The DRBD driver

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 1327 insertions, 0 deletions

diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
new file mode 100644
index 000000000000..b61057e77882
--- /dev/null
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -0,0 +1,1327 @@
+/*
+   drbd_bitmap.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2004-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2004-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2004-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/bitops.h>
+#include <linux/vmalloc.h>
+#include <linux/string.h>
+#include <linux/drbd.h>
+#include <asm/kmap_types.h>
+#include "drbd_int.h"
+
+/* OPAQUE outside this file!
+ * interface defined in drbd_int.h
+
+ * 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...
+ */
+
+/*
+ * NOTE
+ *  Access to the *bm_pages is protected by bm_lock.
+ *  It is safe to read the other members within the lock.
+ *
+ *  drbd_bm_set_bits is called from bio_endio callbacks,
+ *  We may be called with irq already disabled,
+ *  so we need spin_lock_irqsave().
+ *  And we need the kmap_atomic.
+ */
+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...)
+         */
+        unsigned long bm_set;       /* nr of set bits; THINK maybe atomic_t? */
+        unsigned long bm_bits;
+        size_t   bm_words;
+        size_t   bm_number_of_pages;
+        sector_t bm_dev_capacity;
+        struct semaphore bm_change; /* serializes resize operations */
+
+        atomic_t bm_async_io;
+        wait_queue_head_t bm_io_wait;
+
+        unsigned long  bm_flags;
+
+        /* debugging aid, in case we are still racy somewhere */
+        char          *bm_why;
+        struct task_struct *bm_task;
+};
+
+/* definition of bits in bm_flags */
+#define BM_LOCKED       0
+#define BM_MD_IO_ERROR  1
+#define BM_P_VMALLOCED  2
+
+static int bm_is_locked(struct drbd_bitmap *b)
+{
+        return test_bit(BM_LOCKED, &b->bm_flags);
+}
+
+#define bm_print_lock_info(m) __bm_print_lock_info(m, __func__)
+static void __bm_print_lock_info(struct drbd_conf *mdev, const char *func)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        if (!__ratelimit(&drbd_ratelimit_state))
+                return;
+        dev_err(DEV, "FIXME %s in %s, bitmap locked for '%s' by %s\n",
+            current == mdev->receiver.task ? "receiver" :
+            current == mdev->asender.task  ? "asender"  :
+            current == mdev->worker.task   ? "worker"   : current->comm,
+            func, b->bm_why ?: "?",
+            b->bm_task == mdev->receiver.task ? "receiver" :
+            b->bm_task == mdev->asender.task  ? "asender"  :
+            b->bm_task == mdev->worker.task   ? "worker"   : "?");
+}
+
+void drbd_bm_lock(struct drbd_conf *mdev, char *why)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        int trylock_failed;
+
+        if (!b) {
+                dev_err(DEV, "FIXME no bitmap in drbd_bm_lock!?\n");
+                return;
+        }
+
+        trylock_failed = down_trylock(&b->bm_change);
+
+        if (trylock_failed) {
+                dev_warn(DEV, "%s going to '%s' but bitmap already locked for '%s' by %s\n",
+                    current == mdev->receiver.task ? "receiver" :
+                    current == mdev->asender.task  ? "asender"  :
+                    current == mdev->worker.task   ? "worker"   : current->comm,
+                    why, b->bm_why ?: "?",
+                    b->bm_task == mdev->receiver.task ? "receiver" :
+                    b->bm_task == mdev->asender.task  ? "asender"  :
+                    b->bm_task == mdev->worker.task   ? "worker"   : "?");
+                down(&b->bm_change);
+        }
+        if (__test_and_set_bit(BM_LOCKED, &b->bm_flags))
+                dev_err(DEV, "FIXME bitmap already locked in bm_lock\n");
+
+        b->bm_why  = why;
+        b->bm_task = current;
+}
+
+void drbd_bm_unlock(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        if (!b) {
+                dev_err(DEV, "FIXME no bitmap in drbd_bm_unlock!?\n");
+                return;
+        }
+
+        if (!__test_and_clear_bit(BM_LOCKED, &mdev->bitmap->bm_flags))
+                dev_err(DEV, "FIXME bitmap not locked in bm_unlock\n");
+
+        b->bm_why  = NULL;
+        b->bm_task = NULL;
+        up(&b->bm_change);
+}
+
+/* word offset to long pointer */
+static unsigned long *__bm_map_paddr(struct drbd_bitmap *b, unsigned long offset, const enum km_type km)
+{
+        struct page *page;
+        unsigned long page_nr;
+
+        /* page_nr = (word*sizeof(long)) >> PAGE_SHIFT; */
+        page_nr = offset >> (PAGE_SHIFT - LN2_BPL + 3);
+        BUG_ON(page_nr >= b->bm_number_of_pages);
+        page = b->bm_pages[page_nr];
+
+        return (unsigned long *) kmap_atomic(page, km);
+}
+
+static unsigned long * bm_map_paddr(struct drbd_bitmap *b, unsigned long offset)
+{
+        return __bm_map_paddr(b, offset, KM_IRQ1);
+}
+
+static void __bm_unmap(unsigned long *p_addr, const enum km_type km)
+{
+        kunmap_atomic(p_addr, km);
+};
+
+static void bm_unmap(unsigned long *p_addr)
+{
+        return __bm_unmap(p_addr, KM_IRQ1);
+}
+
+/* long word offset of _bitmap_ sector */
+#define S2W(s)  ((s)<<(BM_EXT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
+/* word offset from start of bitmap to word number _in_page_
+ * modulo longs per page
+#define MLPP(X) ((X) % (PAGE_SIZE/sizeof(long))
+ hm, well, Philipp thinks gcc might not optimze the % into & (... - 1)
+ so do it explicitly:
+ */
+#define MLPP(X) ((X) & ((PAGE_SIZE/sizeof(long))-1))
+
+/* Long words per page */
+#define LWPP (PAGE_SIZE/sizeof(long))
+
+/*
+ * actually most functions herein should take a struct drbd_bitmap*, not a
+ * struct drbd_conf*, but for the debug macros I like to have the mdev around
+ * to be able to report device specific.
