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author | Lars Ellenberg <lars.ellenberg@linbit.com> | 2010-12-14 15:13:04 +0100 |
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committer | Philipp Reisner <philipp.reisner@linbit.com> | 2011-03-10 11:43:24 +0100 |
commit | 4b0715f09655e76ca24c35a9e25e7c464c2f7346 (patch) | |
tree | e98706a35b1e18cad09f01d2346d9a1c938c081c /drivers/block/drbd/drbd_bitmap.c | |
parent | 19f843aa08e2d8f87a09b4c2edc43b00638423a8 (diff) | |
download | kernel_samsung_crespo-4b0715f09655e76ca24c35a9e25e7c464c2f7346.zip kernel_samsung_crespo-4b0715f09655e76ca24c35a9e25e7c464c2f7346.tar.gz kernel_samsung_crespo-4b0715f09655e76ca24c35a9e25e7c464c2f7346.tar.bz2 |
drbd: allow petabyte storage on 64bit arch
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Diffstat (limited to 'drivers/block/drbd/drbd_bitmap.c')
-rw-r--r-- | drivers/block/drbd/drbd_bitmap.c | 170 |
1 files changed, 106 insertions, 64 deletions
diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c index 72cd41a..0e31e57 100644 --- a/drivers/block/drbd/drbd_bitmap.c +++ b/drivers/block/drbd/drbd_bitmap.c @@ -37,10 +37,46 @@ * convention: * function name drbd_bm_... => used elsewhere, "public". * function name bm_... => internal to implementation, "private". + */ + - * Note that since find_first_bit returns int, at the current granularity of - * the bitmap (4KB per byte), this implementation "only" supports up to - * 1<<(32+12) == 16 TB... +/* + * LIMITATIONS: + * We want to support >= peta byte of backend storage, while for now still using + * a granularity of one bit per 4KiB of storage. + * 1 << 50 bytes backend storage (1 PiB) + * 1 << (50 - 12) bits needed + * 38 --> we need u64 to index and count bits + * 1 << (38 - 3) bitmap bytes needed + * 35 --> we still need u64 to index and count bytes + * (that's 32 GiB of bitmap for 1 PiB storage) + * 1 << (35 - 2) 32bit longs needed + * 33 --> we'd even need u64 to index and count 32bit long words. + * 1 << (35 - 3) 64bit longs needed + * 32 --> we could get away with a 32bit unsigned int to index and count + * 64bit long words, but I rather stay with unsigned long for now. + * We probably should neither count nor point to bytes or long words + * directly, but either by bitnumber, or by page index and offset. + * 1 << (35 - 12) + * 22 --> we need that much 4KiB pages of bitmap. + * 1 << (22 + 3) --> on a 64bit arch, + * we need 32 MiB to store the array of page pointers. + * + * Because I'm lazy, and because the resulting patch was too large, too ugly + * and still incomplete, on 32bit we still "only" support 16 TiB (minus some), + * (1 << 32) bits * 4k storage. + * + + * bitmap storage and IO: + * Bitmap is stored little endian on disk, and is kept little endian in + * core memory. Currently we still hold the full bitmap in core as long + * as we are "attached" to a local disk, which at 32 GiB for 1PiB storage + * seems excessive. + * + * We plan to reduce the amount of in-core bitmap pages by pageing them in + * and out against their on-disk location as necessary, but need to make + * sure we don't cause too much meta data IO, and must not deadlock in + * tight memory situations. This needs some more work. */ /* @@ -56,13 +92,9 @@ struct drbd_bitmap { struct page **bm_pages; spinlock_t bm_lock; - /* WARNING unsigned long bm_*: - * 32bit number of bit offset is just enough for 512 MB bitmap. - * it will blow up if we make the bitmap bigger... - * not that it makes much sense to have a bitmap that large, - * rather change the granularity to 16k or 64k or something. - * (that