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Commit 46a53cca authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: look for acls during btrfs_read_locked_inode 



This changes btrfs_read_locked_inode() to peek ahead in the btree for acl items.
If it is certain a given inode has no acls, it will set the in memory acl
fields to null to avoid acl lookups completely.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 7b1a14bb

fs/btrfs/inode.c

+62 −0
Original line number Diff line number Diff line
@@ -2015,6 +2015,57 @@ void btrfs_orphan_cleanup(struct btrfs_root *root) 
	btrfs_free_path(path);

}



/*

 * very simple check to peek ahead in the leaf looking for xattrs.  If we

 * don't find any xattrs, we know there can't be any acls.

 *

 * slot is the slot the inode is in, objectid is the objectid of the inode

 */

static noinline int acls_after_inode_item(struct extent_buffer *leaf,

					  int slot, u64 objectid)

{

	u32 nritems = btrfs_header_nritems(leaf);

	struct btrfs_key found_key;

	int scanned = 0;



	slot++;

	while (slot < nritems) {

		btrfs_item_key_to_cpu(leaf, &found_key, slot);



		/* we found a different objectid, there must not be acls */

		if (found_key.objectid != objectid)

			return 0;



		/* we found an xattr, assume we've got an acl */

		if (found_key.type == BTRFS_XATTR_ITEM_KEY)

			return 1;



		/*

		 * we found a key greater than an xattr key, there can't

		 * be any acls later on

		 */

		if (found_key.type > BTRFS_XATTR_ITEM_KEY)

			return 0;



		slot++;

		scanned++;



		/*

		 * it goes inode, inode backrefs, xattrs, extents,

		 * so if there are a ton of hard links to an inode there can

		 * be a lot of backrefs.  Don't waste time searching too hard,

		 * this is just an optimization

		 */

		if (scanned >= 8)

			break;

	}

	/* we hit the end of the leaf before we found an xattr or

	 * something larger than an xattr.  We have to assume the inode

	 * has acls

	 */

	return 1;

}



/*

 * read an inode from the btree into the in-memory inode

 */
@@ -2026,6 +2077,7 @@ void btrfs_read_locked_inode(struct inode *inode) 
	struct btrfs_timespec *tspec;

	struct btrfs_root *root = BTRFS_I(inode)->root;

	struct btrfs_key location;

	int maybe_acls;

	u64 alloc_group_block;

	u32 rdev;

	int ret;
@@ -2072,6 +2124,16 @@ void btrfs_read_locked_inode(struct inode *inode) 


	alloc_group_block = btrfs_inode_block_group(leaf, inode_item);



	/*

	 * try to precache a NULL acl entry for files that don't have

	 * any xattrs or acls

	 */

	maybe_acls = acls_after_inode_item(leaf, path->slots[0], inode->i_ino);

	if (!maybe_acls) {

		BTRFS_I(inode)->i_acl = NULL;

		BTRFS_I(inode)->i_default_acl = NULL;

	}



	BTRFS_I(inode)->block_group = btrfs_find_block_group(root, 0,

						alloc_group_block, 0);

	btrfs_free_path(path);