+ */
+
+static void bm_free_pages(struct page **pages, unsigned long number)
+{
+        unsigned long i;
+        if (!pages)
+                return;
+
+        for (i = 0; i < number; i++) {
+                if (!pages[i]) {
+                        printk(KERN_ALERT "drbd: bm_free_pages tried to free "
+                                          "a NULL pointer; i=%lu n=%lu\n",
+                                          i, number);
+                        continue;
+                }
+                __free_page(pages[i]);
+                pages[i] = NULL;
+        }
+}
+
+static void bm_vk_free(void *ptr, int v)
+{
+        if (v)
+                vfree(ptr);
+        else
+                kfree(ptr);
+}
+
+/*
+ * "have" and "want" are NUMBER OF PAGES.
+ */
+static struct page **bm_realloc_pages(struct drbd_bitmap *b, unsigned long want)
+{
+        struct page **old_pages = b->bm_pages;
+        struct page **new_pages, *page;
+        unsigned int i, bytes, vmalloced = 0;
+        unsigned long have = b->bm_number_of_pages;
+
+        BUG_ON(have == 0 && old_pages != NULL);
+        BUG_ON(have != 0 && old_pages == NULL);
+
+        if (have == want)
+                return old_pages;
+
+        /* Trying kmalloc first, falling back to vmalloc.
+         * GFP_KERNEL is ok, as this is done when a lower level disk is
+         * "attached" to the drbd.  Context is receiver thread or cqueue
+         * thread.  As we have no disk yet, we are not in the IO path,
+         * not even the IO path of the peer. */
+        bytes = sizeof(struct page *)*want;
+        new_pages = kmalloc(bytes, GFP_KERNEL);
+        if (!new_pages) {
+                new_pages = vmalloc(bytes);
+                if (!new_pages)
+                        return NULL;
+                vmalloced = 1;
+        }
+
+        memset(new_pages, 0, bytes);
+        if (want >= have) {
+                for (i = 0; i < have; i++)
+                        new_pages[i] = old_pages[i];
+                for (; i < want; i++) {
+                        page = alloc_page(GFP_HIGHUSER);
+                        if (!page) {
+                                bm_free_pages(new_pages + have, i - have);
+                                bm_vk_free(new_pages, vmalloced);
+                                return NULL;
+                        }
+                        new_pages[i] = page;
+                }
+        } else {
+                for (i = 0; i < want; i++)
+                        new_pages[i] = old_pages[i];
+                /* NOT HERE, we are outside the spinlock!
+                bm_free_pages(old_pages + want, have - want);
+                */
+        }
+
+        if (vmalloced)
+                set_bit(BM_P_VMALLOCED, &b->bm_flags);
+        else
+                clear_bit(BM_P_VMALLOCED, &b->bm_flags);
+
+        return new_pages;
+}
+
+/*
+ * called on driver init only. TODO call when a device is created.
+ * allocates the drbd_bitmap, and stores it in mdev->bitmap.
+ */
+int drbd_bm_init(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        WARN_ON(b != NULL);
+        b = kzalloc(sizeof(struct drbd_bitmap), GFP_KERNEL);
+        if (!b)
+                return -ENOMEM;
+        spin_lock_init(&b->bm_lock);
+        init_MUTEX(&b->bm_change);
+        init_waitqueue_head(&b->bm_io_wait);
+
+        mdev->bitmap = b;
+
+        return 0;
+}
+
+sector_t drbd_bm_capacity(struct drbd_conf *mdev)
+{
+        ERR_IF(!mdev->bitmap) return 0;
+        return mdev->bitmap->bm_dev_capacity;
+}
+
+/* called on driver unload. TODO: call when a device is destroyed.
+ */
+void drbd_bm_cleanup(struct drbd_conf *mdev)
+{
+        ERR_IF (!mdev->bitmap) return;
+        bm_free_pages(mdev->bitmap->bm_pages, mdev->bitmap->bm_number_of_pages);
+        bm_vk_free(mdev->bitmap->bm_pages, test_bit(BM_P_VMALLOCED, &mdev->bitmap->bm_flags));
+        kfree(mdev->bitmap);
+        mdev->bitmap = NULL;
+}
+
+/*
+ * since (b->bm_bits % BITS_PER_LONG) != 0,
+ * this masks out the remaining bits.
+ * Returns the number of bits cleared.
