kernel/linux.git/drivers/md/bcache/writeback.h, branch linux-4.20.y

bcache: add identifier names to arguments of function definitions

2018-08-11T21:46:41+00:00

There are many function definitions do not have identifier argument names, scripts/checkpatch.pl complains warnings like this, WARNING: function definition argument 'struct bcache_device *' should also have an identifier name #16735: FILE: writeback.h:120: +void bch_sectors_dirty_init(struct bcache_device *); This patch adds identifier argument names to all bcache function definitions to fix such warnings. Signed-off-by: Coly Li Reviewed: Shenghui Wang Signed-off-by: Jens Axboe

bcache: style fix to replace 'unsigned' by 'unsigned int'

2018-08-11T21:46:41+00:00

This patch fixes warning reported by checkpatch.pl by replacing 'unsigned' with 'unsigned int'. Signed-off-by: Coly Li Reviewed-by: Shenghui Wang Signed-off-by: Jens Axboe

bcache: simplify the calculation of the total amount of flash dirty data

2018-07-27T15:15:46+00:00

Currently we calculate the total amount of flash only devices dirty data by adding the dirty data of each flash only device under registering locker. It is very inefficient. In this patch, we add a member flash_dev_dirty_sectors in struct cache_set to record the total amount of flash only devices dirty data in real time, so we didn't need to calculate the total amount of dirty data any more. Signed-off-by: Tang Junhui Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: Fix indentation

2018-03-19T02:15:20+00:00

This patch avoids that smatch complains about inconsistent indentation. Signed-off-by: Bart Van Assche Reviewed-by: Michael Lyle Reviewed-by: Coly Li Signed-off-by: Jens Axboe

bcache: fix cached_dev->count usage for bch_cache_set_error()

2018-03-19T02:15:20+00:00

When bcache metadata I/O fails, bcache will call bch_cache_set_error() to retire the whole cache set. The expected behavior to retire a cache set is to unregister the cache set, and unregister all backing device attached to this cache set, then remove sysfs entries of the cache set and all attached backing devices, finally release memory of structs cache_set, cache, cached_dev and bcache_device. In my testing when journal I/O failure triggered by disconnected cache device, sometimes the cache set cannot be retired, and its sysfs entry /sys/fs/bcache/ still exits and the backing device also references it. This is not expected behavior. When metadata I/O failes, the call senquence to retire whole cache set is, bch_cache_set_error() bch_cache_set_unregister() bch_cache_set_stop() __cache_set_unregister() <- called as callback by calling clousre_queue(&c->caching) cache_set_flush() <- called as a callback when refcount of cache_set->caching is 0 cache_set_free() <- called as a callback when refcount of catch_set->cl is 0 bch_cache_set_release() <- called as a callback when refcount of catch_set->kobj is 0 I find if kernel thread bch_writeback_thread() quits while-loop when kthread_should_stop() is true and searched_full_index is false, clousre callback cache_set_flush() set by continue_at() will never be called. The result is, bcache fails to retire whole cache set. cache_set_flush() will be called when refcount of closure c->caching is 0, and in function bcache_device_detach() refcount of closure c->caching is released to 0 by clousre_put(). In metadata error code path, function bcache_device_detach() is called by cached_dev_detach_finish(). This is a callback routine being called when cached_dev->count is 0. This refcount is decreased by cached_dev_put(). The above dependence indicates, cache_set_flush() will be called when refcount of cache_set->cl is 0, and refcount of cache_set->cl to be 0 when refcount of cache_dev->count is 0. The reason why sometimes cache_dev->count is not 0 (when metadata I/O fails and bch_cache_set_error() called) is, in bch_writeback_thread(), refcount of cache_dev is not decreased properly. In bch_writeback_thread(), cached_dev_put() is called only when searched_full_index is true and cached_dev->writeback_keys is empty, a.k.a there is no dirty data on cache. In most of run time it is correct, but when bch_writeback_thread() quits the while-loop while cache is still dirty, current code forget to call cached_dev_put() before this kernel thread exits. This is why sometimes cache_set_flush() is not executed and cache set fails to be retired. The reason to call cached_dev_put() in bch_writeback_rate() is, when the cache device changes from clean to dirty, cached_dev_get() is called, to make sure during writeback operatiions both backing and cache devices won't be released. Adding following code in bch_writeback_thread() does not work, static int bch_writeback_thread(void *arg) } + if (atomic_read(&dc->has_dirty)) + cached_dev_put() + return 0; } because writeback kernel thread can be waken up and start via sysfs entry: echo 1 > /sys/block/bcache/bcache/writeback_running It is difficult to check whether backing device is dirty without race and extra lock. So the above modification will introduce potential refcount underflow in some conditions. The correct fix is, to take cached dev refcount when creating the kernel thread, and put it before the kernel thread exits. Then bcache does not need to take a cached dev refcount when cache turns from clean to dirty, or to put a cached dev refcount when cache turns from ditry to clean. The writeback kernel thread is alwasy safe to reference data structure from cache set, cache and cached device (because a refcount of cache device is taken for it already), and no matter the kernel thread is stopped by I/O errors or system reboot, cached_dev->count can always be used correctly. The patch is simple, but understanding how it works is quite complicated. Changelog: v2: set dc->writeback_thread to NULL in this patch, as suggested by Hannes. v1: initial version for review. Signed-off-by: Coly Li Reviewed-by: Hannes Reinecke Reviewed-by: Michael Lyle Cc: Michael Lyle Cc: Junhui Tang Signed-off-by: Jens Axboe

