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2012-08-03block: Don't use static to define "void *p" in show_partition_start()Jianpeng Ma
I met a odd prblem:read /proc/partitions may return zero. I wrote a file test.c: int main() { char buff[4096]; int ret; int fd; printf("pid=%d\n",getpid()); while (1) { fd = open("/proc/partitions", O_RDONLY); if (fd < 0) { printf("open error %s\n", strerror(errno)); return 0; } ret = read(fd, buff, 4096); if (ret <= 0) printf("ret=%d, %s, %ld\n", ret, strerror(errno), lseek(fd,0,SEEK_CUR)); close(fd); } exit(0); } You can reproduce by: 1:while true;do cat /proc/partitions > /dev/null ;done 2:./test I reviewed the code and found: >> static void *show_partition_start(struct seq_file *seqf, loff_t *pos) >> { >> static void *p; >> >> p = disk_seqf_start(seqf, pos); >> if (!IS_ERR_OR_NULL(p) && !*pos) >> seq_puts(seqf, "major minor #blocks name\n\n"); >> return p; >> } test cat /proc/partitions p = disk_seqf_start()(Not NULL) p = disk_seqf_start()(NULL because pos) if (!IS_ERR_OR_NULL(p) && !*pos) Signed-off-by: Jianpeng Ma <majianpeng@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-08-02block: Add blk_bio_map_sg() helperAsias He
Add a helper to map a bio to a scatterlist, modelled after blk_rq_map_sg. This helper is useful for any driver that wants to create a scatterlist from its ->make_request_fn method. Changes in v2: - Use __blk_segment_map_sg to avoid duplicated code - Add cocbook style function comment Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Christoph Hellwig <hch@lst.de> Cc: Tejun Heo <tj@kernel.org> Cc: Shaohua Li <shli@kernel.org> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: virtualization@lists.linux-foundation.org Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: Asias He <asias@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-08-02block: Introduce __blk_segment_map_sg() helperAsias He
Split the mapping code in blk_rq_map_sg() to a helper __blk_segment_map_sg(), so that other mapping function, e.g. blk_bio_map_sg(), can share the code. Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Christoph Hellwig <hch@lst.de> Cc: Tejun Heo <tj@kernel.org> Cc: Shaohua Li <shli@kernel.org> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: virtualization@lists.linux-foundation.org Suggested-by: Jens Axboe <axboe@kernel.dk> Suggested-by: Tejun Heo <tj@kernel.org> Signed-off-by: Asias He <asias@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-08-02block: split discard into aligned requestsPaolo Bonzini
When a disk has large discard_granularity and small max_discard_sectors, discards are not split with optimal alignment. In the limit case of discard_granularity == max_discard_sectors, no request could be aligned correctly, so in fact you might end up with no discarded logical blocks at all. Another example that helps showing the condition in the patch is with discard_granularity == 64, max_discard_sectors == 128. A request that is submitted for 256 sectors 2..257 will be split in two: 2..129, 130..257. However, only 2 aligned blocks out of 3 are included in the request; 128..191 may be left intact and not discarded. With this patch, the first request will be truncated to ensure good alignment of what's left, and the split will be 2..127, 128..255, 256..257. The patch will also take into account the discard_alignment. At most one extra request will be introduced, because the first request will be reduced by at most granularity-1 sectors, and granularity must be less than max_discard_sectors. Subsequent requests will run on round_down(max_discard_sectors, granularity) sectors, as in the current code. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Tested-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-08-02block: reorganize rounding of max_discard_sectorsPaolo Bonzini
Mostly a preparation for the next patch. In principle this fixes an infinite loop if max_discard_sectors < granularity, but that really shouldn't happen. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Tested-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-08-01Merge branch 'for-3.6/drivers' of git://git.kernel.dk/linux-blockLinus Torvalds
Pull block driver changes from Jens Axboe: - Making the plugging support for drivers a bit more sane from Neil. This supersedes the plugging change from Shaohua as well. - The usual round of drbd updates. - Using a tail add instead of a head add in the request completion for ndb, making us find the most completed request more quickly. - A few floppy changes, getting rid of a duplicated flag and also running the floppy init async (since it takes forever in boot terms) from Andi. * 'for-3.6/drivers' of git://git.kernel.dk/linux-block: floppy: remove duplicated flag FD_RAW_NEED_DISK blk: pass from_schedule to non-request unplug functions. block: stack unplug blk: centralize non-request unplug handling. md: remove plug_cnt feature of plugging. block/nbd: micro-optimization in nbd request completion drbd: announce FLUSH/FUA capability to upper layers drbd: fix max_bio_size to be unsigned drbd: flush drbd work queue before invalidate/invalidate remote drbd: fix potential access after free drbd: call local-io-error handler early drbd: do not reset rs_pending_cnt too early drbd: reset congestion information before reporting it in /proc/drbd drbd: report congestion if we are waiting for some userland callback drbd: differentiate between normal and forced detach drbd: cleanup, remove two unused global flags floppy: Run floppy initialization asynchronous