+ */
+static int bm_clear_surplus(struct drbd_bitmap *b)
+{
+        const unsigned long mask = (1UL << (b->bm_bits & (BITS_PER_LONG-1))) - 1;
+        size_t w = b->bm_bits >> LN2_BPL;
+        int cleared = 0;
+        unsigned long *p_addr, *bm;
+
+        p_addr = bm_map_paddr(b, w);
+        bm = p_addr + MLPP(w);
+        if (w < b->bm_words) {
+                cleared = hweight_long(*bm & ~mask);
+                *bm &= mask;
+                w++; bm++;
+        }
+
+        if (w < b->bm_words) {
+                cleared += hweight_long(*bm);
+                *bm = 0;
+        }
+        bm_unmap(p_addr);
+        return cleared;
+}
+
+static void bm_set_surplus(struct drbd_bitmap *b)
+{
+        const unsigned long mask = (1UL << (b->bm_bits & (BITS_PER_LONG-1))) - 1;
+        size_t w = b->bm_bits >> LN2_BPL;
+        unsigned long *p_addr, *bm;
+
+        p_addr = bm_map_paddr(b, w);
+        bm = p_addr + MLPP(w);
+        if (w < b->bm_words) {
+                *bm |= ~mask;
+                bm++; w++;
+        }
+
+        if (w < b->bm_words) {
+                *bm = ~(0UL);
+        }
+        bm_unmap(p_addr);
+}
+
+static unsigned long __bm_count_bits(struct drbd_bitmap *b, const int swap_endian)
+{
+        unsigned long *p_addr, *bm, offset = 0;
+        unsigned long bits = 0;
+        unsigned long i, do_now;
+
+        while (offset < b->bm_words) {
+                i = do_now = min_t(size_t, b->bm_words-offset, LWPP);
+                p_addr = __bm_map_paddr(b, offset, KM_USER0);
+                bm = p_addr + MLPP(offset);
+                while (i--) {
+#ifndef __LITTLE_ENDIAN
+                        if (swap_endian)
+                                *bm = lel_to_cpu(*bm);
+#endif
+                        bits += hweight_long(*bm++);
+                }
+                __bm_unmap(p_addr, KM_USER0);
+                offset += do_now;
+                cond_resched();
+        }
+
+        return bits;
+}
+
+static unsigned long bm_count_bits(struct drbd_bitmap *b)
+{
+        return __bm_count_bits(b, 0);
+}
+
+static unsigned long bm_count_bits_swap_endian(struct drbd_bitmap *b)
+{
+        return __bm_count_bits(b, 1);
+}
+
+/* offset and len in long words.*/
+static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
+{
+        unsigned long *p_addr, *bm;
+        size_t do_now, end;
+
+#define BM_SECTORS_PER_BIT (BM_BLOCK_SIZE/512)
+
+        end = offset + len;
+
+        if (end > b->bm_words) {
+                printk(KERN_ALERT "drbd: bm_memset end > bm_words\n");
+                return;
+        }
+
+        while (offset < end) {
+                do_now = min_t(size_t, ALIGN(offset + 1, LWPP), end) - offset;
+                p_addr = bm_map_paddr(b, offset);
+                bm = p_addr + MLPP(offset);
+                if (bm+do_now > p_addr + LWPP) {
+                        printk(KERN_ALERT "drbd: BUG BUG BUG! p_addr:%p bm:%p do_now:%d\n",
+                               p_addr, bm, (int)do_now);
+                        break; /* breaks to after catch_oob_access_end() only! */
+                }
+                memset(bm, c, do_now * sizeof(long));
+                bm_unmap(p_addr);
+                offset += do_now;
+        }
+}
+
+/*
+ * make sure the bitmap has enough room for the attached storage,
+ * if necessary, resize.
+ * called whenever we may have changed the device size.
+ * returns -ENOMEM if we could not allocate enough memory, 0 on success.
+ * In case this is actually a resize, we copy the old bitmap into the new one.
+ * Otherwise, the bitmap is initialized to all bits set.
+ */
+int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long bits, words, owords, obits, *p_addr, *bm;
+        unsigned long want, have, onpages; /* number of pages */
+        struct page **npages, **opages = NULL;
+        int err = 0, growing;
+        int opages_vmalloced;
+
+        ERR_IF(!b) return -ENOMEM;
+
+        drbd_bm_lock(mdev, "resize");
+
+        dev_info(DEV, "drbd_bm_resize called with capacity == %llu\n",
+                        (unsigned long long)capacity);
+
+        if (capacity == b->bm_dev_capacity)
+                goto out;
+
+        opages_vmalloced = test_bit(BM_P_VMALLOCED, &b->bm_flags);
+
+        if (capacity == 0) {
+                spin_lock_irq(&b->bm_lock);
+                opages = b->bm_pages;
+                onpages = b->bm_number_of_pages;
+                owords = b->bm_words;
+                b->bm_pages = NULL;
+                b->bm_number_of_pages =
+                b->bm_set   =
+                b->bm_bits  =
+                b->bm_words =
+                b->bm_dev_capacity = 0;
+                spin_unlock_irq(&b->bm_lock);
+                bm_free_pages(opages, onpages);
+                bm_vk_free(opages, opages_vmalloced);
+                goto out;
+        }
+        bits  = BM_SECT_TO_BIT(ALIGN(capacity, BM_SECT_PER_BIT));
+
+        /* if we would use
+           words = ALIGN(bits,BITS_PER_LONG) >> LN2_BPL;
+           a 32bit host could present the wrong number of words
+           to a 64bit host.
