btrfs: btrfs_multi_bio replaced with btrfs_bio

btrfs_bio is a bio abstraction able to split and not complete after the last
bio has returned (like the old btrfs_multi_bio). Additionally, btrfs_bio
tracks the mirror_num used to read data which can be used for error
correction purposes.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>

1 files changed, 68 insertions, 60 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f2a4cc79da61..9db4d7962f9b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2848,7 +2848,7 @@ static int find_live_mirror(struct map_lookup *map, int first, int num,
 
 static int __btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
                              u64 logical, u64 *length,
-                             struct btrfs_multi_bio **multi_ret,
+                             struct btrfs_bio **bbio_ret,
                              int mirror_num)
 {
         struct extent_map *em;
@@ -2866,18 +2866,18 @@ static int __btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
         int i;
         int num_stripes;
         int max_errors = 0;
-        struct btrfs_multi_bio *multi = NULL;
+        struct btrfs_bio *bbio = NULL;
 
-        if (multi_ret && !(rw & (REQ_WRITE | REQ_DISCARD)))
+        if (bbio_ret && !(rw & (REQ_WRITE | REQ_DISCARD)))
                 stripes_allocated = 1;
 again:
-        if (multi_ret) {
-                multi = kzalloc(btrfs_multi_bio_size(stripes_allocated),
+        if (bbio_ret) {
+                bbio = kzalloc(btrfs_bio_size(stripes_allocated),
                                 GFP_NOFS);
-                if (!multi)
+                if (!bbio)
                         return -ENOMEM;
 
-                atomic_set(&multi->error, 0);
+                atomic_set(&bbio->error, 0);
         }
 
         read_lock(&em_tree->lock);
@@ -2898,7 +2898,7 @@ again:
         if (mirror_num > map->num_stripes)
                 mirror_num = 0;
 
-        /* if our multi bio struct is too small, back off and try again */
+        /* if our btrfs_bio struct is too small, back off and try again */
         if (rw & REQ_WRITE) {
                 if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |
                                  BTRFS_BLOCK_GROUP_DUP)) {
@@ -2917,11 +2917,11 @@ again:
                         stripes_required = map->num_stripes;
                 }
         }
-        if (multi_ret && (rw & (REQ_WRITE | REQ_DISCARD)) &&
+        if (bbio_ret && (rw & (REQ_WRITE | REQ_DISCARD)) &&
             stripes_allocated < stripes_required) {
                 stripes_allocated = map->num_stripes;
                 free_extent_map(em);
-                kfree(multi);
+                kfree(bbio);
                 goto again;
         }
         stripe_nr = offset;
@@ -2950,7 +2950,7 @@ again:
                 *length = em->len - offset;
         }
 
-        if (!multi_ret)
+        if (!bbio_ret)
                 goto out;
 
         num_stripes = 1;
@@ -2975,13 +2975,17 @@ again:
                         stripe_index = find_live_mirror(map, 0,
                                             map->num_stripes,
                                             current->pid % map->num_stripes);
+                        mirror_num = stripe_index + 1;
                 }
 
         } else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
-                if (rw & (REQ_WRITE | REQ_DISCARD))
+                if (rw & (REQ_WRITE | REQ_DISCARD)) {
                         num_stripes = map->num_stripes;
-                else if (mirror_num)
+                } else if (mirror_num) {
                         stripe_index = mirror_num - 1;
+                } else {
+                        mirror_num = 1;
+                }
 
         } else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
                 int factor = map->num_stripes / map->sub_stripes;
@@ -3001,6 +3005,7 @@ again:
                         stripe_index = find_live_mirror(map, stripe_index,
                                               map->sub_stripes, stripe_index +
                                               current->pid % map->sub_stripes);
+                        mirror_num = stripe_index + 1;
                 }
         } else {
                 /*
@@ -3009,15 +3014,16 @@ again:
                  * stripe_index is the number of our device in the stripe array
                  */
                 stripe_index = do_div(stripe_nr, map->num_stripes);
+                mirror_num = stripe_index + 1;
         }
         BUG_ON(stripe_index >= map->num_stripes);
 
         if (rw & REQ_DISCARD) {
                 for (i = 0; i < num_stripes; i++) {
-                        multi->stripes[i].physical =
+                        bbio->stripes[i].physical =
                                 map->stripes[stripe_index].physical +
                                 stripe_offset + stripe_nr * map->stripe_len;
-                        multi->stripes[i].dev = map->stripes[stripe_index].dev;
+                        bbio->stripes[i].dev = map->stripes[stripe_index].dev;
 