2012-08-01Merge branch 'for-3.6/core' of git://git.kernel.dk/linux-blockLinus Torvalds
Pull core block IO bits from Jens Axboe: "The most complicated part if this is the request allocation rework by Tejun, which has been queued up for a long time and has been in for-next ditto as well. There are a few commits from yesterday and today, mostly trivial and obvious fixes. So I'm pretty confident that it is sound. It's also smaller than usual." * 'for-3.6/core' of git://git.kernel.dk/linux-block: block: remove dead func declaration block: add partition resize function to blkpg ioctl block: uninitialized ioc->nr_tasks triggers WARN_ON block: do not artificially constrain max_sectors for stacking drivers blkcg: implement per-blkg request allocation block: prepare for multiple request_lists block: add q->nr_rqs[] and move q->rq.elvpriv to q->nr_rqs_elvpriv blkcg: inline bio_blkcg() and friends block: allocate io_context upfront block: refactor get_request[_wait]() block: drop custom queue draining used by scsi_transport_{iscsi|fc} mempool: add @gfp_mask to mempool_create_node() blkcg: make root blkcg allocation use %GFP_KERNEL blkcg: __blkg_lookup_create() doesn't need radix preload
2012-08-01block: remove dead func declarationYuanhan Liu
__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>
2012-08-01block: add partition resize function to blkpg ioctlVivek Goyal
Add a new operation code (BLKPG_RESIZE_PARTITION) to the BLKPG ioctl that allows altering the size of an existing partition, even if it is currently in use. This patch converts hd_struct->nr_sects into sequence counter because One might extend a partition while IO is happening to it and update of nr_sects can be non-atomic on 32bit machines with 64bit sector_t. This can lead to issues like reading inconsistent size of a partition. Sequence counter have been used so that readers don't have to take bdev mutex lock as we call sector_in_part() very frequently. Now all the access to hd_struct->nr_sects should happen using sequence counter read/update helper functions part_nr_sects_read/part_nr_sects_write. There is one exception though, set_capacity()/get_capacity(). I think theoritically race should exist there too but this patch does not modify set_capacity()/get_capacity() due to sheer number of call sites and I am afraid that change might break something. I have left that as a TODO item. We can handle it later if need be. This patch does not introduce any new races as such w.r.t set_capacity()/get_capacity(). v2: Add CONFIG_LBDAF test to UP preempt case as suggested by Phillip. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Phillip Susi <psusi@ubuntu.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-08-01block: uninitialized ioc->nr_tasks triggers WARN_ONOlof Johansson
Hi, I'm using the old-fashioned 'dump' backup tool, and I noticed that it spews the below warning as of 3.5-rc1 and later (3.4 is fine): [ 10.886893] ------------[ cut here ]------------ [ 10.886904] WARNING: at include/linux/iocontext.h:140 copy_process+0x1488/0x1560() [ 10.886905] Hardware name: Bochs [ 10.886906] Modules linked in: [ 10.886908] Pid: 2430, comm: dump Not tainted 3.5.0-rc7+ #27 [ 10.886908] Call Trace: [ 10.886911] [<ffffffff8107ce8a>] warn_slowpath_common+0x7a/0xb0 [ 10.886912] [<ffffffff8107ced5>] warn_slowpath_null+0x15/0x20 [ 10.886913] [<ffffffff8107c088>] copy_process+0x1488/0x1560 [ 10.886914] [<ffffffff8107c244>] do_fork+0xb4/0x340 [ 10.886918] [<ffffffff8108effa>] ? recalc_sigpending+0x1a/0x50 [ 10.886919] [<ffffffff8108f6b2>] ? __set_task_blocked+0x32/0x80 [ 10.886920] [<ffffffff81091afa>] ? __set_current_blocked+0x3a/0x60 [ 10.886923] [<ffffffff81051db3>] sys_clone+0x23/0x30 [ 10.886925] [<ffffffff8179bd73>] stub_clone+0x13/0x20 [ 10.886927] [<ffffffff8179baa2>] ? system_call_fastpath+0x16/0x1b [ 10.886928] ---[ end trace 32a14af7ee6a590b ]--- Reproducing is easy, I can hit it on a KVM system with a very basic config (x86_64 make defconfig + enable the drivers needed). To hit it, just install dump (on debian/ubuntu, not sure what the package might be called on Fedora), and: dump -o -f /tmp/foo / You'll see the warning in dmesg once it forks off the I/O process and starts dumping filesystem contents. I bisected it down to the following commit: commit f6e8d01bee036460e03bd4f6a79d014f98ba712e Author: Tejun Heo <tj@kernel.org> Date: Mon Mar 5 13:15:26 2012 -0800 block: add io_context->active_ref Currently ioc->nr_tasks is used to decide two things - whether an ioc is done issuing IOs and whether it's shared by multiple tasks. This patch separate out the first into ioc->active_ref, which is acquired and released using {get|put}_io_context_active() respectively. This will be used to associate bio's with a given task. This patch doesn't introduce any visible behavior change. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> It seems like the init of ioc->nr_tasks was removed in that patch, so it starts out at 0 instead of 1. Tejun, is the right thing here to add back the init, or should something else be done? The below patch removes the warning, but I haven't done any more extensive testing on it. Signed-off-by: Olof Johansson <olof@lixom.net> Acked-by: Tejun Heo <tj@kernel.org> Cc: stable@kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-08-01block: do not artificially constrain max_sectors for stacking driversMike Snitzer