+        */
+        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));
+                put_ldev(mdev);
+        }
+
+        /* one extra long to catch off by one errors */
+        want = ALIGN((words+1)*sizeof(long), PAGE_SIZE) >> PAGE_SHIFT;
+        have = b->bm_number_of_pages;
+        if (want == have) {
+                D_ASSERT(b->bm_pages != NULL);
+                npages = b->bm_pages;
+        } else {
+                if (FAULT_ACTIVE(mdev, DRBD_FAULT_BM_ALLOC))
+                        npages = NULL;
+                else
+                        npages = bm_realloc_pages(b, want);
+        }
+
+        if (!npages) {
+                err = -ENOMEM;
+                goto out;
+        }
+
+        spin_lock_irq(&b->bm_lock);
+        opages = b->bm_pages;
+        owords = b->bm_words;
+        obits  = b->bm_bits;
+
+        growing = bits > obits;
+        if (opages)
+                bm_set_surplus(b);
+
+        b->bm_pages = npages;
+        b->bm_number_of_pages = want;
+        b->bm_bits  = bits;
+        b->bm_words = words;
+        b->bm_dev_capacity = capacity;
+
+        if (growing) {
+                bm_memset(b, owords, 0xff, words-owords);
+                b->bm_set += bits - obits;
+        }
+
+        if (want < have) {
+                /* implicit: (opages != NULL) && (opages != npages) */
+                bm_free_pages(opages + want, have - want);
+        }
+
+        p_addr = bm_map_paddr(b, words);
+        bm = p_addr + MLPP(words);
+        *bm = DRBD_MAGIC;
+        bm_unmap(p_addr);
+
+        (void)bm_clear_surplus(b);
+
+        spin_unlock_irq(&b->bm_lock);
+        if (opages != npages)
+                bm_vk_free(opages, opages_vmalloced);
+        if (!growing)
+                b->bm_set = bm_count_bits(b);
+        dev_info(DEV, "resync bitmap: bits=%lu words=%lu\n", bits, words);
+
+ out:
+        drbd_bm_unlock(mdev);
+        return err;
+}
+
+/* inherently racy:
+ * if not protected by other means, return value may be out of date when
+ * leaving this function...
+ * we still need to lock it, since it is important that this returns
+ * bm_set == 0 precisely.
+ *
+ * maybe bm_set should be atomic_t ?
+ */
+static unsigned long _drbd_bm_total_weight(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long s;
+        unsigned long flags;
+
+        ERR_IF(!b) return 0;
+        ERR_IF(!b->bm_pages) return 0;
+
+        spin_lock_irqsave(&b->bm_lock, flags);
+        s = b->bm_set;
+        spin_unlock_irqrestore(&b->bm_lock, flags);
+
+        return s;
+}
+
+unsigned long drbd_bm_total_weight(struct drbd_conf *mdev)
+{
+        unsigned long s;
+        /* if I don't have a disk, I don't know about out-of-sync status */
+        if (!get_ldev_if_state(mdev, D_NEGOTIATING))
+                return 0;
+        s = _drbd_bm_total_weight(mdev);
+        put_ldev(mdev);
+        return s;
+}
+
+size_t drbd_bm_words(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        ERR_IF(!b) return 0;
+        ERR_IF(!b->bm_pages) return 0;
+
+        return b->bm_words;
+}
+
+unsigned long drbd_bm_bits(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        ERR_IF(!b) return 0;
+
+        return b->bm_bits;
+}
+
+/* merge number words from buffer into the bitmap starting at offset.
+ * buffer[i] is expected to be little endian unsigned long.
+ * bitmap must be locked by drbd_bm_lock.
+ * currently only used from receive_bitmap.
+ */
+void drbd_bm_merge_lel(struct drbd_conf *mdev, size_t offset, size_t number,
+                        unsigned long *buffer)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long *p_addr, *bm;
+        unsigned long word, bits;
+        size_t end, do_now;
+
+        end = offset + number;
+
+        ERR_IF(!b) return;
+        ERR_IF(!b->bm_pages) return;
+        if (number == 0)
+                return;
+        WARN_ON(offset >= b->bm_words);
+        WARN_ON(end    >  b->bm_words);
+
+        spin_lock_irq(&b->bm_lock);
+        while (offset < end) {
+                do_now = min_t(size_t, ALIGN(offset+1, LWPP), end) - offset;
+                p_addr = bm_map_paddr(b, offset);
+                bm = p_addr + MLPP(offset);
+                offset += do_now;
+                while (do_now--) {
+                        bits = hweight_long(*bm);
+                        word = *bm | lel_to_cpu(*buffer++);
+                        *bm++ = word;
+                        b->bm_set += hweight_long(word) - bits;
+                }
+                bm_unmap(p_addr);
+        }
+        /* with 32bit <-> 64bit cross-platform connect
+         * this is only correct for current usage,
+         * where we _know_ that we are 64 bit aligned,
+         * and know that this function is used in this way, too...
+         */
+        if (end == b->bm_words)
+                b->bm_set -= bm_clear_surplus(b);
+
+        spin_unlock_irq(&b->bm_lock);
+}
+
+/* copy number words from the bitmap starting at offset into the buffer.
+ * buffer[i] will be little endian unsigned long.
+ */
+void drbd_bm_get_lel(struct drbd_conf *mdev, size_t offset, size_t number,
+                     unsigned long *buffer)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long *p_addr, *bm;
+        size_t end, do_now;
+
+        end = offset + number;
+
+        ERR_IF(!b) return;
+        ERR_IF(!b->bm_pages) return;
+
+        spin_lock_irq(&b->bm_lock);
+        if ((offset >= b->bm_words) ||
+            (end    >  b->bm_words) ||
+            (number <= 0))
+                dev_err(DEV, "offset=%lu number=%lu bm_words=%lu\n",
+                        (unsigned long) offset,
+                        (unsigned long) number,
+                        (unsigned long) b->bm_words);
+        else {
+                while (offset < end) {
+                        do_now = min_t(size_t, ALIGN(offset+1, LWPP), end) - offset;
+                        p_addr = bm_map_paddr(b, offset);
+                        bm = p_addr + MLPP(offset);
+                        offset += do_now;
+                        while (do_now--)
+                                *buffer++ = cpu_to_lel(*bm++);
+                        bm_unmap(p_addr);
+                }
+        }
+        spin_unlock_irq(&b->bm_lock);
+}
+
+/* set all bits in the bitmap */
+void drbd_bm_set_all(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        ERR_IF(!b) return;
+        ERR_IF(!b->bm_pages) return;
+
+        spin_lock_irq(&b->bm_lock);
+        bm_memset(b, 0, 0xff, b->bm_words);
+        (void)bm_clear_surplus(b);
+        b->bm_set = b->bm_bits;
+        spin_unlock_irq(&b->bm_lock);
+}
+
+/* clear all bits in the bitmap */
+void drbd_bm_clear_all(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        ERR_IF(!b) return;
+        ERR_IF(!b->bm_pages) return;
+
+        spin_lock_irq(&b->bm_lock);
+        bm_memset(b, 0, 0, b->bm_words);
+        b->bm_set = 0;
+        spin_unlock_irq(&b->bm_lock);
+}
+
+static void bm_async_io_complete(struct bio *bio, int error)
+{
+        struct drbd_bitmap *b = bio->bi_private;
+        int uptodate = bio_flagged(bio, BIO_UPTODATE);
+
+
+        /* strange behavior of some lower level drivers...
