raid1.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _RAID1_H
  3#define _RAID1_H
  4
  5/*
  6 * each barrier unit size is 64MB fow now
  7 * note: it must be larger than RESYNC_DEPTH
  8 */
  9#define BARRIER_UNIT_SECTOR_BITS	17
 10#define BARRIER_UNIT_SECTOR_SIZE	(1<<17)
 11/*
 12 * In struct r1conf, the following members are related to I/O barrier
 13 * buckets,
 14 *	atomic_t	*nr_pending;
 15 *	atomic_t	*nr_waiting;
 16 *	atomic_t	*nr_queued;
 17 *	atomic_t	*barrier;
 18 * Each of them points to array of atomic_t variables, each array is
 19 * designed to have BARRIER_BUCKETS_NR elements and occupy a single
 20 * memory page. The data width of atomic_t variables is 4 bytes, equal
 21 * to 1<<(ilog2(sizeof(atomic_t))), BARRIER_BUCKETS_NR_BITS is defined
 22 * as (PAGE_SHIFT - ilog2(sizeof(int))) to make sure an array of
 23 * atomic_t variables with BARRIER_BUCKETS_NR elements just exactly
 24 * occupies a single memory page.
 25 */
 26#define BARRIER_BUCKETS_NR_BITS		(PAGE_SHIFT - ilog2(sizeof(atomic_t)))
 27#define BARRIER_BUCKETS_NR		(1<<BARRIER_BUCKETS_NR_BITS)
 28
 29/* Note: raid1_info.rdev can be set to NULL asynchronously by raid1_remove_disk.
 30 * There are three safe ways to access raid1_info.rdev.
 31 * 1/ when holding mddev->reconfig_mutex
 32 * 2/ when resync/recovery is known to be happening - i.e. in code that is
 33 *    called as part of performing resync/recovery.
 34 * 3/ while holding rcu_read_lock(), use rcu_dereference to get the pointer
 35 *    and if it is non-NULL, increment rdev->nr_pending before dropping the
 36 *    RCU lock.
 37 * When .rdev is set to NULL, the nr_pending count checked again and if it has
 38 * been incremented, the pointer is put back in .rdev.
 39 */
 40
 41struct raid1_info {
 42	struct md_rdev	*rdev;
 43	sector_t	head_position;
 44
 45	/* When choose the best device for a read (read_balance())
 46	 * we try to keep sequential reads one the same device
 47	 */
 48	sector_t	next_seq_sect;
 49	sector_t	seq_start;
 50};
 51
 52struct r1conf {
 53	struct mddev		*mddev;
 54	struct raid1_info	*mirrors;	/* twice 'raid_disks' to
 55						 * allow for replacements.
 56						 */
 57	int			raid_disks;
 58	int			nonrot_disks;
 59
 60	spinlock_t		device_lock;
 61
 62	/* list of 'struct r1bio' that need to be processed by raid1d,
 63	 * whether to retry a read, writeout a resync or recovery
 64	 * block, or anything else.
 65	 */
 66	struct list_head	retry_list;
 67	/* A separate list of r1bio which just need raid_end_bio_io called.
 68	 * This mustn't happen for writes which had any errors if the superblock
 69	 * needs to be written.
 70	 */
 71	struct list_head	bio_end_io_list;
 72
 73	/* queue pending writes to be submitted on unplug */
 74	struct bio_list		pending_bio_list;
 75
 76	/* for use when syncing mirrors:
 77	 * We don't allow both normal IO and resync/recovery IO at
 78	 * the same time - resync/recovery can only happen when there
 79	 * is no other IO.  So when either is active, the other has to wait.
 80	 * See more details description in raid1.c near raise_barrier().
 81	 */
 82	wait_queue_head_t	wait_barrier;
 83	spinlock_t		resync_lock;
 84	atomic_t		nr_sync_pending;
 85	atomic_t		*nr_pending;
 86	atomic_t		*nr_waiting;
 87	atomic_t		*nr_queued;
 88	atomic_t		*barrier;
 89	int			array_frozen;
 90
 91	/* Set to 1 if a full sync is needed, (fresh device added).
 92	 * Cleared when a sync completes.
 93	 */
 94	int			fullsync;
 95
 96	/* When the same as mddev->recovery_disabled we don't allow
 97	 * recovery to be attempted as we expect a read error.
 98	 */
 99	int			recovery_disabled;
100
101	mempool_t		*r1bio_pool;
102	mempool_t		r1buf_pool;
103
104	struct bio_set		bio_split;
105
106	/* temporary buffer to synchronous IO when attempting to repair
107	 * a read error.
108	 */
109	struct page		*tmppage;
110
111	/* When taking over an array from a different personality, we store
112	 * the new thread here until we fully activate the array.
113	 */
114	struct md_thread __rcu	*thread;
115
116	/* Keep track of cluster resync window to send to other
117	 * nodes.
118	 */
119	sector_t		cluster_sync_low;
120	sector_t		cluster_sync_high;
121
122};
123
124/*
125 * this is our 'private' RAID1 bio.
126 *
127 * it contains information about what kind of IO operations were started
128 * for this RAID1 operation, and about their status:
129 */
130
131struct r1bio {
132	atomic_t		remaining; /* 'have we finished' count,
133					    * used from IRQ handlers
134					    */
135	atomic_t		behind_remaining; /* number of write-behind ios remaining
136						 * in this BehindIO request
137						 */
138	sector_t		sector;
139	int			sectors;
140	unsigned long		state;
141	struct mddev		*mddev;
142	/*
143	 * original bio going to /dev/mdx
144	 */
145	struct bio		*master_bio;
146	/*
147	 * if the IO is in READ direction, then this is where we read
148	 */
149	int			read_disk;
150
151	struct list_head	retry_list;
152
153	/*
154	 * When R1BIO_BehindIO is set, we store pages for write behind
155	 * in behind_master_bio.
156	 */
157	struct bio		*behind_master_bio;
158
159	/*
160	 * if the IO is in WRITE direction, then multiple bios are used.
161	 * We choose the number when they are allocated.
162	 */
163	struct bio		*bios[];
164	/* DO NOT PUT ANY NEW FIELDS HERE - bios array is contiguously alloced*/
165};
166
167/* bits for r1bio.state */
168enum r1bio_state {
169	R1BIO_Uptodate,
170	R1BIO_IsSync,
171	R1BIO_BehindIO,
172/* Set ReadError on bios that experience a readerror so that
173 * raid1d knows what to do with them.
174 */
175	R1BIO_ReadError,
176/* For write-behind requests, we call bi_end_io when
177 * the last non-write-behind device completes, providing
178 * any write was successful.  Otherwise we call when
179 * any write-behind write succeeds, otherwise we call
180 * with failure when last write completes (and all failed).
181 *
182 * And for bio_split errors, record that bi_end_io was called
183 * with this flag...
184 */
185	R1BIO_Returned,
186/* If a write for this request means we can clear some
187 * known-bad-block records, we set this flag
188 */
189	R1BIO_MadeGood,
190	R1BIO_WriteError,
191	R1BIO_FailFast,
192};
193
194static inline int sector_to_idx(sector_t sector)
195{
196	return hash_long(sector >> BARRIER_UNIT_SECTOR_BITS,
197			 BARRIER_BUCKETS_NR_BITS);
198}
199#endif