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Commit bb739cf0 authored by Edmund Nadolski's avatar Edmund Nadolski Committed by David Sterba
Browse files

btrfs: btrfs_check_shared should manage its own transaction 



Commit afce772e ("btrfs: fix check_shared for fiemap ioctl") added
transaction semantics around calls to btrfs_check_shared() in order to
provide accurate accounting of delayed refs. The transaction management
should be done inside btrfs_check_shared(), so that callers do not need
to manage transactions individually.

Signed-off-by: default avatarEdmund Nadolski <enadolski@suse.com>
Signed-off-by: default avatarJeff Mahoney <jeffm@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent e0c476b1

fs/btrfs/backref.c

+19 −11
Original line number Diff line number Diff line
@@ -1580,20 +1580,21 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans, 
/**

 * btrfs_check_shared - tell us whether an extent is shared

 *

 * @trans: optional trans handle

 *

 * btrfs_check_shared uses the backref walking code but will short

 * circuit as soon as it finds a root or inode that doesn't match the

 * one passed in. This provides a significant performance benefit for

 * callers (such as fiemap) which want to know whether the extent is

 * shared but do not need a ref count.

 *

 * This attempts to allocate a transaction in order to account for

 * delayed refs, but continues on even when the alloc fails.

 *

 * Return: 0 if extent is not shared, 1 if it is shared, < 0 on error.

 */

int btrfs_check_shared(struct btrfs_trans_handle *trans,

		       struct btrfs_fs_info *fs_info, u64 root_objectid,

		       u64 inum, u64 bytenr)

int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr)

{

	struct btrfs_fs_info *fs_info = root->fs_info;

	struct btrfs_trans_handle *trans;

	struct ulist *tmp = NULL;

	struct ulist *roots = NULL;

	struct ulist_iterator uiter;
@@ -1609,14 +1610,18 @@ int btrfs_check_shared(struct btrfs_trans_handle *trans, 
		return -ENOMEM;

	}



	if (trans)

		btrfs_get_tree_mod_seq(fs_info, &elem);

	else

	trans = btrfs_join_transaction(root);

	if (IS_ERR(trans)) {

		trans = NULL;

		down_read(&fs_info->commit_root_sem);

	} else {

		btrfs_get_tree_mod_seq(fs_info, &elem);

	}



	ULIST_ITER_INIT(&uiter);

	while (1) {

		ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,

					roots, NULL, root_objectid, inum, 1);

					roots, NULL, root->objectid, inum, 1);

		if (ret == BACKREF_FOUND_SHARED) {

			/* this is the only condition under which we return 1 */

			ret = 1;
@@ -1631,10 +1636,13 @@ int btrfs_check_shared(struct btrfs_trans_handle *trans, 
		bytenr = node->val;

		cond_resched();

	}

	if (trans)



	if (trans) {

		btrfs_put_tree_mod_seq(fs_info, &elem);

	else

		btrfs_end_transaction(trans);

	} else {

		up_read(&fs_info->commit_root_sem);

	}

	ulist_free(tmp);

	ulist_free(roots);

	return ret;

fs/btrfs/backref.h

+1 −3
Original line number Diff line number Diff line
@@ -68,9 +68,7 @@ int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid, 
			  u64 start_off, struct btrfs_path *path,

			  struct btrfs_inode_extref **ret_extref,

			  u64 *found_off);

int btrfs_check_shared(struct btrfs_trans_handle *trans,

		       struct btrfs_fs_info *fs_info, u64 root_objectid,

		       u64 inum, u64 bytenr);

int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr);



int __init btrfs_prelim_ref_init(void);

void btrfs_prelim_ref_exit(void);

fs/btrfs/extent_io.c

+3 −19
Original line number Diff line number Diff line
@@ -20,7 +20,6 @@ 
#include "locking.h"

#include "rcu-string.h"

#include "backref.h"

#include "transaction.h"



static struct kmem_cache *extent_state_cache;

static struct kmem_cache *extent_buffer_cache;
@@ -4606,24 +4605,11 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, 
			flags |= (FIEMAP_EXTENT_DELALLOC |

				  FIEMAP_EXTENT_UNKNOWN);

		} else if (fieinfo->fi_extents_max) {

			struct btrfs_trans_handle *trans;



			u64 bytenr = em->block_start -

				(em->start - em->orig_start);



			disko = em->block_start + offset_in_extent;



			/*

			 * We need a trans handle to get delayed refs

			 */

			trans = btrfs_join_transaction(root);

			/*

			 * It's OK if we can't start a trans we can still check

			 * from commit_root

			 */

			if (IS_ERR(trans))

				trans = NULL;



			/*

			 * As btrfs supports shared space, this information

			 * can be exported to userspace tools via
@@ -4631,11 +4617,9 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, 
			 * then we're just getting a count and we can skip the

			 * lookup stuff.

			 */

			ret = btrfs_check_shared(trans, root->fs_info,

					root->objectid,

					btrfs_ino(BTRFS_I(inode)), bytenr);

			if (trans)

				btrfs_end_transaction(trans);

			ret = btrfs_check_shared(root,

						 btrfs_ino(BTRFS_I(inode)),

						 bytenr);

			if (ret < 0)

				goto out_free;

			if (ret)