bcache: fix fifo index swapping condition in journal_pin_cmp() (c0e0954e) · Commits · 戴 / test

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>

drivers/md/bcache/btree.c

+26 −0

Original line number	Diff line number	Diff line
		@@ -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);

drivers/md/bcache/journal.h

+0 −4

Original line number	Diff line number	Diff line
		@@ -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) \

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