blk_set_stacking_limits is intended to allow stacking drivers to build up the limits of the stacked device based on the underlying devices' limits. But defaulting 'max_sectors' to BLK_DEF_MAX_SECTORS (1024) doesn't allow the stacking driver to inherit a max_sectors larger than 1024 -- due to blk_stack_limits' use of min_not_zero. It is now clear that this artificial limit is getting in the way so change blk_set_stacking_limits's max_sectors to UINT_MAX (which allows stacking drivers like dm-multipath to inherit 'max_sectors' from the underlying paths). Reported-by: Vijay Chauhan <vijay.chauhan@netapp.com> Tested-by: Vijay Chauhan <vijay.chauhan@netapp.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-07-31blk: pass from_schedule to non-request unplug functions.NeilBrown
This will allow md/raid to know why the unplug was called, and will be able to act according - if !from_schedule it is safe to perform tasks which could themselves schedule. Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-07-31block: stack unplugShaohua Li
MD raid1 prepares to dispatch request in unplug callback. If make_request in low level queue also uses unplug callback to dispatch request, the low level queue's unplug callback will not be called. Recheck the callback list helps this case. Signed-off-by: Shaohua Li <shli@fusionio.com> Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-07-31blk: centralize non-request unplug handling.NeilBrown
Both md and umem has similar code for getting notified on an blk_finish_plug event. Centralize this code in block/ and allow each driver to provide its distinctive difference. Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-07-20[SCSI] block: Fix blk_execute_rq_nowait() dead queue handlingMuthukumar Ratty
If the queue is dead blk_execute_rq_nowait() doesn't invoke the done() callback function. That will result in blk_execute_rq() being stuck in wait_for_completion(). Avoid this by initializing rq->end_io to the done() callback before we check the queue state. Also, make sure the queue lock is held around the invocation of the done() callback. Found this through source code review. Signed-off-by: Muthukumar Ratty <muthur@gmail.com> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Tejun Heo <tj@kernel.org> Acked-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: James Bottomley <JBottomley@Parallels.com>
2012-06-26blkcg: implement per-blkg request allocationTejun Heo
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 <rni@google.com>. 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 <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-25block: prepare for multiple request_listsTejun Heo
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>
2012-06-25block: add q->nr_rqs[] and move q->rq.elvpriv to q->nr_rqs_elvprivTejun Heo
Add q->nr_rqs[] which currently behaves the same as q->rq.count[] and move q->rq.elvpriv to q->nr_rqs_elvpriv. blk_drain_queue() is updated to use q->nr_rqs[] instead of q->rq.count[]. These counters separates queue-wide request statistics from the request list and allow implementation of per-queue request allocation. While at it, properly indent fields of struct request_list. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-25blkcg: inline bio_blkcg() and friendsTejun Heo
Make bio_blkcg() and friends inline. They all are very simple and used only in few places. This patch is to prepare for further updates to request allocation path. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-25block: allocate io_context upfrontTejun Heo
Block layer very lazy allocation of ioc. It waits until the moment ioc is absolutely necessary; unfortunately, that time could be inside queue lock and __get_request() performs unlock - try alloc - retry dancing. Just allocate it up-front on entry to block layer. We're not saving the rain forest by deferring it to the last possible moment and complicating things unnecessarily. This patch is to prepare for further updates to request allocation path. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-25block: refactor get_request[_wait]()Tejun Heo
