1 files changed, 211 insertions, 45 deletions

diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index ec6d675bf766..38efa7071dd7 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -6,6 +6,7 @@
 
 #include "dm.h"
 #include "dm-bio-list.h"
+#include "dm-bio-record.h"
 #include "dm-io.h"
 #include "dm-log.h"
 #include "kcopyd.h"
@@ -141,6 +142,7 @@ struct mirror_set {
         struct bio_list failures;
 
         struct dm_io_client *io_client;
+        mempool_t *read_record_pool;
 
         /* recovery */
         region_t nr_regions;
@@ -647,24 +649,30 @@ static void rh_start_recovery(struct region_hash *rh)
         wake(rh->ms);
 }
 
+#define MIN_READ_RECORDS 20
+struct dm_raid1_read_record {
+        struct mirror *m;
+        struct dm_bio_details details;
+};
+
 /*
  * Every mirror should look like this one.
  */
 #define DEFAULT_MIRROR 0
 
 /*
- * This is yucky.  We squirrel the mirror_set struct away inside
- * bi_next for write buffers.  This is safe since the bh
+ * This is yucky.  We squirrel the mirror struct away inside
+ * bi_next for read/write buffers.  This is safe since the bh
  * doesn't get submitted to the lower levels of block layer.
  */
-static struct mirror_set *bio_get_ms(struct bio *bio)
+static struct mirror *bio_get_m(struct bio *bio)
 {
-        return (struct mirror_set *) bio->bi_next;
+        return (struct mirror *) bio->bi_next;
 }
 
-static void bio_set_ms(struct bio *bio, struct mirror_set *ms)
+static void bio_set_m(struct bio *bio, struct mirror *m)
 {
-        bio->bi_next = (struct bio *) ms;
+        bio->bi_next = (struct bio *) m;
 }
 
 static struct mirror *get_default_mirror(struct mirror_set *ms)
@@ -857,17 +865,105 @@ static void do_recovery(struct mirror_set *ms)
  *---------------------------------------------------------------*/
 static struct mirror *choose_mirror(struct mirror_set *ms, sector_t sector)
 {
-        /* FIXME: add read balancing */
-        return get_default_mirror(ms);
+        struct mirror *m = get_default_mirror(ms);
+
+        do {
+                if (likely(!atomic_read(&m->error_count)))
+                        return m;
+
+                if (m-- == ms->mirror)
+                        m += ms->nr_mirrors;
+        } while (m != get_default_mirror(ms));
+
+        return NULL;
+}
+
+static int default_ok(struct mirror *m)
+{
+        struct mirror *default_mirror = get_default_mirror(m->ms);
+
+        return !atomic_read(&default_mirror->error_count);
+}
+
+static int mirror_available(struct mirror_set *ms, struct bio *bio)
+{
+        region_t region = bio_to_region(&ms->rh, bio);
+
+        if (ms->rh.log->type->in_sync(ms->rh.log, region, 0))
+                return choose_mirror(ms,  bio->bi_sector) ? 1 : 0;
+
+        return 0;
 }
 
 /*
  * remap a buffer to a particular mirror.
  */
-static void map_bio(struct mirror_set *ms, struct mirror *m, struct bio *bio)
+static sector_t map_sector(struct mirror *m, struct bio *bio)
+{
+        return m->offset + (bio->bi_sector - m->ms->ti->begin);
+}
+
+static void map_bio(struct mirror *m, struct bio *bio)
 {
         bio->bi_bdev = m->dev->bdev;
-        bio->bi_sector = m->offset + (bio->bi_sector - ms->ti->begin);
+        bio->bi_sector = map_sector(m, bio);
+}
+
+static void map_region(struct io_region *io, struct mirror *m,
+                       struct bio *bio)
+{
+        io->bdev = m->dev->bdev;
+        io->sector = map_sector(m, bio);
+        io->count = bio->bi_size >> 9;
+}
+
+/*-----------------------------------------------------------------
+ * Reads
+ *---------------------------------------------------------------*/
+static void read_callback(unsigned long error, void *context)
+{
+        struct bio *bio = context;
+        struct mirror *m;
+
+        m = bio_get_m(bio);
+        bio_set_m(bio, NULL);
+
+        if (likely(!error)) {
+                bio_endio(bio, 0);
+                return;
+        }
+
+        fail_mirror(m, DM_RAID1_READ_ERROR);
+
+        if (likely(default_ok(m)) || mirror_available(m->ms, bio)) {
+                DMWARN_LIMIT("Read failure on mirror device %s.  "
+                             "Trying alternative device.",
+                             m->dev->name);
+                queue_bio(m->ms, bio, bio_rw(bio));
+                return;
+        }
+
+        DMERR_LIMIT("Read failure on mirror device %s.  Failing I/O.",
+                    m->dev->name);
+        bio_endio(bio, -EIO);
+}
+
+/* Asynchronous read. */
+static void read_async_bio(struct mirror *m, struct bio *bio)
+{
+        struct io_region io;
+        struct dm_io_request io_req = {
+                .bi_rw = READ,
+                .mem.type = DM_IO_BVEC,
+                .mem.ptr.bvec = bio->bi_io_vec + bio->bi_idx,
+                .notify.fn = read_callback,
+                .notify.context = bio,
+                .client = m->ms->io_client,
+        };
+
+        map_region(&io, m, bio);
+        bio_set_m(bio, m);
+        (void) dm_io(&io_req, 1, &io, NULL);
 }
 
