Commit 95a06077 authored by Jan Schmidt's avatar Jan Schmidt
Browse files

Btrfs: use delayed ref sequence numbers for all fs-tree updates 



The sequence number for delayed refs is needed to postpone certain delayed
refs for a very short period while walking backrefs. Before the tree
modification log, we thought we'd only have to hold back those references
that don't have a counter operation.

While now we've the tree mod log, we're rewinding fs tree blocks to a
defined consistent state. We cannot know in advance for which tree block
we'll be doing rewind operations later. Therefore, we must postpone all the
delayed refs for fs-tree blocks, even those having a counter operation.

Signed-off-by: default avatarJan Schmidt <list.btrfs@jan-o-sch.net>
parent 20b297d6

fs/btrfs/ctree.h

+7 −0
Original line number Diff line number Diff line
@@ -3121,4 +3121,11 @@ void btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info, 
void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,

			    struct seq_list *elem);



static inline int is_fstree(u64 rootid)

{

	if (rootid == BTRFS_FS_TREE_OBJECTID ||

	    (s64)rootid >= (s64)BTRFS_FIRST_FREE_OBJECTID)

		return 1;

	return 0;

}

#endif

fs/btrfs/delayed-ref.c

+6 −4
Original line number Diff line number Diff line
@@ -525,7 +525,7 @@ static noinline void add_delayed_tree_ref(struct btrfs_fs_info *fs_info, 
	ref->is_head = 0;

	ref->in_tree = 1;



	if (need_ref_seq(for_cow, ref_root))

	if (is_fstree(ref_root))

		seq = inc_delayed_seq(delayed_refs);

	ref->seq = seq;
@@ -584,7 +584,7 @@ static noinline void add_delayed_data_ref(struct btrfs_fs_info *fs_info, 
	ref->is_head = 0;

	ref->in_tree = 1;



	if (need_ref_seq(for_cow, ref_root))

	if (is_fstree(ref_root))

		seq = inc_delayed_seq(delayed_refs);

	ref->seq = seq;
@@ -658,10 +658,11 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info, 
	add_delayed_tree_ref(fs_info, trans, &ref->node, bytenr,

				   num_bytes, parent, ref_root, level, action,

				   for_cow);

	if (!need_ref_seq(for_cow, ref_root) &&

	if (!is_fstree(ref_root) &&

	    waitqueue_active(&delayed_refs->seq_wait))

		wake_up(&delayed_refs->seq_wait);

	spin_unlock(&delayed_refs->lock);



	return 0;

}
@@ -706,10 +707,11 @@ int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info, 
	add_delayed_data_ref(fs_info, trans, &ref->node, bytenr,

				   num_bytes, parent, ref_root, owner, offset,

				   action, for_cow);

	if (!need_ref_seq(for_cow, ref_root) &&

	if (!is_fstree(ref_root) &&

	    waitqueue_active(&delayed_refs->seq_wait))

		wake_up(&delayed_refs->seq_wait);

	spin_unlock(&delayed_refs->lock);



	return 0;

}

fs/btrfs/delayed-ref.h

+0 −19
Original line number Diff line number Diff line
@@ -224,25 +224,6 @@ btrfs_put_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs, 
int btrfs_check_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs,

			    u64 seq);



/*

 * delayed refs with a ref_seq > 0 must be held back during backref walking.

 * this only applies to items in one of the fs-trees. for_cow items never need

 * to be held back, so they won't get a ref_seq number.

 */

static inline int need_ref_seq(int for_cow, u64 rootid)

{

	if (for_cow)

		return 0;



	if (rootid == BTRFS_FS_TREE_OBJECTID)

		return 1;



	if ((s64)rootid >= (s64)BTRFS_FIRST_FREE_OBJECTID)

		return 1;



	return 0;

}



/*

 * a node might live in a head or a regular ref, this lets you

 * test for the proper type to use.

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