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2019-05-21treewide: Add SPDX license identifier - Makefile/KconfigThomas Gleixner1-0/+1
Add SPDX license identifiers to all Make/Kconfig files which: - Have no license information of any form These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-01bcache: make is_discard_enabled() staticJens Axboe1-1/+1
It's not used outside this file. Fixes: 631207314d88 ("bcache: fix failure in journal relplay") Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-30block: remove the i argument to bio_for_each_segment_allChristoph Hellwig1-2/+1
We only have two callers that need the integer loop iterator, and they can easily maintain it themselves. Suggested-by: Matthew Wilcox <willy@infradead.org> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Acked-by: David Sterba <dsterba@suse.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Acked-by: Coly Li <colyli@suse.de> Reviewed-by: Matthew Wilcox <willy@infradead.org> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-30bcache: clean up do_btree_node_write a bitChristoph Hellwig1-4/+5
Use a variable containing the buffer address instead of the to be removed integer iterator from bio_for_each_segment_all. Suggested-by: Matthew Wilcox <willy@infradead.org> Reviewed-by: Hannes Reinecke <hare@suse.com> Acked-by: Coly Li <colyli@suse.de> Reviewed-by: Matthew Wilcox <willy@infradead.org> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-30bcache: remove redundant LIST_HEAD(journal) from run_cache_set()Coly Li1-1/+0
Commit 95f18c9d1310 ("bcache: avoid potential memleak of list of journal_replay(s) in the CACHE_SYNC branch of run_cache_set") forgets to remove the original define of LIST_HEAD(journal), which makes the change no take effect. This patch removes redundant variable LIST_HEAD(journal) from run_cache_set(), to make Shenghui's fix working. Fixes: 95f18c9d1310 ("bcache: avoid potential memleak of list of journal_replay(s) in the CACHE_SYNC branch of run_cache_set") Reported-by: Juha Aatrokoski <juha.aatrokoski@aalto.fi> Cc: Shenghui Wang <shhuiw@foxmail.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: avoid potential memleak of list of journal_replay(s) in the CACHE_SYNC branch of run_cache_setShenghui Wang1-0/+8
In the CACHE_SYNC branch of run_cache_set(), LIST_HEAD(journal) is used to collect journal_replay(s) and filled by bch_journal_read(). If all goes well, bch_journal_replay() will release the list of jounal_replay(s) at the end of the branch. If something goes wrong, code flow will jump to the label "err:" and leave the list unreleased. This patch will release the list of journal_replay(s) in the case of error detected. v1 -> v2: * Move the release code to the location after label 'err:' to simply the change. Signed-off-by: Shenghui Wang <shhuiw@foxmail.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: fix wrong usage use-after-freed on keylist in out_nocoalesce branch of btree_gc_coalesceShenghui Wang1-1/+1
Elements of keylist should be accessed before the list is freed. Move bch_keylist_free() calling after the while loop to avoid wrong content accessed. Signed-off-by: Shenghui Wang <shhuiw@foxmail.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: fix failure in journal relplayTang Junhui1-4/+21
journal replay failed with messages: Sep 10 19:10:43 ceph kernel: bcache: error on bb379a64-e44e-4812-b91d-a5599871a3b1: bcache: journal entries 2057493-2057567 missing! (replaying 2057493-2076601), disabling caching The reason is in journal_reclaim(), when discard is enabled, we send discard command and reclaim those journal buckets whose seq is old than the last_seq_now, but before we write a journal with last_seq_now, the machine is restarted, so the journal with the last_seq_now is not written to the journal bucket, and the last_seq_wrote in the newest journal is old than last_seq_now which we expect to be, so when we doing replay, journals from last_seq_wrote to last_seq_now are missing. It's hard to write a journal immediately after journal_reclaim(), and it harmless if those missed journal are caused by discarding since those journals are already wrote to btree node. So, if miss seqs are started from the beginning journal, we treat it as normal, and only print a message to show the miss journal, and point out it maybe caused by discarding. Patch v2 add a judgement condition to ignore the missed journal only when discard enabled as Coly suggested. (Coly Li: rebase the patch with other changes in bch_journal_replay()) Signed-off-by: Tang Junhui <tang.junhui.linux@gmail.com> Tested-by: Dennis Schridde <devurandom@gmx.net> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: improve bcache_reboot()Coly Li1-2/+10
This patch tries to release mutex bch_register_lock early, to give chance to stop cache set and bcache device early. This patch also expends time out of stopping all bcache device from 2 seconds to 10 seconds, because stopping writeback rate update worker may delay for 5 seconds, 2 seconds is not enough. After this patch applied, stopping bcache devices during system reboot or shutdown is very hard to be observed any more. Signed-off-by: Coly Li <colyli@suse.de> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: add comments for closure_fn to be called in closure_queue()Coly Li1-0/+6
Add code comments to explain which call back function might be called for the closure_queue(). This is an effort to make code to be more understandable for readers. Signed-off-by: Coly Li <colyli@suse.de> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: Add comments for blkdev_put() in registration code pathColy Li1-0/+8
