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Commit 8ca17f0f authored by Josef Bacik's avatar Josef Bacik Committed by David Sterba
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Btrfs: use FLUSH_LIMIT for relocation in reserve_metadata_bytes 



We used to allow you to set FLUSH_ALL and then just wouldn't do things like
commit transactions or wait on ordered extents if we noticed you were in a
transaction.  However now that all the flushing for FLUSH_ALL is asynchronous
we've lost the ability to tell, and we could end up deadlocking.  So instead use
FLUSH_LIMIT in reserve_metadata_bytes in relocation and then return -EAGAIN if
we error out to preserve the previous behavior.  I've also added an ASSERT() to
catch anybody else who tries to do this.  Thanks,

Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent ac2fabac

fs/btrfs/extent-tree.c

+2 −0
Original line number Diff line number Diff line
@@ -5135,6 +5135,8 @@ static int __reserve_metadata_bytes(struct btrfs_root *root, 
	int ret = 0;



	ASSERT(orig_bytes);

	ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_ALL);



	spin_lock(&space_info->lock);

	ret = -ENOSPC;

	used = space_info->bytes_used + space_info->bytes_reserved +

fs/btrfs/relocation.c

+20 −17
Original line number Diff line number Diff line
@@ -2604,25 +2604,28 @@ static int reserve_metadata_space(struct btrfs_trans_handle *trans, 


	trans->block_rsv = rc->block_rsv;

	rc->reserved_bytes += num_bytes;



	/*

	 * We are under a transaction here so we can only do limited flushing.

	 * If we get an enospc just kick back -EAGAIN so we know to drop the

	 * transaction and try to refill when we can flush all the things.

	 */

	ret = btrfs_block_rsv_refill(root, rc->block_rsv, num_bytes,

				BTRFS_RESERVE_FLUSH_ALL);

				BTRFS_RESERVE_FLUSH_LIMIT);

	if (ret) {

		if (ret == -EAGAIN) {

			tmp = rc->extent_root->nodesize *

				RELOCATION_RESERVED_NODES;

		tmp = rc->extent_root->nodesize * RELOCATION_RESERVED_NODES;

		while (tmp <= rc->reserved_bytes)

			tmp <<= 1;

		/*

		 * only one thread can access block_rsv at this point,

		 * so we don't need hold lock to protect block_rsv.

		 * we expand more reservation size here to allow enough

			 * space for relocation and we will return earlier in

		 * space for relocation and we will return eailer in

		 * enospc case.

		 */

		rc->block_rsv->size = tmp + rc->extent_root->nodesize *

			RELOCATION_RESERVED_NODES;

		}

		return ret;

		return -EAGAIN;

	}



	return 0;