                         if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
                                 u64 stripes;
@@ -3038,16 +3044,16 @@ again:
                                 }
                                 stripes = stripe_nr_end - 1 - j;
                                 do_div(stripes, map->num_stripes);
-                                multi->stripes[i].length = map->stripe_len *
+                                bbio->stripes[i].length = map->stripe_len *
                                         (stripes - stripe_nr + 1);
 
                                 if (i == 0) {
-                                        multi->stripes[i].length -=
+                                        bbio->stripes[i].length -=
                                                 stripe_offset;
                                         stripe_offset = 0;
                                 }
                                 if (stripe_index == last_stripe)
-                                        multi->stripes[i].length -=
+                                        bbio->stripes[i].length -=
                                                 stripe_end_offset;
                         } else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
                                 u64 stripes;
@@ -3072,11 +3078,11 @@ again:
                                 }
                                 stripes = stripe_nr_end - 1 - j;
                                 do_div(stripes, factor);
-                                multi->stripes[i].length = map->stripe_len *
+                                bbio->stripes[i].length = map->stripe_len *
                                         (stripes - stripe_nr + 1);
 
                                 if (i < map->sub_stripes) {
-                                        multi->stripes[i].length -=
+                                        bbio->stripes[i].length -=
                                                 stripe_offset;
                                         if (i == map->sub_stripes - 1)
                                                 stripe_offset = 0;
@@ -3084,11 +3090,11 @@ again:
                                 if (stripe_index >= last_stripe &&
                                     stripe_index <= (last_stripe +
                                                      map->sub_stripes - 1)) {
-                                        multi->stripes[i].length -=
+                                        bbio->stripes[i].length -=
                                                 stripe_end_offset;
                                 }
                         } else
-                                multi->stripes[i].length = *length;
+                                bbio->stripes[i].length = *length;
 
                         stripe_index++;
                         if (stripe_index == map->num_stripes) {
@@ -3099,19 +3105,20 @@ again:
                 }
         } else {
                 for (i = 0; i < num_stripes; i++) {
-                        multi->stripes[i].physical =
+                        bbio->stripes[i].physical =
                                 map->stripes[stripe_index].physical +
                                 stripe_offset +
                                 stripe_nr * map->stripe_len;
-                        multi->stripes[i].dev =
+                        bbio->stripes[i].dev =
                                 map->stripes[stripe_index].dev;
                         stripe_index++;
                 }
         }
-        if (multi_ret) {
-                *multi_ret = multi;
-                multi->num_stripes = num_stripes;
-                multi->max_errors = max_errors;
+        if (bbio_ret) {
+                *bbio_ret = bbio;
+                bbio->num_stripes = num_stripes;
+                bbio->max_errors = max_errors;
+                bbio->mirror_num = mirror_num;
         }
 out:
         free_extent_map(em);
@@ -3120,9 +3127,9 @@ out:
 
 int btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
                       u64 logical, u64 *length,
-                      struct btrfs_multi_bio **multi_ret, int mirror_num)
+                      struct btrfs_bio **bbio_ret, int mirror_num)
 {
-        return __btrfs_map_block(map_tree, rw, logical, length, multi_ret,
+        return __btrfs_map_block(map_tree, rw, logical, length, bbio_ret,
                                  mirror_num);
 }
 
@@ -3191,28 +3198,28 @@ int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
         return 0;
 }
 
-static void end_bio_multi_stripe(struct bio *bio, int err)
+static void btrfs_end_bio(struct bio *bio, int err)
 {
-        struct btrfs_multi_bio *multi = bio->bi_private;
+        struct btrfs_bio *bbio = bio->bi_private;
         int is_orig_bio = 0;
 
         if (err)
-                atomic_inc(&multi->error);
+                atomic_inc(&bbio->error);
 
-        if (bio == multi->orig_bio)
+        if (bio == bbio->orig_bio)
                 is_orig_bio = 1;
 