+         * fail the request by clearing the uptodate flag,
+         * but do not return any error?!
+         * do we want to WARN() on this? */
+        if (!error && !uptodate)
+                error = -EIO;
+
+        if (error) {
+                /* doh. what now?
+                 * for now, set all bits, and flag MD_IO_ERROR */
+                __set_bit(BM_MD_IO_ERROR, &b->bm_flags);
+        }
+        if (atomic_dec_and_test(&b->bm_async_io))
+                wake_up(&b->bm_io_wait);
+
+        bio_put(bio);
+}
+
+static void bm_page_io_async(struct drbd_conf *mdev, struct drbd_bitmap *b, int page_nr, int rw) __must_hold(local)
+{
+        /* we are process context. we always get a bio */
+        struct bio *bio = bio_alloc(GFP_KERNEL, 1);
+        unsigned int len;
+        sector_t on_disk_sector =
+                mdev->ldev->md.md_offset + mdev->ldev->md.bm_offset;
+        on_disk_sector += ((sector_t)page_nr) << (PAGE_SHIFT-9);
+
+        /* this might happen with very small
+         * flexible external meta data device */
+        len = min_t(unsigned int, PAGE_SIZE,
+                (drbd_md_last_sector(mdev->ldev) - on_disk_sector + 1)<<9);
+
+        bio->bi_bdev = mdev->ldev->md_bdev;
+        bio->bi_sector = on_disk_sector;
+        bio_add_page(bio, b->bm_pages[page_nr], len, 0);
+        bio->bi_private = b;
+        bio->bi_end_io = bm_async_io_complete;
+
+        if (FAULT_ACTIVE(mdev, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD)) {
+                bio->bi_rw |= rw;
+                bio_endio(bio, -EIO);
+        } else {
+                submit_bio(rw, bio);
+        }
+}
+
+# if defined(__LITTLE_ENDIAN)
+        /* nothing to do, on disk == in memory */
+# define bm_cpu_to_lel(x) ((void)0)
+# else
+void bm_cpu_to_lel(struct drbd_bitmap *b)
+{
+        /* need to cpu_to_lel all the pages ...
+         * this may be optimized by using
+         * cpu_to_lel(-1) == -1 and cpu_to_lel(0) == 0;
+         * the following is still not optimal, but better than nothing */
+        unsigned int i;
+        unsigned long *p_addr, *bm;
+        if (b->bm_set == 0) {
+                /* no page at all; avoid swap if all is 0 */
+                i = b->bm_number_of_pages;
+        } else if (b->bm_set == b->bm_bits) {
+                /* only the last page */
+                i = b->bm_number_of_pages - 1;
+        } else {
+                /* all pages */
+                i = 0;
+        }
+        for (; i < b->bm_number_of_pages; i++) {
+                p_addr = kmap_atomic(b->bm_pages[i], KM_USER0);
+                for (bm = p_addr; bm < p_addr + PAGE_SIZE/sizeof(long); bm++)
+                        *bm = cpu_to_lel(*bm);
+                kunmap_atomic(p_addr, KM_USER0);
+        }
+}
+# endif
+/* lel_to_cpu == cpu_to_lel */
+# define bm_lel_to_cpu(x) bm_cpu_to_lel(x)
+
+/*
+ * bm_rw: read/write the whole bitmap from/to its on disk location.
+ */
+static int bm_rw(struct drbd_conf *mdev, int rw) __must_hold(local)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        /* sector_t sector; */
+        int bm_words, num_pages, i;
+        unsigned long now;
+        char ppb[10];
+        int err = 0;
+
+        WARN_ON(!bm_is_locked(b));
+
+        /* no spinlock here, the drbd_bm_lock should be enough! */
+
+        bm_words  = drbd_bm_words(mdev);
+        num_pages = (bm_words*sizeof(long) + PAGE_SIZE-1) >> PAGE_SHIFT;
+
+        /* on disk bitmap is little endian */
+        if (rw == WRITE)
+                bm_cpu_to_lel(b);
+
+        now = jiffies;
+        atomic_set(&b->bm_async_io, num_pages);
+        __clear_bit(BM_MD_IO_ERROR, &b->bm_flags);
+
+        /* let the layers below us try to merge these bios... */
+        for (i = 0; i < num_pages; i++)
+                bm_page_io_async(mdev, b, i, rw);
+
+        drbd_blk_run_queue(bdev_get_queue(mdev->ldev->md_bdev));
+        wait_event(b->bm_io_wait, atomic_read(&b->bm_async_io) == 0);
+
+        if (test_bit(BM_MD_IO_ERROR, &b->bm_flags)) {
+                dev_alert(DEV, "we had at least one MD IO ERROR during bitmap IO\n");
+                drbd_chk_io_error(mdev, 1, TRUE);
+                err = -EIO;
+        }
+
+        now = jiffies;
+        if (rw == WRITE) {
+                /* swap back endianness */
+                bm_lel_to_cpu(b);
+                /* flush bitmap to stable storage */
+                drbd_md_flush(mdev);
+        } else /* rw == READ */ {
+                /* just read, if necessary adjust endianness */
+                b->bm_set = bm_count_bits_swap_endian(b);
+                dev_info(DEV, "recounting of set bits took additional %lu jiffies\n",
+                     jiffies - now);
+        }
+        now = b->bm_set;
+
+        dev_info(DEV, "%s (%lu bits) marked out-of-sync by on disk bit-map.\n",
+             ppsize(ppb, now << (BM_BLOCK_SHIFT-10)), now);
+
+        return err;
+}
+
+/**
+ * drbd_bm_read() - Read the whole bitmap from its on disk location.