Currently, there are two request allocation functions - get_request() and get_request_wait(). The former tries to allocate a request once and the latter keeps retrying until it succeeds. The latter wraps the former and keeps retrying until allocation succeeds. The combination of two functions deliver fallible non-wait allocation, fallible wait allocation and unfailing wait allocation. However, given that forward progress is guaranteed, fallible wait allocation isn't all that useful and in fact nobody uses it. This patch simplifies the interface as follows. * get_request() is renamed to __get_request() and is only used by the wrapper function. * get_request_wait() is renamed to get_request(). It now takes @gfp_mask and retries iff it contains %__GFP_WAIT. This patch doesn't introduce any functional change and is to prepare for further updates to request allocation path. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-25block: drop custom queue draining used by scsi_transport_{iscsi|fc}Tejun Heo
iscsi_remove_host() uses bsg_remove_queue() which implements custom queue draining. fc_bsg_remove() open-codes mostly identical logic. The draining logic isn't correct in that blk_stop_queue() doesn't prevent new requests from being queued - it just stops processing, so nothing prevents new requests to be queued after the logic determines that the queue is drained. blk_cleanup_queue() now implements proper queue draining and these custom draining logics aren't necessary. Drop them and use bsg_unregister_queue() + blk_cleanup_queue() instead. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Mike Christie <michaelc@cs.wisc.edu> Acked-by: Vivek Goyal <vgoyal@redhat.com> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Cc: James Smart <james.smart@emulex.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-25mempool: add @gfp_mask to mempool_create_node()Tejun Heo
mempool_create_node() currently assumes %GFP_KERNEL. Its only user, blk_init_free_list(), is about to be updated to use other allocation flags - add @gfp_mask argument to the function. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-25blkcg: make root blkcg allocation use %GFP_KERNELTejun Heo
Currently, blkcg_activate_policy() depends on %GFP_ATOMIC allocation from __blkg_lookup_create() for root blkcg creation. This could make policy fail unnecessarily. Make blkg_alloc() take @gfp_mask, __blkg_lookup_create() take an optional @new_blkg for preallocated blkg, and blkcg_activate_policy() preload radix tree and preallocate blkg with %GFP_KERNEL before trying to create the root blkg. v2: __blkg_lookup_create() was returning %NULL on blkg alloc failure instead of ERR_PTR() value. Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-25blkcg: __blkg_lookup_create() doesn't need radix preloadTejun Heo
There's no point in calling radix_tree_preload() if preloading doesn't use more permissible GFP mask. Drop preloading from __blkg_lookup_create(). While at it, drop sparse locking annotation which no longer applies. v2: Vivek pointed out the odd preload usage. Instead of updating, just drop it. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-15scsi: Silence unnecessary warnings about ioctl to partitionJan Kara
Sometimes, warnings about ioctls to partition happen often enough that they form majority of the warnings in the kernel log and users complain. In some cases warnings are about ioctls such as SG_IO so it's not good to get rid of the warnings completely as they can ease debugging of userspace problems when ioctl is refused. Since I have seen warnings from lots of commands, including some proprietary userspace applications, I don't think disallowing the ioctls for processes with CAP_SYS_RAWIO will happen in the near future if ever. So lets just stop warning for processes with CAP_SYS_RAWIO for which ioctl is allowed. CC: Paolo Bonzini <pbonzini@redhat.com> CC: James Bottomley <JBottomley@parallels.com> CC: linux-scsi@vger.kernel.org Acked-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-15block: Drop dead function blk_abort_queue()Asias He
This function was only used by btrfs code in btrfs_abort_devices() (seems in a wrong way). It was removed in commit d07eb9117050c9ed3f78296ebcc06128b52693be, So, Let's remove the dead code to avoid any confusion. Changes in v2: update commit log, btrfs_abort_devices() was removed already. Cc: Jens Axboe <axboe@kernel.dk> Cc: linux-kernel@vger.kernel.org Cc: Chris Mason <chris.mason@oracle.com> Cc: linux-btrfs@vger.kernel.org Cc: David Sterba <dave@jikos.cz> Signed-off-by: Asias He <asias@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-15block: Mitigate lock unbalance caused by lock switchingAsias He
