kernel.git/drivers/md/bcache/journal.c, branch linux-5.18.y

bcache: avoid journal no-space deadlock by reserving 1 journal bucket

2022-06-09T08:30:53Z

commit 32feee36c30ea06e38ccb8ae6e5c44c6eec790a6 upstream. The journal no-space deadlock was reported time to time. Such deadlock can happen in the following situation. When all journal buckets are fully filled by active jset with heavy write I/O load, the cache set registration (after a reboot) will load all active jsets and inserting them into the btree again (which is called journal replay). If a journaled bkey is inserted into a btree node and results btree node split, new journal request might be triggered. For example, the btree grows one more level after the node split, then the root node record in cache device super block will be upgrade by bch_journal_meta() from bch_btree_set_root(). But there is no space in journal buckets, the journal replay has to wait for new journal bucket to be reclaimed after at least one journal bucket replayed. This is one example that how the journal no-space deadlock happens. The solution to avoid the deadlock is to reserve 1 journal bucket in run time, and only permit the reserved journal bucket to be used during cache set registration procedure for things like journal replay. Then the journal space will never be fully filled, there is no chance for journal no-space deadlock to happen anymore. This patch adds a new member "bool do_reserve" in struct journal, it is inititalized to 0 (false) when struct journal is allocated, and set to 1 (true) by bch_journal_space_reserve() when all initialization done in run_cache_set(). In the run time when journal_reclaim() tries to allocate a new journal bucket, free_journal_buckets() is called to check whether there are enough free journal buckets to use. If there is only 1 free journal bucket and journal->do_reserve is 1 (true), the last bucket is reserved and free_journal_buckets() will return 0 to indicate no free journal bucket. Then journal_reclaim() will give up, and try next time to see whetheer there is free journal bucket to allocate. By this method, there is always 1 jouranl bucket reserved in run time. During the cache set registration, journal->do_reserve is 0 (false), so the reserved journal bucket can be used to avoid the no-space deadlock. Reported-by: Nikhil Kshirsagar Signed-off-by: Coly Li Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220524102336.10684-5-colyli@suse.de Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

bcache: put bch_bio_map() back to correct location in journal_write_unlocked()

2022-04-19T17:28:17Z

Commit a7c50c940477 ("block: pass a block_device and opf to bio_reset") moves bch_bio_map() inside journal_write_unlocked() next to the location where the modified bio_reset() was called. This change is wrong because calling bch_bio_map() immediately after bio_reset(), a BUG_ON(!bio->bi_iter.bi_size) inside bch_bio_map() will be triggered and panic the kernel. This patch puts bch_bio_map() back to its original correct location in journal_write_unlocked() and avoid the BUG_ON(). Fixes: a7c50c940477 ("block: pass a block_device and opf to bio_reset") Signed-off-by: Coly Li Cc: Christoph Hellwig Cc: Chaitanya Kulkarni Link: https://lore.kernel.org/r/20220419160425.4148-2-colyli@suse.de Signed-off-by: Jens Axboe

block: pass a block_device and opf to bio_reset

2022-02-02T14:50:00Z

Pass the block_device that we plan to use this bio for and the operation to bio_reset to optimize the assigment. A NULL block_device can be passed, both for the passthrough case on a raw request_queue and to temporarily avoid refactoring some nasty code. Signed-off-by: Christoph Hellwig Reviewed-by: Chaitanya Kulkarni Link: https://lore.kernel.org/r/20220124091107.642561-20-hch@lst.de Signed-off-by: Jens Axboe

block: pass a block_device and opf to bio_init

2022-02-02T14:49:59Z

Pass the block_device that we plan to use this bio for and the operation to bio_init to optimize the assignment. A NULL block_device can be passed, both for the passthrough case on a raw request_queue and to temporarily avoid refactoring some nasty code. Signed-off-by: Christoph Hellwig Reviewed-by: Chaitanya Kulkarni Link: https://lore.kernel.org/r/20220124091107.642561-19-hch@lst.de Signed-off-by: Jens Axboe

md: bcache: Trivial typo fixes in the file journal.c

2021-04-11T14:37:56Z

s/condidate/candidate/ s/folowing/following/ Signed-off-by: Bhaskar Chowdhury Signed-off-by: Coly Li Link: https://lore.kernel.org/r/20210411134316.80274-6-colyli@suse.de Signed-off-by: Jens Axboe

bcache: remove PTR_CACHE

2021-04-11T14:37:55Z

Remove the PTR_CACHE inline and replace it with a direct dereference of c->cache. (Coly Li: fix the typo from PTR_BUCKET to PTR_CACHE in commit log) Signed-off-by: Christoph Hellwig Signed-off-by: Coly Li Link: https://lore.kernel.org/r/20210411134316.80274-3-colyli@suse.de Signed-off-by: Jens Axboe

bcache: Move journal work to new flush wq

2021-02-10T15:06:00Z

This is potentially long running and not latency sensitive, let's get it out of the way of other latency sensitive events. As observed in the previous commit, the `system_wq` comes easily congested by bcache, and this fixes a few more stalls I was observing every once in a while. Let's not make this `WQ_MEM_RECLAIM` as it showed to reduce performance of boot and file system operations in my tests. Also, without `WQ_MEM_RECLAIM`, I no longer see desktop stalls. This matches the previous behavior as `system_wq` also does no memory reclaim: > // workqueue.c: > system_wq = alloc_workqueue("events", 0, 0); Cc: Coly Li Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Kai Krakow Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: remove embedded struct cache_sb from struct cache_set

2020-10-02T20:25:30Z

Since bcache code was merged into mainline kerrnel, each cache set only as one single cache in it. The multiple caches framework is here but the code is far from completed. Considering the multiple copies of cached data can also be stored on e.g. md raid1 devices, it is unnecessary to support multiple caches in one cache set indeed. The previous preparation patches fix the dependencies of explicitly making a cache set only have single cache. Now we don't have to maintain an embedded partial super block in struct cache_set, the in-memory super block can be directly referenced from struct cache. This patch removes the embedded struct cache_sb from struct cache_set, and fixes all locations where the superb lock was referenced from this removed super block by referencing the in-memory super block of struct cache. Signed-off-by: Coly Li Reviewed-by: Hannes Reinecke Signed-off-by: Jens Axboe

bcache: check and set sync status on cache's in-memory super block

2020-10-02T20:25:30Z

Currently the cache's sync status is checked and set on cache set's in- memory partial super block. After removing the embedded struct cache_sb from cache set and reference cache's in-memory super block from struct cache_set, the sync status can set and check directly on cache's super block. This patch checks and sets the cache sync status directly on cache's in-memory super block. This is a preparation for later removing embedded struct cache_sb from struct cache_set. Signed-off-by: Coly Li Reviewed-by: Hannes Reinecke Signed-off-by: Jens Axboe

bcache: only use block_bytes() on struct cache

2020-10-02T20:25:30Z

Because struct cache_set and struct cache both have struct cache_sb, therefore macro block_bytes() can be used on both of them. When removing the embedded struct cache_sb from struct cache_set, this macro won't be used on struct cache_set anymore. This patch unifies all block_bytes() usage only on struct cache, this is one of the preparation to remove the embedded struct cache_sb from struct cache_set. Signed-off-by: Coly Li Reviewed-by: Hannes Reinecke Signed-off-by: Jens Axboe