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2019-11-13bcache: remove the extra cflags for request.oChristoph Hellwig
There is no block directory this file needs includes from. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-13bcache: at least try to shrink 1 node in bch_mca_scan()Coly Li
In bch_mca_scan(), the number of shrinking btree node is calculated by code like this, unsigned long nr = sc->nr_to_scan; nr /= c->btree_pages; nr = min_t(unsigned long, nr, mca_can_free(c)); variable sc->nr_to_scan is number of objects (here is bcache B+tree nodes' number) to shrink, and pointer variable sc is sent from memory management code as parametr of a callback. If sc->nr_to_scan is smaller than c->btree_pages, after the above calculation, variable 'nr' will be 0 and nothing will be shrunk. It is frequeently observed that only 1 or 2 is set to sc->nr_to_scan and make nr to be zero. Then bch_mca_scan() will do nothing more then acquiring and releasing mutex c->bucket_lock. This patch checkes whether nr is 0 after the above calculation, if 0 is the result then set 1 to variable 'n'. Then at least bch_mca_scan() will try to shrink a single B+tree node. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-13bcache: add idle_max_writeback_rate sysfs interfaceColy Li
For writeback mode, if there is no regular I/O request for a while, the writeback rate will be set to the maximum value (1TB/s for now). This is good for most of the storage workload, but there are still people don't what the maximum writeback rate in I/O idle time. This patch adds a sysfs interface file idle_max_writeback_rate to permit people to disable maximum writeback rate. Then the minimum writeback rate can be advised by writeback_rate_minimum in the bcache device's sysfs interface. Reported-by: Christian Balzer <chibi@gol.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-13bcache: add code comments in bch_btree_leaf_dirty()Coly Li
This patch adds code comments in bch_btree_leaf_dirty() to explain why w->journal should always reference the eldest journal pin of all the writing bkeys in the btree node. To make the bcache journal code to be easier to be understood. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-13bcache: fix deadlock in bcache_allocatorAndrea Righi
bcache_allocator can call the following: bch_allocator_thread() -> bch_prio_write() -> bch_bucket_alloc() -> wait on &ca->set->bucket_wait But the wake up event on bucket_wait is supposed to come from bch_allocator_thread() itself => deadlock: [ 1158.490744] INFO: task bcache_allocato:15861 blocked for more than 10 seconds. [ 1158.495929] Not tainted 5.3.0-050300rc3-generic #201908042232 [ 1158.500653] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 1158.504413] bcache_allocato D 0 15861 2 0x80004000 [ 1158.504419] Call Trace: [ 1158.504429] __schedule+0x2a8/0x670 [ 1158.504432] schedule+0x2d/0x90 [ 1158.504448] bch_bucket_alloc+0xe5/0x370 [bcache] [ 1158.504453] ? wait_woken+0x80/0x80 [ 1158.504466] bch_prio_write+0x1dc/0x390 [bcache] [ 1158.504476] bch_allocator_thread+0x233/0x490 [bcache] [ 1158.504491] kthread+0x121/0x140 [ 1158.504503] ? invalidate_buckets+0x890/0x890 [bcache] [ 1158.504506] ? kthread_park+0xb0/0xb0 [ 1158.504510] ret_from_fork+0x35/0x40 Fix by making the call to bch_prio_write() non-blocking, so that bch_allocator_thread() never waits on itself. Moreover, make sure to wake up the garbage collector thread when bch_prio_write() is failing to allocate buckets. BugLink: https://bugs.launchpad.net/bugs/1784665 BugLink: https://bugs.launchpad.net/bugs/1796292 Signed-off-by: Andrea Righi <andrea.righi@canonical.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-13bcache: add code comment bch_keylist_pop() and bch_keylist_pop_front()Coly Li
This patch adds simple code comments for bch_keylist_pop() and bch_keylist_pop_front() in bset.c, to make the code more easier to be understand. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-13bcache: deleted code comments for dead code in bch_data_insert_keys()Coly Li
In request.c:bch_data_insert_keys(), there is code comment for a piece of dead code. This patch deletes the dead code and its code comment since they are useless in practice. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-13bcache: add more accurate error messages in read_super()Coly Li
Previous code only returns "Not a bcache superblock" for both bcache super block offset and magic error. This patch addss more accurate error messages, - for super block unmatched offset: "Not a bcache superblock (bad offset)" - for super block unmatched magic number: "Not a bcache superblock (bad magic)" Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-13bcache: fix static checker warning in bcache_device_free()Coly Li
Commit cafe56359144 ("bcache: A block layer cache") leads to the following static checker warning: ./drivers/md/bcache/super.c:770 bcache_device_free() warn: variable dereferenced before check 'd->disk' (see line 766) drivers/md/bcache/super.c 762 static void bcache_device_free(struct bcache_device *d) 763 { 764 lockdep_assert_held(&bch_register_lock); 765 766 pr_info("%s stopped", d->disk->disk_name); ^^^^^^^^^ Unchecked dereference. 767 768 if (d->c) 769 bcache_device_detach(d); 770 if (d->disk && d->disk->flags & GENHD_FL_UP) ^^^^^^^ Check too late. 771 del_gendisk(d->disk); 772 if (d->disk && d->disk->queue) 773 blk_cleanup_queue(d->disk->queue); 774 if (d->disk) { 775 ida_simple_remove(&bcache_device_idx, 776 first_minor_to_idx(d->disk->first_minor)); 777 put_disk(d->disk); 778 } 779 It is not 100% sure that the gendisk struct of bcache device will always be there, the warning makes sense when there is problem in block core. This patch tries to remove the static checking warning by checking d->disk to avoid NULL pointer deferences. Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-13bcache: fix a lost wake-up problem caused by mca_cannibalize_lockGuoju Fang