implies other problems, however...) - */ + + /* see LIMITATIONS: above */ + unsigned long bm_set; /* nr of set bits; THINK maybe atomic_t? */ unsigned long bm_bits; size_t bm_words; @@ -517,43 +549,39 @@ static void bm_set_surplus(struct drbd_bitmap *b) bm_unmap(p_addr); } +/* you better not modify the bitmap while this is running, + * or its results will be stale */ static unsigned long bm_count_bits(struct drbd_bitmap *b) { - unsigned long *p_addr, *bm, offset = 0; + unsigned long *p_addr; unsigned long bits = 0; - unsigned long i, do_now; - unsigned long words; - - /* 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_pidx(b, bm_word_to_page_idx(b, offset), KM_USER0); - bm = p_addr + MLPP(offset); - while (i--) { - bits += hweight_long(*bm++); - } - 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; - } + unsigned long mask = (1UL << (b->bm_bits & BITS_PER_LONG_MASK)) -1; + int idx, last_page, i, last_word; + + /* because of the "extra long to catch oob access" we allocate in + * drbd_bm_resize, bm_number_of_pages -1 is not necessarily the page + * containing the last _relevant_ bitmap word */ + last_page = bm_bit_to_page_idx(b, b->bm_bits-1); + + /* all but last page */ + for (idx = 0; idx < last_page; idx++) { + p_addr = __bm_map_pidx(b, idx, KM_USER0); + for (i = 0; i < LWPP; i++) + bits += hweight_long(p_addr[i]); __bm_unmap(p_addr, KM_USER0); cond_resched(); } - + /* last (or only) page */ + last_word = ((b->bm_bits - 1) & BITS_PER_PAGE_MASK) >> LN2_BPL; + p_addr = __bm_map_pidx(b, idx, KM_USER0); + for (i = 0; i < last_word; i++) + bits += hweight_long(p_addr[i]); + p_addr[last_word] &= cpu_to_lel(mask); + bits += hweight_long(p_addr[last_word]); + /* 32bit arch, may have an unused padding long */ + if (BITS_PER_LONG == 32 && (last_word & 1) == 0) + p_addr[last_word+1] = 0; + __bm_unmap(p_addr, KM_USER0); return bits; } @@ -564,8 +592,6 @@ static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len) unsigned int idx; size_t do_now, end; -#define BM_SECTORS_PER_BIT (BM_BLOCK_SIZE/512) - end = offset + len; if (end > b->bm_words) { @@ -645,8 +671,14 @@ int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity, int set_new_bits) words = ALIGN(bits, 64) >> LN2_BPL; if (get_ldev(mdev)) { - D_ASSERT((u64)bits <= (((u64)mdev->ldev->md.md_size_sect-MD_BM_OFFSET) << 12)); + u64 bits_on_disk = ((u64)mdev->ldev->md.md_size_sect-MD_BM_OFFSET) << 12; put_ldev(mdev); + if (bits > bits_on_disk) { + dev_info(DEV, "bits = %lu\n", bits); + dev_info(DEV, "bits_on_disk = %llu\n", bits_on_disk); + err = -ENOSPC; + goto out; + } } /* one extra long to catch off by one errors */ @@ -1113,9 +1145,12 @@ int drbd_bm_write_lazy(struct drbd_conf *mdev, unsigned upper_idx) __must_hold(l * @mdev: DRBD device. * @idx: bitmap page index * - * We don't want to special case on logical_block_size of the underlaying - * device, so we submit PAGE_SIZE aligned pieces containing the requested enr. + * We don't want to special case on logical_block_size of the backend device, + * so we submit PAGE_SIZE aligned pieces. * Note that on "most" systems, PAGE_SIZE is 4k. + * + * In case this becomes an issue on systems with larger PAGE_SIZE, + * we may want to change this again to write 4k aligned 4k pieces. */ int drbd_bm_write_page(struct drbd_conf *mdev, unsigned int idx) __must_hold(local) { @@ -1144,52 +1179,57 @@ int drbd_bm_write_page(struct drbd_conf *mdev, unsigned int idx) __must_hold(loc /* NOTE * find_first_bit returns int, we return unsigned long. - * should not make much difference anyways, but ... + * For this to work on 