drivers/md/dm-bio-prison-v2.h

0001 /*
0002  * Copyright (C) 2011-2017 Red Hat, Inc.
0003  *
0004  * This file is released under the GPL.
0005  */
0006
0007 #ifndef DM_BIO_PRISON_V2_H
0008 #define DM_BIO_PRISON_V2_H
0009
0010 #include "persistent-data/dm-block-manager.h" /* FIXME: for dm_block_t */
0011 #include "dm-thin-metadata.h" /* FIXME: for dm_thin_id */
0012
0013 #include <linux/bio.h>
0014 #include <linux/rbtree.h>
0015 #include <linux/workqueue.h>
0016
0017 /*----------------------------------------------------------------*/
0018
0019 int dm_bio_prison_init_v2(void);
0020 void dm_bio_prison_exit_v2(void);
0021
0022 /*
0023  * Sometimes we can't deal with a bio straight away.  We put them in prison
0024  * where they can't cause any mischief.  Bios are put in a cell identified
0025  * by a key, multiple bios can be in the same cell.  When the cell is
0026  * subsequently unlocked the bios become available.
0027  */
0028 struct dm_bio_prison_v2;
0029
0030 /*
0031  * Keys define a range of blocks within either a virtual or physical
0032  * device.
0033  */
0034 struct dm_cell_key_v2 {
0035     int virtual;
0036     dm_thin_id dev;
0037     dm_block_t block_begin, block_end;
0038 };
0039
0040 /*
0041  * Treat this as opaque, only in header so callers can manage allocation
0042  * themselves.
0043  */
0044 struct dm_bio_prison_cell_v2 {
0045     // FIXME: pack these
0046     bool exclusive_lock;
0047     unsigned exclusive_level;
0048     unsigned shared_count;
0049     struct work_struct *quiesce_continuation;
0050
0051     struct rb_node node;
0052     struct dm_cell_key_v2 key;
0053     struct bio_list bios;
0054 };
0055
0056 struct dm_bio_prison_v2 *dm_bio_prison_create_v2(struct workqueue_struct *wq);
0057 void dm_bio_prison_destroy_v2(struct dm_bio_prison_v2 *prison);
0058
0059 /*
0060  * These two functions just wrap a mempool.  This is a transitory step:
0061  * Eventually all bio prison clients should manage their own cell memory.
0062  *
0063  * Like mempool_alloc(), dm_bio_prison_alloc_cell_v2() can only fail if called
0064  * in interrupt context or passed GFP_NOWAIT.
0065  */
0066 struct dm_bio_prison_cell_v2 *dm_bio_prison_alloc_cell_v2(struct dm_bio_prison_v2 *prison,
0067                             gfp_t gfp);
0068 void dm_bio_prison_free_cell_v2(struct dm_bio_prison_v2 *prison,
0069                 struct dm_bio_prison_cell_v2 *cell);
0070
0071 /*
0072  * Shared locks have a bio associated with them.
0073  *
0074  * If the lock is granted the caller can continue to use the bio, and must
0075  * call dm_cell_put_v2() to drop the reference count when finished using it.
0076  *
0077  * If the lock cannot be granted then the bio will be tracked within the
0078  * cell, and later given to the holder of the exclusive lock.
0079  *
0080  * See dm_cell_lock_v2() for discussion of the lock_level parameter.
0081  *
0082  * Compare *cell_result with cell_prealloc to see if the prealloc was used.
0083  * If cell_prealloc was used then inmate wasn't added to it.
0084  *
0085  * Returns true if the lock is granted.
0086  */
0087 bool dm_cell_get_v2(struct dm_bio_prison_v2 *prison,
0088             struct dm_cell_key_v2 *key,
0089             unsigned lock_level,
0090             struct bio *inmate,
0091             struct dm_bio_prison_cell_v2 *cell_prealloc,
0092             struct dm_bio_prison_cell_v2 **cell_result);
0093
0094 /*
0095  * Decrement the shared reference count for the lock.  Returns true if
0096  * returning ownership of the cell (ie. you should free it).
0097  */
0098 bool dm_cell_put_v2(struct dm_bio_prison_v2 *prison,
0099             struct dm_bio_prison_cell_v2 *cell);
0100
0101 /*
0102  * Locks a cell.  No associated bio.  Exclusive locks get priority.  These
0103  * locks constrain whether the io locks are granted according to level.
0104  *
0105  * Shared locks will still be granted if the lock_level is > (not = to) the
0106  * exclusive lock level.
0107  *
0108  * If an _exclusive_ lock is already held then -EBUSY is returned.
0109  *
0110  * Return values:
0111  *  < 0 - error
0112  *  0   - locked; no quiescing needed
0113  *  1   - locked; quiescing needed
0114  */
0115 int dm_cell_lock_v2(struct dm_bio_prison_v2 *prison,
0116             struct dm_cell_key_v2 *key,
0117             unsigned lock_level,
0118             struct dm_bio_prison_cell_v2 *cell_prealloc,
0119             struct dm_bio_prison_cell_v2 **cell_result);
0120
0121 void dm_cell_quiesce_v2(struct dm_bio_prison_v2 *prison,
0122             struct dm_bio_prison_cell_v2 *cell,
0123             struct work_struct *continuation);
0124
0125 /*
0126  * Promotes an _exclusive_ lock to a higher lock level.
0127  *
0128  * Return values:
0129  *  < 0 - error
0130  *  0   - promoted; no quiescing needed
0131  *  1   - promoted; quiescing needed
0132  */
0133 int dm_cell_lock_promote_v2(struct dm_bio_prison_v2 *prison,
0134                 struct dm_bio_prison_cell_v2 *cell,
0135                 unsigned new_lock_level);
0136
0137 /*
0138  * Adds any held bios to the bio list.
0139  *
0140  * There may be shared locks still held at this point even if you quiesced
0141  * (ie. different lock levels).
0142  *
0143  * Returns true if returning ownership of the cell (ie. you should free
0144  * it).
0145  */
0146 bool dm_cell_unlock_v2(struct dm_bio_prison_v2 *prison,
0147                struct dm_bio_prison_cell_v2 *cell,
0148                struct bio_list *bios);
0149
0150 /*----------------------------------------------------------------*/
0151
0152 #endif