Add comments to explain why in register_bcache() blkdev_put() won't be called in two location. Add comments to explain why blkdev_put() must be called in register_cache() when cache_alloc() failed. Signed-off-by: Coly Li <colyli@suse.de> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: add error check for calling register_bdev()Coly Li1-6/+10
This patch adds return value to register_bdev(). Then if failure happens inside register_bdev(), its caller register_bcache() may detect and handle the failure more properly. Signed-off-by: Coly Li <colyli@suse.de> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: return error immediately in bch_journal_replay()Coly Li1-3/+6
When failure happens inside bch_journal_replay(), calling cache_set_err_on() and handling the failure in async way is not a good idea. Because after bch_journal_replay() returns, registering code will continue to execute following steps, and unregistering code triggered by cache_set_err_on() is running in same time. First it is unnecessary to handle failure and unregister cache set in an async way, second there might be potential race condition to run register and unregister code for same cache set. So in this patch, if failure happens in bch_journal_replay(), we don't call cache_set_err_on(), and just print out the same error message to kernel message buffer, then return -EIO immediately caller. Then caller can detect such failure and handle it in synchrnozied way. Signed-off-by: Coly Li <colyli@suse.de> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: add comments for kobj release callback routineColy Li1-0/+4
Bcache has several routines to release resources in implicit way, they are called when the associated kobj released. This patch adds code comments to notice when and which release callback will be called, - When dc->disk.kobj released: void bch_cached_dev_release(struct kobject *kobj) - When d->kobj released: void bch_flash_dev_release(struct kobject *kobj) - When c->kobj released: void bch_cache_set_release(struct kobject *kobj) - When ca->kobj released void bch_cache_release(struct kobject *kobj) Signed-off-by: Coly Li <colyli@suse.de> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: add failure check to run_cache_set() for journal replayColy Li1-5/+12
Currently run_cache_set() has no return value, if there is failure in bch_journal_replay(), the caller of run_cache_set() has no idea about such failure and just continue to execute following code after run_cache_set(). The internal failure is triggered inside bch_journal_replay() and being handled in async way. This behavior is inefficient, while failure handling inside bch_journal_replay(), cache register code is still running to start the cache set. Registering and unregistering code running as same time may introduce some rare race condition, and make the code to be more hard to be understood. This patch adds return value to run_cache_set(), and returns -EIO if bch_journal_rreplay() fails. Then caller of run_cache_set() may detect such failure and stop registering code flow immedidately inside register_cache_set(). If journal replay fails, run_cache_set() can report error immediately to register_cache_set(). This patch makes the failure handling for bch_journal_replay() be in synchronized way, easier to understand and debug, and avoid poetential race condition for register-and-unregister in same time. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: never set KEY_PTRS of journal key to 0 in journal_reclaim()Coly Li1-4/+7
In journal_reclaim() ja->cur_idx of each cache will be update to reclaim available journal buckets. Variable 'int n' is used to count how many cache is successfully reclaimed, then n is set to c->journal.key by SET_KEY_PTRS(). Later in journal_write_unlocked(), a for_each_cache() loop will write the jset data onto each cache. The problem is, if all jouranl buckets on each cache is full, the following code in journal_reclaim(), 529 for_each_cache(ca, c, iter) { 530 struct journal_device *ja = &ca->journal; 531 unsigned int next = (ja->cur_idx + 1) % ca->sb.njournal_buckets; 532 533 /* No space available on this device */ 534 if (next == ja->discard_idx) 535 continue; 536 537 ja->cur_idx = next; 538 k->ptr[n++] = MAKE_PTR(0, 539 bucket_to_sector(c, ca->sb.d[ja->cur_idx]), 540 ca->sb.nr_this_dev); 541 } 542 543 bkey_init(k); 544 SET_KEY_PTRS(k, n); If there is no available bucket to reclaim, the if() condition at line 534 will always true, and n remains 0. Then at line 544, SET_KEY_PTRS() will set KEY_PTRS field of c->journal.key to 0. Setting KEY_PTRS field of c->journal.key to 0 is wrong. Because in journal_write_unlocked() the journal data is written in following loop, 649 for (i = 0; i < KEY_PTRS(k); i++) { 650-671 submit journal data to cache device 672 } If KEY_PTRS field is set to 0 in jouranl_reclaim(), the journal data won't be written to cache device here. If system crahed or rebooted before bkeys of the lost journal entries written into btree nodes, data corruption will be reported during bcache reload after rebooting the system. Indeed there is only one cache in a cache set, there is no need to set KEY_PTRS field in journal_reclaim() at all. But in order to keep the for_each_cache() logic consistent for now, this patch fixes the above problem by not setting 0 KEY_PTRS of journal key, if there is no bucket available to reclaim. Signed-off-by: Coly Li <colyli@suse.de> Reviewed-by: Hannes Reinecke <hare@suse.com> Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: move definition of 'int ret' out of macro read_bucket()Coly Li1-2/+3
