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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
    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>.
 
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/bitmap.h>
 #include <linux/vmalloc.h>
 #include <linux/string.h>
 #include <linux/drbd.h>
 #include <linux/slab.h>
 #include <linux/highmem.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".
  */
 
 
 /*
  * 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 paging 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.
  */
 
 /*
  * 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;
 
     /* exclusively to be used by __al_write_transaction(),
      * drbd_bm_mark_for_writeout() and
      * and drbd_bm_write_hinted() -> bm_rw() called from there.
      */
     unsigned int n_bitmap_hints;
     unsigned int al_bitmap_hints[AL_UPDATES_PER_TRANSACTION];
 
     /* see LIMITATIONS: above */
 
     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 mutex bm_change; /* serializes resize operations */
 
     wait_queue_head_t bm_io_wait; /* used to serialize IO of single pages */
 
     enum bm_flag bm_flags;
 
     /* debugging aid, in case we are still racy somewhere */
     char          *bm_why;
     struct task_struct *bm_task;
 };
 
 #define bm_print_lock_info(m) __bm_print_lock_info(m, __func__)
 static void __bm_print_lock_info(struct drbd_device *device, const char *func)
 {
     struct drbd_bitmap *b = device->bitmap;
     if (!__ratelimit(&drbd_ratelimit_state))
         return;
     drbd_err(device, "FIXME %s[%d] in %s, bitmap locked for '%s' by %s[%d]\n",
          current->comm, task_pid_nr(current),
          func, b->bm_why ?: "?",
          b->bm_task->comm, task_pid_nr(b->bm_task));
 }
 
 void drbd_bm_lock(struct drbd_device *device, char *why, enum bm_flag flags)
 {
     struct drbd_bitmap *b = device->bitmap;
     int trylock_failed;
 
     if (!b) {
         drbd_err(device, "FIXME no bitmap in drbd_bm_lock!?\n");
         return;
     }
 
     trylock_failed = !mutex_trylock(&b->bm_change);
 
     if (trylock_failed) {
         drbd_warn(device, "%s[%d] going to '%s' but bitmap already locked for '%s' by %s[%d]\n",
               current->comm, task_pid_nr(current),
               why, b->bm_why ?: "?",
               b->bm_task->comm, task_pid_nr(b->bm_task));
         mutex_lock(&b->bm_change);
     }
     if (BM_LOCKED_MASK & b->bm_flags)
         drbd_err(device, "FIXME bitmap already locked in bm_lock\n");
     b->bm_flags |= flags & BM_LOCKED_MASK;
 
     b->bm_why  = why;
     b->bm_task = current;
 }
 
 void drbd_bm_unlock(struct drbd_device *device)
 {
     struct drbd_bitmap *b = device->bitmap;
     if (!b) {
         drbd_err(device, "FIXME no bitmap in drbd_bm_unlock!?\n");
         return;
     }
 
     if (!(BM_LOCKED_MASK & device->bitmap->bm_flags))
         drbd_err(device, "FIXME bitmap not locked in bm_unlock\n");
 
     b->bm_flags &= ~BM_LOCKED_MASK;
     b->bm_why  = NULL;
     b->bm_task = NULL;
     mutex_unlock(&b->bm_change);
 }
 
 /* we store some "meta" info about our pages in page->private */
 /* at a granularity of 4k storage per bitmap bit:
  * one peta byte storage: 1<<50 byte, 1<<38 * 4k storage blocks
  *  1<<38 bits,
  *  1<<23 4k bitmap pages.
  * Use 24 bits as page index, covers 2 peta byte storage
  * at a granularity of 4k per bit.
  * Used to report the failed page idx on io error from the endio handlers.
  */
 #define BM_PAGE_IDX_MASK    ((1UL<<24)-1)
 /* this page is currently read in, or written back */
 #define BM_PAGE_IO_LOCK     31
 /* if there has been an IO error for this page */
 #define BM_PAGE_IO_ERROR    30
 /* this is to be able to intelligently skip disk IO,
  * set if bits have been set since last IO. */
 #define BM_PAGE_NEED_WRITEOUT   29
 /* to mark for lazy writeout once syncer cleared all clearable bits,
  * we if bits have been cleared since last IO. */
 #define BM_PAGE_LAZY_WRITEOUT   28
 /* pages marked with this "HINT" will be considered for writeout
  * on activity log transactions */
 #define BM_PAGE_HINT_WRITEOUT   27
 
