kernel.git/drivers/md/bcache/btree.c, branch linux-5.8.y

bcache: allocate meta data pages as compound pages

2020-08-21T11:14:56Z

commit 5fe48867856367142d91a82f2cbf7a57a24cbb70 upstream. There are some meta data of bcache are allocated by multiple pages, and they are used as bio bv_page for I/Os to the cache device. for example cache_set->uuids, cache->disk_buckets, journal_write->data, bset_tree->data. For such meta data memory, all the allocated pages should be treated as a single memory block. Then the memory management and underlying I/O code can treat them more clearly. This patch adds __GFP_COMP flag to all the location allocating >0 order pages for the above mentioned meta data. Then their pages are treated as compound pages now. Signed-off-by: Coly Li Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

bcache: fix potential deadlock problem in btree_gc_coalesce

2020-06-14T22:47:56Z

coccicheck reports: drivers/md//bcache/btree.c:1538:1-7: preceding lock on line 1417 In btree_gc_coalesce func, if the coalescing process fails, we will goto to out_nocoalesce tag directly without releasing new_nodes[i]->write_lock. Then, it will cause a deadlock when trying to acquire new_nodes[i]-> write_lock for freeing new_nodes[i] before return. btree_gc_coalesce func details as follows: if alloc new_nodes[i] fails: goto out_nocoalesce; // obtain new_nodes[i]->write_lock mutex_lock(&new_nodes[i]->write_lock) // main coalescing process for (i = nodes - 1; i > 0; --i) [snipped] if coalescing process fails: // Here, directly goto out_nocoalesce // tag will cause a deadlock goto out_nocoalesce; [snipped] // release new_nodes[i]->write_lock mutex_unlock(&new_nodes[i]->write_lock) // coalesing succ, return return; out_nocoalesce: btree_node_free(new_nodes[i]) // free new_nodes[i] // obtain new_nodes[i]->write_lock mutex_lock(&new_nodes[i]->write_lock); // set flag for reuse clear_bit(BTREE_NODE_dirty, &ew_nodes[i]->flags); // release new_nodes[i]->write_lock mutex_unlock(&new_nodes[i]->write_lock); To fix the problem, we add a new tag 'out_unlock_nocoalesce' for releasing new_nodes[i]->write_lock before out_nocoalesce tag. If coalescing process fails, we will go to out_unlock_nocoalesce tag for releasing new_nodes[i]->write_lock before free new_nodes[i] in out_nocoalesce tag. (Coly Li helps to clean up commit log format.) Fixes: 2a285686c109816 ("bcache: btree locking rework") Signed-off-by: Zhiqiang Liu Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: Convert pr_ uses to a more typical style

2020-05-27T11:19:36Z

Remove the trailing newline from the define of pr_fmt and add newlines to the uses. Miscellanea: o Convert bch_bkey_dump from multiple uses of pr_err to pr_cont as the earlier conversion was inappropriate done causing multiple lines to be emitted where only a single output line was desired o Use vsprintf extension %pV in bch_cache_set_error to avoid multiple line output where only a single line output was desired o Coalesce formats Fixes: 6ae63e3501c4 ("bcache: replace printk() by pr_*() routines") Signed-off-by: Joe Perches Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: remove redundant variables i and n

2020-05-27T11:19:36Z

Variables i and n are being assigned but are never used. They are redundant and can be removed. Signed-off-by: Colin Ian King Signed-off-by: Coly Li Addresses-Coverity: ("Unused value") Signed-off-by: Jens Axboe

bcache: optimize barrier usage for atomic operations

2020-03-22T16:06:57Z

The idea of this patch is from Davidlohr Bueso, he posts a patch for bcache to optimize barrier usage for read-modify-write atomic bitops. Indeed such optimization can also apply on other locations where smp_mb() is used before or after an atomic operation. This patch replaces smp_mb() with smp_mb__before_atomic() or smp_mb__after_atomic() in btree.c and writeback.c, where it is used to synchronize memory cache just earlier on other cores. Although the locations are not on hot code path, it is always not bad to mkae things a little better. Signed-off-by: Coly Li Cc: Davidlohr Bueso Signed-off-by: Jens Axboe

bcache: make bch_btree_check() to be multithreaded

2020-03-22T16:06:57Z

When registering a cache device, bch_btree_check() is called to check all btree nodes, to make sure the btree is consistent and not corrupted. bch_btree_check() is recursively executed in a single thread, when there are a lot of data cached and the btree is huge, it may take very long time to check all the btree nodes. In my testing, I observed it took around 50 minutes to finish bch_btree_check(). When checking the bcache btree nodes, the cache set is not running yet, and indeed the whole tree is in read-only state, it is safe to create multiple threads to check the btree in parallel. This patch tries to create multiple threads, and each thread tries to one-by-one check the sub-tree indexed by a key from the btree root node. The parallel thread number depends on how many keys in the btree root node. At most BCH_BTR_CHKTHREAD_MAX (64) threads can be created, but in practice is should be min(cpu-number/2, root-node-keys-number). Signed-off-by: Coly Li Cc: Christoph Hellwig Signed-off-by: Jens Axboe

bcache: add bcache_ prefix to btree_root() and btree() macros

2020-03-22T16:06:57Z

This patch changes macro btree_root() and btree() to bcache_btree_root() and bcache_btree(), to avoid potential generic name clash in future. NOTE: for product kernel maintainers, this patch can be skipped if you feel the rename stuffs introduce inconvenince to patch backport. Suggested-by: Christoph Hellwig Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: move macro btree() and btree_root() into btree.h

2020-03-22T16:06:57Z

In order to accelerate bcache registration speed, the macro btree() and btree_root() will be referenced out of btree.c. This patch moves them from btree.c into btree.h with other relative function declaration in btree.h, for the following changes. Signed-off-by: Coly Li Signed-off-by: Jens Axboe

Revert "bcache: ignore pending signals when creating gc and allocator thread"

2020-03-03T03:01:32Z

This reverts commit 0b96da639a4874311e9b5156405f69ef9fc3bef8. We can't just go flushing random signals, under the assumption that the OOM killer will just do something else. It's not safe from the OOM perspective, and it could also cause other signals to get randomly lost. Signed-off-by: Jens Axboe

bcache: ignore pending signals when creating gc and allocator thread

2020-02-13T15:53:49Z

When run a cache set, all the bcache btree node of this cache set will be checked by bch_btree_check(). If the bcache btree is very large, iterating all the btree nodes will occupy too much system memory and the bcache registering process might be selected and killed by system OOM killer. kthread_run() will fail if current process has pending signal, therefore the kthread creating in run_cache_set() for gc and allocator kernel threads are very probably failed for a very large bcache btree. Indeed such OOM is safe and the registering process will exit after the registration done. Therefore this patch flushes pending signals during the cache set start up, specificly in bch_cache_allocator_start() and bch_gc_thread_start(), to make sure run_cache_set() won't fail for large cahced data set. Signed-off-by: Coly Li Signed-off-by: Jens Axboe