Commit 777eb1bf15b8532c396821774bf6451e563438f5 disconnects externally supplied queue_lock before blk_drain_queue(). Switching the lock would introduce lock unbalance because theads which have taken the external lock might unlock the internal lock in the during the queue drain. This patch mitigate this by disconnecting the lock after the queue draining since queue draining makes a lot of request_queue users go away. However, please note, this patch only makes the problem less likely to happen. Anyone who still holds a ref might try to issue a new request on a dead queue after the blk_cleanup_queue() finishes draining, the lock unbalance might still happen in this case. ===================================== [ BUG: bad unlock balance detected! ] 3.4.0+ #288 Not tainted ------------------------------------- fio/17706 is trying to release lock (&(&q->__queue_lock)->rlock) at: [<ffffffff81329372>] blk_queue_bio+0x2a2/0x380 but there are no more locks to release! other info that might help us debug this: 1 lock held by fio/17706: #0: (&(&vblk->lock)->rlock){......}, at: [<ffffffff81327f1a>] get_request_wait+0x19a/0x250 stack backtrace: Pid: 17706, comm: fio Not tainted 3.4.0+ #288 Call Trace: [<ffffffff81329372>] ? blk_queue_bio+0x2a2/0x380 [<ffffffff810dea49>] print_unlock_inbalance_bug+0xf9/0x100 [<ffffffff810dfe4f>] lock_release_non_nested+0x1df/0x330 [<ffffffff811dae24>] ? dio_bio_end_aio+0x34/0xc0 [<ffffffff811d6935>] ? bio_check_pages_dirty+0x85/0xe0 [<ffffffff811daea1>] ? dio_bio_end_aio+0xb1/0xc0 [<ffffffff81329372>] ? blk_queue_bio+0x2a2/0x380 [<ffffffff81329372>] ? blk_queue_bio+0x2a2/0x380 [<ffffffff810e0079>] lock_release+0xd9/0x250 [<ffffffff81a74553>] _raw_spin_unlock_irq+0x23/0x40 [<ffffffff81329372>] blk_queue_bio+0x2a2/0x380 [<ffffffff81328faa>] generic_make_request+0xca/0x100 [<ffffffff81329056>] submit_bio+0x76/0xf0 [<ffffffff8115470c>] ? set_page_dirty_lock+0x3c/0x60 [<ffffffff811d69e1>] ? bio_set_pages_dirty+0x51/0x70 [<ffffffff811dd1a8>] do_blockdev_direct_IO+0xbf8/0xee0 [<ffffffff811d8620>] ? blkdev_get_block+0x80/0x80 [<ffffffff811dd4e5>] __blockdev_direct_IO+0x55/0x60 [<ffffffff811d8620>] ? blkdev_get_block+0x80/0x80 [<ffffffff811d92e7>] blkdev_direct_IO+0x57/0x60 [<ffffffff811d8620>] ? blkdev_get_block+0x80/0x80 [<ffffffff8114c6ae>] generic_file_aio_read+0x70e/0x760 [<ffffffff810df7c5>] ? __lock_acquire+0x215/0x5a0 [<ffffffff811e9924>] ? aio_run_iocb+0x54/0x1a0 [<ffffffff8114bfa0>] ? grab_cache_page_nowait+0xc0/0xc0 [<ffffffff811e82cc>] aio_rw_vect_retry+0x7c/0x1e0 [<ffffffff811e8250>] ? aio_fsync+0x30/0x30 [<ffffffff811e9936>] aio_run_iocb+0x66/0x1a0 [<ffffffff811ea9b0>] do_io_submit+0x6f0/0xb80 [<ffffffff8134de2e>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff811eae50>] sys_io_submit+0x10/0x20 [<ffffffff81a7c9e9>] system_call_fastpath+0x16/0x1b Changes since v2: Update commit log to explain how the code is still broken even if we delay the lock switching after the drain. Changes since v1: Update commit log as Tejun suggested. Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Asias He <asias@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-15block: Avoid missed wakeup in request waitqueueAsias He
After hot-unplug a stressed disk, I found that rl->wait[] is not empty while rl->count[] is empty and there are theads still sleeping on get_request after the queue cleanup. With simple debug code, I found there are exactly nr_sleep - nr_wakeup of theads in D state. So there are missed wakeup. $ dmesg | grep nr_sleep [ 52.917115] ---> nr_sleep=1046, nr_wakeup=873, delta=173 $ vmstat 1 1 173 0 712640 24292 96172 0 0 0 0 419 757 0 0 0 100 0 To quote Tejun: Ah, okay, freed_request() wakes up single waiter with the assumption that after the wakeup there will at least be one successful allocation which in turn will continue the wakeup chain until the wait list is empty - ie. waiter wakeup is dependent on successful request allocation happening after each wakeup. With queue marked dead, any woken up waiter fails the allocation path, so the wakeup chaining is lost and we're left with hung waiters. What we need is wake_up_all() after drain completion. This patch fixes the missed wakeup by waking up all the theads which are sleeping on wait queue after queue drain. Changes in v2: Drop waitqueue_active() optimization Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Asias He <asias@redhat.com> Fixed a bug by me, where stacked devices would oops on calling blk_drain_queue() since ->rq.wait[] do not get initialized unless it's a full queue setup. Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-06blkcg: drop local variable @q from blkg_destroy()Tejun Heo
blkg_destroy() caches @blkg->q in local variable @q. While there are two places which needs @blkg->q, only lockdep_assert_held() used the local variable leading to unused local variable warning if lockdep is configured out. Drop the local variable and just use @blkg->q directly. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Rakesh Iyer <rni@google.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-04blkcg: fix blkg_alloc() failure pathTejun Heo
When policy data allocation fails in the middle, blkg_alloc() invokes blkg_free() to destroy the half constructed blkg. This ends up calling pd_exit_fn() on policy datas which didn't go through pd_init_fn(). Fix it by making blkg_alloc() call pd_init_fn() immediately after each policy data allocation. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-04block: blkcg_policy_cfq shouldn't be used if !CONFIG_CFQ_GROUP_IOSCHEDTejun Heo
