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![Coly Li](/assets/img/avatar_default.png)
The kworker routine update_writeback_rate() is schedued to update the writeback rate in every 5 seconds by default. Before calling __update_writeback_rate() to do real job, semaphore dc->writeback_lock should be held by the kworker routine. At the same time, bcache writeback thread routine bch_writeback_thread() also needs to hold dc->writeback_lock before flushing dirty data back into the backing device. If the dirty data set is large, it might be very long time for bch_writeback_thread() to scan all dirty buckets and releases dc->writeback_lock. In such case update_writeback_rate() can be starved for long enough time so that kernel reports a soft lockup warn- ing started like: watchdog: BUG: soft lockup - CPU#246 stuck for 23s! [kworker/246:31:179713] Such soft lockup condition is unnecessary, because after the writeback thread finishes its job and releases dc->writeback_lock, the kworker update_writeback_rate() may continue to work and everything is fine indeed. This patch avoids the unnecessary soft lockup by the following method, - Add new member to struct cached_dev - dc->rate_update_retry (0 by default) - In update_writeback_rate() call down_read_trylock(&dc->writeback_lock) firstly, if it fails then lock contention happens. - If dc->rate_update_retry <= BCH_WBRATE_UPDATE_MAX_SKIPS (15), doesn't acquire the lock and reschedules the kworker for next try. - If dc->rate_update_retry > BCH_WBRATE_UPDATE_MAX_SKIPS, no retry anymore and call down_read(&dc->writeback_lock) to wait for the lock. By the above method, at worst case update_writeback_rate() may retry for 1+ minutes before blocking on dc->writeback_lock by calling down_read(). For a 4TB cache device with 1TB dirty data, 90%+ of the unnecessary soft lockup warning message can be avoided. When retrying to acquire dc->writeback_lock in update_writeback_rate(), of course the writeback rate cannot be updated. It is fair, because when the kworker is blocked on the lock contention of dc->writeback_lock, the writeback rate cannot be updated neither. This change follows Jens Axboe's suggestion to a more clear and simple version. Signed-off-by: Coly Li <colyli@suse.de> Link: https://lore.kernel.org/r/20220528124550.32834-2-colyli@suse.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
1048 lines
32 KiB
C
1048 lines
32 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _BCACHE_H
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#define _BCACHE_H
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/*
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* SOME HIGH LEVEL CODE DOCUMENTATION:
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*
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* Bcache mostly works with cache sets, cache devices, and backing devices.
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*
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* Support for multiple cache devices hasn't quite been finished off yet, but
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* it's about 95% plumbed through. A cache set and its cache devices is sort of
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* like a md raid array and its component devices. Most of the code doesn't care
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* about individual cache devices, the main abstraction is the cache set.
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*
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* Multiple cache devices is intended to give us the ability to mirror dirty
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* cached data and metadata, without mirroring clean cached data.
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*
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* Backing devices are different, in that they have a lifetime independent of a
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* cache set. When you register a newly formatted backing device it'll come up
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* in passthrough mode, and then you can attach and detach a backing device from
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* a cache set at runtime - while it's mounted and in use. Detaching implicitly
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* invalidates any cached data for that backing device.
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*
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* A cache set can have multiple (many) backing devices attached to it.
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*
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* There's also flash only volumes - this is the reason for the distinction
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* between struct cached_dev and struct bcache_device. A flash only volume
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* works much like a bcache device that has a backing device, except the
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* "cached" data is always dirty. The end result is that we get thin
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* provisioning with very little additional code.
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*
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* Flash only volumes work but they're not production ready because the moving
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* garbage collector needs more work. More on that later.
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*
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* BUCKETS/ALLOCATION:
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*
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* Bcache is primarily designed for caching, which means that in normal
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* operation all of our available space will be allocated. Thus, we need an
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* efficient way of deleting things from the cache so we can write new things to
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* it.
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*
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* To do this, we first divide the cache device up into buckets. A bucket is the
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* unit of allocation; they're typically around 1 mb - anywhere from 128k to 2M+
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* works efficiently.
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*
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* Each bucket has a 16 bit priority, and an 8 bit generation associated with
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* it. The gens and priorities for all the buckets are stored contiguously and
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* packed on disk (in a linked list of buckets - aside from the superblock, all
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* of bcache's metadata is stored in buckets).
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*
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* The priority is used to implement an LRU. We reset a bucket's priority when
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* we allocate it or on cache it, and every so often we decrement the priority
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* of each bucket. It could be used to implement something more sophisticated,
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* if anyone ever gets around to it.
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*
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* The generation is used for invalidating buckets. Each pointer also has an 8
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* bit generation embedded in it; for a pointer to be considered valid, its gen
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* must match the gen of the bucket it points into. Thus, to reuse a bucket all
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* we have to do is increment its gen (and write its new gen to disk; we batch
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* this up).
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*
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* Bcache is entirely COW - we never write twice to a bucket, even buckets that
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* contain metadata (including btree nodes).
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*
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* THE BTREE:
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*
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* Bcache is in large part design around the btree.
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*
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* At a high level, the btree is just an index of key -> ptr tuples.
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*
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* Keys represent extents, and thus have a size field. Keys also have a variable
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* number of pointers attached to them (potentially zero, which is handy for
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* invalidating the cache).
