Commit 3eb42344 authored by Filipe Manana's avatar Filipe Manana Committed by David Sterba
Browse files

btrfs: remove outdated logic from overwrite_item() and add assertion 



As of commit 193df624 ("btrfs: search for last logged dir index if
it's not cached in the inode"), the overwrite_item() function is always
called for a root that is from a fs/subvolume tree. In other words, now
it's only used during log replay to modify a fs/subvolume tree. Therefore
we can remove the logic that checks if we are dealing with a log tree at
overwrite_item().

So remove that logic, replacing it with an assertion and document that if
we ever need to support a log root there, we will need to clone the leaf
from the fs/subvolume tree and then release it before modifying the log
tree, which is needed to avoid a potential deadlock, similar to the one
recently fixed by a patch with the subject:

  "btrfs: do not modify log tree while holding a leaf from fs tree locked"

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 3a8d1db3

fs/btrfs/tree-log.c

+9 −5
Original line number Diff line number Diff line
@@ -391,11 +391,16 @@ static int overwrite_item(struct btrfs_trans_handle *trans, 
	int save_old_i_size = 0;

	unsigned long src_ptr;

	unsigned long dst_ptr;

	int overwrite_root = 0;

	bool inode_item = key->type == BTRFS_INODE_ITEM_KEY;



	if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)

		overwrite_root = 1;

	/*

	 * This is only used during log replay, so the root is always from a

	 * fs/subvolume tree. In case we ever need to support a log root, then

	 * we'll have to clone the leaf in the path, release the path and use

	 * the leaf before writing into the log tree. See the comments at

	 * copy_items() for more details.

	 */

	ASSERT(root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID);



	item_size = btrfs_item_size(eb, slot);

	src_ptr = btrfs_item_ptr_offset(eb, slot);
@@ -548,8 +553,7 @@ static int overwrite_item(struct btrfs_trans_handle *trans, 
			goto no_copy;

		}



		if (overwrite_root &&

		    S_ISDIR(btrfs_inode_mode(eb, src_item)) &&

		if (S_ISDIR(btrfs_inode_mode(eb, src_item)) &&

		    S_ISDIR(btrfs_inode_mode(path->nodes[0], dst_item))) {

			save_old_i_size = 1;

			saved_i_size = btrfs_inode_size(path->nodes[0],