'int ret' is defined as a local variable inside macro read_bucket(). Since this macro is called multiple times, and following patches will use a 'int ret' variable in bch_journal_read(), this patch moves definition of 'int ret' from macro read_bucket() to range of function bch_journal_read(). Signed-off-by: Coly Li <colyli@suse.de> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: fix a race between cache register and cacheset unregisterLiang Chen1-1/+1
There is a race between cache device register and cache set unregister. For an already registered cache device, register_bcache will call bch_is_open to iterate through all cachesets and check every cache there. The race occurs if cache_set_free executes at the same time and clears the caches right before ca is dereferenced in bch_is_open_cache. To close the race, let's make sure the clean up work is protected by the bch_register_lock as well. This issue can be reproduced as follows, while true; do echo /dev/XXX> /sys/fs/bcache/register ; done& while true; do echo 1> /sys/block/XXX/bcache/set/unregister ; done & and results in the following oops, [ +0.000053] BUG: unable to handle kernel NULL pointer dereference at 0000000000000998 [ +0.000457] #PF error: [normal kernel read fault] [ +0.000464] PGD 800000003ca9d067 P4D 800000003ca9d067 PUD 3ca9c067 PMD 0 [ +0.000388] Oops: 0000 [#1] SMP PTI [ +0.000269] CPU: 1 PID: 3266 Comm: bash Not tainted 5.0.0+ #6 [ +0.000346] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.fc28 04/01/2014 [ +0.000472] RIP: 0010:register_bcache+0x1829/0x1990 [bcache] [ +0.000344] Code: b0 48 83 e8 50 48 81 fa e0 e1 10 c0 0f 84 a9 00 00 00 48 89 c6 48 89 ca 0f b7 ba 54 04 00 00 4c 8b 82 60 0c 00 00 85 ff 74 2f <49> 3b a8 98 09 00 00 74 4e 44 8d 47 ff 31 ff 49 c1 e0 03 eb 0d [ +0.000839] RSP: 0018:ffff92ee804cbd88 EFLAGS: 00010202 [ +0.000328] RAX: ffffffffc010e190 RBX: ffff918b5c6b5000 RCX: ffff918b7d8e0000 [ +0.000399] RDX: ffff918b7d8e0000 RSI: ffffffffc010e190 RDI: 0000000000000001 [ +0.000398] RBP: ffff918b7d318340 R08: 0000000000000000 R09: ffffffffb9bd2d7a [ +0.000385] R10: ffff918b7eb253c0 R11: ffffb95980f51200 R12: ffffffffc010e1a0 [ +0.000411] R13: fffffffffffffff2 R14: 000000000000000b R15: ffff918b7e232620 [ +0.000384] FS: 00007f955bec2740(0000) GS:ffff918b7eb00000(0000) knlGS:0000000000000000 [ +0.000420] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ +0.000801] CR2: 0000000000000998 CR3: 000000003cad6000 CR4: 00000000001406e0 [ +0.000837] Call Trace: [ +0.000682] ? _cond_resched+0x10/0x20 [ +0.000691] ? __kmalloc+0x131/0x1b0 [ +0.000710] kernfs_fop_write+0xfa/0x170 [ +0.000733] __vfs_write+0x2e/0x190 [ +0.000688] ? inode_security+0x10/0x30 [ +0.000698] ? selinux_file_permission+0xd2/0x120 [ +0.000752] ? security_file_permission+0x2b/0x100 [ +0.000753] vfs_write+0xa8/0x1a0 [ +0.000676] ksys_write+0x4d/0xb0 [ +0.000699] do_syscall_64+0x3a/0xf0 [ +0.000692] entry_SYSCALL_64_after_hwframe+0x44/0xa9 Signed-off-by: Liang Chen <liangchen.linux@gmail.com> Cc: stable@vger.kernel.org Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: Clean up bch_get_congested()George Spelvin3-15/+28
There are a few nits in this function. They could in theory all be separate patches, but that's probably taking small commits too far. 1) I added a brief comment saying what it does. 2) I like to declare pointer parameters "const" where possible for documentation reasons. 3) It uses bitmap_weight(&rand, BITS_PER_LONG) to compute the Hamming weight of a 32-bit random number (giving a random integer with mean 16 and variance 8). Passing by reference in a 64-bit variable is silly; just use hweight32(). 4) Its helper function fract_exp_two is unnecessarily tangled. Gcc can optimize the multiply by (1 << x) to a shift, but it can be written in a much more straightforward way at the cost of one more bit of internal precision. Some analysis reveals that this bit is always available. This shrinks the object code for fract_exp_two(x, 6) from 23 bytes: 0000000000000000 <foo1>: 0: 89 f9 mov %edi,%ecx 2: c1 e9 06 shr $0x6,%ecx 5: b8 01 00 00 00 mov $0x1,%eax a: d3 e0 shl %cl,%eax c: 83 e7 3f and $0x3f,%edi f: d3 e7 shl %cl,%edi 11: c1 ef 06 shr $0x6,%edi 14: 01 f8 add %edi,%eax 16: c3 retq To 19: 0000000000000017 <foo2>: 17: 89 f8 mov %edi,%eax 19: 83 e0 3f and $0x3f,%eax 1c: 83 c0 40 add $0x40,%eax 1f: 89 f9 mov %edi,%ecx 21: c1 e9 06 shr $0x6,%ecx 24: d3 e0 shl %cl,%eax 26: c1 e8 06 shr $0x6,%eax 29: c3 retq (Verified with 0 <= frac_bits <= 8, 0 <= x < 16<<frac_bits; both versions produce the same output.) 5) And finally, the call to bch_get_congested() in check_should_bypass() is separated from the use of the value by multiple tests which could moot the need to compute it. Move the computation down to where it's needed. This also saves a local register to hold the computed value. Signed-off-by: George Spelvin <lkml@sdf.org> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: use kmemdup_nul for CACHED_LABEL bufferGeliang Tang1-6/+4
This patch uses kmemdup_nul to create a NUL-terminated string from dc->sb.label. This is better than open coding it. With this, we can move env[2] initialization into env[] array to make code more elegant. Signed-off-by: Geliang Tang <geliangtang@gmail.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: avoid clang -Wunintialized warningArnd Bergmann1-2/+3
