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c6b4fcbad0
Add a target that allows a fast device such as an SSD to be used as a cache for a slower device such as a disk. A plug-in architecture was chosen so that the decisions about which data to migrate and when are delegated to interchangeable tunable policy modules. The first general purpose module we have developed, called "mq" (multiqueue), follows in the next patch. Other modules are under development. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Heinz Mauelshagen <mauelshagen@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
111 lines
3.4 KiB
C
111 lines
3.4 KiB
C
/*
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* Copyright (C) 2011-2012 Red Hat, Inc.
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*
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* This file is released under the GPL.
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*/
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#ifndef DM_BIO_PRISON_H
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#define DM_BIO_PRISON_H
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#include "persistent-data/dm-block-manager.h" /* FIXME: for dm_block_t */
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#include "dm-thin-metadata.h" /* FIXME: for dm_thin_id */
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#include <linux/list.h>
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#include <linux/bio.h>
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/*----------------------------------------------------------------*/
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/*
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* Sometimes we can't deal with a bio straight away. We put them in prison
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* where they can't cause any mischief. Bios are put in a cell identified
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* by a key, multiple bios can be in the same cell. When the cell is
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* subsequently unlocked the bios become available.
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*/
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struct dm_bio_prison;
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/* FIXME: this needs to be more abstract */
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struct dm_cell_key {
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int virtual;
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dm_thin_id dev;
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dm_block_t block;
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};
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/*
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* Treat this as opaque, only in header so callers can manage allocation
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* themselves.
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*/
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struct dm_bio_prison_cell {
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struct hlist_node list;
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struct dm_cell_key key;
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struct bio *holder;
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struct bio_list bios;
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};
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struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells);
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void dm_bio_prison_destroy(struct dm_bio_prison *prison);
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/*
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* These two functions just wrap a mempool. This is a transitory step:
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* Eventually all bio prison clients should manage their own cell memory.
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*
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* Like mempool_alloc(), dm_bio_prison_alloc_cell() can only fail if called
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* in interrupt context or passed GFP_NOWAIT.
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*/
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struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
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gfp_t gfp);
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void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
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struct dm_bio_prison_cell *cell);
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/*
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* Creates, or retrieves a cell for the given key.
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*
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* Returns 1 if pre-existing cell returned, zero if new cell created using
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* @cell_prealloc.
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*/
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int dm_get_cell(struct dm_bio_prison *prison,
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struct dm_cell_key *key,
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struct dm_bio_prison_cell *cell_prealloc,
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struct dm_bio_prison_cell **cell_result);
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/*
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* An atomic op that combines retrieving a cell, and adding a bio to it.
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*
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* Returns 1 if the cell was already held, 0 if @inmate is the new holder.
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*/
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int dm_bio_detain(struct dm_bio_prison *prison,
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struct dm_cell_key *key,
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struct bio *inmate,
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struct dm_bio_prison_cell *cell_prealloc,
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struct dm_bio_prison_cell **cell_result);
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void dm_cell_release(struct dm_bio_prison *prison,
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struct dm_bio_prison_cell *cell,
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struct bio_list *bios);
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void dm_cell_release_no_holder(struct dm_bio_prison *prison,
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struct dm_bio_prison_cell *cell,
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struct bio_list *inmates);
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void dm_cell_error(struct dm_bio_prison *prison,
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struct dm_bio_prison_cell *cell);
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/*----------------------------------------------------------------*/
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/*
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* We use the deferred set to keep track of pending reads to shared blocks.
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* We do this to ensure the new mapping caused by a write isn't performed
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* until these prior reads have completed. Otherwise the insertion of the
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* new mapping could free the old block that the read bios are mapped to.
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*/
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struct dm_deferred_set;
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struct dm_deferred_entry;
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struct dm_deferred_set *dm_deferred_set_create(void);
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void dm_deferred_set_destroy(struct dm_deferred_set *ds);
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struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
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void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
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int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
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/*----------------------------------------------------------------*/
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#endif
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