 /* store_page_idx uses non-atomic assignment. It is only used directly after
  * allocating the page.  All other bm_set_page_* and bm_clear_page_* need to
  * use atomic bit manipulation, as set_out_of_sync (and therefore bitmap
  * changes) may happen from various contexts, and wait_on_bit/wake_up_bit
  * requires it all to be atomic as well. */
 static void bm_store_page_idx(struct page *page, unsigned long idx)
 {
     BUG_ON(0 != (idx & ~BM_PAGE_IDX_MASK));
     set_page_private(page, idx);
 }
 
 static unsigned long bm_page_to_idx(struct page *page)
 {
     return page_private(page) & BM_PAGE_IDX_MASK;
 }
 
 /* As is very unlikely that the same page is under IO from more than one
  * context, we can get away with a bit per page and one wait queue per bitmap.
  */
 static void bm_page_lock_io(struct drbd_device *device, int page_nr)
 {
     struct drbd_bitmap *b = device->bitmap;
     void *addr = &page_private(b->bm_pages[page_nr]);
     wait_event(b->bm_io_wait, !test_and_set_bit(BM_PAGE_IO_LOCK, addr));
 }
 
 static void bm_page_unlock_io(struct drbd_device *device, int page_nr)
 {
     struct drbd_bitmap *b = device->bitmap;
     void *addr = &page_private(b->bm_pages[page_nr]);
     clear_bit_unlock(BM_PAGE_IO_LOCK, addr);
     wake_up(&device->bitmap->bm_io_wait);
 }
 
 /* set _before_ submit_io, so it may be reset due to being changed
  * while this page is in flight... will get submitted later again */
 static void bm_set_page_unchanged(struct page *page)
 {
     /* use cmpxchg? */
     clear_bit(BM_PAGE_NEED_WRITEOUT, &page_private(page));
     clear_bit(BM_PAGE_LAZY_WRITEOUT, &page_private(page));
 }
 
 static void bm_set_page_need_writeout(struct page *page)
 {
     set_bit(BM_PAGE_NEED_WRITEOUT, &page_private(page));
 }
 
 void drbd_bm_reset_al_hints(struct drbd_device *device)
 {
     device->bitmap->n_bitmap_hints = 0;
 }
 
 /**
  * drbd_bm_mark_for_writeout() - mark a page with a "hint" to be considered for writeout
  * @device: DRBD device.
  * @page_nr:    the bitmap page to mark with the "hint" flag
  *
  * From within an activity log transaction, we mark a few pages with these
  * hints, then call drbd_bm_write_hinted(), which will only write out changed
  * pages which are flagged with this mark.
  */
 void drbd_bm_mark_for_writeout(struct drbd_device *device, int page_nr)
 {
     struct drbd_bitmap *b = device->bitmap;
     struct page *page;
     if (page_nr >= device->bitmap->bm_number_of_pages) {
         drbd_warn(device, "BAD: page_nr: %u, number_of_pages: %u\n",
              page_nr, (int)device->bitmap->bm_number_of_pages);
         return;
     }
     page = device->bitmap->bm_pages[page_nr];
     BUG_ON(b->n_bitmap_hints >= ARRAY_SIZE(b->al_bitmap_hints));
     if (!test_and_set_bit(BM_PAGE_HINT_WRITEOUT, &page_private(page)))
         b->al_bitmap_hints[b->n_bitmap_hints++] = page_nr;
 }
 
 static int bm_test_page_unchanged(struct page *page)
 {
     volatile const unsigned long *addr = &page_private(page);
     return (*addr & ((1UL<<BM_PAGE_NEED_WRITEOUT)|(1UL<<BM_PAGE_LAZY_WRITEOUT))) == 0;
 }
 
 static void bm_set_page_io_err(struct page *page)
 {
     set_bit(BM_PAGE_IO_ERROR, &page_private(page));
 }
 
 static void bm_clear_page_io_err(struct page *page)
 {
     clear_bit(BM_PAGE_IO_ERROR, &page_private(page));
 }
 
 static void bm_set_page_lazy_writeout(struct page *page)
 {
     set_bit(BM_PAGE_LAZY_WRITEOUT, &page_private(page));
 }
 
 static int bm_test_page_lazy_writeout(struct page *page)
 {
     return test_bit(BM_PAGE_LAZY_WRITEOUT, &page_private(page));
 }
 
