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112 lines
3.0 KiB
C
112 lines
3.0 KiB
C
/*
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* Copyright (C) 2018 Red Hat, Inc. All rights reserved.
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*
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* This file is part of LVM2.
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*
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* This copyrighted material is made available to anyone wishing to use,
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* modify, copy, or redistribute it subject to the terms and conditions
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* of the GNU Lesser General Public License v.2.1.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef BCACHE_H
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#define BCACHE_H
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#include <stdint.h>
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#include <stdbool.h>
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#include "libdevmapper.h"
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/*----------------------------------------------------------------*/
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typedef uint64_t block_address;
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typedef uint64_t sector_t;
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struct bcache;
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struct block {
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/* clients may only access these three fields */
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int fd;
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uint64_t index;
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void *data;
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struct bcache *cache;
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struct dm_list list;
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struct dm_list hash;
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unsigned flags;
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unsigned ref_count;
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int error;
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};
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struct bcache *bcache_create(sector_t block_size, unsigned nr_cache_blocks);
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void bcache_destroy(struct bcache *cache);
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enum bcache_get_flags {
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/*
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* The block will be zeroed before get_block returns it. This
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* potentially avoids a read if the block is not already in the cache.
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* GF_DIRTY is implicit.
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*/
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GF_ZERO = (1 << 0),
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/*
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* Indicates the caller is intending to change the data in the block, a
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* writeback will occur after the block is released.
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*/
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GF_DIRTY = (1 << 1)
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};
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typedef uint64_t block_address;
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unsigned bcache_nr_cache_blocks(struct bcache *cache);
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/*
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* Use the prefetch method to take advantage of asynchronous IO. For example,
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* if you wanted to read a block from many devices concurrently you'd do
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* something like this:
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*
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* dm_list_iterate_items (dev, &devices)
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* bcache_prefetch(cache, dev->fd, block);
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*
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* dm_list_iterate_items (dev, &devices) {
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* if (!bcache_get(cache, dev->fd, block, &b))
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* fail();
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*
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* process_block(b);
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* }
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*
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* It's slightly sub optimal, since you may not run the gets in the order that
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* they complete. But we're talking a very small difference, and it's worth it
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* to keep callbacks out of this interface.
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*/
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void bcache_prefetch(struct bcache *cache, int fd, block_address index);
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/*
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* Returns true on success.
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*/
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bool bcache_get(struct bcache *cache, int fd, block_address index,
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unsigned flags, struct block **result);
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void bcache_put(struct block *b);
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int bcache_flush(struct bcache *cache);
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/*
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* Removes a block from the cache. If the block is dirty it will be written
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* back first. If the block is currently held a warning will be issued, and it
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* will not be removed.
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*/
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void bcache_invalidate(struct bcache *cache, int fd, block_address index);
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/*
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* Invalidates all blocks on the given descriptor. Call this before closing
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* the descriptor to make sure everything is written back.
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*/
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void bcache_invalidate_fd(struct bcache *cache, int fd);
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/*----------------------------------------------------------------*/
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#endif
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