cfq may be built w/ or w/o blkcg support depending on CONFIG_CFQ_CGROUP_IOSCHED. If blkcg support is disabled, most of related code is ifdef'd out but some part is left dangling - blkcg_policy_cfq is left zero-filled and blkcg_policy_[un]register() calls are made on it. Feeding zero filled policy to blkcg_policy_register() is incorrect and triggers the following WARN_ON() if CONFIG_BLK_CGROUP && !CONFIG_CFQ_GROUP_IOSCHED. ------------[ cut here ]------------ WARNING: at block/blk-cgroup.c:867 Modules linked in: Modules linked in: CPU: 3 Not tainted 3.4.0-09547-gfb21aff #1 Process swapper/0 (pid: 1, task: 000000003ff80000, ksp: 000000003ff7f8b8) Krnl PSW : 0704100180000000 00000000003d76ca (blkcg_policy_register+0xca/0xe0) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:0 CC:1 PM:0 EA:3 Krnl GPRS: 0000000000000000 00000000014b85ec 00000000014b85b0 0000000000000000 000000000096fb60 0000000000000000 00000000009a8e78 0000000000000048 000000000099c070 0000000000b6f000 0000000000000000 000000000099c0b8 00000000014b85b0 0000000000667580 000000003ff7fd98 000000003ff7fd70 Krnl Code: 00000000003d76be: a7280001 lhi %r2,1 00000000003d76c2: a7f4ffdf brc 15,3d7680 #00000000003d76c6: a7f40001 brc 15,3d76c8 >00000000003d76ca: a7c8ffea lhi %r12,-22 00000000003d76ce: a7f4ffce brc 15,3d766a 00000000003d76d2: a7f40001 brc 15,3d76d4 00000000003d76d6: a7c80000 lhi %r12,0 00000000003d76da: a7f4ffc2 brc 15,3d765e Call Trace: ([<0000000000b6f000>] initcall_debug+0x0/0x4) [<0000000000989e8a>] cfq_init+0x62/0xd4 [<00000000001000ba>] do_one_initcall+0x3a/0x170 [<000000000096fb60>] kernel_init+0x214/0x2bc [<0000000000623202>] kernel_thread_starter+0x6/0xc [<00000000006231fc>] kernel_thread_starter+0x0/0xc no locks held by swapper/0/1. Last Breaking-Event-Address: [<00000000003d76c6>] blkcg_policy_register+0xc6/0xe0 ---[ end trace b8ef4903fcbf9dd3 ]--- This patch fixes the problem by ensuring all blkcg support code is inside CONFIG_CFQ_GROUP_IOSCHED. * blkcg_policy_cfq declaration and blkg_to_cfqg() definition are moved inside the first CONFIG_CFQ_GROUP_IOSCHED block. __maybe_unused is dropped from blkcg_policy_cfq decl. * blkcg_deactivate_poilcy() invocation is moved inside ifdef. This also makes the activation logic match cfq_init_queue(). * All blkcg_policy_[un]register() invocations are moved inside ifdef. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com> LKML-Reference: <20120601112954.GC3535@osiris.boeblingen.de.ibm.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-04block: fix return value on cfq_init() failureTejun Heo
cfq_init() would return zero after kmem cache creation failure. Fix so that it returns -ENOMEM. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-05-31block: avoid infinite loop in get_task_io_context()Eric Dumazet
Calling get_task_io_context() on a exiting task which isn't %current can loop forever. This triggers at boot time on my dev machine. BUG: soft lockup - CPU#3 stuck for 22s ! [mountall.1603] Fix this by making create_task_io_context() returns -EBUSY in this case to break the loop. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Tejun Heo <tj@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Alan Cox <alan@linux.intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-05-30Merge branch 'for-3.5/core' of git://git.kernel.dk/linux-blockLinus Torvalds
Merge block/IO core bits from Jens Axboe: "This is a bit bigger on the core side than usual, but that is purely because we decided to hold off on parts of Tejun's submission on 3.4 to give it a bit more time to simmer. As a consequence, it's seen a long cycle in for-next. It contains: - Bug fix from Dan, wrong locking type. - Relax splice gifting restriction from Eric. - A ton of updates from Tejun, primarily for blkcg. This improves the code a lot, making the API nicer and cleaner, and also includes fixes for how we handle and tie policies and re-activate on switches. The changes also include generic bug fixes. - A simple fix from Vivek, along with a fix for doing proper delayed allocation of the blkcg stats." Fix up annoying conflict just due to different merge resolution in Documentation/feature-removal-schedule.txt * 'for-3.5/core' of git://git.kernel.dk/linux-block: (92 commits) blkcg: tg_stats_alloc_lock is an irq lock vmsplice: relax alignement requirements for SPLICE_F_GIFT blkcg: use radix tree to index blkgs from blkcg blkcg: fix blkcg->css ref leak in __blkg_lookup_create() block: fix elvpriv allocation failure handling block: collapse blk_alloc_request() into get_request() blkcg: collapse blkcg_policy_ops into blkcg_policy blkcg: embed struct blkg_policy_data in policy specific data blkcg: mass rename of blkcg API blkcg: style cleanups for blk-cgroup.h blkcg: remove blkio_group->path[] blkcg: blkg_rwstat_read() was missing inline blkcg: shoot down blkgs if all policies are deactivated blkcg: drop stuff unused after per-queue policy activation update blkcg: implement per-queue policy activation blkcg: add request_queue->root_blkg blkcg: make request_queue bypassing on allocation blkcg: make sure blkg_lookup() returns %NULL if @q is bypassing blkcg: make blkg_conf_prep() take @pol and return with queue lock held blkcg: remove static policy ID enums ...