This patch fix a lost wake-up problem caused by the race between mca_cannibalize_lock and bch_cannibalize_unlock. Consider two processes, A and B. Process A is executing mca_cannibalize_lock, while process B takes c->btree_cache_alloc_lock and is executing bch_cannibalize_unlock. The problem happens that after process A executes cmpxchg and will execute prepare_to_wait. In this timeslice process B executes wake_up, but after that process A executes prepare_to_wait and set the state to TASK_INTERRUPTIBLE. Then process A goes to sleep but no one will wake up it. This problem may cause bcache device to dead. Signed-off-by: Guoju Fang <fangguoju@gmail.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-13bcache: fix fifo index swapping condition in journal_pin_cmp()Coly Li
Fifo structure journal.pin is implemented by a cycle buffer, if the back index reaches highest location of the cycle buffer, it will be swapped to 0. Once the swapping happens, it means a smaller fifo index might be associated to a newer journal entry. So the btree node with oldest journal entry won't be selected in bch_btree_leaf_dirty() to reference the dirty B+tree leaf node. This problem may cause bcache journal won't protect unflushed oldest B+tree dirty leaf node in power failure, and this B+tree leaf node is possible to beinconsistent after reboot from power failure. This patch fixes the fifo index comparing logic in journal_pin_cmp(), to avoid potential corrupted B+tree leaf node when the back index of journal pin is swapped. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-11md/raid10: prevent access of uninitialized resync_pages offsetJohn Pittman
Due to unneeded multiplication in the out_free_pages portion of r10buf_pool_alloc(), when using a 3-copy raid10 layout, it is possible to access a resync_pages offset that has not been initialized. This access translates into a crash of the system within resync_free_pages() while passing a bad pointer to put_page(). Remove the multiplication, preventing access to the uninitialized area. Fixes: f0250618361db ("md: raid10: don't use bio's vec table to manage resync pages") Cc: stable@vger.kernel.org # 4.12+ Signed-off-by: John Pittman <jpittman@redhat.com> Suggested-by: David Jeffery <djeffery@redhat.com> Reviewed-by: Laurence Oberman <loberman@redhat.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-11-11md: avoid invalid memory access for array sb->dev_rolesYufen Yu
we need to gurantee 'desc_nr' valid before access array of sb->dev_roles. In addition, we should avoid .load_super always return '0' when level is LEVEL_MULTIPATH, which is not expected. Reported-by: coverity-bot <keescook+coverity-bot@chromium.org> Addresses-Coverity-ID: 1487373 ("Memory - illegal accesses") Fixes: 6a5cb53aaa4e ("md: no longer compare spare disk superblock events in super_load") Signed-off-by: Yufen Yu <yuyufen@huawei.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-11-11md/raid1: avoid soft lockup under high loadHannes Reinecke
As all I/O is being pushed through a kernel thread the softlockup watchdog might be triggered under high load. Signed-off-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-11-07dm: add zone open, close and finish supportAjay Joshi
Implement REQ_OP_ZONE_OPEN, REQ_OP_ZONE_CLOSE and REQ_OP_ZONE_FINISH support to allow explicit control of zone states. Contains contributions from Matias Bjorling, Hans Holmberg and Damien Le Moal. Acked-by: Mike Snitzer <snitzer@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ajay Joshi <ajay.joshi@wdc.com> Signed-off-by: Matias Bjorling <matias.bjorling@wdc.com> Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-07Merge branch 'for-5.5/block' into for-5.5/driversJens Axboe
Pull in dependencies for the new zoned open/close/finish support. * for-5.5/block: (32 commits) block: add zone open, close and finish ioctl support block: add zone open, close and finish operations block: Simplify REQ_OP_ZONE_RESET_ALL handling block: Remove REQ_OP_ZONE_RESET plugging block: Warn if elevator= parameter is used block: avoid blk_bio_segment_split for small I/O operations blk-mq: make sure that line break can be printed block: sed-opal: Introduce Opal Datastore UID block: sed-opal: Add support to read/write opal tables generically block: sed-opal: Generalizing write data to any opal table bdev: Refresh bdev size for disks without partitioning bdev: Factor out bdev revalidation into a common helper blk-mq: avoid sysfs buffer overflow with too many CPU cores blk-mq: Make blk_mq_run_hw_queue() return void fcntl: fix typo in RWH_WRITE_LIFE_NOT_SET r/w hint name blk-mq: fill header with kernel-doc blk-mq: remove needless goto from blk_mq_get_driver_tag block: reorder bio::__bi_remaining for better packing block: Reduce the amount of memory used for tag sets block: Reduce the amount of memory required per request queue ...