+ * @mdev:       DRBD device.
+ */
+int drbd_bm_read(struct drbd_conf *mdev) __must_hold(local)
+{
+        return bm_rw(mdev, READ);
+}
+
+/**
+ * drbd_bm_write() - Write the whole bitmap to its on disk location.
+ * @mdev:       DRBD device.
+ */
+int drbd_bm_write(struct drbd_conf *mdev) __must_hold(local)
+{
+        return bm_rw(mdev, WRITE);
+}
+
+/**
+ * drbd_bm_write_sect: Writes a 512 (MD_SECTOR_SIZE) byte piece of the bitmap
+ * @mdev:       DRBD device.
+ * @enr:        Extent number in the resync lru (happens to be sector offset)
+ *
+ * The BM_EXT_SIZE is on purpose exactly the amount of the bitmap covered
+ * by a single sector write. Therefore enr == sector offset from the
+ * start of the bitmap.
+ */
+int drbd_bm_write_sect(struct drbd_conf *mdev, unsigned long enr) __must_hold(local)
+{
+        sector_t on_disk_sector = enr + mdev->ldev->md.md_offset
+                                      + mdev->ldev->md.bm_offset;
+        int bm_words, num_words, offset;
+        int err = 0;
+
+        mutex_lock(&mdev->md_io_mutex);
+        bm_words  = drbd_bm_words(mdev);
+        offset    = S2W(enr);   /* word offset into bitmap */
+        num_words = min(S2W(1), bm_words - offset);
+        if (num_words < S2W(1))
+                memset(page_address(mdev->md_io_page), 0, MD_SECTOR_SIZE);
+        drbd_bm_get_lel(mdev, offset, num_words,
+                        page_address(mdev->md_io_page));
+        if (!drbd_md_sync_page_io(mdev, mdev->ldev, on_disk_sector, WRITE)) {
+                int i;
+                err = -EIO;
+                dev_err(DEV, "IO ERROR writing bitmap sector %lu "
+                    "(meta-disk sector %llus)\n",
+                    enr, (unsigned long long)on_disk_sector);
+                drbd_chk_io_error(mdev, 1, TRUE);
+                for (i = 0; i < AL_EXT_PER_BM_SECT; i++)
+                        drbd_bm_ALe_set_all(mdev, enr*AL_EXT_PER_BM_SECT+i);
+        }
+        mdev->bm_writ_cnt++;
+        mutex_unlock(&mdev->md_io_mutex);
+        return err;
+}
+
+/* NOTE
+ * find_first_bit returns int, we return unsigned long.
+ * should not make much difference anyways, but ...
+ *
+ * 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. */
+
+        if (bm_fo > b->bm_bits) {
+                dev_err(DEV, "bm_fo=%lu bm_bits=%lu\n", bm_fo, b->bm_bits);
+        } else {
+                while (bm_fo < b->bm_bits) {
+                        unsigned long offset;
+                        bit_offset = bm_fo & ~BPP_MASK; /* bit offset of the page */
+                        offset = bit_offset >> LN2_BPL;    /* word offset of the page */
+                        p_addr = __bm_map_paddr(b, offset, km);
+
+                        if (find_zero_bit)
+                                i = find_next_zero_bit(p_addr, PAGE_SIZE*8, bm_fo & BPP_MASK);
+                        else
+                                i = find_next_bit(p_addr, PAGE_SIZE*8, bm_fo & BPP_MASK);
+
+                        __bm_unmap(p_addr, km);
+                        if (i < PAGE_SIZE*8) {
+                                i = bit_offset + i;
+                                if (i >= b->bm_bits)
+                                        break;
+                                goto found;
+                        }
+                        bm_fo = bit_offset + PAGE_SIZE*8;
+                }
+                i = -1UL;
+        }
+ found:
+        return i;
+}
+
+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;
+
+        ERR_IF(!b) return i;
+        ERR_IF(!b->bm_pages) return i;
+
+        spin_lock_irq(&b->bm_lock);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+
+        i = __bm_find_next(mdev, bm_fo, find_zero_bit, KM_IRQ1);
+
+        spin_unlock_irq(&b->bm_lock);
+        return i;
+}
+
+unsigned long drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+        return bm_find_next(mdev, bm_fo, 0);
+}
+
+#if 0
+/* not yet needed for anything. */
+unsigned long drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+        return bm_find_next(mdev, bm_fo, 1);
+}
+#endif
+
+/* does not spin_lock_irqsave.
+ * you must take drbd_bm_lock() first */
+unsigned long _drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+        /* WARN_ON(!bm_is_locked(mdev)); */
+        return __bm_find_next(mdev, bm_fo, 0, KM_USER1);
+}
+
+unsigned long _drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+        /* WARN_ON(!bm_is_locked(mdev)); */
+        return __bm_find_next(mdev, bm_fo, 1, KM_USER1);
+}
+
+/* returns number of bits actually changed.