clang has identified a code path in which it thinks a variable may be unused: drivers/md/bcache/alloc.c:333:4: error: variable 'bucket' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized] fifo_pop(&ca->free_inc, bucket); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/md/bcache/util.h:219:27: note: expanded from macro 'fifo_pop' #define fifo_pop(fifo, i) fifo_pop_front(fifo, (i)) ^~~~~~~~~~~~~~~~~~~~~~~~~ drivers/md/bcache/util.h:189:6: note: expanded from macro 'fifo_pop_front' if (_r) { \ ^~ drivers/md/bcache/alloc.c:343:46: note: uninitialized use occurs here allocator_wait(ca, bch_allocator_push(ca, bucket)); ^~~~~~ drivers/md/bcache/alloc.c:287:7: note: expanded from macro 'allocator_wait' if (cond) \ ^~~~ drivers/md/bcache/alloc.c:333:4: note: remove the 'if' if its condition is always true fifo_pop(&ca->free_inc, bucket); ^ drivers/md/bcache/util.h:219:27: note: expanded from macro 'fifo_pop' #define fifo_pop(fifo, i) fifo_pop_front(fifo, (i)) ^ drivers/md/bcache/util.h:189:2: note: expanded from macro 'fifo_pop_front' if (_r) { \ ^ drivers/md/bcache/alloc.c:331:15: note: initialize the variable 'bucket' to silence this warning long bucket; ^ This cannot happen in practice because we only enter the loop if there is at least one element in the list. Slightly rearranging the code makes this clearer to both the reader and the compiler, which avoids the warning. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: fix inaccurate result of unused bucketsGuoju Fang1-2/+0
To get the amount of unused buckets in sysfs_priority_stats, the code count the buckets which GC_SECTORS_USED is zero. It's correct and should not be overwritten by the count of buckets which prio is zero. Signed-off-by: Guoju Fang <fangguoju@gmail.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-04-24bcache: fix crashes stopping bcache device before read miss doneGuoju Fang1-5/+21
The bio from upper layer is considered completed when bio_complete() returns. In most scenarios bio_complete() is called in search_free(), but when read miss happens, the bio_compete() is called when backing device reading completed, while the struct search is still in use until cache inserting finished. If someone stops the bcache device just then, the device may be closed and released, but after cache inserting finished the struct search will access a freed struct cached_dev. This patch add the reference of bcache device before bio_complete() when read miss happens, and put it after the search is not used. Signed-off-by: Guoju Fang <fangguoju@gmail.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-15block: allow bio_for_each_segment_all() to iterate over multi-page bvecMing Lei1-1/+2
This patch introduces one extra iterator variable to bio_for_each_segment_all(), then we can allow bio_for_each_segment_all() to iterate over multi-page bvec. Given it is just one mechannical & simple change on all bio_for_each_segment_all() users, this patch does tree-wide change in one single patch, so that we can avoid to use a temporary helper for this conversion. Reviewed-by: Omar Sandoval <osandov@fb.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-15bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages()Ming Lei1-1/+5
bch_bio_alloc_pages() is always called on one new bio, so it is safe to access the bvec table directly. Given it is the only kind of this case, open code the bvec table access since bio_for_each_segment_all() will be changed to support for iterating over multipage bvec. Acked-by: Coly Li <colyli@suse.de> Reviewed-by: Omar Sandoval <osandov@fb.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: use (REQ_META|REQ_PRIO) to indicate bio for metadataColy Li1-3/+4
In 'commit 752f66a75aba ("bcache: use REQ_PRIO to indicate bio for metadata")' REQ_META is replaced by REQ_PRIO to indicate metadata bio. This assumption is not always correct, e.g. XFS uses REQ_META to mark metadata bio other than REQ_PRIO. This is why Nix noticed that bcache does not cache metadata for XFS after the above commit. Thanks to Dave Chinner, he explains the difference between REQ_META and REQ_PRIO from view of file system developer. Here I quote part of his explanation from mailing list, REQ_META is used for metadata. REQ_PRIO is used to communicate to the lower layers that the submitter considers this IO to be more important that non REQ_PRIO IO and so dispatch should be expedited. IOWs, if the filesystem considers metadata IO to be more important that user data IO, then it will use REQ_PRIO | REQ_META rather than just REQ_META. Then it seems bios with REQ_META or REQ_PRIO should both be cached for performance optimation, because they are all probably low I/O latency demand by upper layer (e.g. file system). So in this patch, when we want to decide whether to bypass the cache, REQ_META and REQ_PRIO are both checked. Then both metadata and high priority I/O requests will be handled properly. Reported-by: Nix <nix@esperi.org.uk> Signed-off-by: Coly Li <colyli@suse.de> Reviewed-by: Andre Noll <maan@tuebingen.mpg.de> Tested-by: Nix <nix@esperi.org.uk> Cc: stable@vger.kernel.org Cc: Dave Chinner <david@fromorbit.com> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: fix input overflow to cache set sysfs file io_error_halflifeColy Li1-2/+11
