forked from luck/tmp_suning_uos_patched
3cdf93f9d8
Rather than always releasing the prisoners in a cell, the client may want to promote one of them to be the new holder. There is a race here though between releasing an empty cell, and other threads adding new inmates. So this function makes the decision with its lock held. This function can have two outcomes: i) An inmate is promoted to be the holder of the cell (return value of 0). ii) The cell has no inmate for promotion and is released (return value of 1). Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
139 lines
4.4 KiB
C
139 lines
4.4 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/bio.h>
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#include <linux/rbtree.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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/*
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* Keys define a range of blocks within either a virtual or physical
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* device.
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*/
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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_begin, block_end;
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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 list_head user_list; /* for client use */
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struct rb_node node;
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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(void);
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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 that overlaps 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 or creating a cell, and adding a
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* 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, int error);
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/*
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* Visits the cell and then releases. Guarantees no new inmates are
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* inserted between the visit and release.
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*/
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void dm_cell_visit_release(struct dm_bio_prison *prison,
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void (*visit_fn)(void *, struct dm_bio_prison_cell *),
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void *context, struct dm_bio_prison_cell *cell);
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/*
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* Rather than always releasing the prisoners in a cell, the client may
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* want to promote one of them to be the new holder. There is a race here
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* though between releasing an empty cell, and other threads adding new
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* inmates. So this function makes the decision with its lock held.
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*
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* This function can have two outcomes:
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* i) An inmate is promoted to be the holder of the cell (return value of 0).
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* ii) The cell has no inmate for promotion and is released (return value of 1).
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*/
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int dm_cell_promote_or_release(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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