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*
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* The key itself is an inode:offset pair. The inode number corresponds to a
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* backing device or a flash only volume. The offset is the ending offset of the
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* extent within the inode - not the starting offset; this makes lookups
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* slightly more convenient.
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*
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* Pointers contain the cache device id, the offset on that device, and an 8 bit
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* generation number. More on the gen later.
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*
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* Index lookups are not fully abstracted - cache lookups in particular are
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* still somewhat mixed in with the btree code, but things are headed in that
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* direction.
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*
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* Updates are fairly well abstracted, though. There are two different ways of
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* updating the btree; insert and replace.
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*
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* BTREE_INSERT will just take a list of keys and insert them into the btree -
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* overwriting (possibly only partially) any extents they overlap with. This is
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* used to update the index after a write.
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*
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* BTREE_REPLACE is really cmpxchg(); it inserts a key into the btree iff it is
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* overwriting a key that matches another given key. This is used for inserting
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* data into the cache after a cache miss, and for background writeback, and for
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* the moving garbage collector.
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*
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* There is no "delete" operation; deleting things from the index is
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* accomplished by either by invalidating pointers (by incrementing a bucket's
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* gen) or by inserting a key with 0 pointers - which will overwrite anything
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* previously present at that location in the index.
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*
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* This means that there are always stale/invalid keys in the btree. They're
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* filtered out by the code that iterates through a btree node, and removed when
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* a btree node is rewritten.
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*
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* BTREE NODES:
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*
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* Our unit of allocation is a bucket, and we we can't arbitrarily allocate and
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* free smaller than a bucket - so, that's how big our btree nodes are.
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*
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* (If buckets are really big we'll only use part of the bucket for a btree node
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* - no less than 1/4th - but a bucket still contains no more than a single
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* btree node. I'd actually like to change this, but for now we rely on the
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* bucket's gen for deleting btree nodes when we rewrite/split a node.)
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*
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* Anyways, btree nodes are big - big enough to be inefficient with a textbook
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* btree implementation.
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*
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* The way this is solved is that btree nodes are internally log structured; we
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* can append new keys to an existing btree node without rewriting it. This
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* means each set of keys we write is sorted, but the node is not.
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*
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* We maintain this log structure in memory - keeping 1Mb of keys sorted would
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* be expensive, and we have to distinguish between the keys we have written and
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* the keys we haven't. So to do a lookup in a btree node, we have to search
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* each sorted set. But we do merge written sets together lazily, so the cost of
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* these extra searches is quite low (normally most of the keys in a btree node
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* will be in one big set, and then there'll be one or two sets that are much
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* smaller).
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*
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* This log structure makes bcache's btree more of a hybrid between a
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* conventional btree and a compacting data structure, with some of the
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* advantages of both.
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*
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* GARBAGE COLLECTION:
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*
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* We can't just invalidate any bucket - it might contain dirty data or
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* metadata. If it once contained dirty data, other writes might overwrite it
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* later, leaving no valid pointers into that bucket in the index.
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*
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* Thus, the primary purpose of garbage collection is to find buckets to reuse.
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* It also counts how much valid data it each bucket currently contains, so that
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* allocation can reuse buckets sooner when they've been mostly overwritten.
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*
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* It also does some things that are really internal to the btree
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* implementation. If a btree node contains pointers that are stale by more than
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* some threshold, it rewrites the btree node to avoid the bucket's generation
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* wrapping around. It also merges adjacent btree nodes if they're empty enough.
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*
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* THE JOURNAL:
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*
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* Bcache's journal is not necessary for consistency; we always strictly
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* order metadata writes so that the btree and everything else is consistent on
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* disk in the event of an unclean shutdown, and in fact bcache had writeback
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* caching (with recovery from unclean shutdown) before journalling was
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* implemented.
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*
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* Rather, the journal is purely a performance optimization; we can't complete a
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* write until we've updated the index on disk, otherwise the cache would be
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* inconsistent in the event of an unclean shutdown. This means that without the
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* journal, on random write workloads we constantly have to update all the leaf
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* nodes in the btree, and those writes will be mostly empty (appending at most
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* a few keys each) - highly inefficient in terms of amount of metadata writes,
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* and it puts more strain on the various btree resorting/compacting code.
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*
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* The journal is just a log of keys we've inserted; on startup we just reinsert
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* all the keys in the open journal entries. That means that when we're updating
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* a node in the btree, we can wait until a 4k block of keys fills up before
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* writing them out.
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*
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* For simplicity, we only journal updates to leaf nodes; updates to parent
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* nodes are rare enough (since our leaf nodes are huge) that it wasn't worth
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* the complexity to deal with journalling them (in particular, journal replay)
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* - updates to non leaf nodes just happen synchronously (see btree_split()).
