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| author | Lars Ellenberg <lars.ellenberg@linbit.com> | 2010-12-15 23:21:39 +0100 |
|---|---|---|
| committer | Philipp Reisner <philipp.reisner@linbit.com> | 2011-03-10 11:36:38 +0100 |
| commit | 7777a8ba1fc980e5edfe492ebf5a1676497b8db2 (patch) | |
| tree | 9eb81d2bee5bf63a796ae4df0b9cf352b3f0360b /drivers/block/drbd | |
| parent | 1b881ef77537f1077482f9946a6a99b4e2dd54b2 (diff) | |
| download | linux-next-7777a8ba1fc980e5edfe492ebf5a1676497b8db2.tar.gz | |
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: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Diffstat (limited to 'drivers/block/drbd')
| -rw-r--r-- | drivers/block/drbd/drbd_bitmap.c | 25 |
1 files changed, 22 insertions, 3 deletions
diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c index 9390e9526786..c5361487cf47 100644 --- a/drivers/block/drbd/drbd_bitmap.c +++ b/drivers/block/drbd/drbd_bitmap.c @@ -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(); } |