+ * for val != 0, we change 0 -> 1, return code positive
+ * for val == 0, we change 1 -> 0, return code negative
+ * wants bitnr, not sector.
+ * expected to be called for only a few bits (e - s about BITS_PER_LONG).
+ * Must hold bitmap lock already. */
+int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
+        unsigned long e, int val, const enum km_type km)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long *p_addr = NULL;
+        unsigned long bitnr;
+        unsigned long last_page_nr = -1UL;
+        int c = 0;
+
+        if (e >= b->bm_bits) {
+                dev_err(DEV, "ASSERT FAILED: bit_s=%lu bit_e=%lu bm_bits=%lu\n",
+                                s, e, b->bm_bits);
+                e = b->bm_bits ? b->bm_bits -1 : 0;
+        }
+        for (bitnr = s; bitnr <= e; bitnr++) {
+                unsigned long offset = bitnr>>LN2_BPL;
+                unsigned long page_nr = offset >> (PAGE_SHIFT - LN2_BPL + 3);
+                if (page_nr != last_page_nr) {
+                        if (p_addr)
+                                __bm_unmap(p_addr, km);
+                        p_addr = __bm_map_paddr(b, offset, km);
+                        last_page_nr = page_nr;
+                }
+                if (val)
+                        c += (0 == __test_and_set_bit(bitnr & BPP_MASK, p_addr));
+                else
+                        c -= (0 != __test_and_clear_bit(bitnr & BPP_MASK, p_addr));
+        }
+        if (p_addr)
+                __bm_unmap(p_addr, km);
+        b->bm_set += c;
+        return c;
+}
+
+/* returns number of bits actually changed.
+ * for val != 0, we change 0 -> 1, return code positive
+ * for val == 0, we change 1 -> 0, return code negative
+ * wants bitnr, not sector */
+int bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
+        const unsigned long e, int val)
+{
+        unsigned long flags;
+        struct drbd_bitmap *b = mdev->bitmap;
+        int c = 0;
+
+        ERR_IF(!b) return 1;
+        ERR_IF(!b->bm_pages) return 0;
+
+        spin_lock_irqsave(&b->bm_lock, flags);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+
+        c = __bm_change_bits_to(mdev, s, e, val, KM_IRQ1);
+
+        spin_unlock_irqrestore(&b->bm_lock, flags);
+        return c;
+}
+
+/* returns number of bits changed 0 -> 1 */
+int drbd_bm_set_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+        return bm_change_bits_to(mdev, s, e, 1);
+}
+
+/* returns number of bits changed 1 -> 0 */
+int drbd_bm_clear_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+        return -bm_change_bits_to(mdev, s, e, 0);
+}
+
+/* sets all bits in full words,
+ * from first_word up to, but not including, last_word */
+static inline void bm_set_full_words_within_one_page(struct drbd_bitmap *b,
+                int page_nr, int first_word, int last_word)
+{
+        int i;
+        int bits;
+        unsigned long *paddr = kmap_atomic(b->bm_pages[page_nr], KM_USER0);
+        for (i = first_word; i < last_word; i++) {
+                bits = hweight_long(paddr[i]);
+                paddr[i] = ~0UL;
+                b->bm_set += BITS_PER_LONG - bits;
+        }
+        kunmap_atomic(paddr, KM_USER0);
+}
+
+/* Same thing as drbd_bm_set_bits, but without taking the spin_lock_irqsave.
+ * You must first drbd_bm_lock().
+ * Can be called to set the whole bitmap in one go.
+ * Sets bits from s to e _inclusive_. */
+void _drbd_bm_set_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+        /* First set_bit from the first bit (s)
+         * up to the next long boundary (sl),
+         * then assign full words up to the last long boundary (el),
+         * then set_bit up to and including the last bit (e).
+         *
+         * Do not use memset, because we must account for changes,
+         * so we need to loop over the words with hweight() anyways.
+         */
+        unsigned long sl = ALIGN(s,BITS_PER_LONG);
+        unsigned long el = (e+1) & ~((unsigned long)BITS_PER_LONG-1);
+        int first_page;
+        int last_page;
+        int page_nr;
+        int first_word;
+        int last_word;
+
+        if (e - s <= 3*BITS_PER_LONG) {
+                /* don't bother; el and sl may even be wrong. */
+                __bm_change_bits_to(mdev, s, e, 1, KM_USER0);
+                return;
+        }
+
+        /* difference is large enough that we can trust sl and el */
+
+        /* bits filling the current long */
+        if (sl)
+                __bm_change_bits_to(mdev, s, sl-1, 1, KM_USER0);
+
+        first_page = sl >> (3 + PAGE_SHIFT);
+        last_page = el >> (3 + PAGE_SHIFT);
+
+        /* MLPP: modulo longs per page */
+        /* LWPP: long words per page */
+        first_word = MLPP(sl >> LN2_BPL);
+        last_word = LWPP;
+
+        /* first and full pages, unless first page == last page */
+        for (page_nr = first_page; page_nr < last_page; page_nr++) {
+                bm_set_full_words_within_one_page(mdev->bitmap, page_nr, first_word, last_word);
+                cond_resched();
+                first_word = 0;
+        }
+
+        /* last page (respectively only page, for first page == last page) */
+        last_word = MLPP(el >> LN2_BPL);
+        bm_set_full_words_within_one_page(mdev->bitmap, last_page, first_word, last_word);
+
+        /* possibly trailing bits.
+         * example: (e & 63) == 63, el will be e+1.
+         * if that even was the very last bit,
+         * it would trigger an assert in __bm_change_bits_to()
+         */
+        if (el <= e)
+                __bm_change_bits_to(mdev, el, e, 1, KM_USER0);
+}
+
+/* returns bit state
+ * wants bitnr, NOT sector.
