btrfs: migrate the dirty bg writeout code

This can be easily migrated over now.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update comments ]
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 0 insertions, 518 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 519cf2cb5cef..0b78e5dcfe48 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2511,524 +2511,6 @@ int btrfs_dec_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 	return __btrfs_mod_ref(trans, root, buf, full_backref, 0);
 }
 
-static int write_one_cache_group(struct btrfs_trans_handle *trans,
-				 struct btrfs_path *path,
-				 struct btrfs_block_group_cache *cache)
-{
-	struct btrfs_fs_info *fs_info = trans->fs_info;
-	int ret;
-	struct btrfs_root *extent_root = fs_info->extent_root;
-	unsigned long bi;
-	struct extent_buffer *leaf;
-
-	ret = btrfs_search_slot(trans, extent_root, &cache->key, path, 0, 1);
-	if (ret) {
-		if (ret > 0)
-			ret = -ENOENT;
-		goto fail;
-	}
-
-	leaf = path->nodes[0];
-	bi = btrfs_item_ptr_offset(leaf, path->slots[0]);
-	write_extent_buffer(leaf, &cache->item, bi, sizeof(cache->item));
-	btrfs_mark_buffer_dirty(leaf);
-fail:
-	btrfs_release_path(path);
-	return ret;
-
-}
-
-static int cache_save_setup(struct btrfs_block_group_cache *block_group,
-			    struct btrfs_trans_handle *trans,
-			    struct btrfs_path *path)
-{
-	struct btrfs_fs_info *fs_info = block_group->fs_info;
-	struct btrfs_root *root = fs_info->tree_root;
-	struct inode *inode = NULL;
-	struct extent_changeset *data_reserved = NULL;
-	u64 alloc_hint = 0;
-	int dcs = BTRFS_DC_ERROR;
-	u64 num_pages = 0;
-	int retries = 0;
-	int ret = 0;
-
-	/*
-	 * If this block group is smaller than 100 megs don't bother caching the
-	 * block group.
-	 */
-	if (block_group->key.offset < (100 * SZ_1M)) {
-		spin_lock(&block_group->lock);
-		block_group->disk_cache_state = BTRFS_DC_WRITTEN;
-		spin_unlock(&block_group->lock);
-		return 0;
-	}
-
-	if (trans->aborted)
-		return 0;
-again:
-	inode = lookup_free_space_inode(block_group, path);
-	if (IS_ERR(inode) && PTR_ERR(inode) != -ENOENT) {
-		ret = PTR_ERR(inode);
-		btrfs_release_path(path);
-		goto out;
-	}
-
-	if (IS_ERR(inode)) {
-		BUG_ON(retries);
-		retries++;
-
-		if (block_group->ro)
-			goto out_free;
-
-		ret = create_free_space_inode(trans, block_group, path);
-		if (ret)
-			goto out_free;
-		goto again;
-	}
-
-	/*
-	 * We want to set the generation to 0, that way if anything goes wrong
-	 * from here on out we know not to trust this cache when we load up next
-	 * time.
-	 */
-	BTRFS_I(inode)->generation = 0;
-	ret = btrfs_update_inode(trans, root, inode);
-	if (ret) {
-		/*
-		 * So theoretically we could recover from this, simply set the
-		 * super cache generation to 0 so we know to invalidate the
-		 * cache, but then we'd have to keep track of the block groups
-		 * that fail this way so we know we _have_ to reset this cache
-		 * before the next commit or risk reading stale cache.  So to
-		 * limit our exposure to horrible edge cases lets just abort the
-		 * transaction, this only happens in really bad situations
-		 * anyway.
-		 */
-		btrfs_abort_transaction(trans, ret);
-		goto out_put;
-	}
-	WARN_ON(ret);
-
-	/* We've already setup this transaction, go ahead and exit */
-	if (block_group->cache_generation == trans->transid &&
-	    i_size_read(inode)) {
-		dcs = BTRFS_DC_SETUP;
-		goto out_put;
-	}
-
-	if (i_size_read(inode) > 0) {
-		ret = btrfs_check_trunc_cache_free_space(fs_info,
-					&fs_info->global_block_rsv);
-		if (ret)
-			goto out_put;
-
-		ret = btrfs_truncate_free_space_cache(trans, NULL, inode);
-		if (ret)
-			goto out_put;
-	}
-
-	spin_lock(&block_group->lock);
-	if (block_group->cached != BTRFS_CACHE_FINISHED ||
-	    !btrfs_test_opt(fs_info, SPACE_CACHE)) {
-		/*
-		 * don't bother trying to write stuff out _if_
-		 * a) we're not cached,
-		 * b) we're with nospace_cache mount option,
-		 * c) we're with v2 space_cache (FREE_SPACE_TREE).