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*/
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#define pr_fmt(fmt) "bcache: %s() " fmt, __func__
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#include <linux/bio.h>
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#include <linux/kobject.h>
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#include <linux/list.h>
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#include <linux/mutex.h>
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#include <linux/rbtree.h>
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#include <linux/rwsem.h>
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#include <linux/refcount.h>
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#include <linux/types.h>
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#include <linux/workqueue.h>
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#include <linux/kthread.h>
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#include "bcache_ondisk.h"
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#include "bset.h"
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#include "util.h"
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#include "closure.h"
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struct bucket {
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atomic_t pin;
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uint16_t prio;
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uint8_t gen;
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uint8_t last_gc; /* Most out of date gen in the btree */
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uint16_t gc_mark; /* Bitfield used by GC. See below for field */
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};
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/*
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* I'd use bitfields for these, but I don't trust the compiler not to screw me
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* as multiple threads touch struct bucket without locking
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*/
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BITMASK(GC_MARK, struct bucket, gc_mark, 0, 2);
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#define GC_MARK_RECLAIMABLE 1
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#define GC_MARK_DIRTY 2
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#define GC_MARK_METADATA 3
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#define GC_SECTORS_USED_SIZE 13
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#define MAX_GC_SECTORS_USED (~(~0ULL << GC_SECTORS_USED_SIZE))
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BITMASK(GC_SECTORS_USED, struct bucket, gc_mark, 2, GC_SECTORS_USED_SIZE);
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BITMASK(GC_MOVE, struct bucket, gc_mark, 15, 1);
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#include "journal.h"
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#include "stats.h"
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struct search;
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struct btree;
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struct keybuf;
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struct keybuf_key {
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struct rb_node node;
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BKEY_PADDED(key);
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void *private;
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};
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struct keybuf {
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struct bkey last_scanned;
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spinlock_t lock;
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/*
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* Beginning and end of range in rb tree - so that we can skip taking
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* lock and checking the rb tree when we need to check for overlapping
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* keys.
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*/
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struct bkey start;
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struct bkey end;
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struct rb_root keys;
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#define KEYBUF_NR 500
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DECLARE_ARRAY_ALLOCATOR(struct keybuf_key, freelist, KEYBUF_NR);
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};
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struct bcache_device {
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struct closure cl;
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struct kobject kobj;
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struct cache_set *c;
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unsigned int id;
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#define BCACHEDEVNAME_SIZE 12
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char name[BCACHEDEVNAME_SIZE];
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struct gendisk *disk;
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unsigned long flags;
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#define BCACHE_DEV_CLOSING 0
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#define BCACHE_DEV_DETACHING 1
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#define BCACHE_DEV_UNLINK_DONE 2
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#define BCACHE_DEV_WB_RUNNING 3
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#define BCACHE_DEV_RATE_DW_RUNNING 4
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int nr_stripes;
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unsigned int stripe_size;
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atomic_t *stripe_sectors_dirty;
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unsigned long *full_dirty_stripes;
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struct bio_set bio_split;
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unsigned int data_csum:1;
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int (*cache_miss)(struct btree *b, struct search *s,
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struct bio *bio, unsigned int sectors);
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int (*ioctl)(struct bcache_device *d, fmode_t mode,
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unsigned int cmd, unsigned long arg);
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};
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struct io {
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/* Used to track sequential IO so it can be skipped */
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struct hlist_node hash;
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struct list_head lru;
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unsigned long jiffies;
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unsigned int sequential;
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sector_t last;
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};
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enum stop_on_failure {
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BCH_CACHED_DEV_STOP_AUTO = 0,
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BCH_CACHED_DEV_STOP_ALWAYS,
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BCH_CACHED_DEV_STOP_MODE_MAX,
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};
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struct cached_dev {
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struct list_head list;
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struct bcache_device disk;
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struct block_device *bdev;
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struct cache_sb sb;
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struct cache_sb_disk *sb_disk;
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struct bio sb_bio;
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struct bio_vec sb_bv[1];
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struct closure sb_write;
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struct semaphore sb_write_mutex;
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/* Refcount on the cache set. Always nonzero when we're caching. */
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refcount_t count;
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struct work_struct detach;
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/*
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* Device might not be running if it's dirty and the cache set hasn't
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* showed up yet.
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*/
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atomic_t running;
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/*
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* Writes take a shared lock from start to finish; scanning for dirty
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* data to refill the rb tree requires an exclusive lock.
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*/
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struct rw_semaphore writeback_lock;
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/*
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* Nonzero, and writeback has a refcount (d->count), iff there is dirty
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* data in the cache. Protected by writeback_lock; must have an
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* shared lock to set and exclusive lock to clear.
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*/
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atomic_t has_dirty;
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#define BCH_CACHE_READA_ALL 0
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#define BCH_CACHE_READA_META_ONLY 1
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unsigned int cache_readahead_policy;
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struct bch_ratelimit writeback_rate;
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struct delayed_work writeback_rate_update;
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/* Limit number of writeback bios in flight */
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struct semaphore in_flight;
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struct task_struct *writeback_thread;
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struct workqueue_struct *writeback_write_wq;
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struct keybuf writeback_keys;
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struct task_struct *status_update_thread;
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/*
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* Order the write-half of writeback operations strongly in dispatch
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* order. (Maintain LBA order; don't allow reads completing out of
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* order to re-order the writes...)
