUE_ORDERED_* are removed and QUEUE_FSEQ_* are moved into
blk-flush.c.* REQ_FLUSH w/o data can also be directly passed to drivers without
sequencing but some drivers assume that zero length requests don't
have rq->bio which isn't true for these requests requiring the use
of proxy requests.* REQ_COMMON_MASK now includes REQ_FLUSH | REQ_FUA so that they are
copied from bio to request.* WRITE_BARRIER is marked deprecated and WRITE_FLUSH, WRITE_FUA and
WRITE_FLUSH_FUA are added.Signed-off-by: Tejun Heo
Cc: Christoph Hellwig
Signed-off-by: Jens Axboe -
With ordering requirements dropped, barrier and ordered are misnomers.
Now all block layer does is sequencing FLUSH and FUA. Rename them to
flush.Signed-off-by: Tejun Heo
Cc: Christoph Hellwig
Signed-off-by: Jens Axboe -
Filesystems will take all the responsibilities for ordering requests
around commit writes and will only indicate how the commit writes
themselves should be handled by block layers. This patch drops
barrier ordering by queue draining from block layer. Ordering by
draining implementation was somewhat invasive to request handling.
List of notable changes follow.* Each queue has 1 bit color which is flipped on each barrier issue.
This is used to track whether a given request is issued before the
current barrier or not. REQ_ORDERED_COLOR flag and coloring
implementation in __elv_add_request() are removed.* Requests which shouldn't be processed yet for draining were stalled
by returning -EAGAIN from blk_do_ordered() according to the test
result between blk_ordered_req_seq() and blk_blk_ordered_cur_seq().
This logic is removed.* Draining completion logic in elv_completed_request() removed.
* All barrier sequence requests were queued to request queue and then
trckled to lower layer according to progress and thus maintaining
request orders during requeue was necessary. This is replaced by
queueing the next request in the barrier sequence only after the
current one is complete from blk_ordered_complete_seq(), which
removes the need for multiple proxy requests in struct request_queue
and the request sorting logic in the ELEVATOR_INSERT_REQUEUE path of
elv_insert().* As barriers no longer have ordering constraints, there's no need to
dump the whole elevator onto the dispatch queue on each barrier.
Insert barriers at the front instead.* If other barrier requests come to the front of the dispatch queue
while one is already in progress, they are stored in
q->pending_barriers and restored to dispatch queue one-by-one after
each barrier completion from blk_ordered_complete_seq().Signed-off-by: Tejun Heo
Cc: Christoph Hellwig
Signed-off-by: Jens Axboe -
Make the following cleanups in preparation of barrier/flush update.
* blk_do_ordered() declaration is moved from include/linux/blkdev.h to
block/blk.h.* blk_do_ordered() now returns pointer to struct request, with %NULL
meaning "try the next request" and ERR_PTR(-EAGAIN) "try again
later". The third case will be dropped with further changes.* In the initialization of proxy barrier request, data direction is
already set by init_request_from_bio(). Drop unnecessary explicit
REQ_WRITE setting and move init_request_from_bio() above REQ_FUA
flag setting.* add_request() is collapsed into __make_request().
These changes don't make any functional difference.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
While testing CPU DLPAR, the following problem was discovered.
We were DLPAR removing the first CPU, which in this case was
logical CPUs 0-3. CPUs 0-2 were already marked offline and
we were in the process of offlining CPU 3. After marking
the CPU inactive and offline in cpu_disable, but before the
cpu was completely idle (cpu_die), we ended up in __make_request
on CPU 3. There we looked at the topology map to see which CPU
to complete the I/O on and found no CPUs in the cpu_sibling_map.
This resulted in the block layer setting the completion cpu
to be NR_CPUS, which then caused an oops when we tried to
complete the I/O.Fix this by sanity checking the value we return from blk_cpu_to_group
to be a valid cpu value.Signed-off-by: Brian King
Signed-off-by: Jens Axboe
08 Aug, 2010
1 commit
-
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
Signed-off-by: Jens Axboe
11 Sep, 2009
1 commit
-
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
Cc: Niel Lambrechts
Signed-off-by: Jens Axboe
27 May, 2009
1 commit
-
The commit below in 2.6-block/for-2.6.31 causes no diskstat problem
because the blk_discard_rq() check was added with '&&'.
It should be 'blk_fs_request() || blk_discard_rq()'.
This patch does it and fixes the no diskstat problem.
