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* block,elevator: use new hashtable implementationSasha Levin2013-01-111-1/+1
| | | | | | | | | | | | | | | Switch elevator to use the new hashtable implementation. This reduces the amount of generic unrelated code in the elevator. This also removes the dymanic allocation of the hash table. The size of the table is constant so there's no point in paying the price of an extra dereference when accessing it. This patch depends on d9b482c ("hashtable: introduce a small and naive hashtable") which was merged in v3.6. Signed-off-by: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: Avoid that request_fn is invoked on a dead queueBart Van Assche2012-12-061-0/+2
| | | | | | | | | | | | | | | | | | A block driver may start cleaning up resources needed by its request_fn as soon as blk_cleanup_queue() finished, so request_fn must not be invoked after draining finished. This is important when blk_run_queue() is invoked without any requests in progress. As an example, if blk_drain_queue() and scsi_run_queue() run in parallel, blk_drain_queue() may have finished all requests after scsi_run_queue() has taken a SCSI device off the starved list but before that last function has had a chance to run the queue. Signed-off-by: Bart Van Assche <bvanassche@acm.org> Cc: James Bottomley <JBottomley@Parallels.com> Cc: Mike Christie <michaelc@cs.wisc.edu> Cc: Chanho Min <chanho.min@lge.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: Rename queue dead flagBart Van Assche2012-12-061-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <bvanassche@acm.org> Acked-by: Tejun Heo <tj@kernel.org> Cc: James Bottomley <JBottomley@Parallels.com> Cc: Mike Christie <michaelc@cs.wisc.edu> Cc: Jens Axboe <axboe@kernel.dk> Cc: Chanho Min <chanho.min@lge.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: Clean up special command handling logicMartin K. Petersen2012-09-201-3/+2
| | | | | | | | | | | | | | 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>
* block: remove dead func declarationYuanhan Liu2012-08-011-1/+0
| | | | | | | | | __generic_unplug_device() function is removed with commit 7eaceaccab5f40bbfda044629a6298616aeaed50, which forgot to remove the declaration at meantime. Here remove it. Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: prepare for multiple request_listsTejun Heo2012-06-251-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | 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 <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* Merge branch 'for-3.5' of ../cgroup into block/for-3.5/core-mergedTejun Heo2012-04-011-16/+0
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cgroup/for-3.5 contains the following changes which blk-cgroup needs to proceed with the on-going cleanup. * Dynamic addition and removal of cftypes to make config/stat file handling modular for policies. * cgroup removal update to not wait for css references to drain to fix blkcg removal hang caused by cfq caching cfqgs. Pull in cgroup/for-3.5 into block/for-3.5/core. This causes the following conflicts in block/blk-cgroup.c. * 761b3ef50e "cgroup: remove cgroup_subsys argument from callbacks" conflicts with blkiocg_pre_destroy() addition and blkiocg_attach() removal. Resolved by removing @subsys from all subsys methods. * 676f7c8f84 "cgroup: relocate cftype and cgroup_subsys definitions in controllers" conflicts with ->pre_destroy() and ->attach() updates and removal of modular config. Resolved by dropping forward declarations of the methods and applying updates to the relocated blkio_subsys. * 4baf6e3325 "cgroup: convert all non-memcg controllers to the new cftype interface" builds upon the previous item. Resolved by adding ->base_cftypes to the relocated blkio_subsys. Signed-off-by: Tejun Heo <tj@kernel.org>
| * Merge branch 'linus' into sched/coreIngo Molnar2012-03-011-0/+2
| |\ | | | | | | | | | | | | | | | Merge reason: we'll queue up dependent patches. Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * | sched, block: Unify cache detectionPeter Zijlstra2012-01-271-16/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The block layer has some code trying to determine if two CPUs share a cache, the scheduler has a similar function. Expose the function used by the scheduler and make the block layer use it, thereby removing the block layers usage of CONFIG_SCHED* and topology bits. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Jens Axboe <axboe@kernel.dk> Link: http://lkml.kernel.org/r/1327579450.2446.95.camel@twins
* | | block: interface update for ioc/icq creation functionsTejun Heo2012-03-061-13/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Make the following interface updates to prepare for future ioc related changes. * create_io_context() returning ioc only works for %current because it doesn't increment ref on the ioc. Drop @task parameter from it and always assume %current. * Make create_io_context_slowpath() return 0 or -errno and rename it to create_task_io_context(). * Make ioc_create_icq() take @ioc as parameter instead of assuming that of %current. The caller, get_request(), is updated to create ioc explicitly and then pass it into ioc_create_icq(). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | | blkcg: add blkcg_{init|drain|exit}_queue()Tejun Heo2012-03-061-2/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | | block: implement blk_queue_bypass_start/end()Tejun Heo2012-03-061-4/+2