Cache set sysfs entry io_error_halflife is used to set c->error_decay. c->error_decay is in type unsigned int, and it is converted by strtoul_or_return(), therefore overflow to c->error_decay is possible for a large input value. This patch fixes the overflow by using strtoul_safe_clamp() to convert input string to an unsigned long value in range [0, UINT_MAX], then divides by 88 and set it to c->error_decay. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: fix input overflow to cache set io_error_limitColy Li1-2/+1
c->error_limit is in type unsigned int, it is set via cache set sysfs file io_error_limit. Inside the bcache code, input string is converted by strtoul_or_return() and set the converted value to c->error_limit. Because the converted value is unsigned long, and c->error_limit is unsigned int, if the input is large enought, overflow will happen to c->error_limit. This patch uses sysfs_strtoul_clamp() to convert input string, and set the range in [0, UINT_MAX] to avoid the potential overflow. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: fix input overflow to journal_delay_msColy Li1-1/+3
c->journal_delay_ms is in type unsigned short, it is set via sysfs interface and converted by sysfs_strtoul() from input string to unsigned short value. Therefore overflow to unsigned short might be happen when the converted value exceed USHRT_MAX. e.g. writing 65536 into sysfs file journal_delay_ms, c->journal_delay_ms is set to 0. This patch uses sysfs_strtoul_clamp() to convert the input string and limit value range in [0, USHRT_MAX], to avoid the input overflow. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: fix input overflow to writeback_rate_minimumColy Li1-1/+3
dc->writeback_rate_minimum is type unsigned integer variable, it is set via sysfs interface, and converte from input string to unsigned integer by d_strtoul_nonzero(). When the converted input value is larger than UINT_MAX, overflow to unsigned integer happens. This patch fixes the overflow by using sysfs_strotoul_clamp() to convert input string and limit the value in range [1, UINT_MAX], then the overflow can be avoided. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: fix potential div-zero error of writeback_rate_p_term_inverseColy Li1-1/+3
Current code already uses d_strtoul_nonzero() to convert input string to an unsigned integer, to make sure writeback_rate_p_term_inverse won't be zero value. But overflow may happen when converting input string to an unsigned integer value by d_strtoul_nonzero(), then dc->writeback_rate_p_term_inverse can still be set to 0 even if the sysfs file input value is not zero, e.g. 4294967296 (a.k.a UINT_MAX+1). If dc->writeback_rate_p_term_inverse is set to 0, it might cause a dev-zero error in following code from __update_writeback_rate(), int64_t proportional_scaled = div_s64(error, dc->writeback_rate_p_term_inverse); This patch replaces d_strtoul_nonzero() by sysfs_strtoul_clamp() and limit the value range in [1, UINT_MAX]. Then the unsigned integer overflow and dev-zero error can be avoided. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: fix potential div-zero error of writeback_rate_i_term_inverseColy Li1-1/+3
dc->writeback_rate_i_term_inverse can be set via sysfs interface. It is in type unsigned int, and convert from input string by d_strtoul(). The problem is d_strtoul() does not check valid range of the input, if 4294967296 is written into sysfs file writeback_rate_i_term_inverse, an overflow of unsigned integer will happen and value 0 is set to dc->writeback_rate_i_term_inverse. In writeback.c:__update_writeback_rate(), there are following lines of code, integral_scaled = div_s64(dc->writeback_rate_integral, dc->writeback_rate_i_term_inverse); If dc->writeback_rate_i_term_inverse is set to 0 via sysfs interface, a div-zero error might be triggered in the above code. Therefore we need to add a range limitation in the sysfs interface, this is what this patch does, use sysfs_stroul_clamp() to replace d_strtoul() and restrict the input range in [1, UINT_MAX]. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: fix input overflow to writeback_delayColy Li1-1/+1
Sysfs file writeback_delay is used to configure dc->writeback_delay which is type unsigned int. But bcache code uses sysfs_strtoul() to convert the input string, therefore it might be overflowed if the input value is too large. E.g. input value is 4294967296 but indeed 0 is set to dc->writeback_delay. This patch uses sysfs_strtoul_clamp() to convert the input string and set the result value range in [0, UINT_MAX] to avoid such unsigned integer overflow. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: use sysfs_strtoul_bool() to set bit-field variablesColy Li1-8/+8
When setting bcache parameters via sysfs, there are some variables are defined as bit-field value. Current bcache code in sysfs.c uses either d_strtoul() or sysfs_strtoul() to convert the input string to unsigned integer value and set it to the corresponded bit-field value. The problem is, the bit-field value only takes the lowest bit of the converted value. If input is 2, the expected value (like bool value) of the bit-field value should be 1, but indeed it is 0. The following sysfs files for bit-field variables have such problem, bypass_torture_test, for dc->bypass_torture_test writeback_metadata, for dc->writeback_metadata writeback_running, for dc->writeback_running verify, for c->verify key_merging_disabled, for c->key_merging_disabled gc_always_rewrite, for c->gc_always_rewrite btree_shrinker_disabled,for c->shrinker_disabled copy_gc_enabled, for c->copy_gc_enabled This patch uses sysfs_strtoul_bool() to set such bit-field variables, then if the converted value is non-zero, the bit-field variables will be set to 1, like setting a bool value like expensive_debug_checks. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: add sysfs_strtoul_bool() for setting bit-field variablesColy Li1-0/+10