 /* on a 32bit box, this would allow for exactly (2<<38) bits. */
 static unsigned int bm_word_to_page_idx(struct drbd_bitmap *b, unsigned long long_nr)
 {
     /* page_nr = (word*sizeof(long)) >> PAGE_SHIFT; */
     unsigned int page_nr = long_nr >> (PAGE_SHIFT - LN2_BPL + 3);
     BUG_ON(page_nr >= b->bm_number_of_pages);
     return page_nr;
 }
 
 static unsigned int bm_bit_to_page_idx(struct drbd_bitmap *b, u64 bitnr)
 {
     /* page_nr = (bitnr/8) >> PAGE_SHIFT; */
     unsigned int page_nr = bitnr >> (PAGE_SHIFT + 3);
     BUG_ON(page_nr >= b->bm_number_of_pages);
     return page_nr;
 }
 
 static unsigned long *__bm_map_pidx(struct drbd_bitmap *b, unsigned int idx)
 {
     struct page *page = b->bm_pages[idx];
     return (unsigned long *) kmap_atomic(page);
 }
 
 static unsigned long *bm_map_pidx(struct drbd_bitmap *b, unsigned int idx)
 {
     return __bm_map_pidx(b, idx);
 }
 
 static void __bm_unmap(unsigned long *p_addr)
 {
     kunmap_atomic(p_addr);
 };
 
 static void bm_unmap(unsigned long *p_addr)
 {
     return __bm_unmap(p_addr);
 }
 
 /* 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 optimize 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_device*, but for the debug macros I like to have the device 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]) {
             pr_alert("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 inline void bm_vk_free(void *ptr)
 {
     kvfree(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;
     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_NOIO, as this is called while drbd IO is "suspended",
      * and during resize or attach on diskless Primary,
      * we must not block on IO to ourselves.
      * Context is receiver thread or dmsetup. */
     bytes = sizeof(struct page *)*want;
     new_pages = kzalloc(bytes, GFP_NOIO | __GFP_NOWARN);
     if (!new_pages) {
         new_pages = __vmalloc(bytes, GFP_NOIO | __GFP_ZERO);
         if (!new_pages)
             return NULL;
     }
 
     if (want >= have) {
         for (i = 0; i < have; i++)
             new_pages[i] = old_pages[i];
         for (; i < want; i++) {
             page = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
             if (!page) {
                 bm_free_pages(new_pages + have, i - have);
                 bm_vk_free(new_pages);
                 return NULL;
             }
             /* we want to know which page it is
              * from the endio handlers */
             bm_store_page_idx(page, i);
             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);
         */
     }
 
     return new_pages;
 }
 
 /*
  * allocates the drbd_bitmap and stores it in device->bitmap.
  */
 int drbd_bm_init(struct drbd_device *device)
 {
     struct drbd_bitmap *b = device->bitmap;
     WARN_ON(b != NULL);
     b = kzalloc(sizeof(struct drbd_bitmap), GFP_KERNEL);
     if (!b)
         return -ENOMEM;
     spin_lock_init(&b->bm_lock);
     mutex_init(&b->bm_change);
     init_waitqueue_head(&b->bm_io_wait);
 
     device->bitmap = b;
 
     return 0;
 }
 
 sector_t drbd_bm_capacity(struct drbd_device *device)
 {
     if (!expect(device->bitmap))
         return 0;
     return device->bitmap->bm_dev_capacity;
 }
 
 /* called on driver unload. TODO: call when a device is destroyed.
  */
 void drbd_bm_cleanup(struct drbd_device *device)
 {
     if (!expect(device->bitmap))
         return;
     bm_free_pages(device->bitmap->bm_pages, device->bitmap->bm_number_of_pages);
     bm_vk_free(device->bitmap->bm_pages);
     kfree(device->bitmap);
     device->bitmap = NULL;
 }
 
 /*
  * since (b->bm_bits % BITS_PER_LONG) != 0,
  * this masks out the remaining bits.
  * Returns the number of bits cleared.
  */
 #ifndef BITS_PER_PAGE
 #define BITS_PER_PAGE       (1UL << (PAGE_SHIFT + 3))
 #define BITS_PER_PAGE_MASK  (BITS_PER_PAGE - 1)
 #else
 # if BITS_PER_PAGE != (1UL << (PAGE_SHIFT + 3))
 #  error "ambiguous BITS_PER_PAGE"
 # endif
 #endif
 #define BITS_PER_LONG_MASK  (BITS_PER_LONG - 1)
 static int bm_clear_surplus(struct drbd_bitmap *b)
 {
     unsigned long mask;
     unsigned long *p_addr, *bm;
     int tmp;
     int cleared = 0;
 