2012-05-23blkcg: tg_stats_alloc_lock is an irq lockTejun Heo
tg_stats_alloc_lock nests inside queue lock and should always be held with irq disabled. throtl_pd_{init|exit}() were using non-irqsafe spinlock ops which triggered inverse lock ordering via irq warning via RCU freeing of blkg invoking throtl_pd_exit() w/o disabling IRQ. Update both functions to use irq safe operations. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Sasha Levin <sasha.levin@oracle.com> LKML-Reference: <1335339396.16988.80.camel@lappy> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-05-22Merge branch 'for-3.5' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup Pull cgroup updates from Tejun Heo: "cgroup file type addition / removal is updated so that file types are added and removed instead of individual files so that dynamic file type addition / removal can be implemented by cgroup and used by controllers. blkio controller changes which will come through block tree are dependent on this. Other changes include res_counter cleanup and disallowing kthread / PF_THREAD_BOUND threads to be attached to non-root cgroups. There's a reported bug with the file type addition / removal handling which can lead to oops on cgroup umount. The issue is being looked into. It shouldn't cause problems for most setups and isn't a security concern." Fix up trivial conflict in Documentation/feature-removal-schedule.txt * 'for-3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits) res_counter: Account max_usage when calling res_counter_charge_nofail() res_counter: Merge res_counter_charge and res_counter_charge_nofail cgroups: disallow attaching kthreadd or PF_THREAD_BOUND threads cgroup: remove cgroup_subsys->populate() cgroup: get rid of populate for memcg cgroup: pass struct mem_cgroup instead of struct cgroup to socket memcg cgroup: make css->refcnt clearing on cgroup removal optional cgroup: use negative bias on css->refcnt to block css_tryget() cgroup: implement cgroup_rm_cftypes() cgroup: introduce struct cfent cgroup: relocate __d_cgrp() and __d_cft() cgroup: remove cgroup_add_file[s]() cgroup: convert memcg controller to the new cftype interface memcg: always create memsw files if CONFIG_CGROUP_MEM_RES_CTLR_SWAP cgroup: convert all non-memcg controllers to the new cftype interface cgroup: relocate cftype and cgroup_subsys definitions in controllers cgroup: merge cft_release_agent cftype array into the base files array cgroup: implement cgroup_add_cftypes() and friends cgroup: build list of all cgroups under a given cgroupfs_root cgroup: move cgroup_clear_directory() call out of cgroup_populate_dir() ...
2012-05-21Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux Pull s390 updates from Martin Schwidefsky: "Just a random collection of bug-fixes and cleanups, nothing new in this merge request." * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (46 commits) s390/ap: Fix wrong or missing comments s390/ap: move receive callback to message struct s390/dasd: re-prioritize partition detection message s390/qeth: reshuffle initialization s390/qeth: cleanup drv attr usage s390/claw: cleanup drv attr usage s390/lcs: cleanup drv attr usage s390/ctc: cleanup drv attr usage s390/ccwgroup: remove ccwgroup_create_from_string s390/qeth: stop using struct ccwgroup driver for discipline callbacks s390/qeth: switch to ccwgroup_create_dev s390/claw: switch to ccwgroup_create_dev s390/lcs: switch to ccwgroup_create_dev s390/ctcm: switch to ccwgroup_create_dev s390/ccwgroup: exploit ccwdev_by_dev_id s390/ccwgroup: introduce ccwgroup_create_dev s390: fix race on TIF_MCCK_PENDING s390/barrier: make use of fast-bcr facility s390/barrier: cleanup barrier functions s390/claw: remove "eieio" calls ...