-		 */
-		dcs = BTRFS_DC_WRITTEN;
-		spin_unlock(&block_group->lock);
-		goto out_put;
-	}
-	spin_unlock(&block_group->lock);
-
-	/*
-	 * We hit an ENOSPC when setting up the cache in this transaction, just
-	 * skip doing the setup, we've already cleared the cache so we're safe.
-	 */
-	if (test_bit(BTRFS_TRANS_CACHE_ENOSPC, &trans->transaction->flags)) {
-		ret = -ENOSPC;
-		goto out_put;
-	}
-
-	/*
-	 * Try to preallocate enough space based on how big the block group is.
-	 * Keep in mind this has to include any pinned space which could end up
-	 * taking up quite a bit since it's not folded into the other space
-	 * cache.
-	 */
-	num_pages = div_u64(block_group->key.offset, SZ_256M);
-	if (!num_pages)
-		num_pages = 1;
-
-	num_pages *= 16;
-	num_pages *= PAGE_SIZE;
-
-	ret = btrfs_check_data_free_space(inode, &data_reserved, 0, num_pages);
-	if (ret)
-		goto out_put;
-
-	ret = btrfs_prealloc_file_range_trans(inode, trans, 0, 0, num_pages,
-					      num_pages, num_pages,
-					      &alloc_hint);
-	/*
-	 * Our cache requires contiguous chunks so that we don't modify a bunch
-	 * of metadata or split extents when writing the cache out, which means
-	 * we can enospc if we are heavily fragmented in addition to just normal
-	 * out of space conditions.  So if we hit this just skip setting up any
-	 * other block groups for this transaction, maybe we'll unpin enough
-	 * space the next time around.
-	 */
-	if (!ret)
-		dcs = BTRFS_DC_SETUP;
-	else if (ret == -ENOSPC)
-		set_bit(BTRFS_TRANS_CACHE_ENOSPC, &trans->transaction->flags);
-
-out_put:
-	iput(inode);
-out_free:
-	btrfs_release_path(path);
-out:
-	spin_lock(&block_group->lock);
-	if (!ret && dcs == BTRFS_DC_SETUP)
-		block_group->cache_generation = trans->transid;
-	block_group->disk_cache_state = dcs;
-	spin_unlock(&block_group->lock);
-
-	extent_changeset_free(data_reserved);
-	return ret;
-}
-
-int btrfs_setup_space_cache(struct btrfs_trans_handle *trans)
-{
-	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_block_group_cache *cache, *tmp;
-	struct btrfs_transaction *cur_trans = trans->transaction;
-	struct btrfs_path *path;
-
-	if (list_empty(&cur_trans->dirty_bgs) ||
-	    !btrfs_test_opt(fs_info, SPACE_CACHE))
-		return 0;
-
-	path = btrfs_alloc_path();
-	if (!path)
-		return -ENOMEM;
-
-	/* Could add new block groups, use _safe just in case */
-	list_for_each_entry_safe(cache, tmp, &cur_trans->dirty_bgs,
-				 dirty_list) {
-		if (cache->disk_cache_state == BTRFS_DC_CLEAR)
-			cache_save_setup(cache, trans, path);
-	}
-
-	btrfs_free_path(path);
-	return 0;
-}
-
-/*
- * transaction commit does final block group cache writeback during a
- * critical section where nothing is allowed to change the FS.  This is
- * required in order for the cache to actually match the block group,
- * but can introduce a lot of latency into the commit.
- *
- * So, btrfs_start_dirty_block_groups is here to kick off block group
- * cache IO.  There's a chance we'll have to redo some of it if the
- * block group changes again during the commit, but it greatly reduces
- * the commit latency by getting rid of the easy block groups while
- * we're still allowing others to join the commit.
- */
-int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans)
-{
-	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_block_group_cache *cache;
-	struct btrfs_transaction *cur_trans = trans->transaction;
-	int ret = 0;
-	int should_put;
-	struct btrfs_path *path = NULL;
-	LIST_HEAD(dirty);
-	struct list_head *io = &cur_trans->io_bgs;
-	int num_started = 0;
-	int loops = 0;
-
-	spin_lock(&cur_trans->dirty_bgs_lock);
-	if (list_empty(&cur_trans->dirty_bgs)) {
-		spin_unlock(&cur_trans->dirty_bgs_lock);
-		return 0;
-	}
-	list_splice_init(&cur_trans->dirty_bgs, &dirty);
-	spin_unlock(&cur_trans->dirty_bgs_lock);
-
-again:
-	/*
-	 * make sure all the block groups on our dirty list actually
-	 * exist
-	 */
-	btrfs_create_pending_block_groups(trans);
-
-	if (!path) {
-		path = btrfs_alloc_path();
-		if (!path)
-			return -ENOMEM;
-	}
-
-	/*
-	 * cache_write_mutex is here only to save us from balance or automatic
-	 * removal of empty block groups deleting this block group while we are
-	 * writing out the cache
-	 */
-	mutex_lock(&trans->transaction->cache_write_mutex);
-	while (!list_empty(&dirty)) {
-		bool drop_reserve = true;
-
-		cache = list_first_entry(&dirty,
-					 struct btrfs_block_group_cache,
-					 dirty_list);
-		/*
-		 * this can happen if something re-dirties a block
-		 * group that is already under IO.  Just wait for it to
-		 * finish and then do it all again
-		 */
-		if (!list_empty(&cache->io_list)) {
-			list_del_init(&cache->io_list);
-			btrfs_wait_cache_io(trans, cache, path);
-			btrfs_put_block_group(cache);
-		}
-
-
-		/*
-		 * btrfs_wait_cache_io uses the cache->dirty_list to decide
-		 * if it should update the cache_state.  Don't delete
-		 * until after we wait.
