xref: /linux/drivers/md/raid1.h (revision 3839a7460721b87501134697b7b90c45dcc7825d)
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 
41 struct 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 
52 /*
53  * memory pools need a pointer to the mddev, so they can force an unplug
54  * when memory is tight, and a count of the number of drives that the
55  * pool was allocated for, so they know how much to allocate and free.
56  * mddev->raid_disks cannot be used, as it can change while a pool is active
57  * These two datums are stored in a kmalloced struct.
58  * The 'raid_disks' here is twice the raid_disks in r1conf.
59  * This allows space for each 'real' device can have a replacement in the
60  * second half of the array.
61  */
62 
63 struct pool_info {
64 	struct mddev *mddev;
65 	int	raid_disks;
66 };
67 
68 struct r1conf {
69 	struct mddev		*mddev;
70 	struct raid1_info	*mirrors;	/* twice 'raid_disks' to
71 						 * allow for replacements.
72 						 */
73 	int			raid_disks;
74 
75 	spinlock_t		device_lock;
76 
77 	/* list of 'struct r1bio' that need to be processed by raid1d,
78 	 * whether to retry a read, writeout a resync or recovery
79 	 * block, or anything else.
80 	 */
81 	struct list_head	retry_list;
82 	/* A separate list of r1bio which just need raid_end_bio_io called.
83 	 * This mustn't happen for writes which had any errors if the superblock
84 	 * needs to be written.
85 	 */
86 	struct list_head	bio_end_io_list;
87 
88 	/* queue pending writes to be submitted on unplug */
89 	struct bio_list		pending_bio_list;
90 	int			pending_count;
91 
92 	/* for use when syncing mirrors:
93 	 * We don't allow both normal IO and resync/recovery IO at
94 	 * the same time - resync/recovery can only happen when there
95 	 * is no other IO.  So when either is active, the other has to wait.
96 	 * See more details description in raid1.c near raise_barrier().
97 	 */
98 	wait_queue_head_t	wait_barrier;
99 	spinlock_t		resync_lock;
100 	atomic_t		nr_sync_pending;
101 	atomic_t		*nr_pending;
102 	atomic_t		*nr_waiting;
103 	atomic_t		*nr_queued;
104 	atomic_t		*barrier;
105 	int			array_frozen;
106 
107 	/* Set to 1 if a full sync is needed, (fresh device added).
108 	 * Cleared when a sync completes.
109 	 */
110 	int			fullsync;
111 
112 	/* When the same as mddev->recovery_disabled we don't allow
113 	 * recovery to be attempted as we expect a read error.
114 	 */
115 	int			recovery_disabled;
116 
117 	/* poolinfo contains information about the content of the
118 	 * mempools - it changes when the array grows or shrinks
119 	 */
120 	struct pool_info	*poolinfo;
121 	mempool_t		r1bio_pool;
122 	mempool_t		r1buf_pool;
123 
124 	struct bio_set		bio_split;
125 
126 	/* temporary buffer to synchronous IO when attempting to repair
127 	 * a read error.
128 	 */
129 	struct page		*tmppage;
130 
131 	/* When taking over an array from a different personality, we store
132 	 * the new thread here until we fully activate the array.
133 	 */
134 	struct md_thread	*thread;
135 
136 	/* Keep track of cluster resync window to send to other
137 	 * nodes.
138 	 */
139 	sector_t		cluster_sync_low;
140 	sector_t		cluster_sync_high;
141 
142 };
143 
144 /*
145  * this is our 'private' RAID1 bio.
146  *
147  * it contains information about what kind of IO operations were started
148  * for this RAID1 operation, and about their status:
149  */
150 
151 struct r1bio {
152 	atomic_t		remaining; /* 'have we finished' count,
153 					    * used from IRQ handlers
154 					    */
155 	atomic_t		behind_remaining; /* number of write-behind ios remaining
156 						 * in this BehindIO request
157 						 */
158 	sector_t		sector;
159 	int			sectors;
160 	unsigned long		state;
161 	struct mddev		*mddev;
162 	/*
163 	 * original bio going to /dev/mdx
164 	 */
165 	struct bio		*master_bio;
166 	/*
167 	 * if the IO is in READ direction, then this is where we read
168 	 */
169 	int			read_disk;
170 
171 	struct list_head	retry_list;
172 
173 	/*
174 	 * When R1BIO_BehindIO is set, we store pages for write behind
175 	 * in behind_master_bio.
176 	 */
177 	struct bio		*behind_master_bio;
178 
179 	/*
180 	 * if the IO is in WRITE direction, then multiple bios are used.
181 	 * We choose the number when they are allocated.
182 	 */
183 	struct bio		*bios[];
184 	/* DO NOT PUT ANY NEW FIELDS HERE - bios array is contiguously alloced*/
185 };
186 
187 /* bits for r1bio.state */
188 enum r1bio_state {
189 	R1BIO_Uptodate,
190 	R1BIO_IsSync,
191 	R1BIO_Degraded,
192 	R1BIO_BehindIO,
193 /* Set ReadError on bios that experience a readerror so that
194  * raid1d knows what to do with them.
195  */
196 	R1BIO_ReadError,
197 /* For write-behind requests, we call bi_end_io when
198  * the last non-write-behind device completes, providing
199  * any write was successful.  Otherwise we call when
200  * any write-behind write succeeds, otherwise we call
201  * with failure when last write completes (and all failed).
202  * Record that bi_end_io was called with this flag...
203  */
204 	R1BIO_Returned,
205 /* If a write for this request means we can clear some
206  * known-bad-block records, we set this flag
207  */
208 	R1BIO_MadeGood,
209 	R1BIO_WriteError,
210 	R1BIO_FailFast,
211 };
212 
213 static inline int sector_to_idx(sector_t sector)
214 {
215 	return hash_long(sector >> BARRIER_UNIT_SECTOR_BITS,
216 			 BARRIER_BUCKETS_NR_BITS);
217 }
218 #endif
219