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*/
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struct closure_waitlist writeback_ordering_wait;
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atomic_t writeback_sequence_next;
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/* For tracking sequential IO */
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#define RECENT_IO_BITS 7
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#define RECENT_IO (1 << RECENT_IO_BITS)
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struct io io[RECENT_IO];
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struct hlist_head io_hash[RECENT_IO + 1];
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struct list_head io_lru;
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spinlock_t io_lock;
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struct cache_accounting accounting;
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/* The rest of this all shows up in sysfs */
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unsigned int sequential_cutoff;
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unsigned int io_disable:1;
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unsigned int verify:1;
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unsigned int bypass_torture_test:1;
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unsigned int partial_stripes_expensive:1;
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unsigned int writeback_metadata:1;
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unsigned int writeback_running:1;
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unsigned int writeback_consider_fragment:1;
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unsigned char writeback_percent;
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unsigned int writeback_delay;
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uint64_t writeback_rate_target;
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int64_t writeback_rate_proportional;
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int64_t writeback_rate_integral;
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int64_t writeback_rate_integral_scaled;
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int32_t writeback_rate_change;
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unsigned int writeback_rate_update_seconds;
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unsigned int writeback_rate_i_term_inverse;
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unsigned int writeback_rate_p_term_inverse;
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unsigned int writeback_rate_fp_term_low;
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unsigned int writeback_rate_fp_term_mid;
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unsigned int writeback_rate_fp_term_high;
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unsigned int writeback_rate_minimum;
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enum stop_on_failure stop_when_cache_set_failed;
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#define DEFAULT_CACHED_DEV_ERROR_LIMIT 64
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atomic_t io_errors;
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unsigned int error_limit;
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unsigned int offline_seconds;
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/*
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* Retry to update writeback_rate if contention happens for
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* down_read(dc->writeback_lock) in update_writeback_rate()
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*/
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#define BCH_WBRATE_UPDATE_MAX_SKIPS 15
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unsigned int rate_update_retry;
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};
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enum alloc_reserve {
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RESERVE_BTREE,
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RESERVE_PRIO,
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RESERVE_MOVINGGC,
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RESERVE_NONE,
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RESERVE_NR,
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};
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struct cache {
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struct cache_set *set;
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struct cache_sb sb;
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struct cache_sb_disk *sb_disk;
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struct bio sb_bio;
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struct bio_vec sb_bv[1];
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struct kobject kobj;
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struct block_device *bdev;
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struct task_struct *alloc_thread;
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struct closure prio;
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struct prio_set *disk_buckets;
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/*
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* When allocating new buckets, prio_write() gets first dibs - since we
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* may not be allocate at all without writing priorities and gens.
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* prio_last_buckets[] contains the last buckets we wrote priorities to
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* (so gc can mark them as metadata), prio_buckets[] contains the
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* buckets allocated for the next prio write.
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*/
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uint64_t *prio_buckets;
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uint64_t *prio_last_buckets;
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/*
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* free: Buckets that are ready to be used
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*
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* free_inc: Incoming buckets - these are buckets that currently have
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* cached data in them, and we can't reuse them until after we write
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* their new gen to disk. After prio_write() finishes writing the new
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|
* gens/prios, they'll be moved to the free list (and possibly discarded
|
|
* in the process)
|
|
*/
|
|
DECLARE_FIFO(long, free)[RESERVE_NR];
|
|
DECLARE_FIFO(long, free_inc);
|
|
|
|
size_t fifo_last_bucket;
|
|
|
|
/* Allocation stuff: */
|
|
struct bucket *buckets;
|
|
|
|
DECLARE_HEAP(struct bucket *, heap);
|
|
|
|
/*
|
|
* If nonzero, we know we aren't going to find any buckets to invalidate
|
|
* until a gc finishes - otherwise we could pointlessly burn a ton of
|
|
* cpu
|
|
*/
|
|
unsigned int invalidate_needs_gc;
|
|
|
|
bool discard; /* Get rid of? */
|
|
|
|
struct journal_device journal;
|
|
|
|
/* The rest of this all shows up in sysfs */
|
|
#define IO_ERROR_SHIFT 20
|
|
atomic_t io_errors;
|
|
atomic_t io_count;
|
|
|
|
atomic_long_t meta_sectors_written;
|
|
atomic_long_t btree_sectors_written;
|
|
atomic_long_t sectors_written;
|
|
};
|
|
|
|
struct gc_stat {
|
|
size_t nodes;
|
|
size_t nodes_pre;
|
|
size_t key_bytes;
|
|
|
|
size_t nkeys;
|
|
uint64_t data; /* sectors */
|
|
unsigned int in_use; /* percent */
|
|
};
|
|
|
|
/*
|
|
* Flag bits, for how the cache set is shutting down, and what phase it's at:
|
|
*
|
|
* CACHE_SET_UNREGISTERING means we're not just shutting down, we're detaching
|
|
* all the backing devices first (their cached data gets invalidated, and they
|
|
* won't automatically reattach).
|
|
*
|
|
* CACHE_SET_STOPPING always gets set first when we're closing down a cache set;
|
|
* we'll continue to run normally for awhile with CACHE_SET_STOPPING set (i.e.
|
|
* flushing dirty data).
|
|
*
|
|
* CACHE_SET_RUNNING means all cache devices have been registered and journal
|
|
* replay is complete.
|
|
*
|
|
* CACHE_SET_IO_DISABLE is set when bcache is stopping the whold cache set, all
|
|
* external and internal I/O should be denied when this flag is set.
