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author | Qu Wenruo <quwenruo@cn.fujitsu.com> | 2015-04-12 16:59:57 +0800 |
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committer | Chris Mason <clm@fb.com> | 2015-06-10 09:25:28 -0700 |
commit | 823ae5b8e340003dacbe7cd08a355efe018c9f1b (patch) | |
tree | efc852b58959ab5f163078708a14064e0c8cbbd2 /fs/btrfs/qgroup.c | |
parent | d810ef2be5b8b15c9b6f88f9a09b1b4b16e30871 (diff) | |
download | linux-823ae5b8e340003dacbe7cd08a355efe018c9f1b.tar.bz2 |
btrfs: qgroup: Add function qgroup_update_counters().
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 <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
Diffstat (limited to 'fs/btrfs/qgroup.c')
-rw-r--r-- | fs/btrfs/qgroup.c | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index 81773176d01f..2f185eee2387 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1865,6 +1865,126 @@ 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, |