When setting bool values via sysfs interface, e.g. writeback_metadata, if writing 1 into writeback_metadata file, dc->writeback_metadata is set to 1, but if writing 2 into the file, dc->writeback_metadata is 0. This is misleading, a better result should be 1 for all non-zero input value. It is because dc->writeback_metadata is a bit-field variable, and current code simply use d_strtoul() to convert a string into integer and takes the lowest bit value. To fix such error, we need a routine to convert the input string into unsigned integer, and set target variable to 1 if the converted integer is non-zero. This patch introduces a new macro called sysfs_strtoul_bool(), it can be used to convert input string into bool value, we can use it to set bool value for bit-field vairables. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: fix input overflow to sequential_cutoffColy Li1-1/+3
People may set sequential_cutoff of a cached device via sysfs file, but current code does not check input value overflow. E.g. if value 4294967295 (UINT_MAX) is written to file sequential_cutoff, its value is 4GB, but if 4294967296 (UINT_MAX + 1) is written into, its value will be 0. This is an unexpected behavior. This patch replaces d_strtoi_h() by sysfs_strtoul_clamp() to convert input string to unsigned integer value, and limit its range in [0, UINT_MAX]. Then the input overflow can be fixed. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: fix input integer overflow of congested thresholdColy Li1-4/+6
Cache set congested threshold values congested_read_threshold_us and congested_write_threshold_us can be set via sysfs interface. These two values are 'unsigned int' type, but sysfs interface uses strtoul to convert input string. So if people input a large number like 9999999999, the value indeed set is 1410065407, which is not expected behavior. This patch replaces sysfs_strtoul() by sysfs_strtoul_clamp() when convert input string to unsigned int value, and set value range in [0, UINT_MAX], to avoid the above integer overflow errors. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: improve sysfs_strtoul_clamp()Coly Li1-3/+10
Currently sysfs_strtoul_clamp() is defined as, 82 #define sysfs_strtoul_clamp(file, var, min, max) \ 83 do { \ 84 if (attr == &sysfs_ ## file) \ 85 return strtoul_safe_clamp(buf, var, min, max) \ 86 ?: (ssize_t) size; \ 87 } while (0) The problem is, if bit width of var is less then unsigned long, min and max may not protect var from integer overflow, because overflow happens in strtoul_safe_clamp() before checking min and max. To fix such overflow in sysfs_strtoul_clamp(), to make min and max take effect, this patch adds an unsigned long variable, and uses it to macro strtoul_safe_clamp() to convert an unsigned long value in range defined by [min, max]. Then assign this value to var. By this method, if bit width of var is less than unsigned long, integer overflow won't happen before min and max are checking. Now sysfs_strtoul_clamp() can properly handle smaller data type like unsigned int, of cause min and max should be defined in range of unsigned int too. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: treat stale && dirty keys as bad keysTang Junhui1-6/+7
Stale && dirty keys can be produced in the follow way: After writeback in write_dirty_finish(), dirty keys k1 will replace by clean keys k2 ==>ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key); ==>btree_insert_fn(struct btree_op *b_op, struct btree *b) ==>static int bch_btree_insert_node(struct btree *b, struct btree_op *op, struct keylist *insert_keys, atomic_t *journal_ref, Then two steps: A) update k1 to k2 in btree node memory; bch_btree_insert_keys(b, op, insert_keys, replace_key) B) Write the bset(contains k2) to cache disk by a 30s delay work bch_btree_leaf_dirty(b, journal_ref). But before the 30s delay work write the bset to cache device, these things happened: A) GC works, and reclaim the bucket k2 point to; B) Allocator works, and invalidate the bucket k2 point to, and increase the gen of the bucket, and place it into free_inc fifo; C) Until now, the 30s delay work still does not finish work, so in the disk, the key still is k1, it is dirty and stale (its gen is smaller than the gen of the bucket). and then the machine power off suddenly happens; D) When the machine power on again, after the btree reconstruction, the stale dirty key appear. In bch_extent_bad(), when expensive_debug_checks is off, it would treat the dirty key as good even it is stale keys, and it would cause bellow probelms: A) In read_dirty() it would cause machine crash: BUG_ON(ptr_stale(dc->disk.c, &w->key, 0)); B) It could be worse when reads hits stale dirty keys, it would read old incorrect data. This patch tolerate the existence of these stale && dirty keys, and treat them as bad key in bch_extent_bad(). (Coly Li: fix indent which was modified by sender's email client) Signed-off-by: Tang Junhui <tang.junhui.linux@gmail.com> Cc: stable@vger.kernel.org Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: fix indentation issue, remove tabs on a hunk of codeColin Ian King1-15/+15
