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| author | Hou Tao <houtao1@huawei.com> | 2019-12-03 14:42:58 +0300 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2019-12-05 23:27:52 +0300 |
| commit | 474e559567fa631dea8fb8407ab1b6090c903755 (patch) | |
| tree | c63e8ab7002b64e30b1895bd67e3164f1bb5ec20 /drivers/md | |
| parent | 484e0d2b11e1fdd0d17702b282eb2ed56148385f (diff) | |
| download | linux-474e559567fa631dea8fb8407ab1b6090c903755.tar.xz | |
dm btree: increase rebalance threshold in __rebalance2()
We got the following warnings from thin_check during thin-pool setup:
$ thin_check /dev/vdb
examining superblock
examining devices tree
missing devices: [1, 84]
too few entries in btree_node: 41, expected at least 42 (block 138, max_entries = 126)
examining mapping tree
The phenomenon is the number of entries in one node of details_info tree is
less than (max_entries / 3). And it can be easily reproduced by the following
procedures:
$ new a thin pool
$ presume the max entries of details_info tree is 126
$ new 127 thin devices (e.g. 1~127) to make the root node being full
and then split
$ remove the first 43 (e.g. 1~43) thin devices to make the children
reblance repeatedly
$ stop the thin pool
$ thin_check
The root cause is that the B-tree removal procedure in __rebalance2()
doesn't guarantee the invariance: the minimal number of entries in
non-root node should be >= (max_entries / 3).
Simply fix the problem by increasing the rebalance threshold to
make sure the number of entries in each child will be greater
than or equal to (max_entries / 3 + 1), so no matter which
child is used for removal, the number will still be valid.
Cc: stable@vger.kernel.org
Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/persistent-data/dm-btree-remove.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/md/persistent-data/dm-btree-remove.c b/drivers/md/persistent-data/dm-btree-remove.c index 21ea537bd55e..eff04fa23dfa 100644 --- a/drivers/md/persistent-data/dm-btree-remove.c +++ b/drivers/md/persistent-data/dm-btree-remove.c @@ -203,7 +203,13 @@ static void __rebalance2(struct dm_btree_info *info, struct btree_node *parent, struct btree_node *right = r->n; uint32_t nr_left = le32_to_cpu(left->header.nr_entries); uint32_t nr_right = le32_to_cpu(right->header.nr_entries); - unsigned threshold = 2 * merge_threshold(left) + 1; + /* + * Ensure the number of entries in each child will be greater + * than or equal to (max_entries / 3 + 1), so no matter which + * child is used for removal, the number will still be not + * less than (max_entries / 3). + */ + unsigned int threshold = 2 * (merge_threshold(left) + 1); if (nr_left + nr_right < threshold) { /* |