-        if (atomic_dec_and_test(&multi->stripes_pending)) {
+        if (atomic_dec_and_test(&bbio->stripes_pending)) {
                 if (!is_orig_bio) {
                         bio_put(bio);
-                        bio = multi->orig_bio;
+                        bio = bbio->orig_bio;
                 }
-                bio->bi_private = multi->private;
-                bio->bi_end_io = multi->end_io;
+                bio->bi_private = bbio->private;
+                bio->bi_end_io = bbio->end_io;
                 /* only send an error to the higher layers if it is
                  * beyond the tolerance of the multi-bio
                  */
-                if (atomic_read(&multi->error) > multi->max_errors) {
+                if (atomic_read(&bbio->error) > bbio->max_errors) {
                         err = -EIO;
                 } else if (err) {
                         /*
@@ -3222,7 +3229,7 @@ static void end_bio_multi_stripe(struct bio *bio, int err)
                         set_bit(BIO_UPTODATE, &bio->bi_flags);
                         err = 0;
                 }
-                kfree(multi);
+                kfree(bbio);
 
                 bio_endio(bio, err);
         } else if (!is_orig_bio) {
@@ -3302,20 +3309,20 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
         u64 logical = (u64)bio->bi_sector << 9;
         u64 length = 0;
         u64 map_length;
-        struct btrfs_multi_bio *multi = NULL;
         int ret;
         int dev_nr = 0;
         int total_devs = 1;
+        struct btrfs_bio *bbio = NULL;
 
         length = bio->bi_size;
         map_tree = &root->fs_info->mapping_tree;
         map_length = length;
 
-        ret = btrfs_map_block(map_tree, rw, logical, &map_length, &multi,
+        ret = btrfs_map_block(map_tree, rw, logical, &map_length, &bbio,
                               mirror_num);
         BUG_ON(ret);
 
-        total_devs = multi->num_stripes;
+        total_devs = bbio->num_stripes;
         if (map_length < length) {
                 printk(KERN_CRIT "mapping failed logical %llu bio len %llu "
                        "len %llu\n", (unsigned long long)logical,
@@ -3323,25 +3330,28 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
                        (unsigned long long)map_length);
                 BUG();
         }
-        multi->end_io = first_bio->bi_end_io;
-        multi->private = first_bio->bi_private;
-        multi->orig_bio = first_bio;
-        atomic_set(&multi->stripes_pending, multi->num_stripes);
+
+        bbio->orig_bio = first_bio;
+        bbio->private = first_bio->bi_private;
+        bbio->end_io = first_bio->bi_end_io;
+        atomic_set(&bbio->stripes_pending, bbio->num_stripes);
 
         while (dev_nr < total_devs) {
-                if (total_devs > 1) {
-                        if (dev_nr < total_devs - 1) {
-                                bio = bio_clone(first_bio, GFP_NOFS);
-                                BUG_ON(!bio);
-                        } else {
-                                bio = first_bio;
-                        }
-                        bio->bi_private = multi;
-                        bio->bi_end_io = end_bio_multi_stripe;
+                if (dev_nr < total_devs - 1) {
+                        bio = bio_clone(first_bio, GFP_NOFS);
+                        BUG_ON(!bio);
+                } else {
+                        bio = first_bio;
                 }
-                bio->bi_sector = multi->stripes[dev_nr].physical >> 9;
-                dev = multi->stripes[dev_nr].dev;
+                bio->bi_private = bbio;
+                bio->bi_end_io = btrfs_end_bio;
+                bio->bi_sector = bbio->stripes[dev_nr].physical >> 9;
+                dev = bbio->stripes[dev_nr].dev;
                 if (dev && dev->bdev && (rw != WRITE || dev->writeable)) {
+                        pr_debug("btrfs_map_bio: rw %d, secor=%llu, dev=%lu "
+                                 "(%s id %llu), size=%u\n", rw,
+                                 (u64)bio->bi_sector, (u_long)dev->bdev->bd_dev,
+                                 dev->name, dev->devid, bio->bi_size);
                         bio->bi_bdev = dev->bdev;
                         if (async_submit)
                                 schedule_bio(root, dev, rw, bio);
@@ -3354,8 +3364,6 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
                 }
                 dev_nr++;
         }
-        if (total_devs == 1)
-                kfree(multi);
         return 0;
 }