From 3241b1d3e0aaafbfcd320f4d71ade629728cc4f4 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Mon, 31 Oct 2011 20:19:11 +0000 Subject: dm: add persistent data library The persistent-data library offers a re-usable framework for the storage and management of on-disk metadata in device-mapper targets. It's used by the thin-provisioning target in the next patch and in an upcoming hierarchical storage target. For further information, please read Documentation/device-mapper/persistent-data.txt Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon --- drivers/md/persistent-data/dm-block-manager.h | 123 ++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 drivers/md/persistent-data/dm-block-manager.h (limited to 'drivers/md/persistent-data/dm-block-manager.h') diff --git a/drivers/md/persistent-data/dm-block-manager.h b/drivers/md/persistent-data/dm-block-manager.h new file mode 100644 index 0000000..924833d --- /dev/null +++ b/drivers/md/persistent-data/dm-block-manager.h @@ -0,0 +1,123 @@ +/* + * Copyright (C) 2011 Red Hat, Inc. + * + * This file is released under the GPL. + */ + +#ifndef _LINUX_DM_BLOCK_MANAGER_H +#define _LINUX_DM_BLOCK_MANAGER_H + +#include +#include + +/*----------------------------------------------------------------*/ + +/* + * Block number. + */ +typedef uint64_t dm_block_t; +struct dm_block; + +dm_block_t dm_block_location(struct dm_block *b); +void *dm_block_data(struct dm_block *b); + +/*----------------------------------------------------------------*/ + +/* + * @name should be a unique identifier for the block manager, no longer + * than 32 chars. + * + * @max_held_per_thread should be the maximum number of locks, read or + * write, that an individual thread holds at any one time. + */ +struct dm_block_manager; +struct dm_block_manager *dm_block_manager_create( + struct block_device *bdev, unsigned block_size, + unsigned cache_size, unsigned max_held_per_thread); +void dm_block_manager_destroy(struct dm_block_manager *bm); + +unsigned dm_bm_block_size(struct dm_block_manager *bm); +dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm); + +/*----------------------------------------------------------------*/ + +/* + * The validator allows the caller to verify newly-read data and modify + * the data just before writing, e.g. to calculate checksums. It's + * important to be consistent with your use of validators. The only time + * you can change validators is if you call dm_bm_write_lock_zero. + */ +struct dm_block_validator { + const char *name; + void (*prepare_for_write)(struct dm_block_validator *v, struct dm_block *b, size_t block_size); + + /* + * Return 0 if the checksum is valid or < 0 on error. + */ + int (*check)(struct dm_block_validator *v, struct dm_block *b, size_t block_size); +}; + +/*----------------------------------------------------------------*/ + +/* + * You can have multiple concurrent readers or a single writer holding a + * block lock. + */ + +/* + * dm_bm_lock() locks a block and returns through @result a pointer to + * memory that holds a copy of that block. If you have write-locked the + * block then any changes you make to memory pointed to by @result will be + * written back to the disk sometime after dm_bm_unlock is called. + */ +int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b, + struct dm_block_validator *v, + struct dm_block **result); + +int dm_bm_write_lock(struct dm_block_manager *bm, dm_block_t b, + struct dm_block_validator *v, + struct dm_block **result); + +/* + * The *_try_lock variants return -EWOULDBLOCK if the block isn't + * available immediately. + */ +int dm_bm_read_try_lock(struct dm_block_manager *bm, dm_block_t b, + struct dm_block_validator *v, + struct dm_block **result); + +/* + * Use dm_bm_write_lock_zero() when you know you're going to + * overwrite the block completely. It saves a disk read. + */ +int dm_bm_write_lock_zero(struct dm_block_manager *bm, dm_block_t b, + struct dm_block_validator *v, + struct dm_block **result); + +int dm_bm_unlock(struct dm_block *b); + +/* + * An optimisation; we often want to copy a block's contents to a new + * block. eg, as part of the shadowing operation. It's far better for + * bufio to do this move behind the scenes than hold 2 locks and memcpy the + * data. + */ +int dm_bm_unlock_move(struct dm_block *b, dm_block_t n); + +/* + * It's a common idiom to have a superblock that should be committed last. + * + * @superblock should be write-locked on entry. It will be unlocked during + * this function. All dirty blocks are guaranteed to be written and flushed + * before the superblock. + * + * This method always blocks. + */ +int dm_bm_flush_and_unlock(struct dm_block_manager *bm, + struct dm_block *superblock); + +u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor); + +/*----------------------------------------------------------------*/ + +#endif /* _LINUX_DM_BLOCK_MANAGER_H */ -- cgit v1.1