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Commit 94fcca9f authored by Yan, Zheng's avatar Yan, Zheng Committed by Chris Mason
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Btrfs: optimize back reference update during btrfs_drop_snapshot 

This patch reading level 0 tree blocks that already use full backrefs.
Signed-off-by: default avatarYan Zheng <zheng.yan@oracle.com>
Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent efefb143
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Showing with 53 additions and 29 deletions
fs/btrfs/extent-tree.c
View file @ 94fcca9f
......@@ -4911,6 +4911,7 @@ static noinline void reada_walk_down(struct btrfs_trans_handle *trans,
u64 bytenr;
u64 generation;
u64 refs;
u64 flags;
u64 last = 0;
u32 nritems;
u32 blocksize;
......@@ -4948,15 +4949,19 @@ static noinline void reada_walk_down(struct btrfs_trans_handle *trans,
generation <= root->root_key.offset)
continue;
/* We don't lock the tree block, it's OK to be racy here */
ret = btrfs_lookup_extent_info(trans, root, bytenr, blocksize,
&refs, &flags);
BUG_ON(ret);
BUG_ON(refs == 0);
if (wc->stage == DROP_REFERENCE) {
ret = btrfs_lookup_extent_info(trans, root,
bytenr, blocksize,
&refs, NULL);
BUG_ON(ret);
BUG_ON(refs == 0);
if (refs == 1)
goto reada;
if (wc->level == 1 &&
(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
continue;
if (!wc->update_ref ||
generation <= root->root_key.offset)
continue;
......@@ -4965,6 +4970,10 @@ static noinline void reada_walk_down(struct btrfs_trans_handle *trans,
&wc->update_progress);
if (ret < 0)
continue;
} else {
if (wc->level == 1 &&
(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
continue;
}
reada:
ret = readahead_tree_block(root, bytenr, blocksize,
......@@ -4988,7 +4997,7 @@ reada:
static noinline int walk_down_proc(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct btrfs_path *path,
struct walk_control *wc)
struct walk_control *wc, int lookup_info)
{
int level = wc->level;
struct extent_buffer *eb = path->nodes[level];
......@@ -5003,8 +5012,9 @@ static noinline int walk_down_proc(struct btrfs_trans_handle *trans,
* when reference count of tree block is 1, it won't increase
* again. once full backref flag is set, we never clear it.
*/
if ((wc->stage == DROP_REFERENCE && wc->refs[level] != 1) ||
(wc->stage == UPDATE_BACKREF && !(wc->flags[level] & flag))) {
if (lookup_info &&
((wc->stage == DROP_REFERENCE && wc->refs[level] != 1) ||
(wc->stage == UPDATE_BACKREF && !(wc->flags[level] & flag)))) {
BUG_ON(!path->locks[level]);
ret = btrfs_lookup_extent_info(trans, root,
eb->start, eb->len,
......@@ -5065,7 +5075,7 @@ static noinline int walk_down_proc(struct btrfs_trans_handle *trans,
static noinline int do_walk_down(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct btrfs_path *path,
struct walk_control *wc)
struct walk_control *wc, int *lookup_info)
{
u64 bytenr;
u64 generation;
......@@ -5085,8 +5095,10 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
* for the subtree
*/
if (wc->stage == UPDATE_BACKREF &&
generation <= root->root_key.offset)
generation <= root->root_key.offset) {
*lookup_info = 1;
return 1;
}
bytenr = btrfs_node_blockptr(path->nodes[level], path->slots[level]);
blocksize = btrfs_level_size(root, level - 1);
......@@ -5099,14 +5111,19 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
btrfs_tree_lock(next);
btrfs_set_lock_blocking(next);
if (wc->stage == DROP_REFERENCE) {
ret = btrfs_lookup_extent_info(trans, root, bytenr, blocksize,
&wc->refs[level - 1],
&wc->flags[level - 1]);
BUG_ON(ret);
BUG_ON(wc->refs[level - 1] == 0);
ret = btrfs_lookup_extent_info(trans, root, bytenr, blocksize,
&wc->refs[level - 1],
&wc->flags[level - 1]);
BUG_ON(ret);
BUG_ON(wc->refs[level - 1] == 0);
*lookup_info = 0;
if (wc->stage == DROP_REFERENCE) {
if (wc->refs[level - 1] > 1) {
if (level == 1 &&
(wc->flags[0] & BTRFS_BLOCK_FLAG_FULL_BACKREF))
goto skip;
if (!wc->update_ref ||
generation <= root->root_key.offset)
goto skip;
......@@ -5120,12 +5137,17 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
wc->stage = UPDATE_BACKREF;
wc->shared_level = level - 1;
}
} else {
if (level == 1 &&
(wc->flags[0] & BTRFS_BLOCK_FLAG_FULL_BACKREF))
goto skip;
}
if (!btrfs_buffer_uptodate(next, generation)) {
btrfs_tree_unlock(next);
free_extent_buffer(next);
next = NULL;
*lookup_info = 1;
}
if (!next) {
......@@ -5148,21 +5170,22 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
skip:
wc->refs[level - 1] = 0;
wc->flags[level - 1] = 0;
if (wc->stage == DROP_REFERENCE) {
if (wc->flags[level] & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
parent = path->nodes[level]->start;
} else {
BUG_ON(root->root_key.objectid !=
btrfs_header_owner(path->nodes[level]));
parent = 0;
}
if (wc->flags[level] & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
parent = path->nodes[level]->start;
} else {
BUG_ON(root->root_key.objectid !=
btrfs_header_owner(path->nodes[level]));
parent = 0;
ret = btrfs_free_extent(trans, root, bytenr, blocksize, parent,
root->root_key.objectid, level - 1, 0);
BUG_ON(ret);
}
ret = btrfs_free_extent(trans, root, bytenr, blocksize, parent,
root->root_key.objectid, level - 1, 0);
BUG_ON(ret);
btrfs_tree_unlock(next);
free_extent_buffer(next);
*lookup_info = 1;
return 1;
}
......@@ -5276,6 +5299,7 @@ static noinline int walk_down_tree(struct btrfs_trans_handle *trans,
struct walk_control *wc)
{
int level = wc->level;
int lookup_info = 1;
int ret;
while (level >= 0) {
......@@ -5283,14 +5307,14 @@ static noinline int walk_down_tree(struct btrfs_trans_handle *trans,
btrfs_header_nritems(path->nodes[level]))
break;
ret = walk_down_proc(trans, root, path, wc);
ret = walk_down_proc(trans, root, path, wc, lookup_info);
if (ret > 0)
break;
if (level == 0)
break;
ret = do_walk_down(trans, root, path, wc);
ret = do_walk_down(trans, root, path, wc, &lookup_info);
if (ret > 0) {
path->slots[level]++;
continue;
......
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