2019-11-07block: add zone open, close and finish operationsAjay Joshi
Zoned block devices (ZBC and ZAC devices) allow an explicit control over the condition (state) of zones. The operations allowed are: * Open a zone: Transition to open condition to indicate that a zone will actively be written * Close a zone: Transition to closed condition to release the drive resources used for writing to a zone * Finish a zone: Transition an open or closed zone to the full condition to prevent write operations To enable this control for in-kernel zoned block device users, define the new request operations REQ_OP_ZONE_OPEN, REQ_OP_ZONE_CLOSE and REQ_OP_ZONE_FINISH as well as the generic function blkdev_zone_mgmt() for submitting these operations on a range of zones. This results in blkdev_reset_zones() removal and replacement with this new zone magement function. Users of blkdev_reset_zones() (f2fs and dm-zoned) are updated accordingly. Contains contributions from Matias Bjorling, Hans Holmberg, Dmitry Fomichev, Keith Busch, Damien Le Moal and Christoph Hellwig. Reviewed-by: Javier González <javier@javigon.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ajay Joshi <ajay.joshi@wdc.com> Signed-off-by: Matias Bjorling <matias.bjorling@wdc.com> Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com> Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com> Signed-off-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-10-24md: no longer compare spare disk superblock events in super_loadYufen Yu
We have a test case as follow: mdadm -CR /dev/md1 -l 1 -n 4 /dev/sd[a-d] \ --assume-clean --bitmap=internal mdadm -S /dev/md1 mdadm -A /dev/md1 /dev/sd[b-c] --run --force mdadm --zero /dev/sda mdadm /dev/md1 -a /dev/sda echo offline > /sys/block/sdc/device/state echo offline > /sys/block/sdb/device/state sleep 5 mdadm -S /dev/md1 echo running > /sys/block/sdb/device/state echo running > /sys/block/sdc/device/state mdadm -A /dev/md1 /dev/sd[a-c] --run --force When we readd /dev/sda to the array, it started to do recovery. After offline the other two disks in md1, the recovery have been interrupted and superblock update info cannot be written to the offline disks. While the spare disk (/dev/sda) can continue to update superblock info. After stopping the array and assemble it, we found the array run fail, with the follow kernel message: [ 172.986064] md: kicking non-fresh sdb from array! [ 173.004210] md: kicking non-fresh sdc from array! [ 173.022383] md/raid1:md1: active with 0 out of 4 mirrors [ 173.022406] md1: failed to create bitmap (-5) [ 173.023466] md: md1 stopped. Since both sdb and sdc have the value of 'sb->events' smaller than that in sda, they have been kicked from the array. However, the only remained disk sda is in 'spare' state before stop and it cannot be added to conf->mirrors[] array. In the end, raid array assemble and run fail. In fact, we can use the older disk sdb or sdc to assemble the array. That means we should not choose the 'spare' disk as the fresh disk in analyze_sbs(). To fix the problem, we do not compare superblock events when it is a spare disk, as same as validate_super. Signed-off-by: Yufen Yu <yuyufen@huawei.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-10-24md: improve handling of bio with REQ_PREFLUSH in md_flush_request()David Jeffery
If pers->make_request fails in md_flush_request(), the bio is lost. To fix this, pass back a bool to indicate if the original make_request call should continue to handle the I/O and instead of assuming the flush logic will push it to completion. Convert md_flush_request to return a bool and no longer calls the raid driver's make_request function. If the return is true, then the md flush logic has or will complete the bio and the md make_request call is done. If false, then the md make_request function needs to keep processing like it is a normal bio. Let the original call to md_handle_request handle any need to retry sending the bio to the raid driver's make_request function should it be needed. Also mark md_flush_request and the make_request function pointer as __must_check to issue warnings should these critical return values be ignored. Fixes: 2bc13b83e629 ("md: batch flush requests.") Cc: stable@vger.kernel.org # # v4.19+ Cc: NeilBrown <neilb@suse.com> Signed-off-by: David Jeffery <djeffery@redhat.com> Reviewed-by: Xiao Ni <xni@redhat.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-10-24md/bitmap: avoid race window between md_bitmap_resize and bitmap_file_clear_bitGuoqing Jiang
We need to move "spin_lock_irq(&bitmap->counts.lock)" before unmap previous storage, otherwise panic like belows could happen as follows. [ 902.353802] sdl: detected capacity change from 1077936128 to 3221225472 [ 902.616948] general protection fault: 0000 [#1] SMP [snip] [ 902.618588] CPU: 12 PID: 33698 Comm: md0_raid1 Tainted: G O 4.14.144-1-pserver #4.14.144-1.1~deb10 [ 902.618870] Hardware name: Supermicro SBA-7142G-T4/BHQGE, BIOS 3.00 10/24/2012 [ 902.619120] task: ffff9ae1860fc600 task.stack: ffffb52e4c704000 [ 902.619301] RIP: 0010:bitmap_file_clear_bit+0x90/0xd0 [md_mod] [ 902.619464] RSP: 0018:ffffb52e4c707d28 EFLAGS: 00010087 [ 902.619626] RAX: ffe8008b0d061000 RBX: ffff9ad078c87300 RCX: 0000000000000000 [ 902.619792] RDX: ffff9ad986341868 RSI: 0000000000000803 RDI: ffff9ad078c87300 [ 902.619986] RBP: ffff9ad0ed7a8000 R08: 0000000000000000 R09: 0000000000000000 [ 902.620154] R10: ffffb52e4c707ec0 R11: ffff9ad987d1ed44 R12: ffff9ad0ed7a8360 [ 902.620320] R13: 0000000000000003 R14: 0000000000060000 R15: 0000000000000800 [ 902.620487] FS: 0000000000000000(0000) GS:ffff9ad987d00000(0000) knlGS:0000000000000000 [ 902.620738] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 902.620901] CR2: 000055ff12aecec0 CR3: 0000001005207000 CR4: 00000000000406e0 [ 902.621068] Call Trace: [ 