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bcache: fix fifo index swapping condition in journal_pin_cmp() 

Fifo structure journal.pin is implemented by a cycle buffer, if the back
index reaches highest location of the cycle buffer, it will be swapped
to 0. Once the swapping happens, it means a smaller fifo index might be
associated to a newer journal entry. So the btree node with oldest
journal entry won't be selected in bch_btree_leaf_dirty() to reference
the dirty B+tree leaf node. This problem may cause bcache journal won't
protect unflushed oldest B+tree dirty leaf node in power failure, and
this B+tree leaf node is possible to beinconsistent after reboot from
power failure.

This patch fixes the fifo index comparing logic in journal_pin_cmp(),
to avoid potential corrupted B+tree leaf node when the back index of
journal pin is swapped.

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Coly Li 2019-11-13 16:03:15 +08:00 committed by Jens Axboe
parent e2a7b9f4a1
commit c0e0954e90
2 changed files with 26 additions and 4 deletions
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26
drivers/md/bcache/btree.c
View File

@ -528,6 +528,32 @@ static void btree_node_write_work(struct work_struct *w)
mutex_unlock(&b->write_lock);
}
/* return true if journal pin 'l' is newer than 'r' */
static bool journal_pin_cmp(struct cache_set *c,
atomic_t *l,
atomic_t *r)
{
int l_idx, r_idx, f_idx, b_idx;
bool ret = false;
l_idx = fifo_idx(&(c)->journal.pin, (l));
r_idx = fifo_idx(&(c)->journal.pin, (r));
f_idx = (c)->journal.pin.front;
b_idx = (c)->journal.pin.back;
if (l_idx > r_idx)
ret = true;
/* in case fifo back pointer is swapped */
if (b_idx < f_idx) {
if (l_idx <= b_idx && r_idx >= f_idx)
ret = true;
else if (l_idx >= f_idx && r_idx <= b_idx)
ret = false;
}
return ret;
}
static void bch_btree_leaf_dirty(struct btree *b, atomic_t *journal_ref)
{
struct bset *i = btree_bset_last(b);

4
drivers/md/bcache/journal.h
View File

@ -157,10 +157,6 @@ struct journal_device {
};
#define BTREE_FLUSH_NR 8
#define journal_pin_cmp(c, l, r) \
(fifo_idx(&(c)->journal.pin, (l)) > fifo_idx(&(c)->journal.pin, (r)))
#define JOURNAL_PIN 20000
#define journal_full(j) \