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Commit 68a82277 authored by Josef Bacik's avatar Josef Bacik Committed by Chris Mason
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Btrfs: use the global block reserve if we cannot reserve space 



We call use_block_rsv right before we make an allocation in order to make sure
we have enough space.  Now normally people have called btrfs_start_transaction()
with the appropriate amount of space that we need, so we just use some of that
pre-reserved space and move along happily.  The problem is where people use
btrfs_join_transaction(), which doesn't actually reserve any space.  So we try
and reserve space here, but we cannot flush delalloc, so this forces us to
return -ENOSPC when in reality we have plenty of space.  The most common symptom
is seeing a bunch of "couldn't dirty inode" messages in syslog.  With
xfstests 224 we end up falling back to start_transaction and then doing all the
flush delalloc stuff which causes to hang for a very long time.

So instead steal from the global reserve, which is what this is meant for
anyway.  With this patch and the other 2 I have sent xfstests 224 now passes
successfully.  Thanks,

Signed-off-by: default avatarJosef Bacik <josef@redhat.com>
Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent e9e22899

fs/btrfs/extent-tree.c

+27 −1
Original line number Diff line number Diff line
@@ -5646,6 +5646,7 @@ use_block_rsv(struct btrfs_trans_handle *trans, 
	      struct btrfs_root *root, u32 blocksize)

{

	struct btrfs_block_rsv *block_rsv;

	struct btrfs_block_rsv *global_rsv = &root->fs_info->global_block_rsv;

	int ret;



	block_rsv = get_block_rsv(trans, root);
@@ -5653,14 +5654,39 @@ use_block_rsv(struct btrfs_trans_handle *trans, 
	if (block_rsv->size == 0) {

		ret = reserve_metadata_bytes(trans, root, block_rsv,

					     blocksize, 0);

		if (ret)

		/*

		 * If we couldn't reserve metadata bytes try and use some from

		 * the global reserve.

		 */

		if (ret && block_rsv != global_rsv) {

			ret = block_rsv_use_bytes(global_rsv, blocksize);

			if (!ret)

				return global_rsv;

			return ERR_PTR(ret);

		} else if (ret) {

			return ERR_PTR(ret);

		}

		return block_rsv;

	}



	ret = block_rsv_use_bytes(block_rsv, blocksize);

	if (!ret)

		return block_rsv;

	if (ret) {

		WARN_ON(1);

		ret = reserve_metadata_bytes(trans, root, block_rsv, blocksize,

					     0);

		if (!ret) {

			spin_lock(&block_rsv->lock);

			block_rsv->size += blocksize;

			spin_unlock(&block_rsv->lock);

			return block_rsv;

		} else if (ret && block_rsv != global_rsv) {

			ret = block_rsv_use_bytes(global_rsv, blocksize);

			if (!ret)

				return global_rsv;

		}

	}



	return ERR_PTR(-ENOSPC);

}