drivers/md/raid1.h

   1 #ifndef _RAID1_H
   2 #define _RAID1_H
   3
   4 /*
   5  * each barrier unit size is 64MB fow now
   6  * note: it must be larger than RESYNC_DEPTH
   7  */
   8 #define BARRIER_UNIT_SECTOR_BITS        17
   9 #define BARRIER_UNIT_SECTOR_SIZE        (1<<17)
  10 /*
  11  * In struct r1conf, the following members are related to I/O barrier
  12  * buckets,
  13  *      atomic_t        *nr_pending;
  14  *      atomic_t        *nr_waiting;
  15  *      atomic_t        *nr_queued;
  16  *      atomic_t        *barrier;
  17  * Each of them points to array of atomic_t variables, each array is
  18  * designed to have BARRIER_BUCKETS_NR elements and occupy a single
  19  * memory page. The data width of atomic_t variables is 4 bytes, equal
  20  * to 1<<(ilog2(sizeof(atomic_t))), BARRIER_BUCKETS_NR_BITS is defined
  21  * as (PAGE_SHIFT - ilog2(sizeof(int))) to make sure an array of
  22  * atomic_t variables with BARRIER_BUCKETS_NR elements just exactly
  23  * occupies a single memory page.
  24  */
  25 #define BARRIER_BUCKETS_NR_BITS         (PAGE_SHIFT - ilog2(sizeof(atomic_t)))
  26 #define BARRIER_BUCKETS_NR              (1<<BARRIER_BUCKETS_NR_BITS)
  27
  28 struct raid1_info {
  29         struct md_rdev  *rdev;
  30         sector_t        head_position;
  31
  32         /* When choose the best device for a read (read_balance())
  33          * we try to keep sequential reads one the same device
  34          */
  35         sector_t        next_seq_sect;
  36         sector_t        seq_start;
  37 };
  38
  39 /*
  40  * memory pools need a pointer to the mddev, so they can force an unplug
  41  * when memory is tight, and a count of the number of drives that the
  42  * pool was allocated for, so they know how much to allocate and free.
  43  * mddev->raid_disks cannot be used, as it can change while a pool is active
  44  * These two datums are stored in a kmalloced struct.
  45  * The 'raid_disks' here is twice the raid_disks in r1conf.
  46  * This allows space for each 'real' device can have a replacement in the
  47  * second half of the array.
  48  */
  49
  50 struct pool_info {
  51         struct mddev *mddev;
  52         int     raid_disks;
  53 };
  54
  55 struct r1conf {
  56         struct mddev            *mddev;
  57         struct raid1_info       *mirrors;       /* twice 'raid_disks' to
  58                                                  * allow for replacements.
  59                                                  */
  60         int                     raid_disks;
  61
  62         spinlock_t              device_lock;
  63
  64         /* list of 'struct r1bio' that need to be processed by raid1d,
  65          * whether to retry a read, writeout a resync or recovery
  66          * block, or anything else.
  67          */
  68         struct list_head        retry_list;
  69         /* A separate list of r1bio which just need raid_end_bio_io called.
  70          * This mustn't happen for writes which had any errors if the superblock
  71          * needs to be written.
  72          */
  73         struct list_head        bio_end_io_list;
  74
  75         /* queue pending writes to be submitted on unplug */
  76         struct bio_list         pending_bio_list;
  77         int                     pending_count;
  78
  79         /* for use when syncing mirrors:
  80          * We don't allow both normal IO and resync/recovery IO at
  81          * the same time - resync/recovery can only happen when there
  82          * is no other IO.  So when either is active, the other has to wait.
  83          * See more details description in raid1.c near raise_barrier().
  84          */
  85         wait_queue_head_t       wait_barrier;
  86         spinlock_t              resync_lock;
  87         atomic_t                *nr_pending;
  88         atomic_t                *nr_waiting;
  89         atomic_t                *nr_queued;
  90         atomic_t                *barrier;
  91         int                     array_frozen;
  92
  93         /* Set to 1 if a full sync is needed, (fresh device added).
  94          * Cleared when a sync completes.
  95          */
  96         int                     fullsync;
  97
  98         /* When the same as mddev->recovery_disabled we don't allow
  99          * recovery to be attempted as we expect a read error.
 100          */
 101         int                     recovery_disabled;
 102
 103         /* poolinfo contains information about the content of the
 104          * mempools - it changes when the array grows or shrinks
 105          */
 106         struct pool_info        *poolinfo;
 107         mempool_t               *r1bio_pool;
 108         mempool_t               *r1buf_pool;
 109
 110         /* temporary buffer to synchronous IO when attempting to repair
 111          * a read error.
 112          */
 113         struct page             *tmppage;
 114
 115         /* When taking over an array from a different personality, we store
 116          * the new thread here until we fully activate the array.
 117          */
 118         struct md_thread        *thread;
 119
 120         /* Keep track of cluster resync window to send to other
 121          * nodes.
 122          */
 123         sector_t                cluster_sync_low;
 124         sector_t                cluster_sync_high;
 125
 126 };
 127
 128 /*
 129  * this is our 'private' RAID1 bio.
 130  *
 131  * it contains information about what kind of IO operations were started
 132  * for this RAID1 operation, and about their status:
 133  */
 134
 135 struct r1bio {
 136         atomic_t                remaining; /* 'have we finished' count,
 137                                             * used from IRQ handlers
 138                                             */
 139         atomic_t                behind_remaining; /* number of write-behind ios remaining
 140                                                  * in this BehindIO request
 141                                                  */
 142         sector_t                sector;
 143         int                     sectors;
 144         unsigned long           state;
 145         struct mddev            *mddev;
 146         /*
 147          * original bio going to /dev/mdx
 148          */
 149         struct bio              *master_bio;
 150         /*
 151          * if the IO is in READ direction, then this is where we read
 152          */
 153         int                     read_disk;
 154
 155         struct list_head        retry_list;
 156         /* Next two are only valid when R1BIO_BehindIO is set */
 157         struct bio_vec          *behind_bvecs;
 158         int                     behind_page_count;
 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[0];
 164         /* DO NOT PUT ANY NEW FIELDS HERE - bios array is contiguously alloced*/
 165 };
 166
 167 /* bits for r1bio.state */
 168 enum r1bio_state {
 169         R1BIO_Uptodate,
 170         R1BIO_IsSync,
 171         R1BIO_Degraded,
 172         R1BIO_BehindIO,
 173 /* Set ReadError on bios that experience a readerror so that
 174  * raid1d knows what to do with them.
 175  */
 176         R1BIO_ReadError,
 177 /* For write-behind requests, we call bi_end_io when
 178  * the last non-write-behind device completes, providing
 179  * any write was successful.  Otherwise we call when
 180  * any write-behind write succeeds, otherwise we call
 181  * with failure when last write completes (and all failed).
 182  * Record that bi_end_io was called with this flag...
 183  */
 184         R1BIO_Returned,
 185 /* If a write for this request means we can clear some
 186  * known-bad-block records, we set this flag
 187  */
 188         R1BIO_MadeGood,
 189         R1BIO_WriteError,
 190         R1BIO_FailFast,
 191 };
 192
 193 static inline int sector_to_idx(sector_t sector)
 194 {
 195         return hash_long(sector >> BARRIER_UNIT_SECTOR_BITS,
 196                          BARRIER_BUCKETS_NR_BITS);
 197 }
 198 #endif