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | Rename and extend elv_queisce_start/end() to blk_queue_bypass_start/end() which are exported and supports nesting via @q->bypass_depth. Also add blk_queue_bypass() to test bypass state. This will be further extended and used for blkio_group management. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* | block: separate out blk_rq_merge_ok() and blk_try_merge() from elevator ↵Tejun Heo2012-02-081-0/+2
|/ | | | | | | | | | | | | | | | | | | | | | | | | 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>
* block, cfq: move icq creation and rq->elv.icq association to block coreTejun Heo2011-12-141-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block, cfq: move io_cq exit/release to blk-ioc.cTejun Heo2011-12-141-0/+1
| | | | | | | | | | | | | | | | | | | | | | With kmem_cache managed by blk-ioc, io_cq exit/release can be moved to blk-ioc too. The odd ->io_cq->exit/release() callbacks are replaced with elevator_ops->elevator_exit_icq_fn() with unlinking from both ioc and q, and freeing automatically handled by blk-ioc. The elevator operation only need to perform exit operation specific to the elevator - in cfq's case, exiting the cfqq's. Also, clearing of io_cq's on q detach is moved to block core and automatically performed on elevator switch and q release. Because the q io_cq points to might be freed before RCU callback for the io_cq runs, blk-ioc code should remember to which cache the io_cq needs to be freed when the io_cq is released. New field io_cq->__rcu_icq_cache is added for this purpose. As both the new field and rcu_head are used only after io_cq is released and the q/ioc_node fields aren't, they are put into unions. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block, cfq: move io_cq lookup to blk-ioc.cTejun Heo2011-12-141-0/+1
| | | | | | | | | | | | | Now that all io_cq related data structures are in block core layer, io_cq lookup can be moved from cfq-iosched.c to blk-ioc.c. Lookup logic from cfq_cic_lookup() is moved to ioc_lookup_icq() with parameter return type changes (cfqd -> request_queue, cfq_io_cq -> io_cq) and cfq_cic_lookup() becomes thin wrapper around cfq_cic_lookup(). Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: remove elevator_queue->opsTejun Heo2011-12-141-5/+5
| | | | | | | | | | | | | | | elevator_queue->ops points to the same ops struct ->elevator_type.ops is pointing to. The only effect of caching it in elevator_queue is shorter notation - it doesn't save any indirect derefence. Relocate elevator_type->list which used only during module init/exit to the end of the structure, rename elevator_queue->elevator_type to ->type, and replace elevator_queue->ops with elevator_queue->type.ops. This doesn't introduce any functional difference. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block, cfq: replace current_io_context() with create_io_context()Tejun Heo2011-12-141-3/+33
| | | | | | | | | | | | | | | | | | | | | | | | When called under queue_lock, current_io_context() triggers lockdep warning if it hits allocation path. This is because io_context installation is protected by task_lock which is not IRQ safe, so it triggers irq-unsafe-lock -> irq -> irq-safe-lock -> irq-unsafe-lock deadlock warning. Given the restriction, accessor + creator rolled into one doesn't work too well. Drop current_io_context() and let the users access task->io_context directly inside queue_lock combined with explicit creation using create_io_context(). Future ioc updates will further consolidate ioc access and the create interface will be unexported. While at it, relocate ioc internal interface declarations in blk.h and add section comments before and after. This patch does not introduce functional change. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: misc updates to blk_get_queue()Tejun Heo2011-12-141-0/+5
| | | | | | | | | | | | | | | | * blk_get_queue() is peculiar in that it returns 0 on success and 1 on failure instead of 0 / -errno or boolean. Update it such that it returns %true on success and %false on failure. * Make sure the caller checks for the return value. * Separate out __blk_get_queue() which doesn't check whether @q is dead and put it in blk.h. This will be used later. This patch doesn't introduce any functional changes. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: make ioc get/put interface more conventional and fix race on alloctionTejun Heo2011-12-141-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Ignoring copy_io() during fork, io_context can be allocated from two places - current_io_context() and set_task_ioprio(). The former is always called from local task while the latter can be called from different task. The synchornization between them are peculiar and dubious. * current_io_context() doesn't grab task_lock() and assumes that if it saw %NULL ->io_context, it would stay that way until allocation and assignment is complete. It has smp_wmb() between alloc/init and assignment. * set_task_ioprio() grabs task_lock() for assignment and does smp_read_barrier_depends() between "ioc = task->io_context" and "if (ioc)". Unfortunately, this doesn't achieve anything - the latter is not a dependent load of the former. ie, if ioc itself were being dereferenced "ioc->xxx", it would mean something (not sure what tho) but as the code currently stands, the dependent read barrier is noop. As only one of the the two test-assignment sequences is task_lock() protected, the task_lock() can't do much about race between the two. Nothing prevents current_io_context() and set_task_ioprio() allocating its own ioc for the same task and overwriting the other's. Also, set_task_ioprio() can race with exiting task and create a new ioc after exit_io_context() is finished. ioc get/put doesn't have any reason to be complex. The only hot path is accessing the existing ioc of %current, which is simple to achieve given that ->io_context is never destroyed as long as the task is alive. All other paths can happily go through task_lock() like all other task sub structures without impacting anything. This patch updates ioc get/put so that it becomes more conventional. * alloc_io_context() is replaced with get_task_io_context(). This is the only interface which can acquire access to ioc of another task. On return, the caller has an explicit reference to the object which should be put using put_io_context() afterwards. * The functionality of current_io_context() remains the same but when creating a new ioc, it shares the code path with get_task_io_context() and always goes through task_lock(). * get_io_context() now means incrementing ref on an ioc which the caller already has access to (be that an explicit refcnt or implicit %current one). * PF_EXITING inhibits creation of new io_context and once exit_io_context() is finished, it's guaranteed that both ioc acquisition functions return %NULL. * All users are updated. Most are trivial but smp_read_barrier_depends() removal from cfq_get_io_context() needs a bit of explanation. I suppose the original intention was to ensure ioc->ioprio is visible when set_task_ioprio() allocates new io_context and installs it; however, this wouldn't have worked because set_task_ioprio() doesn't have wmb between init and install. There are other problems with this which will be fixed in another patch. * While at it, use NUMA_NO_NODE instead of -1 for wildcard node specification. -v2: Vivek spotted contamination from debug patch. Removed. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block, cfq: move cfqd->cic_index to q->idTejun Heo2011-12-141-0/+3
| | | | | | | | | | | | cfq allocates per-queue id using ida and uses it to index cic radix tree from io_context. Move it to q->id and allocate on queue init and free on queue release. This simplifies cfq a bit and will allow for further improvements of io context life-cycle management. This patch doesn't introduce any functional difference. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: add blk_queue_dead()Tejun Heo2011-12-141-1/+1
| | | | | | | | | | There are a number of QUEUE_FLAG_DEAD tests. Add blk_queue_dead() macro and use it. This patch doesn't introduce any functional difference. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: fix request_queue lifetime handling by making blk_queue_cleanup() ↵Tejun Heo2011-10-191-1/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | properly shutdown 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:[<ffffffff8137d651>] [<ffffffff8137d651>] elv_rqhash_find+0x61/0x100 ... Process test_rawio (pid: 648, threadinfo ffff880019efa000, task ffff880019ef8a80) ... Call Trace: [<ffffffff8137d774>] elv_merge+0x84/0xe0 [<ffffffff81385b54>] blk_queue_bio+0xf4/0x400 [<ffffffff813838ea>] generic_make_request+0xca/0x100 [<ffffffff81383994>] submit_bio+0x74/0x100 [<ffffffff811c53ec>] dio_bio_submit+0xbc/0xc0 [<ffffffff811c610e>] __blockdev_direct_IO+0x92e/0xb40 [<ffffffff811c39f7>] blkdev_direct_IO+0x57/0x60 [<ffffffff8113b1c5>] generic_file_aio_read+0x6d5/0x760 [<ffffffff8118c1ca>] do_sync_read+0xda/0x120 [<ffffffff8118ce55>] vfs_read+0xc5/0x180 [<ffffffff8118cfaa>] sys_pread64+0x9a/0xb0 [<ffffffff81afaf6b>] system_call_fastpath+0x16/0x1b This 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 <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: reorganize throtl_get_tg() and blk_throtl_bio()Tejun Heo2011-10-191-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: reorganize queue drainingTejun Heo2011-10-191-0/+1
| | | | | | | | | | | | | | | | | | 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 <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: move blk_throtl prototypes to block/blk.hTejun Heo2011-10-191-1/+14