|
|
*
|
|
*/
|
|
#define CACHE_SET_UNREGISTERING 0
|
|
#define CACHE_SET_STOPPING 1
|
|
#define CACHE_SET_RUNNING 2
|
|
#define CACHE_SET_IO_DISABLE 3
|
|
|
|
struct cache_set {
|
|
struct closure cl;
|
|
|
|
struct list_head list;
|
|
struct kobject kobj;
|
|
struct kobject internal;
|
|
struct dentry *debug;
|
|
struct cache_accounting accounting;
|
|
|
|
unsigned long flags;
|
|
atomic_t idle_counter;
|
|
atomic_t at_max_writeback_rate;
|
|
|
|
struct cache *cache;
|
|
|
|
struct bcache_device **devices;
|
|
unsigned int devices_max_used;
|
|
atomic_t attached_dev_nr;
|
|
struct list_head cached_devs;
|
|
uint64_t cached_dev_sectors;
|
|
atomic_long_t flash_dev_dirty_sectors;
|
|
struct closure caching;
|
|
|
|
struct closure sb_write;
|
|
struct semaphore sb_write_mutex;
|
|
|
|
mempool_t search;
|
|
mempool_t bio_meta;
|
|
struct bio_set bio_split;
|
|
|
|
/* For the btree cache */
|
|
struct shrinker shrink;
|
|
|
|
/* For the btree cache and anything allocation related */
|
|
struct mutex bucket_lock;
|
|
|
|
/* log2(bucket_size), in sectors */
|
|
unsigned short bucket_bits;
|
|
|
|
/* log2(block_size), in sectors */
|
|
unsigned short block_bits;
|
|
|
|
/*
|
|
* Default number of pages for a new btree node - may be less than a
|
|
* full bucket
|
|
*/
|
|
unsigned int btree_pages;
|
|
|
|
/*
|
|
* Lists of struct btrees; lru is the list for structs that have memory
|
|
* allocated for actual btree node, freed is for structs that do not.
|
|
*
|
|
* We never free a struct btree, except on shutdown - we just put it on
|
|
* the btree_cache_freed list and reuse it later. This simplifies the
|
|
* code, and it doesn't cost us much memory as the memory usage is
|
|
* dominated by buffers that hold the actual btree node data and those
|
|
* can be freed - and the number of struct btrees allocated is
|
|
* effectively bounded.
|
|
*
|
|
* btree_cache_freeable effectively is a small cache - we use it because
|
|
* high order page allocations can be rather expensive, and it's quite
|
|
* common to delete and allocate btree nodes in quick succession. It
|
|
* should never grow past ~2-3 nodes in practice.
|
|
*/
|
|
struct list_head btree_cache;
|
|
struct list_head btree_cache_freeable;
|
|
struct list_head btree_cache_freed;
|
|
|
|
/* Number of elements in btree_cache + btree_cache_freeable lists */
|
|
unsigned int btree_cache_used;
|
|
|
|
/*
|
|
* If we need to allocate memory for a new btree node and that
|
|
* allocation fails, we can cannibalize another node in the btree cache
|
|
* to satisfy the allocation - lock to guarantee only one thread does
|
|
* this at a time:
|
|
*/
|
|
wait_queue_head_t btree_cache_wait;
|
|
struct task_struct *btree_cache_alloc_lock;
|
|
spinlock_t btree_cannibalize_lock;
|
|
|
|
/*
|
|
* When we free a btree node, we increment the gen of the bucket the
|
|
* node is in - but we can't rewrite the prios and gens until we
|
|
* finished whatever it is we were doing, otherwise after a crash the
|
|
* btree node would be freed but for say a split, we might not have the
|
|
* pointers to the new nodes inserted into the btree yet.
|
|
*
|
|
* This is a refcount that blocks prio_write() until the new keys are
|
|
* written.
|
|
*/
|
|
atomic_t prio_blocked;
|
|
wait_queue_head_t bucket_wait;
|
|
|
|
/*
|
|
* For any bio we don't skip we subtract the number of sectors from
|
|
* rescale; when it hits 0 we rescale all the bucket priorities.
|
|
*/
|
|
atomic_t rescale;
|
|
/*
|
|
* used for GC, identify if any front side I/Os is inflight
|
|
*/
|
|
atomic_t search_inflight;
|
|
/*
|
|
* When we invalidate buckets, we use both the priority and the amount
|
|
* of good data to determine which buckets to reuse first - to weight
|
|
* those together consistently we keep track of the smallest nonzero
|
|
* priority of any bucket.
|
|
*/
|
|
uint16_t min_prio;
|
|
|
|
/*
|
|
* max(gen - last_gc) for all buckets. When it gets too big we have to
|
|
* gc to keep gens from wrapping around.
|
|
*/
|
|
uint8_t need_gc;
|
|
struct gc_stat gc_stats;
|
|
size_t nbuckets;
|
|
size_t avail_nbuckets;
|
|
|
|
struct task_struct *gc_thread;
|
|
/* Where in the btree gc currently is */
|
|
struct bkey gc_done;
|
|
|
|
/*
|
|
* For automatical garbage collection after writeback completed, this
|
|
* varialbe is used as bit fields,
|
|
* - 0000 0001b (BCH_ENABLE_AUTO_GC): enable gc after writeback
|
|
* - 0000 0010b (BCH_DO_AUTO_GC): do gc after writeback
|
|
* This is an optimization for following write request after writeback
|
|
* finished, but read hit rate dropped due to clean data on cache is
|
|
* discarded. Unless user explicitly sets it via sysfs, it won't be
|
|
* enabled.
|
|
*/
|
|
#define BCH_ENABLE_AUTO_GC 1
|
|
#define BCH_DO_AUTO_GC 2
|
|
uint8_t gc_after_writeback;
|
|
|
|
/*
|
|
* The allocation code needs gc_mark in struct bucket to be correct, but
|
|
* it's not while a gc is in progress. Protected by bucket_lock.