 static void do_reads(struct mirror_set *ms, struct bio_list *reads)
@@ -878,17 +974,20 @@ static void do_reads(struct mirror_set *ms, struct bio_list *reads)
 
         while ((bio = bio_list_pop(reads))) {
                 region = bio_to_region(&ms->rh, bio);
+                m = get_default_mirror(ms);
 
                 /*
                  * We can only read balance if the region is in sync.
                  */
-                if (rh_in_sync(&ms->rh, region, 1))
+                if (likely(rh_in_sync(&ms->rh, region, 1)))
                         m = choose_mirror(ms, bio->bi_sector);
-                else
-                        m = get_default_mirror(ms);
+                else if (m && atomic_read(&m->error_count))
+                        m = NULL;
 
-                map_bio(ms, m, bio);
-                generic_make_request(bio);
+                if (likely(m))
+                        read_async_bio(m, bio);
+                else
+                        bio_endio(bio, -EIO);
         }
 }
 
@@ -964,8 +1063,8 @@ static void write_callback(unsigned long error, void *context)
         int should_wake = 0;
         unsigned long flags;
 
-        ms = bio_get_ms(bio);
-        bio_set_ms(bio, NULL);
+        ms = bio_get_m(bio)->ms;
+        bio_set_m(bio, NULL);
 
         /*
          * NOTE: We don't decrement the pending count here,
@@ -1008,7 +1107,7 @@ out:
 static void do_write(struct mirror_set *ms, struct bio *bio)
 {
         unsigned int i;
-        struct io_region io[KCOPYD_MAX_REGIONS+1];
+        struct io_region io[ms->nr_mirrors], *dest = io;
         struct mirror *m;
         struct dm_io_request io_req = {
                 .bi_rw = WRITE,
@@ -1019,15 +1118,14 @@ static void do_write(struct mirror_set *ms, struct bio *bio)
                 .client = ms->io_client,
         };
 
-        for (i = 0; i < ms->nr_mirrors; i++) {
-                m = ms->mirror + i;
-
-                io[i].bdev = m->dev->bdev;
-                io[i].sector = m->offset + (bio->bi_sector - ms->ti->begin);
-                io[i].count = bio->bi_size >> 9;
-        }
+        for (i = 0, m = ms->mirror; i < ms->nr_mirrors; i++, m++)
+                map_region(dest++, m, bio);
 
-        bio_set_ms(bio, ms);
+        /*
+         * Use default mirror because we only need it to retrieve the reference
+         * to the mirror set in write_callback().
+         */
+        bio_set_m(bio, get_default_mirror(ms));
 
         (void) dm_io(&io_req, ms->nr_mirrors, io, NULL);
 }
@@ -1092,7 +1190,7 @@ static void do_writes(struct mirror_set *ms, struct bio_list *writes)
                 rh_delay(&ms->rh, bio);
 
         while ((bio = bio_list_pop(&nosync))) {
-                map_bio(ms, get_default_mirror(ms), bio);
+                map_bio(get_default_mirror(ms), bio);
                 generic_make_request(bio);
         }
 }
@@ -1231,9 +1329,19 @@ static struct mirror_set *alloc_context(unsigned int nr_mirrors,
         atomic_set(&ms->suspend, 0);
         atomic_set(&ms->default_mirror, DEFAULT_MIRROR);
 
+        len = sizeof(struct dm_raid1_read_record);
+        ms->read_record_pool = mempool_create_kmalloc_pool(MIN_READ_RECORDS,
+                                                           len);
+        if (!ms->read_record_pool) {
+                ti->error = "Error creating mirror read_record_pool";
+                kfree(ms);
+                return NULL;
+        }
+
         ms->io_client = dm_io_client_create(DM_IO_PAGES);
         if (IS_ERR(ms->io_client)) {
                 ti->error = "Error creating dm_io client";
+                mempool_destroy(ms->read_record_pool);
                 kfree(ms);
                 return NULL;
         }
@@ -1241,6 +1349,7 @@ static struct mirror_set *alloc_context(unsigned int nr_mirrors,
         if (rh_init(&ms->rh, ms, dl, region_size, ms->nr_regions)) {
                 ti->error = "Error creating dirty region hash";
                 dm_io_client_destroy(ms->io_client);
+                mempool_destroy(ms->read_record_pool);
                 kfree(ms);
                 return NULL;
         }
@@ -1256,6 +1365,7 @@ static void free_context(struct mirror_set *ms, struct dm_target *ti,
 
         dm_io_client_destroy(ms->io_client);
         rh_exit(&ms->rh);
+        mempool_destroy(ms->read_record_pool);
         kfree(ms);
 }
 