32bit arch with bitnumbers > (1<<32), + * we'd need to return u64, and get a whole lot of other places + * fixed where we still use unsigned long. * * this returns a bit number, NOT a sector! */ -#define BPP_MASK ((1UL << (PAGE_SHIFT+3)) - 1) static unsigned long __bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo, const int find_zero_bit, const enum km_type km) { struct drbd_bitmap *b = mdev->bitmap; - unsigned long i = -1UL; unsigned long *p_addr; - unsigned long bit_offset; /* bit offset of the mapped page. */ + unsigned long bit_offset; + unsigned i; + if (bm_fo > b->bm_bits) { dev_err(DEV, "bm_fo=%lu bm_bits=%lu\n", bm_fo, b->bm_bits); + bm_fo = DRBD_END_OF_BITMAP; } else { while (bm_fo < b->bm_bits) { /* bit offset of the first bit in the page */ - bit_offset = bm_fo & ~BPP_MASK; + bit_offset = bm_fo & ~BITS_PER_PAGE_MASK; p_addr = __bm_map_pidx(b, bm_bit_to_page_idx(b, bm_fo), km); if (find_zero_bit) - i = generic_find_next_zero_le_bit(p_addr, PAGE_SIZE*8, bm_fo & BPP_MASK); + i = generic_find_next_zero_le_bit(p_addr, + PAGE_SIZE*8, bm_fo & BITS_PER_PAGE_MASK); else - i = generic_find_next_le_bit(p_addr, PAGE_SIZE*8, bm_fo & BPP_MASK); + i = generic_find_next_le_bit(p_addr, + PAGE_SIZE*8, bm_fo & BITS_PER_PAGE_MASK); __bm_unmap(p_addr, km); if (i < PAGE_SIZE*8) { - i = bit_offset + i; - if (i >= b->bm_bits) + bm_fo = bit_offset + i; + if (bm_fo >= b->bm_bits) break; goto found; } bm_fo = bit_offset + PAGE_SIZE*8; } - i = -1UL; + bm_fo = DRBD_END_OF_BITMAP; } found: - return i; + return bm_fo; } static unsigned long bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo, const int find_zero_bit) { struct drbd_bitmap *b = mdev->bitmap; - unsigned long i = -1UL; + unsigned long i = DRBD_END_OF_BITMAP; ERR_IF(!b) return i; ERR_IF(!b->bm_pages) return i; @@ -1267,9 +1307,9 @@ static int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s, last_page_nr = page_nr; } if (val) - c += (0 == generic___test_and_set_le_bit(bitnr & BPP_MASK, p_addr)); + c += (0 == generic___test_and_set_le_bit(bitnr & BITS_PER_PAGE_MASK, p_addr)); else - c -= (0 != generic___test_and_clear_le_bit(bitnr & BPP_MASK, p_addr)); + c -= (0 != generic___test_and_clear_le_bit(bitnr & BITS_PER_PAGE_MASK, p_addr)); } if (p_addr) __bm_unmap(p_addr, km); @@ -1418,7 +1458,7 @@ int drbd_bm_test_bit(struct drbd_conf *mdev, const unsigned long bitnr) bm_print_lock_info(mdev); if (bitnr < b->bm_bits) { p_addr = bm_map_pidx(b, bm_bit_to_page_idx(b, bitnr)); - i = generic_test_le_bit(bitnr & BPP_MASK, p_addr) ? 1 : 0; + i = generic_test_le_bit(bitnr & BITS_PER_PAGE_MASK, p_addr) ? 1 : 0; bm_unmap(p_addr); } else if (bitnr == b->bm_bits) { i = -1; @@ -1517,13 +1557,15 @@ int drbd_bm_e_weight(struct drbd_conf *mdev, unsigned long enr) return count; } -/* set all bits covered by the AL-extent al_enr */ +/* Set all bits covered by the AL-extent al_enr. + * Returns number of bits changed. */ unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev, unsigned long al_enr) { struct drbd_bitmap *b = mdev->bitmap; unsigned long *p_addr, *bm; unsigned long weight; - int count, s, e, i, do_now; + unsigned long s, e; + int count, i, do_now; ERR_IF(!b) return 0; ERR_IF(!b->bm_pages) return 0; @@ -1552,7 +1594,7 @@ unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev, unsigned long al_enr) if (e == b->bm_words) b->bm_set -= bm_clear_surplus(b); } else { - dev_err(DEV, "start offset (%d) too large in drbd_bm_ALe_set_all\n", s); + dev_err(DEV, "start offset (%lu) too large in drbd_bm_ALe_set_all\n", s); } weight = b->bm_set - weight; spin_unlock_irq(&b->bm_lock); |