| | | | | | | | | | | 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 <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* block: fix flush machinery for stacking drivers with differring flush flagsJeff Moyer2011-08-151-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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, Jeff Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
* Merge branch 'for-linus' into for-2.6.40/coreJens Axboe2011-05-201-1/+3
|\ | | | | | | | | | | | | This patch merges in a fix that missed 2.6.39 final. Conflicts: block/blk.h
| * block: add proper state guards to __elv_next_requestJames Bottomley2011-05-181-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | 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 <James.Bottomley@suse.de> Cc: stable@kernel.org Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
* | Merge commit 'v2.6.39' into for-2.6.40/coreJens Axboe2011-05-201-1/+0
|\| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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.c Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * block: get rid of QUEUE_FLAG_REENTERJens Axboe2011-04-191-1/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <jaxboe@fusionio.com>
* | block: hold queue if flush is running for non-queueable flush driveshaohua.li@intel.com2011-05-061-1/+20
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <shaohua.li@intel.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
* block: add blk_run_queue_asyncChristoph Hellwig2011-04-181-0/+1
| | | | | | | | | | 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 <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
* Fix common misspellingsLucas De Marchi2011-03-311-1/+1
| | | | | | Fixes generated by 'codespell' and manually reviewed. Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
* block: attempt to merge with existing requests on plug flushJens Axboe2011-03-211-0/+2
| | | | | | | | | | | | | | | | | | | | 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>
* block: remove per-queue pluggingJens Axboe2011-03-101-2/+0
| | | | | | | | 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 <jaxboe@fusionio.com>
* block: reimplement FLUSH/FUA to support mergeTejun Heo2011-01-251-8/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <tj@kernel.org> Cc: "Darrick J. Wong" <djwong@us.ibm.com> Cc: Shaohua Li <shli@kernel.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
* block: add REQ_FLUSH_SEQTejun Heo2011-01-251-1/+1
| | | | | | | | | | | | | 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 <tj@kernel.org> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
* Revert "block: fix accounting bug on cross partition merges"Jens Axboe2010-10-241-0/+4
| | | | | | | | | | | | | | 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 <jaxboe@fusionio.com>
* Merge branch 'for-2.6.37/barrier' of git://git.kernel.dk/linux-2.6-blockLinus Torvalds2010-10-221-1/+7
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * '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 ...
| * Merge branch 'v2.6.36-rc8' into for-2.6.37/barrierJens Axboe2010-10-191-2/+6
| |\ | | | | | | | | | | | | | | | | | | | | | | | | Conflicts: block/blk-core.c drivers/block/loop.c mm/swapfile.c Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | block: implement REQ_FLUSH/FUA based interface for FLUSH/FUA requestsTejun Heo2010-09-101-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <tj@kernel.org> Cc: Christoph Hellwig <hch@infradead.org> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | block: rename barrier/ordered to flushTejun Heo2010-09-101-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <tj@kernel.org> Cc: Christoph Hellwig <hch@infradead.org> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | block: drop barrier ordering by queue drainingTejun Heo2010-09-101-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <tj@kernel.org> Cc: Christoph Hellwig <hch@infradead.org> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
| * | block: misc cleanups in barrier codeTejun Heo2010-09-101-2/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <tj@kernel.org> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
* | | Merge branch 'for-2.6.37/core' of git://git.kernel.dk/linux-2.6-blockLinus Torvalds2010-10-221-12/+0
|\ \ \ | |_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * '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
| * | block: fix accounting bug on cross partition mergesYasuaki Ishimatsu2010-10-191-4/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | /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>
| * | block/scsi: Provide a limit on the number of integrity segmentsMartin K. Petersen2010-09-101-8/+0
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* / block: Range check cpu in blk_cpu_to_groupBrian King2010-09-101-2/+6
|/ | | | | | | | | | | | | | | | | | | | 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 <brking@linux.vnet.ibm.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
* block: remove wrappers for request type/flagsChristoph Hellwig2010-08-071-2/+4
| | | | | | | | | 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>
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