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Commit 76a05b35 authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: Don't loop forever on metadata IO failures 



When a btrfs metadata read fails, the first thing we try to do is find
a good copy on another mirror of the block.  If this fails, read_tree_block()
ends up returning a buffer that isn't up to date.

The btrfs btree reading code was reworked to drop locks and repeat
the search when IO was done, but the changes didn't add a check for failed
reads.  The end result was looping forever on buffers that were never
going to become up to date.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 2757495c

fs/btrfs/ctree.c

+36 −3
Original line number Diff line number Diff line
@@ -1469,6 +1469,7 @@ read_block_for_search(struct btrfs_trans_handle *trans, 
	u32 blocksize;

	struct extent_buffer *b = *eb_ret;

	struct extent_buffer *tmp;

	int ret;



	blocknr = btrfs_node_blockptr(b, slot);

	gen = btrfs_node_ptr_generation(b, slot);
@@ -1476,6 +1477,10 @@ read_block_for_search(struct btrfs_trans_handle *trans, 


	tmp = btrfs_find_tree_block(root, blocknr, blocksize);

	if (tmp && btrfs_buffer_uptodate(tmp, gen)) {

		/*

		 * we found an up to date block without sleeping, return

		 * right away

		 */

		*eb_ret = tmp;

		return 0;

	}
@@ -1483,7 +1488,9 @@ read_block_for_search(struct btrfs_trans_handle *trans, 
	/*

	 * reduce lock contention at high levels

	 * of the btree by dropping locks before

	 * we read.

	 * we read.  Don't release the lock on the current

	 * level because we need to walk this node to figure

	 * out which blocks to read.

	 */

	btrfs_unlock_up_safe(p, level + 1);

	btrfs_set_path_blocking(p);
@@ -1494,10 +1501,21 @@ read_block_for_search(struct btrfs_trans_handle *trans, 
		reada_for_search(root, p, level, slot, key->objectid);



	btrfs_release_path(NULL, p);



	ret = -EAGAIN;

	tmp = read_tree_block(root, blocknr, blocksize, gen);

	if (tmp)

	if (tmp) {

		/*

		 * If the read above didn't mark this buffer up to date,

		 * it will never end up being up to date.  Set ret to EIO now

		 * and give up so that our caller doesn't loop forever

		 * on our EAGAINs.

		 */

		if (!btrfs_buffer_uptodate(tmp, 0))

			ret = -EIO;

		free_extent_buffer(tmp);

	return -EAGAIN;

	}

	return ret;

}



/*
@@ -1696,6 +1714,9 @@ cow_done: 
			if (ret == -EAGAIN)

				goto again;



			if (ret == -EIO)

				goto done;



			if (!p->skip_locking) {

				int lret;
@@ -1738,6 +1759,8 @@ done: 
	 */

	if (!p->leave_spinning)

		btrfs_set_path_blocking(p);

	if (ret < 0)

		btrfs_release_path(root, p);

	return ret;

}
@@ -4212,6 +4235,11 @@ again: 
		if (ret == -EAGAIN)

			goto again;



		if (ret < 0) {

			btrfs_release_path(root, path);

			goto done;

		}



		if (!path->skip_locking) {

			ret = btrfs_try_spin_lock(next);

			if (!ret) {
@@ -4246,6 +4274,11 @@ again: 
		if (ret == -EAGAIN)

			goto again;



		if (ret < 0) {

			btrfs_release_path(root, path);

			goto done;

		}



		if (!path->skip_locking) {

			btrfs_assert_tree_locked(path->nodes[level]);

			ret = btrfs_try_spin_lock(next);