     /* number of bits modulo bits per page */
     tmp = (b->bm_bits & BITS_PER_PAGE_MASK);
     /* mask the used bits of the word containing the last bit */
     mask = (1UL << (tmp & BITS_PER_LONG_MASK)) -1;
     /* bitmap is always stored little endian,
      * on disk and in core memory alike */
     mask = cpu_to_lel(mask);
 
     p_addr = bm_map_pidx(b, b->bm_number_of_pages - 1);
     bm = p_addr + (tmp/BITS_PER_LONG);
     if (mask) {
         /* If mask != 0, we are not exactly aligned, so bm now points
          * to the long containing the last bit.
          * If mask == 0, bm already points to the word immediately
          * after the last (long word aligned) bit. */
         cleared = hweight_long(*bm & ~mask);
         *bm &= mask;
         bm++;
     }
 
     if (BITS_PER_LONG == 32 && ((bm - p_addr) & 1) == 1) {
         /* on a 32bit arch, we may need to zero out
          * a padding long to align with a 64bit remote */
         cleared += hweight_long(*bm);
         *bm = 0;
     }
     bm_unmap(p_addr);
     return cleared;
 }
 
 static void bm_set_surplus(struct drbd_bitmap *b)
 {
     unsigned long mask;
     unsigned long *p_addr, *bm;
     int tmp;
 
     /* number of bits modulo bits per page */
     tmp = (b->bm_bits & BITS_PER_PAGE_MASK);
     /* mask the used bits of the word containing the last bit */
     mask = (1UL << (tmp & BITS_PER_LONG_MASK)) -1;
     /* bitmap is always stored little endian,
      * on disk and in core memory alike */
     mask = cpu_to_lel(mask);
 
     p_addr = bm_map_pidx(b, b->bm_number_of_pages - 1);
     bm = p_addr + (tmp/BITS_PER_LONG);
     if (mask) {
         /* If mask != 0, we are not exactly aligned, so bm now points
          * to the long containing the last bit.
          * If mask == 0, bm already points to the word immediately
          * after the last (long word aligned) bit. */
         *bm |= ~mask;
         bm++;
     }
 
     if (BITS_PER_LONG == 32 && ((bm - p_addr) & 1) == 1) {
         /* on a 32bit arch, we may need to zero out
          * a padding long to align with a 64bit remote */
         *bm = ~0UL;
     }
     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;
     unsigned long bits = 0;
     unsigned long mask = (1UL << (b->bm_bits & BITS_PER_LONG_MASK)) -1;
     int idx, last_word;
 
     /* all but last page */
     for (idx = 0; idx < b->bm_number_of_pages - 1; idx++) {
         p_addr = __bm_map_pidx(b, idx);
         bits += bitmap_weight(p_addr, BITS_PER_PAGE);
         __bm_unmap(p_addr);
         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);
     bits += bitmap_weight(p_addr, last_word * BITS_PER_LONG);
     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);
     return bits;
 }
 
 /* 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;
     unsigned int idx;
     size_t do_now, end;
 
     end = offset + len;
 
     if (end > b->bm_words) {
         pr_alert("bm_memset end > bm_words\n");
         return;
     }
 
     while (offset < end) {
         do_now = min_t(size_t, ALIGN(offset + 1, LWPP), end) - offset;
         idx = bm_word_to_page_idx(b, offset);
         p_addr = bm_map_pidx(b, idx);
         bm = p_addr + MLPP(offset);
         if (bm+do_now > p_addr + LWPP) {
             pr_alert("BUG BUG BUG! p_addr:%p bm:%p do_now:%d\n",
                    p_addr, bm, (int)do_now);
         } else
             memset(bm, c, do_now * sizeof(long));
         bm_unmap(p_addr);
         bm_set_page_need_writeout(b->bm_pages[idx]);
         offset += do_now;
     }
 }
 
 /* For the layout, see comment above drbd_md_set_sector_offsets(). */
 static u64 drbd_md_on_disk_bits(struct drbd_backing_dev *ldev)
 {
     u64 bitmap_sectors;
     if (ldev->md.al_offset == 8)
         bitmap_sectors = ldev->md.md_size_sect - ldev->md.bm_offset;
     else
         bitmap_sectors = ldev->md.al_offset - ldev->md.bm_offset;
     return bitmap_sectors << (9 + 3);
 }
 
