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Commit b9fab919 authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: avoid sleeping in verify_parent_transid while atomic 



verify_parent_transid needs to lock the extent range to make
sure no IO is underway, and so it can safely clear the
uptodate bits if our checks fail.

But, a few callers are using it with spinlocks held.  Most
of the time, the generation numbers are going to match, and
we don't want to switch to a blocking lock just for the error
case.  This adds an atomic flag to verify_parent_transid,
and changes it to return EAGAIN if it needs to block to
properly verifiy things.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent ea9947b4

fs/btrfs/ctree.c

+17 −9
Original line number Diff line number Diff line
@@ -725,7 +725,7 @@ int btrfs_realloc_node(struct btrfs_trans_handle *trans, 


		cur = btrfs_find_tree_block(root, blocknr, blocksize);

		if (cur)

			uptodate = btrfs_buffer_uptodate(cur, gen);

			uptodate = btrfs_buffer_uptodate(cur, gen, 0);

		else

			uptodate = 0;

		if (!cur || !uptodate) {
@@ -1360,7 +1360,12 @@ static noinline int reada_for_balance(struct btrfs_root *root, 
		block1 = btrfs_node_blockptr(parent, slot - 1);

		gen = btrfs_node_ptr_generation(parent, slot - 1);

		eb = btrfs_find_tree_block(root, block1, blocksize);

		if (eb && btrfs_buffer_uptodate(eb, gen))

		/*

		 * if we get -eagain from btrfs_buffer_uptodate, we

		 * don't want to return eagain here.  That will loop

		 * forever

		 */

		if (eb && btrfs_buffer_uptodate(eb, gen, 1) != 0)

			block1 = 0;

		free_extent_buffer(eb);

	}
@@ -1368,7 +1373,7 @@ static noinline int reada_for_balance(struct btrfs_root *root, 
		block2 = btrfs_node_blockptr(parent, slot + 1);

		gen = btrfs_node_ptr_generation(parent, slot + 1);

		eb = btrfs_find_tree_block(root, block2, blocksize);

		if (eb && btrfs_buffer_uptodate(eb, gen))

		if (eb && btrfs_buffer_uptodate(eb, gen, 1) != 0)

			block2 = 0;

		free_extent_buffer(eb);

	}
@@ -1506,8 +1511,9 @@ read_block_for_search(struct btrfs_trans_handle *trans, 


	tmp = btrfs_find_tree_block(root, blocknr, blocksize);

	if (tmp) {

		if (btrfs_buffer_uptodate(tmp, 0)) {

			if (btrfs_buffer_uptodate(tmp, gen)) {

		/* first we do an atomic uptodate check */

		if (btrfs_buffer_uptodate(tmp, 0, 1) > 0) {

			if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) {

				/*

				 * we found an up to date block without

				 * sleeping, return
@@ -1525,8 +1531,9 @@ read_block_for_search(struct btrfs_trans_handle *trans, 
			free_extent_buffer(tmp);

			btrfs_set_path_blocking(p);



			/* now we're allowed to do a blocking uptodate check */

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

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

			if (tmp && btrfs_buffer_uptodate(tmp, gen, 0) > 0) {

				*eb_ret = tmp;

				return 0;

			}
@@ -1561,7 +1568,7 @@ read_block_for_search(struct btrfs_trans_handle *trans, 
		 * and give up so that our caller doesn't loop forever

		 * on our EAGAINs.

		 */

		if (!btrfs_buffer_uptodate(tmp, 0))

		if (!btrfs_buffer_uptodate(tmp, 0, 0))

			ret = -EIO;

		free_extent_buffer(tmp);

	}
@@ -4045,7 +4052,7 @@ again: 
			tmp = btrfs_find_tree_block(root, blockptr,

					    btrfs_level_size(root, level - 1));



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

			if (tmp && btrfs_buffer_uptodate(tmp, gen, 1) > 0) {

				free_extent_buffer(tmp);

				break;

			}
@@ -4168,7 +4175,8 @@ next: 
				struct extent_buffer *cur;

				cur = btrfs_find_tree_block(root, blockptr,

					    btrfs_level_size(root, level - 1));

				if (!cur || !btrfs_buffer_uptodate(cur, gen)) {

				if (!cur ||

				    btrfs_buffer_uptodate(cur, gen, 1) <= 0) {

					slot++;

					if (cur)

						free_extent_buffer(cur);

fs/btrfs/disk-io.c

+13 −5
Original line number Diff line number Diff line
@@ -323,7 +323,8 @@ static int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf, 
 * in the wrong place.