|
|
*/
|
|
int gc_mark_valid;
|
|
|
|
/* Counts how many sectors bio_insert has added to the cache */
|
|
atomic_t sectors_to_gc;
|
|
wait_queue_head_t gc_wait;
|
|
|
|
struct keybuf moving_gc_keys;
|
|
/* Number of moving GC bios in flight */
|
|
struct semaphore moving_in_flight;
|
|
|
|
struct workqueue_struct *moving_gc_wq;
|
|
|
|
struct btree *root;
|
|
|
|
#ifdef CONFIG_BCACHE_DEBUG
|
|
struct btree *verify_data;
|
|
struct bset *verify_ondisk;
|
|
struct mutex verify_lock;
|
|
#endif
|
|
|
|
uint8_t set_uuid[16];
|
|
unsigned int nr_uuids;
|
|
struct uuid_entry *uuids;
|
|
BKEY_PADDED(uuid_bucket);
|
|
struct closure uuid_write;
|
|
struct semaphore uuid_write_mutex;
|
|
|
|
/*
|
|
* A btree node on disk could have too many bsets for an iterator to fit
|
|
* on the stack - have to dynamically allocate them.
|
|
* bch_cache_set_alloc() will make sure the pool can allocate iterators
|
|
* equipped with enough room that can host
|
|
* (sb.bucket_size / sb.block_size)
|
|
* btree_iter_sets, which is more than static MAX_BSETS.
|
|
*/
|
|
mempool_t fill_iter;
|
|
|
|
struct bset_sort_state sort;
|
|
|
|
/* List of buckets we're currently writing data to */
|
|
struct list_head data_buckets;
|
|
spinlock_t data_bucket_lock;
|
|
|
|
struct journal journal;
|
|
|
|
#define CONGESTED_MAX 1024
|
|
unsigned int congested_last_us;
|
|
atomic_t congested;
|
|
|
|
/* The rest of this all shows up in sysfs */
|
|
unsigned int congested_read_threshold_us;
|
|
unsigned int congested_write_threshold_us;
|
|
|
|
struct time_stats btree_gc_time;
|
|
struct time_stats btree_split_time;
|
|
struct time_stats btree_read_time;
|
|
|
|
atomic_long_t cache_read_races;
|
|
atomic_long_t writeback_keys_done;
|
|
atomic_long_t writeback_keys_failed;
|
|
|
|
atomic_long_t reclaim;
|
|
atomic_long_t reclaimed_journal_buckets;
|
|
atomic_long_t flush_write;
|
|
|
|
enum {
|
|
ON_ERROR_UNREGISTER,
|
|
ON_ERROR_PANIC,
|
|
} on_error;
|
|
#define DEFAULT_IO_ERROR_LIMIT 8
|
|
unsigned int error_limit;
|
|
unsigned int error_decay;
|
|
|
|
unsigned short journal_delay_ms;
|
|
bool expensive_debug_checks;
|
|
unsigned int verify:1;
|
|
unsigned int key_merging_disabled:1;
|
|
unsigned int gc_always_rewrite:1;
|
|
unsigned int shrinker_disabled:1;
|
|
unsigned int copy_gc_enabled:1;
|
|
unsigned int idle_max_writeback_rate_enabled:1;
|
|
|
|
#define BUCKET_HASH_BITS 12
|
|
struct hlist_head bucket_hash[1 << BUCKET_HASH_BITS];
|
|
};
|
|
|
|
struct bbio {
|
|
unsigned int submit_time_us;
|
|
union {
|
|
struct bkey key;
|
|
uint64_t _pad[3];
|
|
/*
|
|
* We only need pad = 3 here because we only ever carry around a
|
|
* single pointer - i.e. the pointer we're doing io to/from.
|
|
*/
|
|
};
|
|
struct bio bio;
|
|
};
|
|
|
|
#define BTREE_PRIO USHRT_MAX
|
|
#define INITIAL_PRIO 32768U
|
|
|
|
#define btree_bytes(c) ((c)->btree_pages * PAGE_SIZE)
|
|
#define btree_blocks(b) \
|
|
((unsigned int) (KEY_SIZE(&b->key) >> (b)->c->block_bits))
|
|
|
|
#define btree_default_blocks(c) \
|
|
((unsigned int) ((PAGE_SECTORS * (c)->btree_pages) >> (c)->block_bits))
|
|
|
|
#define bucket_bytes(ca) ((ca)->sb.bucket_size << 9)
|
|
#define block_bytes(ca) ((ca)->sb.block_size << 9)
|
|
|
|
static inline unsigned int meta_bucket_pages(struct cache_sb *sb)
|
|
{
|
|
unsigned int n, max_pages;
|
|
|
|
max_pages = min_t(unsigned int,
|
|
__rounddown_pow_of_two(USHRT_MAX) / PAGE_SECTORS,
|
|
MAX_ORDER_NR_PAGES);
|
|
|
|
n = sb->bucket_size / PAGE_SECTORS;
