Add function qgroup_update_counters(), which will update related
qgroups' rfer/excl according to old/new_roots.
This is one of the two core functions for the new qgroup implement.
This is based on btrfs_adjust_coutners() but with clearer logic and
comment.
Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
fs/btrfs/qgroup.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 120 insertions(+)
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 17a974c..a780f8f 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1761,6 +1761,126 @@ static int qgroup_update_refcnt(struct btrfs_fs_info
*fs_info,
}
/*
+ * Update qgroup rfer/excl counters.
+ * Rfer update is easy, codes can explain themselves.
+ * Excl update is tricky, the update is split into 2 part.
+ * Part 1: Possible exclusive <-> sharing detect:
+ * | A | !A |
+ * -------------------------------------
+ * B | * | - |
+ * -------------------------------------
+ * !B | + | ** |
+ * -------------------------------------
+ *
+ * Conditions:
+ * A: cur_old_roots < nr_old_roots (not exclusive before)
+ * !A: cur_old_roots == nr_old_roots (possible exclusive before)
+ * B: cur_new_roots < nr_new_roots (not exclusive now)
+ * !B: cur_new_roots == nr_new_roots (possible exclsuive now)
+ *
+ * Results:
+ * +: Possible sharing -> exclusive -: Possible exclusive -> sharing
+ * *: Definitely not changed. **: Possible unchanged.
+ *
+ * For !A and !B condition, the exception is cur_old/new_roots == 0 case.
+ *
+ * To make the logic clear, we first use condition A and B to split
+ * combination into 4 results.
+ *
+ * Then, for result "+" and "-", check old/new_roots == 0 case, as in them
+ * only on variant maybe 0.
+ *
+ * Lastly, check result **, since there are 2 variants maybe 0, split them
+ * again(2x2).
+ * But this time we don't need to consider other things, the codes and logic
+ * is easy to understand now.
+ */
+static int qgroup_update_counters(struct btrfs_fs_info *fs_info,
+ struct ulist *qgroups,
+ u64 nr_old_roots,
+ u64 nr_new_roots,
+ u64 num_bytes, u64 seq)
+{
+ struct ulist_node *unode;
+ struct ulist_iterator uiter;
+ struct btrfs_qgroup *qg;
+ u64 cur_new_count, cur_old_count;
+
+ ULIST_ITER_INIT(&uiter);
+ while ((unode = ulist_next(qgroups, &uiter))) {
+ bool dirty = false;
+
+ qg = u64_to_ptr(unode->aux);
+ cur_old_count = btrfs_qgroup_get_old_refcnt(qg, seq);
+ cur_new_count = btrfs_qgroup_get_new_refcnt(qg, seq);
+
+ /* Rfer update part */
+ if (cur_old_count == 0 && cur_new_count > 0) {
+ qg->rfer += num_bytes;
+ qg->rfer_cmpr += num_bytes;
+ dirty = true;
+ }
+ if (cur_old_count > 0 && cur_new_count == 0) {
+ qg->rfer -= num_bytes;
+ qg->rfer_cmpr -= num_bytes;
+ dirty = true;
+ }
+
+ /* Excl update part */
+ /* Exclusive/none -> shared case */
+ if (cur_old_count == nr_old_roots &&
+ cur_new_count < nr_new_roots) {
+ /* Exclusive -> shared */
+ if (cur_old_count != 0) {
+ qg->excl -= num_bytes;
+ qg->excl_cmpr -= num_bytes;
+ dirty = true;
+ }
+ }
+
+ /* Shared -> exclusive/none case */
+ if (cur_old_count < nr_old_roots &&
+ cur_new_count == nr_new_roots) {
+ /* Shared->exclusive */
+ if (cur_new_count != 0) {
+ qg->excl += num_bytes;
+ qg->excl_cmpr += num_bytes;
+ dirty = true;
+ }
+ }
+
+ /* Exclusive/none -> exclusive/none case */
+ if (cur_old_count == nr_old_roots &&
+ cur_new_count == nr_new_roots) {
+ if (cur_old_count == 0) {
+ /* None -> exclusive/none */
+
+ if (cur_new_count != 0) {
+ /* None -> exclusive */
+ qg->excl += num_bytes;
+ qg->excl_cmpr += num_bytes;
+ dirty = true;
+ }
+ /* None -> none, nothing changed */
+ } else {
+ /* Exclusive -> exclusive/none */
+
+ if (cur_new_count == 0) {
+ /* Exclusive -> none */
+ qg->excl -= num_bytes;
+ qg->excl_cmpr -= num_bytes;
+ dirty = true;
+ }
+ /* Exclusive -> exclusive, nothing changed */
+ }
+ }
+ if (dirty)
+ qgroup_dirty(fs_info, qg);
+ }
+ return 0;
+}
+
+/*
* This adjusts the counters for all referenced qgroups if need be.
*/
static int qgroup_adjust_counters(struct btrfs_fs_info *fs_info,
--
2.3.5
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