linux/drivers/md/dm-bio-prison.h
Joe Thornber b7ca9c9273 dm thin: replace dm_cell_release_singleton with cell_defer_except
Change existing users of the function dm_cell_release_singleton to share
cell_defer_except instead, and then remove the now-unused function.

Everywhere that calls dm_cell_release_singleton, the bio in question
is the holder of the cell.

If there are no non-holder entries in the cell then cell_defer_except
behaves exactly like dm_cell_release_singleton.  Conversely, if there
*are* non-holder entries then dm_cell_release_singleton must not be used
because those entries would need to be deferred.

Consequently, it is safe to replace use of dm_cell_release_singleton
with cell_defer_except.

This patch is a pre-requisite for "dm thin: fix race between
simultaneous io and discards to same block".

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2012-12-21 20:23:31 +00:00

72 lines
2.3 KiB
C

/*
* Copyright (C) 2011-2012 Red Hat, Inc.
*
* This file is released under the GPL.
*/
#ifndef DM_BIO_PRISON_H
#define DM_BIO_PRISON_H
#include "persistent-data/dm-block-manager.h" /* FIXME: for dm_block_t */
#include "dm-thin-metadata.h" /* FIXME: for dm_thin_id */
#include <linux/list.h>
#include <linux/bio.h>
/*----------------------------------------------------------------*/
/*
* Sometimes we can't deal with a bio straight away. We put them in prison
* where they can't cause any mischief. Bios are put in a cell identified
* by a key, multiple bios can be in the same cell. When the cell is
* subsequently unlocked the bios become available.
*/
struct dm_bio_prison;
struct dm_bio_prison_cell;
/* FIXME: this needs to be more abstract */
struct dm_cell_key {
int virtual;
dm_thin_id dev;
dm_block_t block;
};
struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells);
void dm_bio_prison_destroy(struct dm_bio_prison *prison);
/*
* This may block if a new cell needs allocating. You must ensure that
* cells will be unlocked even if the calling thread is blocked.
*
* Returns 1 if the cell was already held, 0 if @inmate is the new holder.
*/
int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
struct bio *inmate, struct dm_bio_prison_cell **ref);
void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios);
void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates);
void dm_cell_error(struct dm_bio_prison_cell *cell);
/*----------------------------------------------------------------*/
/*
* We use the deferred set to keep track of pending reads to shared blocks.
* We do this to ensure the new mapping caused by a write isn't performed
* until these prior reads have completed. Otherwise the insertion of the
* new mapping could free the old block that the read bios are mapped to.
*/
struct dm_deferred_set;
struct dm_deferred_entry;
struct dm_deferred_set *dm_deferred_set_create(void);
void dm_deferred_set_destroy(struct dm_deferred_set *ds);
struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
/*----------------------------------------------------------------*/
#endif