Merge branch 'writeback-workqueue' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq into for-3.10/core

Tejun writes:

-----

This is the pull request for the earlier patchset[1] with the same
name.  It's only three patches (the first one was committed to
workqueue tree) but the merge strategy is a bit involved due to the
dependencies.

* Because the conversion needs features from wq/for-3.10,
  block/for-3.10/core is based on rc3, and wq/for-3.10 has conflicts
  with rc3, I pulled mainline (rc5) into wq/for-3.10 to prevent those
  workqueue conflicts from flaring up in block tree.

* Resolving the issue that Jan and Dave raised about debugging
  requires arch-wide changes.  The patchset is being worked on[2] but
  it'll have to go through -mm after these changes show up in -next,
  and not included in this pull request.

The three commits are located in the following git branch.

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git writeback-workqueue

Pulling it into block/for-3.10/core produces a conflict in
drivers/md/raid5.c between the following two commits.

  e3620a3ad5 ("MD RAID5: Avoid accessing gendisk or queue structs when not available")
  2f6db2a707 ("raid5: use bio_reset()")

The conflict is trivial - one removes an "if ()" conditional while the
other removes "rbi->bi_next = NULL" right above it.  We just need to
remove both.  The merged branch is available at

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git block-test-merge

so that you can use it for verification.  The test merge commit has
proper merge description.

While these changes are a bit of pain to route, they make code simpler
and even have, while minute, measureable performance gain[3] even on a
workload which isn't particularly favorable to showing the benefits of
this conversion.

----

Fixed up the conflict.

Conflicts:
	drivers/md/raid5.c

Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 34 insertions, 5 deletions

diff --git a/drivers/md/dm-verity.c b/drivers/md/dm-verity.c
index 4f06d9adf1ed..b948fd864d45 100644
--- a/drivers/md/dm-verity.c
+++ b/drivers/md/dm-verity.c
@@ -93,6 +93,13 @@ struct dm_verity_io {
          */
 };
 
+struct dm_verity_prefetch_work {
+        struct work_struct work;
+        struct dm_verity *v;
+        sector_t block;
+        unsigned n_blocks;
+};
+
 static struct shash_desc *io_hash_desc(struct dm_verity *v, struct dm_verity_io *io)
 {
         return (struct shash_desc *)(io + 1);
@@ -424,15 +431,18 @@ static void verity_end_io(struct bio *bio, int error)
  * The root buffer is not prefetched, it is assumed that it will be cached
  * all the time.
  */
-static void verity_prefetch_io(struct dm_verity *v, struct dm_verity_io *io)
+static void verity_prefetch_io(struct work_struct *work)
 {
+        struct dm_verity_prefetch_work *pw =
+                container_of(work, struct dm_verity_prefetch_work, work);
+        struct dm_verity *v = pw->v;
         int i;
 
         for (i = v->levels - 2; i >= 0; i--) {
                 sector_t hash_block_start;
                 sector_t hash_block_end;
-                verity_hash_at_level(v, io->block, i, &hash_block_start, NULL);
-                verity_hash_at_level(v, io->block + io->n_blocks - 1, i, &hash_block_end, NULL);
+                verity_hash_at_level(v, pw->block, i, &hash_block_start, NULL);
+                verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);
                 if (!i) {
                         unsigned cluster = ACCESS_ONCE(dm_verity_prefetch_cluster);
 
@@ -452,6 +462,25 @@ no_prefetch_cluster:
                 dm_bufio_prefetch(v->bufio, hash_block_start,
                                   hash_block_end - hash_block_start + 1);
         }
+
+        kfree(pw);
+}
+
+static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
+{
+        struct dm_verity_prefetch_work *pw;
+
+        pw = kmalloc(sizeof(struct dm_verity_prefetch_work),
+                GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
+
+        if (!pw)
+                return;
+
+        INIT_WORK(&pw->work, verity_prefetch_io);
+        pw->v = v;
+        pw->block = io->block;
+        pw->n_blocks = io->n_blocks;
+        queue_work(v->verify_wq, &pw->work);
 }
 
 /*
@@ -498,7 +527,7 @@ static int verity_map(struct dm_target *ti, struct bio *bio)
         memcpy(io->io_vec, bio_iovec(bio),
                io->io_vec_size * sizeof(struct bio_vec));
 
-        verity_prefetch_io(v, io);
+        verity_submit_prefetch(v, io);
 
         generic_make_request(bio);
 
@@ -858,7 +887,7 @@ bad:
 
 static struct target_type verity_target = {
         .name           = "verity",
-        .version        = {1, 1, 1},
+        .version        = {1, 2, 0},
         .module         = THIS_MODULE,
         .ctr            = verity_ctr,
         .dtr            = verity_dtr,