bcache: set writeback_rate_update_seconds in range [1, 60] seconds

2018-02-07T19:50:01+00:00

dc->writeback_rate_update_seconds can be set via sysfs and its value can be set to [1, ULONG_MAX]. It does not make sense to set such a large value, 60 seconds is long enough value considering the default 5 seconds works well for long time. Because dc->writeback_rate_update is a special delayed work, it re-arms itself inside the delayed work routine update_writeback_rate(). When stopping it by cancel_delayed_work_sync(), there should be a timeout to wait and make sure the re-armed delayed work is stopped too. A small max value of dc->writeback_rate_update_seconds is also helpful to decide a reasonable small timeout. This patch limits sysfs interface to set dc->writeback_rate_update_seconds in range of [1, 60] seconds, and replaces the hand-coded number by macros. Changelog: v2: fix a rebase typo in v4, which is pointed out by Michael Lyle. v1: initial version. Signed-off-by: Coly Li Reviewed-by: Hannes Reinecke Reviewed-by: Michael Lyle Signed-off-by: Jens Axboe

bcache: fix writeback target calc on large devices

2018-01-08T20:29:00+00:00

Bcache needs to scale the dirty data in the cache over the multiple backing disks in order to calculate writeback rates for each. The previous code did this by multiplying the target number of dirty sectors by the backing device size, and expected it to fit into a uint64_t; this blows up on relatively small backing devices. The new approach figures out the bdev's share in 16384ths of the overall cached data. This is chosen to cope well when bdevs drastically vary in size and to ensure that bcache can cross the petabyte boundary for each backing device. This has been improved based on Tang Junhui's feedback to ensure that every device gets a share of dirty data, no matter how small it is compared to the total backing pool. The existing mechanism is very limited; this is purely a bug fix to remove limits on volume size. However, there still needs to be change to make this "fair" over many volumes where some are idle. Reported-by: Jack Douglas Signed-off-by: Michael Lyle Reviewed-by: Tang Junhui Signed-off-by: Jens Axboe

bcache: reduce cache_set devices iteration by devices_max_used

2018-01-08T20:29:00+00:00

Member devices of struct cache_set is used to reference all attached bcache devices to this cache set. If it is treated as array of pointers, size of devices[] is indicated by member nr_uuids of struct cache_set. nr_uuids is calculated in drivers/md/super.c:bch_cache_set_alloc(), bucket_bytes(c) / sizeof(struct uuid_entry) Bucket size is determined by user space tool "make-bcache", by default it is 1024 sectors (defined in bcache-tools/make-bcache.c:main()). So default nr_uuids value is 4096 from the above calculation. Every time when bcache code iterates bcache devices of a cache set, all the 4096 pointers are checked even only 1 bcache device is attached to the cache set, that's a wast of time and unncessary. This patch adds a member devices_max_used to struct cache_set. Its value is 1 + the maximum used index of devices[] in a cache set. When iterating all valid bcache devices of a cache set, use c->devices_max_used in for-loop may reduce a lot of useless checking. Personally, my motivation of this patch is not for performance, I use it in bcache debugging, which helps me to narrow down the scape to check valid bcached devices of a cache set. Signed-off-by: Coly Li Reviewed-by: Michael Lyle Reviewed-by: Tang Junhui Signed-off-by: Jens Axboe

bcache: fix wrong return value in bch_debug_init()

