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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: Jan Schmidt <list.btrfs@jan-o-sch.net>
This commit is contained in:
Jan Schmidt 2012-05-29 17:06:54 +02:00
parent 20b297d620
commit 95a06077f7
3 changed files with 13 additions and 23 deletions
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7
fs/btrfs/ctree.h
View File

@ -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

10
fs/btrfs/delayed-ref.c
View File

@ -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;
}

19
fs/btrfs/delayed-ref.h
View File

@ -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.