902.621256] bitmap_daemon_work+0x2dd/0x360 [md_mod] [ 902.621429] ? find_pers+0x70/0x70 [md_mod] [ 902.621597] md_check_recovery+0x51/0x540 [md_mod] [ 902.621762] raid1d+0x5c/0xeb0 [raid1] [ 902.621939] ? try_to_del_timer_sync+0x4d/0x80 [ 902.622102] ? del_timer_sync+0x35/0x40 [ 902.622265] ? schedule_timeout+0x177/0x360 [ 902.622453] ? call_timer_fn+0x130/0x130 [ 902.622623] ? find_pers+0x70/0x70 [md_mod] [ 902.622794] ? md_thread+0x94/0x150 [md_mod] [ 902.622959] md_thread+0x94/0x150 [md_mod] [ 902.623121] ? wait_woken+0x80/0x80 [ 902.623280] kthread+0x119/0x130 [ 902.623437] ? kthread_create_on_node+0x60/0x60 [ 902.623600] ret_from_fork+0x22/0x40 [ 902.624225] RIP: bitmap_file_clear_bit+0x90/0xd0 [md_mod] RSP: ffffb52e4c707d28 Because mdadm was running on another cpu to do resize, so bitmap_resize was called to replace bitmap as below shows. PID: 38801 TASK: ffff9ad074a90e00 CPU: 0 COMMAND: "mdadm" [exception RIP: queued_spin_lock_slowpath+56] [snip] -- <NMI exception stack> -- #5 [ffffb52e60f17c58] queued_spin_lock_slowpath at ffffffff9c0b27b8 #6 [ffffb52e60f17c58] bitmap_resize at ffffffffc0399877 [md_mod] #7 [ffffb52e60f17d30] raid1_resize at ffffffffc0285bf9 [raid1] #8 [ffffb52e60f17d50] update_size at ffffffffc038a31a [md_mod] #9 [ffffb52e60f17d70] md_ioctl at ffffffffc0395ca4 [md_mod] And the procedure to keep resize bitmap safe is allocate new storage space, then quiesce, copy bits, replace bitmap, and re-start. However the daemon (bitmap_daemon_work) could happen even the array is quiesced, which means when bitmap_file_clear_bit is triggered by raid1d, then it thinks it should be fine to access store->filemap since counts->lock is held, but resize could change the storage without the protection of the lock. Cc: Jack Wang <jinpu.wang@cloud.ionos.com> Cc: NeilBrown <neilb@suse.com> Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-10-24md/raid0: Fix an error message in raid0_make_request()Dan Carpenter
The first argument to WARN() is supposed to be a condition. The original code will just print the mdname() instead of the full warning message. Fixes: c84a1372df92 ("md/raid0: avoid RAID0 data corruption due to layout confusion.") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-09-24Merge tag 'for-5.4/post-2019-09-24' of git://git.kernel.dk/linux-blockLinus Torvalds
Pull more block updates from Jens Axboe: "Some later additions that weren't quite done for the first pull request, and also a few fixes that have arrived since. This contains: - Kill silly pktcdvd warning on attempting to register a non-scsi passthrough device (me) - Use symbolic constants for the block t10 protection types, and switch to handling it in core rather than in the drivers (Max) - libahci platform missing node put fix (Nishka) - Small series of fixes for BFQ (Paolo) - Fix possible nbd crash (Xiubo)" * tag 'for-5.4/post-2019-09-24' of git://git.kernel.dk/linux-block: block: drop device references in bsg_queue_rq() block: t10-pi: fix -Wswitch warning pktcdvd: remove warning on attempting to register non-passthrough dev ata: libahci_platform: Add of_node_put() before loop exit nbd: fix possible page fault for nbd disk nbd: rename the runtime flags as NBD_RT_ prefixed block, bfq: push up injection only after setting service time block, bfq: increase update frequency of inject limit block, bfq: reduce upper bound for inject limit to max_rq_in_driver+1 block, bfq: update inject limit only after injection occurred block: centralize PI remapping logic to the block layer block: use symbolic constants for t10_pi type
2019-09-21Merge tag 'for-5.4/dm-changes' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm Pull device mapper updates from Mike Snitzer: - crypto and DM crypt advances that allow the crypto API to reclaim implementation details that do not belong in DM crypt. The wrapper template for ESSIV generation that was factored out will also be used by fscrypt in the future. - Add root hash pkcs#7 signature verification to the DM verity target. - Add a new "clone" DM target that allows for efficient remote replication of a device. - Enhance DM bufio's cache to be tailored to each client based on use. Clients that make heavy use of the cache get more of it, and those that use less have reduced cache usage. - Add a new DM_GET_TARGET_VERSION ioctl to allow userspace to query the version number of a DM target (even if the associated module isn't yet loaded). - Fix invalid memory access in DM zoned target. - Fix the max_discard_sectors limit advertised by the DM raid target; it was mistakenly storing the limit in bytes rather than sectors. - Small optimizations and cleanups in DM writecache target. - Various fixes and cleanups in DM core, DM raid1 and space map portion of DM persistent data library. * tag 'for-5.4/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (22 commits) dm: introduce DM_GET_TARGET_VERSION dm bufio: introduce a global cache replacement dm bufio: remove old-style buffer cleanup dm bufio: introduce a global queue dm bufio: refactor adjust_total_allocated dm bufio: call adjust_total_allocated from __link_buffer and __unlink_buffer dm: add clone target dm raid: fix updating of max_discard_sectors limit dm writecache: skip writecache_wait for pmem mode dm stats: use struct_size() helper dm crypt: omit parsing of the encapsulated cipher dm crypt: switch to ESSIV crypto API template crypto: essiv - create wrapper template for ESSIV generation dm space map common: remove check for impossible sm_find_free() return value dm raid1: use struct_size() with kzalloc() dm writecache: optimize performance by sorting the blocks for writeback_all dm writecache: add unlikely for getting two block with same LBA dm writecache: remove unused member pointer in writeback_struct dm zoned: fix invalid memory access dm verity: add root hash pkcs#7 signature verification ...
