Btrfs: use the global block reserve if we cannot reserve space (68a82277) · Commits · 戴 / test

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:

Josef Bacik <josef@redhat.com> Signed-off-by:

Chris Mason <chris.mason@oracle.com>

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);
		}

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