|
|
if (n > max_pages)
|
|
n = max_pages;
|
|
|
|
return n;
|
|
}
|
|
|
|
static inline unsigned int meta_bucket_bytes(struct cache_sb *sb)
|
|
{
|
|
return meta_bucket_pages(sb) << PAGE_SHIFT;
|
|
}
|
|
|
|
#define prios_per_bucket(ca) \
|
|
((meta_bucket_bytes(&(ca)->sb) - sizeof(struct prio_set)) / \
|
|
sizeof(struct bucket_disk))
|
|
|
|
#define prio_buckets(ca) \
|
|
DIV_ROUND_UP((size_t) (ca)->sb.nbuckets, prios_per_bucket(ca))
|
|
|
|
static inline size_t sector_to_bucket(struct cache_set *c, sector_t s)
|
|
{
|
|
return s >> c->bucket_bits;
|
|
}
|
|
|
|
static inline sector_t bucket_to_sector(struct cache_set *c, size_t b)
|
|
{
|
|
return ((sector_t) b) << c->bucket_bits;
|
|
}
|
|
|
|
static inline sector_t bucket_remainder(struct cache_set *c, sector_t s)
|
|
{
|
|
return s & (c->cache->sb.bucket_size - 1);
|
|
}
|
|
|
|
static inline size_t PTR_BUCKET_NR(struct cache_set *c,
|
|
const struct bkey *k,
|
|
unsigned int ptr)
|
|
{
|
|
return sector_to_bucket(c, PTR_OFFSET(k, ptr));
|
|
}
|
|
|
|
static inline struct bucket *PTR_BUCKET(struct cache_set *c,
|
|
const struct bkey *k,
|
|
unsigned int ptr)
|
|
{
|
|
return c->cache->buckets + PTR_BUCKET_NR(c, k, ptr);
|
|
}
|
|
|
|
static inline uint8_t gen_after(uint8_t a, uint8_t b)
|
|
{
|
|
uint8_t r = a - b;
|
|
|
|
return r > 128U ? 0 : r;
|
|
}
|
|
|
|
static inline uint8_t ptr_stale(struct cache_set *c, const struct bkey *k,
|
|
unsigned int i)
|
|
{
|
|
return gen_after(PTR_BUCKET(c, k, i)->gen, PTR_GEN(k, i));
|
|
}
|
|
|
|
static inline bool ptr_available(struct cache_set *c, const struct bkey *k,
|
|
unsigned int i)
|
|
{
|
|
return (PTR_DEV(k, i) < MAX_CACHES_PER_SET) && c->cache;
|
|
}
|
|
|
|
/* Btree key macros */
|
|
|
|
/*
|
|
* This is used for various on disk data structures - cache_sb, prio_set, bset,
|
|
* jset: The checksum is _always_ the first 8 bytes of these structs
|
|
*/
|
|
#define csum_set(i) \
|
|
bch_crc64(((void *) (i)) + sizeof(uint64_t), \
|
|
((void *) bset_bkey_last(i)) - \
|
|
(((void *) (i)) + sizeof(uint64_t)))
|
|
|
|
/* Error handling macros */
|
|
|
|
#define btree_bug(b, ...) \
|
|
do { \
|
|
if (bch_cache_set_error((b)->c, __VA_ARGS__)) \
|
|
dump_stack(); \
|
|
} while (0)
|
|
|
|
#define cache_bug(c, ...) \
|
|
do { \
|
|
if (bch_cache_set_error(c, __VA_ARGS__)) \
|
|
dump_stack(); \
|
|
} while (0)
|
|
|
|
#define btree_bug_on(cond, b, ...) \
|
|
do { \
|
|
if (cond) \
|
|
btree_bug(b, __VA_ARGS__); \
|
|
} while (0)
|
|
|
|
#define cache_bug_on(cond, c, ...) \
|
|
do { \
|
|
if (cond) \
|
|
cache_bug(c, __VA_ARGS__); \
|
|
} while (0)
|
|
|
|
#define cache_set_err_on(cond, c, ...) \
|
|
do { \
|
|
if (cond) \
|
|
bch_cache_set_error(c, __VA_ARGS__); \
|
|
} while (0)
|
|
|
|
/* Looping macros */
|
|
|
|
#define for_each_bucket(b, ca) \
|
|
for (b = (ca)->buckets + (ca)->sb.first_bucket; \
|
|
b < (ca)->buckets + (ca)->sb.nbuckets; b++)
|
|
|
|
static inline void cached_dev_put(struct cached_dev *dc)
|
|
{
|
|
if (refcount_dec_and_test(&dc->count))
|
|
schedule_work(&dc->detach);
|
|
}
|
|
|
|
static inline bool cached_dev_get(struct cached_dev *dc)
|
|
{
|
|
if (!refcount_inc_not_zero(&dc->count))
|
|
return false;
|
|
|
|
/* Paired with the mb in cached_dev_attach */
|
|
smp_mb__after_atomic();
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* bucket_gc_gen() returns the difference between the bucket's current gen and
|
|
* the oldest gen of any pointer into that bucket in the btree (last_gc).