-		 *
-		 * Since we're not running in the commit critical section
-		 * we need the dirty_bgs_lock to protect from update_block_group
-		 */
-		spin_lock(&cur_trans->dirty_bgs_lock);
-		list_del_init(&cache->dirty_list);
-		spin_unlock(&cur_trans->dirty_bgs_lock);
-
-		should_put = 1;
-
-		cache_save_setup(cache, trans, path);
-
-		if (cache->disk_cache_state == BTRFS_DC_SETUP) {
-			cache->io_ctl.inode = NULL;
-			ret = btrfs_write_out_cache(trans, cache, path);
-			if (ret == 0 && cache->io_ctl.inode) {
-				num_started++;
-				should_put = 0;
-
-				/*
-				 * The cache_write_mutex is protecting the
-				 * io_list, also refer to the definition of
-				 * btrfs_transaction::io_bgs for more details
-				 */
-				list_add_tail(&cache->io_list, io);
-			} else {
-				/*
-				 * if we failed to write the cache, the
-				 * generation will be bad and life goes on
-				 */
-				ret = 0;
-			}
-		}
-		if (!ret) {
-			ret = write_one_cache_group(trans, path, cache);
-			/*
-			 * Our block group might still be attached to the list
-			 * of new block groups in the transaction handle of some
-			 * other task (struct btrfs_trans_handle->new_bgs). This
-			 * means its block group item isn't yet in the extent
-			 * tree. If this happens ignore the error, as we will
-			 * try again later in the critical section of the
-			 * transaction commit.
-			 */
-			if (ret == -ENOENT) {
-				ret = 0;
-				spin_lock(&cur_trans->dirty_bgs_lock);
-				if (list_empty(&cache->dirty_list)) {
-					list_add_tail(&cache->dirty_list,
-						      &cur_trans->dirty_bgs);
-					btrfs_get_block_group(cache);
-					drop_reserve = false;
-				}
-				spin_unlock(&cur_trans->dirty_bgs_lock);
-			} else if (ret) {
-				btrfs_abort_transaction(trans, ret);
-			}
-		}
-
-		/* if it's not on the io list, we need to put the block group */
-		if (should_put)
-			btrfs_put_block_group(cache);
-		if (drop_reserve)
-			btrfs_delayed_refs_rsv_release(fs_info, 1);
-
-		if (ret)
-			break;
-
-		/*
-		 * Avoid blocking other tasks for too long. It might even save
-		 * us from writing caches for block groups that are going to be
-		 * removed.
-		 */
-		mutex_unlock(&trans->transaction->cache_write_mutex);
-		mutex_lock(&trans->transaction->cache_write_mutex);
-	}
-	mutex_unlock(&trans->transaction->cache_write_mutex);
-
-	/*
-	 * go through delayed refs for all the stuff we've just kicked off
-	 * and then loop back (just once)
-	 */
-	ret = btrfs_run_delayed_refs(trans, 0);
-	if (!ret && loops == 0) {
-		loops++;
-		spin_lock(&cur_trans->dirty_bgs_lock);
-		list_splice_init(&cur_trans->dirty_bgs, &dirty);
-		/*
-		 * dirty_bgs_lock protects us from concurrent block group
-		 * deletes too (not just cache_write_mutex).