2019-09-17block: centralize PI remapping logic to the block layerMax Gurtovoy
Currently t10_pi_prepare/t10_pi_complete functions are called during the NVMe and SCSi layers command preparetion/completion, but their actual place should be the block layer since T10-PI is a general data integrity feature that is used by block storage protocols. Introduce .prepare_fn and .complete_fn callbacks within the integrity profile that each type can implement according to its needs. Suggested-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Suggested-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Max Gurtovoy <maxg@mellanox.com> Fixed to not call queue integrity functions if BLK_DEV_INTEGRITY isn't defined in the config. Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-09-17Merge tag 'for-5.4/block-2019-09-16' of git://git.kernel.dk/linux-blockLinus Torvalds
Pull block updates from Jens Axboe: - Two NVMe pull requests: - ana log parse fix from Anton - nvme quirks support for Apple devices from Ben - fix missing bio completion tracing for multipath stack devices from Hannes and Mikhail - IP TOS settings for nvme rdma and tcp transports from Israel - rq_dma_dir cleanups from Israel - tracing for Get LBA Status command from Minwoo - Some nvme-tcp cleanups from Minwoo, Potnuri and Myself - Some consolidation between the fabrics transports for handling the CAP register - reset race with ns scanning fix for fabrics (move fabrics commands to a dedicated request queue with a different lifetime from the admin request queue)." - controller reset and namespace scan races fixes - nvme discovery log change uevent support - naming improvements from Keith - multiple discovery controllers reject fix from James - some regular cleanups from various people - Series fixing (and re-fixing) null_blk debug printing and nr_devices checks (André) - A few pull requests from Song, with fixes from Andy, Guoqing, Guilherme, Neil, Nigel, and Yufen. - REQ_OP_ZONE_RESET_ALL support (Chaitanya) - Bio merge handling unification (Christoph) - Pick default elevator correctly for devices with special needs (Damien) - Block stats fixes (Hou) - Timeout and support devices nbd fixes (Mike) - Series fixing races around elevator switching and device add/remove (Ming) - sed-opal cleanups (Revanth) - Per device weight support for BFQ (Fam) - Support for blk-iocost, a new model that can properly account cost of IO workloads. (Tejun) - blk-cgroup writeback fixes (Tejun) - paride queue init fixes (zhengbin) - blk_set_runtime_active() cleanup (Stanley) - Block segment mapping optimizations (Bart) - lightnvm fixes (Hans/Minwoo/YueHaibing) - Various little fixes and cleanups * tag 'for-5.4/block-2019-09-16' of git://git.kernel.dk/linux-block: (186 commits) null_blk: format pr_* logs with pr_fmt null_blk: match the type of parameter nr_devices null_blk: do not fail the module load with zero devices block: also check RQF_STATS in blk_mq_need_time_stamp() block: make rq sector size accessible for block stats bfq: Fix bfq linkage error raid5: use bio_end_sector in r5_next_bio raid5: remove STRIPE_OPS_REQ_PENDING md: add feature flag MD_FEATURE_RAID0_LAYOUT md/raid0: avoid RAID0 data corruption due to layout confusion. raid5: don't set STRIPE_HANDLE to stripe which is in batch list raid5: don't increment read_errors on EILSEQ return nvmet: fix a wrong error status returned in error log page nvme: send discovery log page change events to userspace nvme: add uevent variables for controller devices nvme: enable aen regardless of the presence of I/O queues nvme-fabrics: allow discovery subsystems accept a kato nvmet: Use PTR_ERR_OR_ZERO() in nvmet_init_discovery() nvme: Remove redundant assignment of cq vector nvme: Assign subsys instance from first ctrl ...
