btrfs: handle checksum generation in the storage layer

Instead of letting the callers of btrfs_submit_bio deal with checksumming
the (meta)data in the bio and making decisions on when to offload the
checksumming to the bio, leave that to btrfs_submit_bio.  Do do so the
existing btrfs_submit_bio function is split into an upper and a lower
half, so that the lower half can be offloaded to a workqueue.

Note that this changes the behavior for direct writes to raid56 volumes so
that async checksum offloading is not skipped when more I/O is expected.
This runs counter to the argument explaining why it was done, although I
can't measure any affects of the change.  Commits later in this series
will make sure the entire direct writes is offloaded to the workqueue
at once and thus make sure it is sent to the raid56 code from a single
thread.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 2 insertions, 153 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 0270226389a7..6278530d5986 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -52,7 +52,6 @@
 #include "relocation.h"
 #include "scrub.h"
 #include "super.h"
-#include "file-item.h"
 
 #define BTRFS_SUPER_FLAG_SUPP	(BTRFS_HEADER_FLAG_WRITTEN |\
 				 BTRFS_HEADER_FLAG_RELOC |\
@@ -80,23 +79,6 @@ static void btrfs_free_csum_hash(struct btrfs_fs_info *fs_info)
 }
 
 /*
- * async submit bios are used to offload expensive checksumming
- * onto the worker threads.  They checksum file and metadata bios
- * just before they are sent down the IO stack.
- */
-struct async_submit_bio {
-	struct btrfs_inode *inode;
-	struct bio *bio;
-	enum btrfs_wq_submit_cmd submit_cmd;
-	int mirror_num;
-
-	/* Optional parameter for used by direct io */
-	u64 dio_file_offset;
-	struct btrfs_work work;
-	blk_status_t status;
-};
-
-/*
  * Compute the csum of a btree block and store the result to provided buffer.
  */
 static void csum_tree_block(struct extent_buffer *buf, u8 *result)
@@ -456,7 +438,7 @@ static int csum_dirty_buffer(struct btrfs_fs_info *fs_info, struct bio_vec *bvec
 	return csum_one_extent_buffer(eb);
 }
 
-static blk_status_t btree_csum_one_bio(struct bio *bio)
+blk_status_t btree_csum_one_bio(struct bio *bio)
 {
 	struct bio_vec *bvec;
 	struct btrfs_root *root;
@@ -719,143 +701,10 @@ err:
 	return ret;
 }
 
-static void run_one_async_start(struct btrfs_work *work)
-{
-	struct async_submit_bio *async;
-	blk_status_t ret;
-
-	async = container_of(work, struct  async_submit_bio, work);
-	switch (async->submit_cmd) {
-	case WQ_SUBMIT_METADATA:
-		ret = btree_csum_one_bio(async->bio);
-		break;
-	case WQ_SUBMIT_DATA:
-	case WQ_SUBMIT_DATA_DIO:
-		ret = btrfs_csum_one_bio(btrfs_bio(async->bio));
-		break;
-	default:
-		/* Can't happen so return something that would prevent the IO. */
-		ret = BLK_STS_IOERR;
-		ASSERT(0);
-	}
-	if (ret)
-		async->status = ret;
-}
-
-/*
- * In order to insert checksums into the metadata in large chunks, we wait
- * until bio submission time.   All the pages in the bio are checksummed and
- * sums are attached onto the ordered extent record.
- *
- * At IO completion time the csums attached on the ordered extent record are
- * inserted into the tree.
- */
-static void run_one_async_done(struct btrfs_work *work)
-{
-	struct async_submit_bio *async =
-		container_of(work, struct  async_submit_bio, work);
-	struct btrfs_inode *inode = async->inode;
-	struct btrfs_bio *bbio = btrfs_bio(async->bio);
-
-	/* If an error occurred we just want to clean up the bio and move on */
-	if (async->status) {
-		btrfs_bio_end_io(bbio, async->status);
-		return;
-	}
-
-	/*
-	 * All of the bios that pass through here are from async helpers.
-	 * Use REQ_CGROUP_PUNT to issue them from the owning cgroup's context.
-	 * This changes nothing when cgroups aren't in use.
-	 */
-	async->bio->bi_opf |= REQ_CGROUP_PUNT;
-	btrfs_submit_bio(inode->root->fs_info, async->bio, async->mirror_num);
-}
-
-static void run_one_async_free(struct btrfs_work *work)
-{
-	struct async_submit_bio *async;
-
-	async = container_of(work, struct  async_submit_bio, work);
-	kfree(async);
-}
-
-/*
- * Submit bio to an async queue.
- *
- * Return:
- * - true if the work has been successfully submitted
- * - false in case of error
- */
-bool btrfs_wq_submit_bio(struct btrfs_inode *inode, struct bio *bio, int mirror_num,
-			 u64 dio_file_offset, enum btrfs_wq_submit_cmd cmd)
-{
-	struct btrfs_fs_info *fs_info = inode->root->fs_info;
-	struct async_submit_bio *async;
-
-	async = kmalloc(sizeof(*async), GFP_NOFS);
-	if (!async)
-		return false;
-
-	async->inode = inode;
-	async->bio = bio;
-	async->mirror_num = mirror_num;
-	async->submit_cmd = cmd;
-
-	btrfs_init_work(&async->work, run_one_async_start, run_one_async_done,
-			run_one_async_free);
-
-	async->dio_file_offset = dio_file_offset;
-
-	async->status = 0;
-
-	if (op_is_sync(bio->bi_opf))
-		btrfs_queue_work(fs_info->hipri_workers, &async->work);
-	else
-		btrfs_queue_work(fs_info->workers, &async->work);
-	return true;
-}
-
-static bool should_async_write(struct btrfs_fs_info *fs_info,
-			     struct btrfs_inode *bi)
-{
-	if (btrfs_is_zoned(fs_info))
-		return false;
-	if (atomic_read(&bi->sync_writers))
-		return false;
-	if (test_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags))
-		return false;
-	return true;
-}
-
 void btrfs_submit_metadata_bio(struct btrfs_inode *inode, struct bio *bio, int mirror_num)
 {
-	struct btrfs_fs_info *fs_info = inode->root->fs_info;
-	struct btrfs_bio *bbio = btrfs_bio(bio);
-	blk_status_t ret;
-
 	bio->bi_opf |= REQ_META;
-
-	if (btrfs_op(bio) != BTRFS_MAP_WRITE) {
-		btrfs_submit_bio(fs_info, bio, mirror_num);
-		return;
-	}
-
-	/*
-	 * Kthread helpers are used to submit writes so that checksumming can
-	 * happen in parallel across all CPUs.
-	 */
-	if (should_async_write(fs_info, inode) &&
-	    btrfs_wq_submit_bio(inode, bio, mirror_num, 0, WQ_SUBMIT_METADATA))
-		return;
-
-	ret = btree_csum_one_bio(bio);
-	if (ret) {
-		btrfs_bio_end_io(bbio, ret);
-		return;
-	}
-
-	btrfs_submit_bio(fs_info, bio, mirror_num);
+	btrfs_submit_bio(inode->root->fs_info, bio, mirror_num);
 }
 
 #ifdef CONFIG_MIGRATION