 /*
  * 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_device *device, sector_t capacity, int set_new_bits)
 {
     struct drbd_bitmap *b = device->bitmap;
     unsigned long bits, words, owords, obits;
     unsigned long want, have, onpages; /* number of pages */
     struct page **npages, **opages = NULL;
     int err = 0;
     bool growing;
 
     if (!expect(b))
         return -ENOMEM;
 
     drbd_bm_lock(device, "resize", BM_LOCKED_MASK);
 
     drbd_info(device, "drbd_bm_resize called with capacity == %llu\n",
             (unsigned long long)capacity);
 
     if (capacity == b->bm_dev_capacity)
         goto out;
 
     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);
         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(device)) {
         u64 bits_on_disk = drbd_md_on_disk_bits(device->ldev);
         put_ldev(device);
         if (bits > bits_on_disk) {
             drbd_info(device, "bits = %lu\n", bits);
             drbd_info(device, "bits_on_disk = %llu\n", bits_on_disk);
             err = -ENOSPC;
             goto out;
         }
     }
 
     want = PFN_UP(words*sizeof(long));
     have = b->bm_number_of_pages;
     if (want == have) {
         D_ASSERT(device, b->bm_pages != NULL);
         npages = b->bm_pages;
     } else {
         if (drbd_insert_fault(device, 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 && growing && set_new_bits)
         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) {
         if (set_new_bits) {
             bm_memset(b, owords, 0xff, words-owords);
             b->bm_set += bits - obits;
         } else
             bm_memset(b, owords, 0x00, words-owords);
 
     }
 
     if (want < have) {
         /* implicit: (opages != NULL) && (opages != npages) */
         bm_free_pages(opages + want, have - want);
     }
 
     (void)bm_clear_surplus(b);
 
     spin_unlock_irq(&b->bm_lock);
     if (opages != npages)
         bm_vk_free(opages);
     if (!growing)
         b->bm_set = bm_count_bits(b);
     drbd_info(device, "resync bitmap: bits=%lu words=%lu pages=%lu\n", bits, words, want);
 
  out:
     drbd_bm_unlock(device);
     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 ?
  */
 unsigned long _drbd_bm_total_weight(struct drbd_device *device)
 {
     struct drbd_bitmap *b = device->bitmap;
     unsigned long s;
     unsigned long flags;
 
     if (!expect(b))
         return 0;
     if (!expect(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_device *device)
 {
     unsigned long s;
     /* if I don't have a disk, I don't know about out-of-sync status */
     if (!get_ldev_if_state(device, D_NEGOTIATING))
         return 0;
     s = _drbd_bm_total_weight(device);
     put_ldev(device);
     return s;
 }
 
 size_t drbd_bm_words(struct drbd_device *device)
 {
     struct drbd_bitmap *b = device->bitmap;
     if (!expect(b))
         return 0;
     if (!expect(b->bm_pages))
         return 0;
 
     return b->bm_words;
 }
 
 unsigned long drbd_bm_bits(struct drbd_device *device)
 {
     struct drbd_bitmap *b = device->bitmap;
     if (!expect(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_device *device, size_t offset, size_t number,
             unsigned long *buffer)
 {
     struct drbd_bitmap *b = device->bitmap;
     unsigned long *p_addr, *bm;
     unsigned long word, bits;
     unsigned int idx;
     size_t end, do_now;
 
     end = offset + number;
 
     if (!expect(b))
         return;
     if (!expect(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;
         idx = bm_word_to_page_idx(b, offset);
         p_addr = bm_map_pidx(b, idx);
         bm = p_addr + MLPP(offset);
         offset += do_now;
         while (do_now--) {
             bits = hweight_long(*bm);
             word = *bm | *buffer++;
             *bm++ = word;
             b->bm_set += hweight_long(word) - bits;
         }
         bm_unmap(p_addr);
         bm_set_page_need_writeout(b->bm_pages[idx]);
     }
     /* 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_device *device, size_t offset, size_t number,
              unsigned long *buffer)
 {
     struct drbd_bitmap *b = device->bitmap;
     unsigned long *p_addr, *bm;
     size_t end, do_now;
 
     end = offset + number;
 
     if (!expect(b))
         return;
     if (!expect(b->bm_pages))
         return;
 
     spin_lock_irq(&b->bm_lock);
     if ((offset >= b->bm_words) ||
         (end    >  b->bm_words) ||
         (number <= 0))
         drbd_err(device, "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_pidx(b, bm_word_to_page_idx(b, offset));
             bm = p_addr + MLPP(offset);
             offset += do_now;
             while (do_now--)
                 *buffer++ = *bm++;
             bm_unmap(p_addr);
         }
     }
     spin_unlock_irq(&b->bm_lock);
 }
 