-		 */
-		if (!list_empty(&dirty)) {
-			spin_unlock(&cur_trans->dirty_bgs_lock);
-			goto again;
-		}
-		spin_unlock(&cur_trans->dirty_bgs_lock);
-	} else if (ret < 0) {
-		btrfs_cleanup_dirty_bgs(cur_trans, fs_info);
-	}
-
-	btrfs_free_path(path);
-	return ret;
-}
-
-int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans)
-{
-	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_block_group_cache *cache;
-	struct btrfs_transaction *cur_trans = trans->transaction;
-	int ret = 0;
-	int should_put;
-	struct btrfs_path *path;
-	struct list_head *io = &cur_trans->io_bgs;
-	int num_started = 0;
-
-	path = btrfs_alloc_path();
-	if (!path)
-		return -ENOMEM;
-
-	/*
-	 * Even though we are in the critical section of the transaction commit,
-	 * we can still have concurrent tasks adding elements to this
-	 * transaction's list of dirty block groups. These tasks correspond to
-	 * endio free space workers started when writeback finishes for a
-	 * space cache, which run inode.c:btrfs_finish_ordered_io(), and can
-	 * allocate new block groups as a result of COWing nodes of the root
-	 * tree when updating the free space inode. The writeback for the space
-	 * caches is triggered by an earlier call to
-	 * btrfs_start_dirty_block_groups() and iterations of the following
-	 * loop.
-	 * Also we want to do the cache_save_setup first and then run the
-	 * delayed refs to make sure we have the best chance at doing this all
-	 * in one shot.
-	 */
-	spin_lock(&cur_trans->dirty_bgs_lock);
-	while (!list_empty(&cur_trans->dirty_bgs)) {
-		cache = list_first_entry(&cur_trans->dirty_bgs,
-					 struct btrfs_block_group_cache,
-					 dirty_list);
-
-		/*
-		 * this can happen if cache_save_setup re-dirties a block
-		 * group that is already under IO.  Just wait for it to
-		 * finish and then do it all again
-		 */
-		if (!list_empty(&cache->io_list)) {
-			spin_unlock(&cur_trans->dirty_bgs_lock);
-			list_del_init(&cache->io_list);
-			btrfs_wait_cache_io(trans, cache, path);
-			btrfs_put_block_group(cache);
-			spin_lock(&cur_trans->dirty_bgs_lock);
-		}
-
-		/*
-		 * don't remove from the dirty list until after we've waited
-		 * on any pending IO
-		 */
-		list_del_init(&cache->dirty_list);
-		spin_unlock(&cur_trans->dirty_bgs_lock);
-		should_put = 1;
-
-		cache_save_setup(cache, trans, path);
-
-		if (!ret)
-			ret = btrfs_run_delayed_refs(trans,
-						     (unsigned long) -1);
-
-		if (!ret && cache->disk_cache_state == BTRFS_DC_SETUP) {
-			cache->io_ctl.inode = NULL;
-			ret = btrfs_write_out_cache(trans, cache, path);
-			if (ret == 0 && cache->io_ctl.inode) {
-				num_started++;
-				should_put = 0;
-				list_add_tail(&cache->io_list, io);
-			} else {
-				/*
-				 * if we failed to write the cache, the
-				 * generation will be bad and life goes on
-				 */
-				ret = 0;
-			}
-		}
-		if (!ret) {
-			ret = write_one_cache_group(trans, path, cache);
-			/*
-			 * One of the free space endio workers might have
-			 * created a new block group while updating a free space
-			 * cache's inode (at inode.c:btrfs_finish_ordered_io())
-			 * and hasn't released its transaction handle yet, in
-			 * which case the new block group is still attached to
-			 * its transaction handle and its creation has not
-			 * finished yet (no block group item in the extent tree
-			 * yet, etc). If this is the case, wait for all free
-			 * space endio workers to finish and retry. This is a
-			 * a very rare case so no need for a more efficient and
-			 * complex approach.
-			 */
-			if (ret == -ENOENT) {
-				wait_event(cur_trans->writer_wait,
-				   atomic_read(&cur_trans->num_writers) == 1);
-				ret = write_one_cache_group(trans, path, cache);
-			}
-			if (ret)
-				btrfs_abort_transaction(trans, ret);
-		}
-
-		/* if its not on the io list, we need to put the block group */
-		if (should_put)
-			btrfs_put_block_group(cache);
-		btrfs_delayed_refs_rsv_release(fs_info, 1);
-		spin_lock(&cur_trans->dirty_bgs_lock);
-	}
-	spin_unlock(&cur_trans->dirty_bgs_lock);
-
-	/*
-	 * Refer to the definition of io_bgs member for details why it's safe
-	 * to use it without any locking
-	 */
-	while (!list_empty(io)) {
-		cache = list_first_entry(io, struct btrfs_block_group_cache,
-					 io_list);
-		list_del_init(&cache->io_list);
-		btrfs_wait_cache_io(trans, cache, path);
-		btrfs_put_block_group(cache);
-	}
-
-	btrfs_free_path(path);
-	return ret;
-}
-
 int btrfs_extent_readonly(struct btrfs_fs_info *fs_info, u64 bytenr)
 {
 	struct btrfs_block_group_cache *block_group;