2018-01-08T20:29:00+00:00

in bch_debug_init(), ret is always 0, and the return value is useless, change it to return 0 if be success after calling debugfs_create_dir(), else return a non-zero value. Signed-off-by: Tang Junhui Reviewed-by: Michael Lyle Signed-off-by: Jens Axboe

Merge branch 'for-4.15/block' of git://git.kernel.dk/linux-block

2017-11-14T23:32:19+00:00

Pull core block layer updates from Jens Axboe: "This is the main pull request for block storage for 4.15-rc1. Nothing out of the ordinary in here, and no API changes or anything like that. Just various new features for drivers, core changes, etc. In particular, this pull request contains: - A patch series from Bart, closing the whole on blk/scsi-mq queue quescing. - A series from Christoph, building towards hidden gendisks (for multipath) and ability to move bio chains around. - NVMe - Support for native multipath for NVMe (Christoph). - Userspace notifications for AENs (Keith). - Command side-effects support (Keith). - SGL support (Chaitanya Kulkarni) - FC fixes and improvements (James Smart) - Lots of fixes and tweaks (Various) - bcache - New maintainer (Michael Lyle) - Writeback control improvements (Michael) - Various fixes (Coly, Elena, Eric, Liang, et al) - lightnvm updates, mostly centered around the pblk interface (Javier, Hans, and Rakesh). - Removal of unused bio/bvec kmap atomic interfaces (me, Christoph) - Writeback series that fix the much discussed hundreds of millions of sync-all units. This goes all the way, as discussed previously (me). - Fix for missing wakeup on writeback timer adjustments (Yafang Shao). - Fix laptop mode on blk-mq (me). - {mq,name} tupple lookup for IO schedulers, allowing us to have alias names. This means you can use 'deadline' on both !mq and on mq (where it's called mq-deadline). (me). - blktrace race fix, oopsing on sg load (me). - blk-mq optimizations (me). - Obscure waitqueue race fix for kyber (Omar). - NBD fixes (Josef). - Disable writeback throttling by default on bfq, like we do on cfq (Luca Miccio). - Series from Ming that enable us to treat flush requests on blk-mq like any other request. This is a really nice cleanup. - Series from Ming that improves merging on blk-mq with schedulers, getting us closer to flipping the switch on scsi-mq again. - BFQ updates (Paolo). - blk-mq atomic flags memory ordering fixes (Peter Z). - Loop cgroup support (Shaohua). - Lots of minor fixes from lots of different folks, both for core and driver code" * 'for-4.15/block' of git://git.kernel.dk/linux-block: (294 commits) nvme: fix visibility of "uuid" ns attribute blk-mq: fixup some comment typos and lengths ide: ide-atapi: fix compile error with defining macro DEBUG blk-mq: improve tag waiting setup for non-shared tags brd: remove unused brd_mutex blk-mq: only run the hardware queue if IO is pending block: avoid null pointer dereference on null disk fs: guard_bio_eod() needs to consider partitions xtensa/simdisk: fix compile error nvme: expose subsys attribute to sysfs nvme: create 'slaves' and 'holders' entries for hidden controllers block: create 'slaves' and 'holders' entries for hidden gendisks nvme: also expose the namespace identification sysfs files for mpath nodes nvme: implement multipath access to nvme subsystems nvme: track shared namespaces nvme: introduce a nvme_ns_ids structure nvme: track subsystems block, nvme: Introduce blk_mq_req_flags_t block, scsi: Make SCSI quiesce and resume work reliably block: Add the QUEUE_FLAG_PREEMPT_ONLY request queue flag ...