There is a hunk of code that is indented one level too deep, fix this by removing the extra tabs. Signed-off-by: Colin Ian King <colin.king@canonical.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: export backing_dev_uuid via sysfsColy Li1-0/+9
When there are multiple bcache devices, after a reboot the name of bcache devices may change (e.g. current /dev/bcache1 was /dev/bcache0 before reboot). Therefore we need the backing device UUID (sb.uuid) to identify each bcache device. Backing device uuid can be found by program bcache-super-show, but directly exporting backing_dev_uuid by sysfs file /sys/block/bcache<?>/bcache/backing_dev_uuid is a much simpler method. With backing_dev_uuid, and partition uuids from /dev/disk/by-partuuid/, now we can identify each bcache device and its partitions conveniently. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: export backing_dev_name via sysfsColy Li1-0/+8
This patch export dc->backing_dev_name to sysfs file /sys/block/bcache<?>/bcache/backing_dev_name, then people or user space tools may know the backing device name of this bcache device. Of cause it can be done by parsing sysfs links, but this method can be much simpler to find the link between bcache device and backing device. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: not use hard coded memset size in bch_cache_accounting_clear()Coly Li1-1/+1
In stats.c:bch_cache_accounting_clear(), a hard coded number '7' is used in memset(). It is because in struct cache_stats, there are 7 atomic_t type members. This is not good when new members added into struct stats, the hard coded number will only clear part of memory. This patch replaces 'sizeof(unsigned long) * 7' by more generic 'sizeof(struct cache_stats))', to avoid potential error if new member added into struct cache_stats. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-09bcache: never writeback a discard operationDaniel Axtens1-0/+3
Some users see panics like the following when performing fstrim on a bcached volume: [ 529.803060] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 [ 530.183928] #PF error: [normal kernel read fault] [ 530.412392] PGD 8000001f42163067 P4D 8000001f42163067 PUD 1f42168067 PMD 0 [ 530.750887] Oops: 0000 [#1] SMP PTI [ 530.920869] CPU: 10 PID: 4167 Comm: fstrim Kdump: loaded Not tainted 5.0.0-rc1+ #3 [ 531.290204] Hardware name: HP ProLiant DL360 Gen9/ProLiant DL360 Gen9, BIOS P89 12/27/2015 [ 531.693137] RIP: 0010:blk_queue_split+0x148/0x620 [ 531.922205] Code: 60 38 89 55 a0 45 31 db 45 31 f6 45 31 c9 31 ff 89 4d 98 85 db 0f 84 7f 04 00 00 44 8b 6d 98 4c 89 ee 48 c1 e6 04 49 03 70 78 <8b> 46 08 44 8b 56 0c 48 8b 16 44 29 e0 39 d8 48 89 55 a8 0f 47 c3 [ 532.838634] RSP: 0018:ffffb9b708df39b0 EFLAGS: 00010246 [ 533.093571] RAX: 00000000ffffffff RBX: 0000000000046000 RCX: 0000000000000000 [ 533.441865] RDX: 0000000000000200 RSI: 0000000000000000 RDI: 0000000000000000 [ 533.789922] RBP: ffffb9b708df3a48 R08: ffff940d3b3fdd20 R09: 0000000000000000 [ 534.137512] R10: ffffb9b708df3958 R11: 0000000000000000 R12: 0000000000000000 [ 534.485329] R13: 0000000000000000 R14: 0000000000000000 R15: ffff940d39212020 [ 534.833319] FS: 00007efec26e3840(0000) GS:ffff940d1f480000(0000) knlGS:0000000000000000 [ 535.224098] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 535.504318] CR2: 0000000000000008 CR3: 0000001f4e256004 CR4: 00000000001606e0 [ 535.851759] Call Trace: [ 535.970308] ? mempool_alloc_slab+0x15/0x20 [ 536.174152] ? bch_data_insert+0x42/0xd0 [bcache] [ 536.403399] blk_mq_make_request+0x97/0x4f0 [ 536.607036] generic_make_request+0x1e2/0x410 [ 536.819164] submit_bio+0x73/0x150 [ 536.980168] ? submit_bio+0x73/0x150 [ 537.149731] ? bio_associate_blkg_from_css+0x3b/0x60 [ 537.391595] ? _cond_resched+0x1a/0x50 [ 537.573774] submit_bio_wait+0x59/0x90 [ 537.756105] blkdev_issue_discard+0x80/0xd0 [ 537.959590] ext4_trim_fs+0x4a9/0x9e0 [ 538.137636] ? ext4_trim_fs+0x4a9/0x9e0 [ 538.324087] ext4_ioctl+0xea4/0x1530 [ 538.497712] ? _copy_to_user+0x2a/0x40 [ 538.679632] do_vfs_ioctl+0xa6/0x600 [ 538.853127] ? __do_sys_newfstat+0x44/0x70 [ 539.051951] ksys_ioctl+0x6d/0x80 [ 539.212785] __x64_sys_ioctl+0x1a/0x20 [ 539.394918] do_syscall_64+0x5a/0x110 [ 539.568674] entry_SYSCALL_64_after_hwframe+0x44/0xa9 We have observed it where both: 1) LVM/devmapper is involved (bcache backing device is LVM volume) and 2) writeback cache is involved (bcache cache_mode is writeback) On one machine, we can reliably reproduce it with: # echo writeback > /sys/block/bcache0/bcache/cache_mode (not sure whether above line is required) # mount /dev/bcache0 /test # for i in {0..10}; do file="$(mktemp /test/zero.XXX)" dd if=/dev/zero of="$file" bs=1M count=256 sync rm $file done # fstrim -v /test Observing this with tracepoints on, we see the following writes: fstrim-18019 [022] .... 91107.302026: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0 DS 4260112 + 196352 hit 0 bypass 1 fstrim-18019 [022] .... 91107.302050: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0 DS 4456464 + 262144 hit 0 bypass 1 fstrim-18019 [022] .... 91107.302075: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0 DS 4718608 + 81920 hit 0 bypass 1 fstrim-18019 [022] .... 91107.302094: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0 DS 5324816 + 180224 hit 0 bypass 1 fstrim-18019 [022] .... 91107.302121: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0 DS 5505040 + 262144 hit 0 bypass 1 fstrim-18019 [022] .... 91107.302145: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0 DS 5767184 + 81920 hit 0 bypass 1 fstrim-18019 [022] .... 