2019-09-16dm: introduce DM_GET_TARGET_VERSIONMikulas Patocka
This commit introduces a new ioctl DM_GET_TARGET_VERSION. It will load a target that is specified in the "name" entry in the parameter structure and return its version. This functionality is intended to be used by cryptsetup, so that it can query kernel capabilities before activating the device. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-13dm bufio: introduce a global cache replacementMikulas Patocka
This commit introduces a global cache replacement (instead of per-client cleanup). If one bufio client uses the cache heavily and another client is not using it, we want to let the first client use most of the cache. The old algorithm would partition the cache equally betwen the clients and that is sub-optimal. For cache replacement, we use the clock algorithm because it doesn't require taking any lock when the buffer is accessed. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-13raid5: use bio_end_sector in r5_next_bioGuoqing Jiang
Actually, we calculate bio's end sector here, so use the common way for the purpose. Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-09-13raid5: remove STRIPE_OPS_REQ_PENDINGGuoqing Jiang
This stripe state is not used anymore after commit 51acbcec6c42b24 ("md: remove CONFIG_MULTICORE_RAID456"), so remove the obsoleted state. gjiang@nb01257:~/md$ grep STRIPE_OPS_REQ_PENDING drivers/md/ -r drivers/md/raid5.c: (1 << STRIPE_OPS_REQ_PENDING) | drivers/md/raid5.h: STRIPE_OPS_REQ_PENDING, Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-09-13md: add feature flag MD_FEATURE_RAID0_LAYOUTNeilBrown
Due to a bug introduced in Linux 3.14 we cannot determine the correctly layout for a multi-zone RAID0 array - there are two possibilities. It is possible to tell the kernel which to chose using a module parameter, but this can be clumsy to use. It would be best if the choice were recorded in the metadata. So add a feature flag for this purpose. If it is set, then the 'layout' field of the superblock is used to determine which layout to use. If this flag is not set, then mddev->layout gets set to -1, which causes the module parameter to be required. Acked-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com> Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-09-13md/raid0: avoid RAID0 data corruption due to layout confusion.NeilBrown
If the drives in a RAID0 are not all the same size, the array is divided into zones. The first zone covers all drives, to the size of the smallest. The second zone covers all drives larger than the smallest, up to the size of the second smallest - etc. A change in Linux 3.14 unintentionally changed the layout for the second and subsequent zones. All the correct data is still stored, but each chunk may be assigned to a different device than in pre-3.14 kernels. This can lead to data corruption. It is not possible to determine what layout to use - it depends which kernel the data was written by. So we add a module parameter to allow the old (0) or new (1) layout to be specified, and refused to assemble an affected array if that parameter is not set. Fixes: 20d0189b1012 ("block: Introduce new bio_split()") cc: stable@vger.kernel.org (3.14+) Acked-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com> Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-09-13raid5: don't set STRIPE_HANDLE to stripe which is in batch listGuoqing Jiang
If stripe in batch list is set with STRIPE_HANDLE flag, then the stripe could be set with STRIPE_ACTIVE by the handle_stripe function. And if error happens to the batch_head at the same time, break_stripe_batch_list is called, then below warning could happen (the same report in [1]), it means a member of batch list was set with STRIPE_ACTIVE. [7028915.431770] stripe state: 2001 [7028915.431815] ------------[ cut here ]------------ [7028915.431828] WARNING: CPU: 18 PID: 29089 at drivers/md/raid5.c:4614 break_stripe_batch_list+0x203/0x240 [raid456] [...] [7028915.431879] CPU: 18 PID: 29089 Comm: kworker/u82:5 Tainted: G O 4.14.86-1-storage #4.14.86-1.2~deb9 [7028915.431881] Hardware name: Supermicro SSG-2028R-ACR24L/X10DRH-iT, BIOS 3.1 06/18/2018 [7028915.431888] Workqueue: raid5wq raid5_do_work [raid456] [7028915.431890] task: ffff9ab0ef36d7c0 task.stack: ffffb72926f84000 [7028915.431896] RIP: 0010:break_stripe_batch_list+0x203/0x240 [raid456] [7028915.431898] RSP: 0018:ffffb72926f87ba8 EFLAGS: 00010286 [7028915.431900] RAX: 0000000000000012 RBX: ffff9aaa84a98000 RCX: 0000000000000000 [7028915.431901] RDX: 0000000000000000 RSI: ffff9ab2bfa15458 RDI: ffff9ab2bfa15458 [7028915.431902] RBP: ffff9aaa8fb4e900 R08: 0000000000000001 R09: 0000000000002eb4 [7028915.431903] R10: 00000000ffffffff R11: 0000000000000000 R12: ffff9ab1736f1b00 [7028915.431904] R13: 0000000000000000 R14: ffff9aaa8fb4e900 R15: 0000000000000001 [7028915.431906] FS: 0000000000000000(0000) GS:ffff9ab2bfa00000(0000) knlGS:0000000000000000 [7028915.431907] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [7028915.431908] CR2: 00007ff953b9f5d8 CR3: 0000000bf4009002 CR4: 00000000003606e0 [7028915.431909] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [7028915.431910] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [7028915.431910] Call Trace: [7028915.431923] handle_stripe+0x8e7/0x2020 [raid456] [7028915.431930] ? __wake_up_common_lock+0x89/0xc0 [7028915.431935] handle_active_stripes.isra.58+0x35f/0x560 [raid456] [7028915.431939] raid5_do_work+0xc6/0x1f0 [raid456] Also commit 59fc630b8b5f9f ("RAID5: batch adjacent full stripe write") said "If a stripe is added to batch list, then only the first stripe of the list should be put to handle_list and run handle_stripe." So don't set STRIPE_HANDLE to stripe which is already in batch list, otherwise the stripe could be put to handle_list and run handle_stripe, then the above warning could be triggered. [1]. https://www.spinics.net/lists/raid/msg62552.html Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-09-13raid5: don't increment read_errors on EILSEQ returnNigel Croxon
While MD continues to count read errors returned by the lower layer. If those errors are -EILSEQ, instead of -EIO, it should NOT increase the read_errors count. When RAID6 is set up on dm-integrity target that detects massive corruption, the leg will be ejected from the array. Even if the issue is correctable with a sector re-write and the array has necessary redundancy to correct it. The leg is ejected because it runs up the rdev->read_errors beyond conf->max_nr_stripes. The return status in dm-drypt when there is a data integrity error is -EILSEQ (BLK_STS_PROTECTION). Signed-off-by: Nigel Croxon <ncroxon@redhat.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-09-13dm bufio: remove old-style buffer cleanupMikulas Patocka