2012-05-16s390/dasd: re-prioritize partition detection messageStefan Haberland
To avoid confusion while formatting a DASD device change the level of the "Expected VOL1 label not found" message from warning to info. Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2012-05-15block: fix buffer overflow when printing partition UUIDsTejun Heo
6d1d8050b4bc8 "block, partition: add partition_meta_info to hd_struct" added part_unpack_uuid() which assumes that the passed in buffer has enough space for sprintfing "%pU" - 37 characters including '\0'. Unfortunately, b5af921ec0233 "init: add support for root devices specified by partition UUID" supplied 33 bytes buffer to the function leading to the following panic with stackprotector enabled. Kernel panic - not syncing: stack-protector: Kernel stack corrupted in: ffffffff81b14c7e [<ffffffff815e226b>] panic+0xba/0x1c6 [<ffffffff81b14c7e>] ? printk_all_partitions+0x259/0x26xb [<ffffffff810566bb>] __stack_chk_fail+0x1b/0x20 [<ffffffff81b15c7e>] printk_all_paritions+0x259/0x26xb [<ffffffff81aedfe0>] mount_block_root+0x1bc/0x27f [<ffffffff81aee0fa>] mount_root+0x57/0x5b [<ffffffff81aee23b>] prepare_namespace+0x13d/0x176 [<ffffffff8107eec0>] ? release_tgcred.isra.4+0x330/0x30 [<ffffffff81aedd60>] kernel_init+0x155/0x15a [<ffffffff81087b97>] ? schedule_tail+0x27/0xb0 [<ffffffff815f4d24>] kernel_thread_helper+0x5/0x10 [<ffffffff81aedc0b>] ? start_kernel+0x3c5/0x3c5 [<ffffffff815f4d20>] ? gs_change+0x13/0x13 Increase the buffer size, remove the dangerous part_unpack_uuid() and use snprintf() directly from printk_all_partitions(). Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Szymon Gruszczynski <sz.gruszczynski@googlemail.com> Cc: Will Drewry <wad@chromium.org> Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-05-01Merge tag 'v3.4-rc5' into for-3.5/coreJens Axboe
The core branch is behind driver commits that we want to build on for 3.5, hence I'm pulling in a later -rc. Linux 3.4-rc5 Conflicts: Documentation/feature-removal-schedule.txt Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20blkcg: use radix tree to index blkgs from blkcgTejun Heo
blkg lookup is currently performed by traversing linked list anchored at blkcg->blkg_list. This is very unscalable and with blk-throttle enabled and enough request queues on the system, this can get very ugly quickly (blk-throttle performs look up on every bio submission). This patch makes blkcg use radix tree to index blkgs combined with simple last-looked-up hint. This is mostly identical to how icqs are indexed from ioc. Note that because __blkg_lookup() may be invoked without holding queue lock, hint is only updated from __blkg_lookup_create(). Due to cfq's cfqq caching, this makes hint updates overly lazy. This will be improved with scheduled blkcg aware request allocation. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20blkcg: fix blkcg->css ref leak in __blkg_lookup_create()Tejun Heo
__blkg_lookup_create() leaked blkcg->css ref if blkg allocation failed. Fix it. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20block: fix elvpriv allocation failure handlingTejun Heo
Request allocation is mempool backed to guarantee forward progress under memory pressure; unfortunately, this property got broken while adding elvpriv data. Failures during elvpriv allocation, including ioc and icq creation failures, currently make get_request() fail as whole. There's no forward progress guarantee for these allocations - they may fail indefinitely under memory pressure stalling IO and deadlocking the system. This patch updates get_request() such that elvpriv allocation failure doesn't make the whole function fail. If elvpriv allocation fails, the allocation is degraded into !ELVPRIV. This will force the request to ELEVATOR_INSERT_BACK disturbing scheduling but elvpriv alloc failures should be rare (nothing is per-request) and anything is better than deadlocking. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20block: collapse blk_alloc_request() into get_request()Tejun Heo
Allocation failure handling in get_request() is about to be updated. To ease the update, collapse blk_alloc_request() into get_request(). This patch doesn't introduce any functional change. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20blkcg: collapse blkcg_policy_ops into blkcg_policyTejun Heo
There's no reason to keep blkcg_policy_ops separate. Collapse it into blkcg_policy. 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>
2012-04-20blkcg: embed struct blkg_policy_data in policy specific dataTejun Heo
Currently blkg_policy_data carries policy specific data as char flex array instead of being embedded in policy specific data. This was forced by oddities around blkg allocation which are all gone now. This patch makes blkg_policy_data embedded in policy specific data - throtl_grp and cfq_group so that it's more conventional and consistent with how io_cq is handled. * blkcg_policy->pdata_size is renamed to ->pd_size. * Functions which used to take void *pdata now takes struct blkg_policy_data *pd. * blkg_to_pdata/pdata_to_blkg() updated to blkg_to_pd/pd_to_blkg(). * Dummy struct blkg_policy_data definition added. Dummy pdata_to_blkg() definition was unused and inconsistent with the non-dummy version - correct dummy pd_to_blkg() added. * throtl and cfq updated accordingly. * As dummy blkg_to_pd/pd_to_blkg() are provided, blkg_to_cfqg/cfqg_to_blkg() don't need to be ifdef'd. Moved outside ifdef block. 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>
2012-04-20blkcg: mass rename of blkcg APITejun Heo
During the recent blkcg cleanup, most of blkcg API has changed to such extent that mass renaming wouldn't cause any noticeable pain. Take the chance and cleanup the naming. * Rename blkio_cgroup to blkcg. * Drop blkio / blkiocg prefixes and consistently use blkcg. * Rename blkio_group to blkcg_gq, which is consistent with io_cq but keep the blkg prefix / variable name. * Rename policy method type and field names to signify they're dealing with policy data. * Rename blkio_policy_type to blkcg_policy. This patch doesn't cause 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>
2012-04-20blkcg: style cleanups for blk-cgroup.hTejun Heo
* Update indentation on struct field declarations. * Uniformly don't use "extern" on function declarations. * Merge the two #ifdef CONFIG_BLK_CGROUP blocks. All changes in this patch are cosmetic. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20blkcg: remove blkio_group->path[]Tejun Heo
blkio_group->path[] stores the path of the associated cgroup and is used only for debug messages. Just format the path from blkg->cgroup when printing debug messages. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>