Please review and apply.------ /proc/diskstat without this patch -------------------------------------
8 0 sda 0 0 0 0 0 0 0 0 0 0 0
----------------------------------------------------------------------------------- /proc/diskstat with this patch applied ---------------------------------
8 0 sda 4186 303 373621 61600 9578 3859 107468 169479 2 89755 231059
--------------------------------------------------------------------------------------------------------------------------------------------------------
commit c69d48540c201394d08cb4d48b905e001313d9b8
Author: Jens Axboe
Date: Fri Apr 24 08:12:19 2009 +0200block: include discard requests in IO accounting
We currently don't do merging on discard requests, but we potentially
could. If we do, then we need to include discard requests in the IO
accounting, or merging would end up decrementing in_flight IO counters
for an IO which never incremented them.So enable accounting for discard requests.
static inline int blk_do_io_stat(struct request *rq)
{
- return rq->rq_disk && blk_rq_io_stat(rq) && blk_fs_request(rq);
+ return rq->rq_disk && blk_rq_io_stat(rq) && blk_fs_request(rq) &&
+ blk_discard_rq(rq);
}
--------------------------------------------------------------------------Signed-off-by: Kiyoshi Ueda
Signed-off-by: Jun'ichi Nomura
Signed-off-by: Jens Axboe
19 May, 2009
1 commit
-
OSD was the last in-tree user of blk_rq_append_bio(). Now
that it is fixed blk_rq_append_bio is un-exported and
is only used internally by block layer.Signed-off-by: Boaz Harrosh
Signed-off-by: Jens Axboe
11 May, 2009
2 commits
-
Till now block layer allowed two separate modes of request execution.
A request is always acquired from the request queue via
elv_next_request(). After that, drivers are free to either dequeue it
or process it without dequeueing. Dequeue allows elv_next_request()
to return the next request so that multiple requests can be in flight.Executing requests without dequeueing has its merits mostly in
allowing drivers for simpler devices which can't do sg to deal with
segments only without considering request boundary. However, the
benefit this brings is dubious and declining while the cost of the API
ambiguity is increasing. Segment based drivers are usually for very
old or limited devices and as converting to dequeueing model isn't
difficult, it doesn't justify the API overhead it puts on block layer
and its more modern users.Previous patches converted all block low level drivers to dequeueing
model. This patch completes the API transition by...* renaming elv_next_request() to blk_peek_request()
* renaming blkdev_dequeue_request() to blk_start_request()
* adding blk_fetch_request() which is combination of peek and start
* disallowing completion of queued (not started) requests
* applying new API to all LLDs
Renamings are for consistency and to break out of tree code so that
it's apparent that out of tree drivers need updating.[ Impact: block request issue API cleanup, no functional change ]
Signed-off-by: Tejun Heo
Cc: Rusty Russell
Cc: James Bottomley
Cc: Mike Miller
Cc: unsik Kim
Cc: Paul Clements
Cc: Tim Waugh
Cc: Geert Uytterhoeven
Cc: David S. Miller
Cc: Laurent Vivier
Cc: Jeff Garzik
Cc: Jeremy Fitzhardinge
Cc: Grant Likely
Cc: Adrian McMenamin
Cc: Stephen Rothwell
Cc: Bartlomiej Zolnierkiewicz
Cc: Borislav Petkov
Cc: Sergei Shtylyov
Cc: Alex Dubov
Cc: Pierre Ossman
Cc: David Woodhouse
Cc: Markus Lidel
Cc: Stefan Weinhuber
Cc: Martin Schwidefsky
Cc: Pete Zaitcev
Cc: FUJITA Tomonori
Signed-off-by: Jens Axboe -
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
Cc: Boaz Harrosh
Signed-off-by: Jens Axboe
28 Apr, 2009
3 commits
-
We currently don't do merging on discard requests, but we potentially
could. If we do, then we need to include discard requests in the IO
accounting, or merging would end up decrementing in_flight IO counters
for an IO which never incremented them.So enable accounting for discard requests.
Problem found by Nikanth Karthikesan
Signed-off-by: Jens Axboe
-
We currently check for file system requests outside of blk_do_io_stat(rq),
but we may as well just include it.Signed-off-by: Jens Axboe
-
Impact: code reorganization
elv_next_request() and elv_dequeue_request() are public block layer
interface than actual elevator implementation. They mostly deal with
how requests interact with block layer and low level drivers at the
beginning of rqeuest processing whereas __elv_next_request() is the
actual eleveator request fetching interface.Move the two functions to blk-core.c. This prepares for further
interface cleanup.Signed-off-by: Tejun Heo
24 Apr, 2009
1 commit
-
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
Signed-off-by: Jens Axboe
15 Apr, 2009
1 commit
-
Credit goes to Andrew Morton for spotting this one.
Signed-off-by: Jens Axboe
07 Apr, 2009
2 commits
-
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
Signed-off-by: Jens Axboe -
Simple helper functions to quiesce the request queue. These are
currently only used for switching IO schedulers on-the-fly, but
we can use them to properly switch IO accounting on and off as well.Signed-off-by: Jerome Marchand
Signed-off-by: Jens Axboe