Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 7777a8ba authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Philipp Reisner
Browse files

drbd: bitmap: don't count unused bits (fix non-terminating resync) 



We trusted the on-disk bitmap to have unused bits cleared.
In case that is not true for whatever reason,
and we take a code path where the unused bits don't get cleared
elsewhere (bm_clear_surplus is not called), we may miscount the bits,
and get confused during resync, waiting for bits to get cleared that we
don't even use: the resync process would not terminate.

Fix this by masking out unused bits in __bm_count_bits.

Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent 1b881ef7

drivers/block/drbd/drbd_bitmap.c

+22 −3
Original line number Diff line number Diff line
@@ -376,9 +376,16 @@ static unsigned long __bm_count_bits(struct drbd_bitmap *b, const int swap_endia 
	unsigned long *p_addr, *bm, offset = 0;

	unsigned long bits = 0;

	unsigned long i, do_now;

	unsigned long words;



	while (offset < b->bm_words) {

		i = do_now = min_t(size_t, b->bm_words-offset, LWPP);

	/* due to 64bit alignment, the last long on a 32bit arch

	 * may be not used at all. The last used long will likely

	 * be only partially used, always. Don't count those bits,

	 * but mask them out. */

	words = (b->bm_bits + BITS_PER_LONG - 1) >> LN2_BPL;



	while (offset < words) {

		i = do_now = min_t(size_t, words-offset, LWPP);

		p_addr = __bm_map_paddr(b, offset, KM_USER0);

		bm = p_addr + MLPP(offset);

		while (i--) {
@@ -388,8 +395,20 @@ static unsigned long __bm_count_bits(struct drbd_bitmap *b, const int swap_endia 
#endif

			bits += hweight_long(*bm++);

		}

		__bm_unmap(p_addr, KM_USER0);

		offset += do_now;

		if (offset == words) {

			/* last word may only be partially used,

			 * see also bm_clear_surplus. */

			i = (1UL << (b->bm_bits & (BITS_PER_LONG-1))) -1;

			if (i) {

				bits -= hweight_long(p_addr[do_now-1] & ~i);

				p_addr[do_now-1] &= i;

			}

			/* 32bit arch, may have an unused padding long */

			if (words != b->bm_words)

				p_addr[do_now] = 0;

		}

		__bm_unmap(p_addr, KM_USER0);

		cond_resched();

	}