|
|
*/
|
|
|
|
static inline uint8_t bucket_gc_gen(struct bucket *b)
|
|
{
|
|
return b->gen - b->last_gc;
|
|
}
|
|
|
|
#define BUCKET_GC_GEN_MAX 96U
|
|
|
|
#define kobj_attribute_write(n, fn) \
|
|
static struct kobj_attribute ksysfs_##n = __ATTR(n, 0200, NULL, fn)
|
|
|
|
#define kobj_attribute_rw(n, show, store) \
|
|
static struct kobj_attribute ksysfs_##n = \
|
|
__ATTR(n, 0600, show, store)
|
|
|
|
static inline void wake_up_allocators(struct cache_set *c)
|
|
{
|
|
struct cache *ca = c->cache;
|
|
|
|
wake_up_process(ca->alloc_thread);
|
|
}
|
|
|
|
static inline void closure_bio_submit(struct cache_set *c,
|
|
struct bio *bio,
|
|
struct closure *cl)
|
|
{
|
|
closure_get(cl);
|
|
if (unlikely(test_bit(CACHE_SET_IO_DISABLE, &c->flags))) {
|
|
bio->bi_status = BLK_STS_IOERR;
|
|
bio_endio(bio);
|
|
return;
|
|
}
|
|
submit_bio_noacct(bio);
|
|
}
|
|
|
|
/*
|
|
* Prevent the kthread exits directly, and make sure when kthread_stop()
|
|
* is called to stop a kthread, it is still alive. If a kthread might be
|
|
* stopped by CACHE_SET_IO_DISABLE bit set, wait_for_kthread_stop() is
|
|
* necessary before the kthread returns.
|
|
*/
|
|
static inline void wait_for_kthread_stop(void)
|
|
{
|
|
while (!kthread_should_stop()) {
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
schedule();
|
|
}
|
|
}
|
|
|
|
/* Forward declarations */
|
|
|
|
void bch_count_backing_io_errors(struct cached_dev *dc, struct bio *bio);
|
|
void bch_count_io_errors(struct cache *ca, blk_status_t error,
|
|
int is_read, const char *m);
|
|
void bch_bbio_count_io_errors(struct cache_set *c, struct bio *bio,
|
|
blk_status_t error, const char *m);
|
|
void bch_bbio_endio(struct cache_set *c, struct bio *bio,
|
|
blk_status_t error, const char *m);
|
|
void bch_bbio_free(struct bio *bio, struct cache_set *c);
|
|
struct bio *bch_bbio_alloc(struct cache_set *c);
|
|
|
|
void __bch_submit_bbio(struct bio *bio, struct cache_set *c);
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void bch_submit_bbio(struct bio *bio, struct cache_set *c,
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struct bkey *k, unsigned int ptr);
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uint8_t bch_inc_gen(struct cache *ca, struct bucket *b);
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void bch_rescale_priorities(struct cache_set *c, int sectors);
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bool bch_can_invalidate_bucket(struct cache *ca, struct bucket *b);
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void __bch_invalidate_one_bucket(struct cache *ca, struct bucket *b);
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void __bch_bucket_free(struct cache *ca, struct bucket *b);
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void bch_bucket_free(struct cache_set *c, struct bkey *k);
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long bch_bucket_alloc(struct cache *ca, unsigned int reserve, bool wait);
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int __bch_bucket_alloc_set(struct cache_set *c, unsigned int reserve,
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struct bkey *k, bool wait);
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int bch_bucket_alloc_set(struct cache_set *c, unsigned int reserve,
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struct bkey *k, bool wait);
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bool bch_alloc_sectors(struct cache_set *c, struct bkey *k,
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unsigned int sectors, unsigned int write_point,
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unsigned int write_prio, bool wait);
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bool bch_cached_dev_error(struct cached_dev *dc);
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__printf(2, 3)
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bool bch_cache_set_error(struct cache_set *c, const char *fmt, ...);
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int bch_prio_write(struct cache *ca, bool wait);
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void bch_write_bdev_super(struct cached_dev *dc, struct closure *parent);
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extern struct workqueue_struct *bcache_wq;
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extern struct workqueue_struct *bch_journal_wq;
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extern struct workqueue_struct *bch_flush_wq;
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extern struct mutex bch_register_lock;
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extern struct list_head bch_cache_sets;
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extern struct kobj_type bch_cached_dev_ktype;
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extern struct kobj_type bch_flash_dev_ktype;
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extern struct kobj_type bch_cache_set_ktype;
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extern struct kobj_type bch_cache_set_internal_ktype;
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extern struct kobj_type bch_cache_ktype;
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void bch_cached_dev_release(struct kobject *kobj);
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void bch_flash_dev_release(struct kobject *kobj);
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void bch_cache_set_release(struct kobject *kobj);
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void bch_cache_release(struct kobject *kobj);
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int bch_uuid_write(struct cache_set *c);
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void bcache_write_super(struct cache_set *c);
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int bch_flash_dev_create(struct cache_set *c, uint64_t size);
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int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c,
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uint8_t *set_uuid);
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void bch_cached_dev_detach(struct cached_dev *dc);
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int bch_cached_dev_run(struct cached_dev *dc);
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void bcache_device_stop(struct bcache_device *d);
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void bch_cache_set_unregister(struct cache_set *c);
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void bch_cache_set_stop(struct cache_set *c);
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struct cache_set *bch_cache_set_alloc(struct cache_sb *sb);
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void bch_btree_cache_free(struct cache_set *c);
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int bch_btree_cache_alloc(struct cache_set *c);
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void bch_moving_init_cache_set(struct cache_set *c);
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int bch_open_buckets_alloc(struct cache_set *c);
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void bch_open_buckets_free(struct cache_set *c);
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int bch_cache_allocator_start(struct cache *ca);
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void bch_debug_exit(void);
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void bch_debug_init(void);
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void bch_request_exit(void);
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int bch_request_init(void);
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void bch_btree_exit(void);
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int bch_btree_init(void);
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#endif /* _BCACHE_H */
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