 */

static int verify_parent_transid(struct extent_io_tree *io_tree,

				 struct extent_buffer *eb, u64 parent_transid)

				 struct extent_buffer *eb, u64 parent_transid,

				 int atomic)

{

	struct extent_state *cached_state = NULL;

	int ret;
@@ -331,6 +332,9 @@ static int verify_parent_transid(struct extent_io_tree *io_tree, 
	if (!parent_transid || btrfs_header_generation(eb) == parent_transid)

		return 0;



	if (atomic)

		return -EAGAIN;



	lock_extent_bits(io_tree, eb->start, eb->start + eb->len - 1,

			 0, &cached_state);

	if (extent_buffer_uptodate(eb) &&
@@ -372,7 +376,8 @@ static int btree_read_extent_buffer_pages(struct btrfs_root *root, 
		ret = read_extent_buffer_pages(io_tree, eb, start,

					       WAIT_COMPLETE,

					       btree_get_extent, mirror_num);

		if (!ret && !verify_parent_transid(io_tree, eb, parent_transid))

		if (!ret && !verify_parent_transid(io_tree, eb,

						   parent_transid, 0))

			break;



		/*
@@ -1202,7 +1207,7 @@ static int __must_check find_and_setup_root(struct btrfs_root *tree_root, 
	root->commit_root = NULL;

	root->node = read_tree_block(root, btrfs_root_bytenr(&root->root_item),

				     blocksize, generation);

	if (!root->node || !btrfs_buffer_uptodate(root->node, generation)) {

	if (!root->node || !btrfs_buffer_uptodate(root->node, generation, 0)) {

		free_extent_buffer(root->node);

		root->node = NULL;

		return -EIO;
@@ -3143,7 +3148,8 @@ int close_ctree(struct btrfs_root *root) 
	return 0;

}



int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid)

int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid,

			  int atomic)

{

	int ret;

	struct inode *btree_inode = buf->pages[0]->mapping->host;
@@ -3153,7 +3159,9 @@ int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid) 
		return ret;



	ret = verify_parent_transid(&BTRFS_I(btree_inode)->io_tree, buf,

				    parent_transid);

				    parent_transid, atomic);

	if (ret == -EAGAIN)

		return ret;

	return !ret;

}

fs/btrfs/disk-io.h

+2 −1
Original line number Diff line number Diff line
@@ -66,7 +66,8 @@ void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr); 
void __btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr);

void btrfs_free_fs_root(struct btrfs_fs_info *fs_info, struct btrfs_root *root);

void btrfs_mark_buffer_dirty(struct extent_buffer *buf);

int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid);

int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid,

			  int atomic);

int btrfs_set_buffer_uptodate(struct extent_buffer *buf);

int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid);

u32 btrfs_csum_data(struct btrfs_root *root, char *data, u32 seed, size_t len);

fs/btrfs/extent-tree.c

+1 −1
Original line number Diff line number Diff line
@@ -6568,7 +6568,7 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans, 
			goto skip;

	}



	if (!btrfs_buffer_uptodate(next, generation)) {

	if (!btrfs_buffer_uptodate(next, generation, 0)) {

		btrfs_tree_unlock(next);

		free_extent_buffer(next);

		next = NULL;

fs/btrfs/tree-log.c

+1 −1
Original line number Diff line number Diff line
@@ -279,7 +279,7 @@ static int process_one_buffer(struct btrfs_root *log, 
						log->fs_info->extent_root,

						eb->start, eb->len);



	if (btrfs_buffer_uptodate(eb, gen)) {

	if (btrfs_buffer_uptodate(eb, gen, 0)) {

		if (wc->write)

			btrfs_write_tree_block(eb);

		if (wc->wait)