@@ -1510,10 +1620,11 @@ static int mirror_map(struct dm_target *ti, struct bio *bio,
         int r, rw = bio_rw(bio);
         struct mirror *m;
         struct mirror_set *ms = ti->private;
-
-        map_context->ll = bio_to_region(&ms->rh, bio);
+        struct dm_raid1_read_record *read_record = NULL;
 
         if (rw == WRITE) {
+                /* Save region for mirror_end_io() handler */
+                map_context->ll = bio_to_region(&ms->rh, bio);
                 queue_bio(ms, bio, rw);
                 return DM_MAPIO_SUBMITTED;
         }
@@ -1523,28 +1634,34 @@ static int mirror_map(struct dm_target *ti, struct bio *bio,
         if (r < 0 && r != -EWOULDBLOCK)
                 return r;
 
-        if (r == -EWOULDBLOCK)  /* FIXME: ugly */
-                r = DM_MAPIO_SUBMITTED;
-
         /*
-         * We don't want to fast track a recovery just for a read
-         * ahead.  So we just let it silently fail.
-         * FIXME: get rid of this.
+         * If region is not in-sync queue the bio.
          */
-        if (!r && rw == READA)
-                return -EIO;
+        if (!r || (r == -EWOULDBLOCK)) {
+                if (rw == READA)
+                        return -EWOULDBLOCK;
 
-        if (!r) {
-                /* Pass this io over to the daemon */
                 queue_bio(ms, bio, rw);
                 return DM_MAPIO_SUBMITTED;
         }
 
+        /*
+         * The region is in-sync and we can perform reads directly.
+         * Store enough information so we can retry if it fails.
+         */
         m = choose_mirror(ms, bio->bi_sector);
-        if (!m)
+        if (unlikely(!m))
                 return -EIO;
 
-        map_bio(ms, m, bio);
+        read_record = mempool_alloc(ms->read_record_pool, GFP_NOIO);
+        if (likely(read_record)) {
+                dm_bio_record(&read_record->details, bio);
+                map_context->ptr = read_record;
+                read_record->m = m;
+        }
+
+        map_bio(m, bio);
+
         return DM_MAPIO_REMAPPED;
 }
 
@@ -1553,15 +1670,64 @@ static int mirror_end_io(struct dm_target *ti, struct bio *bio,
 {
         int rw = bio_rw(bio);
         struct mirror_set *ms = (struct mirror_set *) ti->private;
-        region_t region = map_context->ll;
+        struct mirror *m = NULL;
+        struct dm_bio_details *bd = NULL;
+        struct dm_raid1_read_record *read_record = map_context->ptr;
 
         /*
          * We need to dec pending if this was a write.
          */
-        if (rw == WRITE)
-                rh_dec(&ms->rh, region);
+        if (rw == WRITE) {
+                rh_dec(&ms->rh, map_context->ll);
+                return error;
+        }
 
-        return 0;
+        if (error == -EOPNOTSUPP)
+                goto out;
+
+        if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
+                goto out;
+
+        if (unlikely(error)) {
+                if (!read_record) {
+                        /*
+                         * There wasn't enough memory to record necessary
+                         * information for a retry or there was no other
+                         * mirror in-sync.
+                         */
+                        DMERR_LIMIT("Mirror read failed from %s.",
+                                    m->dev->name);
+                        return -EIO;
+                }
+                DMERR("Mirror read failed from %s. Trying alternative device.",
+                      m->dev->name);
+
+                m = read_record->m;
+                fail_mirror(m, DM_RAID1_READ_ERROR);
+
+                /*
+                 * A failed read is requeued for another attempt using an intact
+                 * mirror.
+                 */
+                if (default_ok(m) || mirror_available(ms, bio)) {
+                        bd = &read_record->details;
+
+                        dm_bio_restore(bd, bio);
+                        mempool_free(read_record, ms->read_record_pool);
+                        map_context->ptr = NULL;
+                        queue_bio(ms, bio, rw);
+                        return 1;
+                }
+                DMERR("All replicated volumes dead, failing I/O");
+        }
+
+out:
+        if (read_record) {
+                mempool_free(read_record, ms->read_record_pool);
+                map_context->ptr = NULL;
+        }
+
+        return error;
 }
 
 static void mirror_presuspend(struct dm_target *ti)