Remove code that cleans up buffers if the cache size grows over the limit. The next commit will introduce a new global cleanup. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-13dm bufio: introduce a global queueMikulas Patocka
Rename param_spinlock to global_spinlock and introduce a global queue of all used buffers. The queue will be used in the following commits. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-13dm bufio: refactor adjust_total_allocatedMikulas Patocka
Refactor adjust_total_allocated() so that it takes a bool argument indicating if it should add or subtract the buffer size. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-13dm bufio: call adjust_total_allocated from __link_buffer and __unlink_bufferMikulas Patocka
Move the call to adjust_total_allocated() to __link_buffer() and __unlink_buffer() so that only used buffers are counted. Reserved buffers are not. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-12dm: add clone targetNikos Tsironis
Add the dm-clone target, which allows cloning of arbitrary block devices. dm-clone produces a one-to-one copy of an existing, read-only source device into a writable destination device: It presents a virtual block device which makes all data appear immediately, and redirects reads and writes accordingly. The main use case of dm-clone is to clone a potentially remote, high-latency, read-only, archival-type block device into a writable, fast, primary-type device for fast, low-latency I/O. The cloned device is visible/mountable immediately and the copy of the source device to the destination device happens in the background, in parallel with user I/O. When the cloning completes, the dm-clone table can be removed altogether and be replaced, e.g., by a linear table, mapping directly to the destination device. For further information and examples of how to use dm-clone, please read Documentation/admin-guide/device-mapper/dm-clone.rst Suggested-by: Vangelis Koukis <vkoukis@arrikto.com> Co-developed-by: Ilias Tsitsimpis <iliastsi@arrikto.com> Signed-off-by: Ilias Tsitsimpis <iliastsi@arrikto.com> Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-11dm raid: fix updating of max_discard_sectors limitMing Lei
Unit of 'chunk_size' is byte, instead of sector, so fix it by setting the queue_limits' max_discard_sectors to rs->md.chunk_sectors. Also, rename chunk_size to chunk_size_bytes. Without this fix, too big max_discard_sectors is applied on the request queue of dm-raid, finally raid code has to split the bio again. This re-split done by raid causes the following nested clone_endio: 1) one big bio 'A' is submitted to dm queue, and served as the original bio 2) one new bio 'B' is cloned from the original bio 'A', and .map() is run on this bio of 'B', and B's original bio points to 'A' 3) raid code sees that 'B' is too big, and split 'B' and re-submit the remainded part of 'B' to dm-raid queue via generic_make_request(). 4) now dm will handle 'B' as new original bio, then allocate a new clone bio of 'C' and run .map() on 'C'. Meantime C's original bio points to 'B'. 5) suppose now 'C' is completed by raid directly, then the following clone_endio() is called recursively: clone_endio(C) ->clone_endio(B) #B is original bio of 'C' ->bio_endio(A) 'A' can be big enough to make hundreds of nested clone_endio(), then stack can be corrupted easily. Fixes: 61697a6abd24a ("dm: eliminate 'split_discard_bios' flag from DM target interface") Cc: stable@vger.kernel.org Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-05block: Delay default elevator initializationDamien Le Moal
When elevator_init_mq() is called from blk_mq_init_allocated_queue(), the only information known about the device is the number of hardware queues as the block device scan by the device driver is not completed yet for most drivers. The device type and elevator required features are not set yet, preventing to correctly select the default elevator most suitable for the device. This currently affects all multi-queue zoned block devices which default to the "none" elevator instead of the required "mq-deadline" elevator. These drives currently include host-managed SMR disks connected to a smartpqi HBA and null_blk block devices with zoned mode enabled. Upcoming NVMe Zoned Namespace devices will also be affected. Fix this by adding the boolean elevator_init argument to blk_mq_init_allocated_queue() to control the execution of elevator_init_mq(). Two cases exist: 1) elevator_init = false is used for calls to blk_mq_init_allocated_queue() within blk_mq_init_queue(). In this case, a call to elevator_init_mq() is added to __device_add_disk(), resulting in the delayed initialization of the queue elevator after the device driver finished probing the device information. This effectively allows elevator_init_mq() access to more information about the device. 2) elevator_init = true preserves the current behavior of initializing the elevator directly from blk_mq_init_allocated_queue(). This case is used for the special request based DM devices where the device gendisk is created before the queue initialization and device information (e.g. queue limits) is already known when the queue initialization is executed. Additionally, to make sure that the elevator initialization is never done while requests are in-flight (there should be none when the device driver calls device_add_disk()), freeze and quiesce the device request queue before calling blk_mq_init_sched() in elevator_init_mq(). Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-09-05dm writecache: skip writecache_wait for pmem modeHuaisheng Ye
The array bio_in_progress[2] only have chance to be increased and decreased with ssd mode. For pmem mode, they are not involved at all. So skip writecache_wait_for_ios in writecache_flush for pmem. Suggested-by: Doris Yu <tyu1@lenovo.com> Signed-off-by: Huaisheng Ye <yehs1@lenovo.com> Acked-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-04dm stats: use struct_size() helperGustavo A. R. Silva