+ * inherently racy... area needs to be locked by means of {al,rs}_lru
+ *  1 ... bit set
+ *  0 ... bit not set
+ * -1 ... first out of bounds access, stop testing for bits!
+ */
+int drbd_bm_test_bit(struct drbd_conf *mdev, const unsigned long bitnr)
+{
+        unsigned long flags;
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long *p_addr;
+        int i;
+
+        ERR_IF(!b) return 0;
+        ERR_IF(!b->bm_pages) return 0;
+
+        spin_lock_irqsave(&b->bm_lock, flags);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+        if (bitnr < b->bm_bits) {
+                unsigned long offset = bitnr>>LN2_BPL;
+                p_addr = bm_map_paddr(b, offset);
+                i = test_bit(bitnr & BPP_MASK, p_addr) ? 1 : 0;
+                bm_unmap(p_addr);
+        } else if (bitnr == b->bm_bits) {
+                i = -1;
+        } else { /* (bitnr > b->bm_bits) */
+                dev_err(DEV, "bitnr=%lu > bm_bits=%lu\n", bitnr, b->bm_bits);
+                i = 0;
+        }
+
+        spin_unlock_irqrestore(&b->bm_lock, flags);
+        return i;
+}
+
+/* returns number of bits set in the range [s, e] */
+int drbd_bm_count_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+        unsigned long flags;
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long *p_addr = NULL, page_nr = -1;
+        unsigned long bitnr;
+        int c = 0;
+        size_t w;
+
+        /* If this is called without a bitmap, that is a bug.  But just to be
+         * robust in case we screwed up elsewhere, in that case pretend there
+         * was one dirty bit in the requested area, so we won't try to do a
+         * local read there (no bitmap probably implies no disk) */
+        ERR_IF(!b) return 1;
+        ERR_IF(!b->bm_pages) return 1;
+
+        spin_lock_irqsave(&b->bm_lock, flags);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+        for (bitnr = s; bitnr <= e; bitnr++) {
+                w = bitnr >> LN2_BPL;
+                if (page_nr != w >> (PAGE_SHIFT - LN2_BPL + 3)) {
+                        page_nr = w >> (PAGE_SHIFT - LN2_BPL + 3);
+                        if (p_addr)
+                                bm_unmap(p_addr);
+                        p_addr = bm_map_paddr(b, w);
+                }
+                ERR_IF (bitnr >= b->bm_bits) {
+                        dev_err(DEV, "bitnr=%lu bm_bits=%lu\n", bitnr, b->bm_bits);
+                } else {
+                        c += (0 != test_bit(bitnr - (page_nr << (PAGE_SHIFT+3)), p_addr));
+                }
+        }
+        if (p_addr)
+                bm_unmap(p_addr);
+        spin_unlock_irqrestore(&b->bm_lock, flags);
+        return c;
+}
+
+
+/* inherently racy...
+ * return value may be already out-of-date when this function returns.
+ * but the general usage is that this is only use during a cstate when bits are
+ * only cleared, not set, and typically only care for the case when the return
+ * value is zero, or we already "locked" this "bitmap extent" by other means.
+ *
+ * enr is bm-extent number, since we chose to name one sector (512 bytes)
+ * worth of the bitmap a "bitmap extent".
+ *
+ * TODO
+ * I think since we use it like a reference count, we should use the real
+ * reference count of some bitmap extent element from some lru instead...
+ *
+ */
+int drbd_bm_e_weight(struct drbd_conf *mdev, unsigned long enr)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        int count, s, e;
+        unsigned long flags;
+        unsigned long *p_addr, *bm;
+
+        ERR_IF(!b) return 0;
+        ERR_IF(!b->bm_pages) return 0;
+
+        spin_lock_irqsave(&b->bm_lock, flags);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+
+        s = S2W(enr);
+        e = min((size_t)S2W(enr+1), b->bm_words);
+        count = 0;
+        if (s < b->bm_words) {
+                int n = e-s;
+                p_addr = bm_map_paddr(b, s);
+                bm = p_addr + MLPP(s);
+                while (n--)
+                        count += hweight_long(*bm++);
+                bm_unmap(p_addr);
+        } else {
+                dev_err(DEV, "start offset (%d) too large in drbd_bm_e_weight\n", s);
+        }
+        spin_unlock_irqrestore(&b->bm_lock, flags);
+        return count;
+}
+
+/* set all bits covered by the AL-extent al_enr */
+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;
+        ERR_IF(!b) return 0;
+        ERR_IF(!b->bm_pages) return 0;
+
+        spin_lock_irq(&b->bm_lock);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+        weight = b->bm_set;
+
+        s = al_enr * BM_WORDS_PER_AL_EXT;
+        e = min_t(size_t, s + BM_WORDS_PER_AL_EXT, b->bm_words);
+        /* assert that s and e are on the same page */
+        D_ASSERT((e-1) >> (PAGE_SHIFT - LN2_BPL + 3)
+              ==  s    >> (PAGE_SHIFT - LN2_BPL + 3));
+        count = 0;
+        if (s < b->bm_words) {
+                i = do_now = e-s;
+                p_addr = bm_map_paddr(b, s);
+                bm = p_addr + MLPP(s);
+                while (i--) {
+                        count += hweight_long(*bm);
+                        *bm = -1UL;
+                        bm++;
+                }
+                bm_unmap(p_addr);
+                b->bm_set += do_now*BITS_PER_LONG - count;
+                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);
+        }
+        weight = b->bm_set - weight;
+        spin_unlock_irq(&b->bm_lock);
+        return weight;
+}