btrfs: remove btrfs_fs_info::compressed_write_workers

The reason why end_bbio_compressed_write() queues a work into
compressed_write_workers wq is for end_compressed_writeback() call, as
it will grab all the involved folioes and clear the writeback flags,
which may sleep.

However now we always run btrfs_bio::end_io() in task context, there is
no need to queue the work anymore.

Just remove btrfs_fs_info::compressed_write_workers and
compressed_bio::write_end_work.

There is a comment about the works queued into
compressed_write_workers, now change to flush endio wq instead, which is
responsible to handle all data endio functions.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: adam900710

fs/btrfs/compression.c

@@ -319,22 +319,6 @@ static noinline void end_compressed_writeback(const struct compressed_bio *cb)
 	/* the inode may be gone now */
 }
 
-static void btrfs_finish_compressed_write_work(struct work_struct *work)
-{
-	struct compressed_bio *cb =
-		container_of(work, struct compressed_bio, write_end_work);
-
-	btrfs_finish_ordered_extent(cb->bbio.ordered, NULL, cb->start, cb->len,
-				    cb->bbio.bio.bi_status == BLK_STS_OK);
-
-	if (cb->writeback)
-		end_compressed_writeback(cb);
-	/* Note, our inode could be gone now */
-
-	btrfs_free_compressed_folios(cb);
-	bio_put(&cb->bbio.bio);
-}
-
 /*
  * Do the cleanup once all the compressed pages hit the disk.  This will clear
  * writeback on the file pages and free the compressed pages.
@@ -345,9 +329,15 @@ static void btrfs_finish_compressed_write_work(struct work_struct *work)
 static void end_bbio_compressed_write(struct btrfs_bio *bbio)
 {
 	struct compressed_bio *cb = to_compressed_bio(bbio);
-	struct btrfs_fs_info *fs_info = bbio->inode->root->fs_info;
 
-	queue_work(fs_info->compressed_write_workers, &cb->write_end_work);
+	btrfs_finish_ordered_extent(cb->bbio.ordered, NULL, cb->start, cb->len,
+				    cb->bbio.bio.bi_status == BLK_STS_OK);
+
+	if (cb->writeback)
+		end_compressed_writeback(cb);
+	/* Note, our inode could be gone now */
+	btrfs_free_compressed_folios(cb);
+	bio_put(&cb->bbio.bio);
 }
 
 static void btrfs_add_compressed_bio_folios(struct compressed_bio *cb)
@@ -400,7 +390,6 @@ void btrfs_submit_compressed_write(struct btrfs_ordered_extent *ordered,
 	cb->compressed_folios = compressed_folios;
 	cb->compressed_len = ordered->disk_num_bytes;
 	cb->writeback = writeback;
-	INIT_WORK(&cb->write_end_work, btrfs_finish_compressed_write_work);
 	cb->nr_folios = nr_folios;
 	cb->bbio.bio.bi_iter.bi_sector = ordered->disk_bytenr >> SECTOR_SHIFT;
 	cb->bbio.ordered = ordered;

fs/btrfs/compression.h

@@ -63,11 +63,8 @@ struct compressed_bio {
 	/* Whether this is a write for writeback. */
 	bool writeback;
 
-	union {
-		/* For reads, this is the bio we are copying the data into */
-		struct btrfs_bio *orig_bbio;
-		struct work_struct write_end_work;
-	};
+	/* For reads, this is the bio we are copying the data into */
+	struct btrfs_bio *orig_bbio;
 
 	/* Must be last. */
 	struct btrfs_bio bbio;

fs/btrfs/disk-io.c

@@ -1774,8 +1774,6 @@ static void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info)
 		destroy_workqueue(fs_info->endio_workers);
 	if (fs_info->rmw_workers)
 		destroy_workqueue(fs_info->rmw_workers);
-	if (fs_info->compressed_write_workers)
-		destroy_workqueue(fs_info->compressed_write_workers);
 	btrfs_destroy_workqueue(fs_info->endio_write_workers);
 	btrfs_destroy_workqueue(fs_info->endio_freespace_worker);
 	btrfs_destroy_workqueue(fs_info->delayed_workers);
@@ -1987,8 +1985,6 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info)
 	fs_info->endio_write_workers =
 		btrfs_alloc_workqueue(fs_info, "endio-write", flags,
 				      max_active, 2);
-	fs_info->compressed_write_workers =
-		alloc_workqueue("btrfs-compressed-write", flags, max_active);
 	fs_info->endio_freespace_worker =
 		btrfs_alloc_workqueue(fs_info, "freespace-write", flags,
 				      max_active, 0);
@@ -2004,7 +2000,6 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info)
 	if (!(fs_info->workers &&
 	      fs_info->delalloc_workers && fs_info->flush_workers &&
 	      fs_info->endio_workers && fs_info->endio_meta_workers &&
-	      fs_info->compressed_write_workers &&
 	      fs_info->endio_write_workers &&
 	      fs_info->endio_freespace_worker && fs_info->rmw_workers &&
 	      fs_info->caching_workers && fs_info->fixup_workers &&
@@ -4291,15 +4286,15 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info)
 
 	/*
 	 * When finishing a compressed write bio we schedule a work queue item
-	 * to finish an ordered extent - btrfs_finish_compressed_write_work()
+	 * to finish an ordered extent - end_bbio_compressed_write()
 	 * calls btrfs_finish_ordered_extent() which in turns does a call to
 	 * btrfs_queue_ordered_fn(), and that queues the ordered extent
 	 * completion either in the endio_write_workers work queue or in the
 	 * fs_info->endio_freespace_worker work queue. We flush those queues
 	 * below, so before we flush them we must flush this queue for the
 	 * workers of compressed writes.
 	 */
-	flush_workqueue(fs_info->compressed_write_workers);
+	flush_workqueue(fs_info->endio_workers);
 
 	/*
 	 * After we parked the cleaner kthread, ordered extents may have

fs/btrfs/fs.h

@@ -654,7 +654,6 @@ struct btrfs_fs_info {
 	struct workqueue_struct *endio_workers;
 	struct workqueue_struct *endio_meta_workers;
 	struct workqueue_struct *rmw_workers;
-	struct workqueue_struct *compressed_write_workers;
 	struct btrfs_workqueue *endio_write_workers;
 	struct btrfs_workqueue *endio_freespace_worker;
 	struct btrfs_workqueue *caching_workers;