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authorKent Overstreet <kmo@daterainc.com>2013-12-17 17:51:02 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-02-06 11:08:16 -0800
commitf4ac67e8e7fa1c9148823da09e913e8e44a8f52b (patch)
treeda490339ef3cee9273a9d1418c4478e8ead0014f /drivers
parent9a8bd082503f4f91176d8fe0b91a23c5b768008e (diff)
bcache: Data corruption fix
commit ef71ec00002d92a08eb27e9d036e3d48835b6597 upstream. The code that handles overlapping extents that we've just read back in from disk was depending on the behaviour of the code that handles overlapping extents as we're inserting into a btree node in the case of an insert that forced an existing extent to be split: on insert, if we had to split we'd also insert a new extent to represent the top part of the old extent - and then that new extent would get written out. The code that read the extents back in thus not bother with splitting extents - if it saw an extent that ovelapped in the middle of an older extent, it would trim the old extent to only represent the bottom part, assuming that the original insert would've inserted a new extent to represent the top part. I still haven't figured out _how_ it can happen, but I'm now pretty convinced (and testing has confirmed) that there's some kind of an obscure corner case (probably involving extent merging, and multiple overwrites in different sets) that breaks this. The fix is to change the mergesort fixup code to split extents itself when required. Signed-off-by: Kent Overstreet <kmo@daterainc.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/md/bcache/bset.c26
1 files changed, 22 insertions, 4 deletions
diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c
index 14032e8c773..1b27cbd822e 100644
--- a/drivers/md/bcache/bset.c
+++ b/drivers/md/bcache/bset.c
@@ -927,7 +927,7 @@ static void sort_key_next(struct btree_iter *iter,
*i = iter->data[--iter->used];
}
-static void btree_sort_fixup(struct btree_iter *iter)
+static struct bkey *btree_sort_fixup(struct btree_iter *iter, struct bkey *tmp)
{
while (iter->used > 1) {
struct btree_iter_set *top = iter->data, *i = top + 1;
@@ -955,9 +955,22 @@ static void btree_sort_fixup(struct btree_iter *iter)
} else {
/* can't happen because of comparison func */
BUG_ON(!bkey_cmp(&START_KEY(top->k), &START_KEY(i->k)));
- bch_cut_back(&START_KEY(i->k), top->k);
+
+ if (bkey_cmp(i->k, top->k) < 0) {
+ bkey_copy(tmp, top->k);
+
+ bch_cut_back(&START_KEY(i->k), tmp);
+ bch_cut_front(i->k, top->k);
+ heap_sift(iter, 0, btree_iter_cmp);
+
+ return tmp;
+ } else {
+ bch_cut_back(&START_KEY(i->k), top->k);
+ }
}
}
+
+ return NULL;
}
static void btree_mergesort(struct btree *b, struct bset *out,
@@ -965,15 +978,20 @@ static void btree_mergesort(struct btree *b, struct bset *out,
bool fixup, bool remove_stale)
{
struct bkey *k, *last = NULL;
+ BKEY_PADDED(k) tmp;
bool (*bad)(struct btree *, const struct bkey *) = remove_stale
? bch_ptr_bad
: bch_ptr_invalid;
while (!btree_iter_end(iter)) {
if (fixup && !b->level)
- btree_sort_fixup(iter);
+ k = btree_sort_fixup(iter, &tmp.k);
+ else
+ k = NULL;
+
+ if (!k)
+ k = bch_btree_iter_next(iter);
- k = bch_btree_iter_next(iter);
if (bad(b, k))
continue;