One of the more common cases of allocation size calculations is finding the size of a structure that has a zero-sized array at the end, along with memory for some number of elements for that array. For example: struct dm_stat { ... struct dm_stat_shared stat_shared[0]; }; Make use of the struct_size() helper instead of an open-coded version in order to avoid any potential type mistakes. So, replace the following form: sizeof(struct dm_stat) + (size_t)n_entries * sizeof(struct dm_stat_shared) with: struct_size(s, stat_shared, n_entries) This code was detected with the help of Coccinelle. Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-03md/raid5: use bio_end_sector to calculate last_sectorGuoqing Jiang
Use the common way to get last_sector. Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-09-03md/raid1: fail run raid1 array when active disk less than oneYufen Yu
When run test case: mdadm -CR /dev/md1 -l 1 -n 4 /dev/sd[a-d] --assume-clean --bitmap=internal mdadm -S /dev/md1 mdadm -A /dev/md1 /dev/sd[b-c] --run --force mdadm --zero /dev/sda mdadm /dev/md1 -a /dev/sda echo offline > /sys/block/sdc/device/state echo offline > /sys/block/sdb/device/state sleep 5 mdadm -S /dev/md1 echo running > /sys/block/sdb/device/state echo running > /sys/block/sdc/device/state mdadm -A /dev/md1 /dev/sd[a-c] --run --force mdadm run fail with kernel message as follow: [ 172.986064] md: kicking non-fresh sdb from array! [ 173.004210] md: kicking non-fresh sdc from array! [ 173.022383] md/raid1:md1: active with 0 out of 4 mirrors [ 173.022406] md1: failed to create bitmap (-5) In fact, when active disk in raid1 array less than one, we need to return fail in raid1_run(). Reviewed-by: NeilBrown <neilb@suse.de> Signed-off-by: Yufen Yu <yuyufen@huawei.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-09-03md raid0/linear: Mark array as 'broken' and fail BIOs if a member is goneGuilherme G. Piccoli
Currently md raid0/linear are not provided with any mechanism to validate if an array member got removed or failed. The driver keeps sending BIOs regardless of the state of array members, and kernel shows state 'clean' in the 'array_state' sysfs attribute. This leads to the following situation: if a raid0/linear array member is removed and the array is mounted, some user writing to this array won't realize that errors are happening unless they check dmesg or perform one fsync per written file. Despite udev signaling the member device is gone, 'mdadm' cannot issue the STOP_ARRAY ioctl successfully, given the array is mounted. In other words, no -EIO is returned and writes (except direct ones) appear normal. Meaning the user might think the wrote data is correctly stored in the array, but instead garbage was written given that raid0 does stripping (and so, it requires all its members to be working in order to not corrupt data). For md/linear, writes to the available members will work fine, but if the writes go to the missing member(s), it'll cause a file corruption situation, whereas the portion of the writes to the missing devices aren't written effectively. This patch changes this behavior: we check if the block device's gendisk is UP when submitting the BIO to the array member, and if it isn't, we flag the md device as MD_BROKEN and fail subsequent I/Os to that device; a read request to the array requiring data from a valid member is still completed. While flagging the device as MD_BROKEN, we also show a rate-limited warning in the kernel log. A new array state 'broken' was added too: it mimics the state 'clean' in every aspect, being useful only to distinguish if the array has some member missing. We rely on the MD_BROKEN flag to put the array in the 'broken' state. This state cannot be written in 'array_state' as it just shows one or more members of the array are missing but acts like 'clean', it wouldn't make sense to write it. With this patch, the filesystem reacts much faster to the event of missing array member: after some I/O errors, ext4 for instance aborts the journal and prevents corruption. Without this change, we're able to keep writing in the disk and after a machine reboot, e2fsck shows some severe fs errors that demand fixing. This patch was tested in ext4 and xfs filesystems, and requires a 'mdadm' counterpart to handle the 'broken' state. Cc: Song Liu <songliubraving@fb.com> Reviewed-by: NeilBrown <neilb@suse.de> Signed-off-by: Guilherme G. Piccoli <gpiccoli@canonical.com> Signed-off-by: Song Liu <songliubraving@fb.com>
2019-09-03dm crypt: omit parsing of the encapsulated cipherArd Biesheuvel
Only the ESSIV IV generation mode used to use cc->cipher so it could instantiate the bare cipher used to encrypt the IV. However, this is now taken care of by the ESSIV template, and so no users of cc->cipher remain. So remove it altogether. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Tested-by: Milan Broz <gmazyland@gmail.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-03dm crypt: switch to ESSIV crypto API templateArd Biesheuvel
Replace the explicit ESSIV handling in the dm-crypt driver with calls into the crypto API, which now possesses the capability to perform this processing within the crypto subsystem. Note that we reorder the AEAD cipher_api string parsing with the TFM instantiation: this is needed because cipher_api is mangled by the ESSIV handling, and throws off the parsing of "authenc(" otherwise. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Tested-by: Milan Broz <gmazyland@gmail.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-09-03closures: fix a race on wakeup from closure_syncKent Overstreet
The race was when a thread using closure_sync() notices cl->s->done == 1 before the thread calling closure_put() calls wake_up_process(). Then, it's possible for that thread to return and exit just before wake_up_process() is called - so we're trying to wake up a process that no longer exists. rcu_read_lock() is sufficient to protect against this, as there's an rcu barrier somewhere in the process teardown path. Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com> Acked-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-09-03bcache: Fix an error code in bch_dump_read()Dan Carpenter
The copy_to_user() function returns the number of bytes remaining to be copied, but the intention here was to return -EFAULT if the copy fails. Fixes: cafe56359144 ("bcache: A block layer cache") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-09-03bcache: add cond_resched() in __bch_cache_cmp()Shile Zhang
Read /sys/fs/bcache/<uuid>/cacheN/priority_stats can take very long time with huge cache after long run. Signed-off-by: Shile Zhang <shile.zhang@linux.alibaba.com> Tested-by: Heitor Alves de Siqueira <halves@canonical.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>