91107.308777: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0 DS 6373392 + 180224 hit 1 bypass 0 <crash> Note the final one has different hit/bypass flags. This is because in should_writeback(), we were hitting a case where the partial stripe condition was returning true and so should_writeback() was returning true early. If that hadn't been the case, it would have hit the would_skip test, and as would_skip == s->iop.bypass == true, should_writeback() would have returned false. Looking at the git history from 'commit 72c270612bd3 ("bcache: Write out full stripes")', it looks like the idea was to optimise for raid5/6: * If a stripe is already dirty, force writes to that stripe to writeback mode - to help build up full stripes of dirty data To fix this issue, make sure that should_writeback() on a discard op never returns true. More details of debugging: https://www.spinics.net/lists/linux-bcache/msg06996.html Previous reports: - https://bugzilla.kernel.org/show_bug.cgi?id=201051 - https://bugzilla.kernel.org/show_bug.cgi?id=196103 - https://www.spinics.net/lists/linux-bcache/msg06885.html (Coly Li: minor modification to follow maximum 75 chars per line rule) Cc: Kent Overstreet <koverstreet@google.com> Cc: stable@vger.kernel.org Fixes: 72c270612bd3 ("bcache: Write out full stripes") Signed-off-by: Daniel Axtens <dja@axtens.net> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-13bcache: print number of keys in trace_bcache_journal_writeGuoju Fang1-1/+1
Sometimes flush journal may be very frequent, so it's useful to dump number of keys every time write journal. Signed-off-by: Guoju Fang <fangguoju@gmail.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-13bcache: set writeback_percent in a flexible rangeColy Li1-1/+2
Because CUTOFF_WRITEBACK is defined as 40, so before the changes of dynamic cutoff writeback values, writeback_percent is limited to [0, CUTOFF_WRITEBACK]. Any value larger than CUTOFF_WRITEBACK will be fixed up to 40. Now cutof writeback limit is a dynamic value bch_cutoff_writeback, so the range of writeback_percent can be a more flexible range as [0, bch_cutoff_writeback]. The flexibility is, it can be expended to a larger or smaller range than [0, 40], depends on how value bch_cutoff_writeback is specified. The default value is still strongly recommended to most of users for most of workloads. But for people who want to do research on bcache writeback perforamnce tuning, they may have chance to specify more flexible writeback_percent in range [0, 70]. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-13bcache: make cutoff_writeback and cutoff_writeback_sync tunableColy Li3-2/+55
Currently the cutoff writeback and cutoff writeback sync thresholds are defined by CUTOFF_WRITEBACK (40) and CUTOFF_WRITEBACK_SYNC (70) as static values. Most of time these they work fine, but when people want to do research on bcache writeback mode performance tuning, there is no chance to modify the soft and hard cutoff writeback values. This patch introduces two module parameters bch_cutoff_writeback_sync and bch_cutoff_writeback which permit people to tune the values when loading bcache.ko. If they are not specified by module loading, current values CUTOFF_WRITEBACK_SYNC and CUTOFF_WRITEBACK will be used as default and nothing changes. When people want to tune this two values, - cutoff_writeback can be set in range [1, 70] - cutoff_writeback_sync can be set in range [1, 90] - cutoff_writeback always <= cutoff_writeback_sync The default values are strongly recommended to most of users for most of workloads. Anyway, if people wants to take their own risk to do research on new writeback cutoff tuning for their own workload, now they can make it. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-13bcache: add MODULE_DESCRIPTION informationColy Li1-3/+4
This patch moves MODULE_AUTHOR and MODULE_LICENSE to end of super.c, and add MODULE_DESCRIPTION("Bcache: a Linux block layer cache"). This is preparation for adding module parameters. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-13bcache: option to automatically run gc thread after writebackColy Li4-0/+52
The option gc_after_writeback is disabled by default, because garbage collection will discard SSD data which drops cached data. Echo 1 into /sys/fs/bcache/<UUID>/internal/gc_after_writeback will enable this option, which wakes up gc thread when writeback accomplished and all cached data is clean. This option is helpful for people who cares writing performance more. In heavy writing workload, all cached data can be clean only happens when writeback thread cleans all cached data in I/O idle time. In such situation a following gc running may help to shrink bcache B+ tree and discard more clean data, which may be helpful for future writing requests. If you are not sure whether this is helpful for your own workload, please leave it as disabled by default. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-13bcache: introduce force_wake_up_gc()Coly Li2-15/+20
Garbage collection thread starts to work when c->sectors_to_gc is negative value, otherwise nothing will happen even the gc thread is woken up by wake_up_gc(). force_wake_up_gc() sets c->sectors_to_gc to -1 before calling wake_up_gc(), then gc thread may have chance to run if no one else sets c->sectors_to_gc to a positive value before gc_should_run(). This routine can be called where the gc thread is woken up and required to run in force. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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