 /* set all bits in the bitmap */
 void drbd_bm_set_all(struct drbd_device *device)
 {
     struct drbd_bitmap *b = device->bitmap;
     if (!expect(b))
         return;
     if (!expect(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_device *device)
 {
     struct drbd_bitmap *b = device->bitmap;
     if (!expect(b))
         return;
     if (!expect(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 drbd_bm_aio_ctx_destroy(struct kref *kref)
 {
     struct drbd_bm_aio_ctx *ctx = container_of(kref, struct drbd_bm_aio_ctx, kref);
     unsigned long flags;
 
     spin_lock_irqsave(&ctx->device->resource->req_lock, flags);
     list_del(&ctx->list);
     spin_unlock_irqrestore(&ctx->device->resource->req_lock, flags);
     put_ldev(ctx->device);
     kfree(ctx);
 }
 
 /* bv_page may be a copy, or may be the original */
 static void drbd_bm_endio(struct bio *bio)
 {
     struct drbd_bm_aio_ctx *ctx = bio->bi_private;
     struct drbd_device *device = ctx->device;
     struct drbd_bitmap *b = device->bitmap;
     unsigned int idx = bm_page_to_idx(bio_first_page_all(bio));
 
     if ((ctx->flags & BM_AIO_COPY_PAGES) == 0 &&
         !bm_test_page_unchanged(b->bm_pages[idx]))
         drbd_warn(device, "bitmap page idx %u changed during IO!\n", idx);
 
     if (bio->bi_status) {
         /* ctx error will hold the completed-last non-zero error code,
          * in case error codes differ. */
         ctx->error = blk_status_to_errno(bio->bi_status);
         bm_set_page_io_err(b->bm_pages[idx]);
         /* Not identical to on disk version of it.
          * Is BM_PAGE_IO_ERROR enough? */
         if (__ratelimit(&drbd_ratelimit_state))
             drbd_err(device, "IO ERROR %d on bitmap page idx %u\n",
                     bio->bi_status, idx);
     } else {
         bm_clear_page_io_err(b->bm_pages[idx]);
         dynamic_drbd_dbg(device, "bitmap page idx %u completed\n", idx);
     }
 
     bm_page_unlock_io(device, idx);
 
     if (ctx->flags & BM_AIO_COPY_PAGES)
         mempool_free(bio->bi_io_vec[0].bv_page, &drbd_md_io_page_pool);
 
     bio_put(bio);
 
     if (atomic_dec_and_test(&ctx->in_flight)) {
         ctx->done = 1;
         wake_up(&device->misc_wait);
         kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
     }
 }
 
 /* For the layout, see comment above drbd_md_set_sector_offsets(). */
 static inline sector_t drbd_md_last_bitmap_sector(struct drbd_backing_dev *bdev)
 {
     switch (bdev->md.meta_dev_idx) {
     case DRBD_MD_INDEX_INTERNAL:
     case DRBD_MD_INDEX_FLEX_INT:
         return bdev->md.md_offset + bdev->md.al_offset -1;
     case DRBD_MD_INDEX_FLEX_EXT:
     default:
         return bdev->md.md_offset + bdev->md.md_size_sect -1;
     }
 }
 
 static void bm_page_io_async(struct drbd_bm_aio_ctx *ctx, int page_nr) __must_hold(local)
 {
     struct drbd_device *device = ctx->device;
     enum req_op op = ctx->flags & BM_AIO_READ ? REQ_OP_READ : REQ_OP_WRITE;
     struct drbd_bitmap *b = device->bitmap;
     struct bio *bio;
     struct page *page;
     sector_t last_bm_sect;
     sector_t first_bm_sect;
     sector_t on_disk_sector;
     unsigned int len;
 
     first_bm_sect = device->ldev->md.md_offset + device->ldev->md.bm_offset;
     on_disk_sector = first_bm_sect + (((sector_t)page_nr) << (PAGE_SHIFT-SECTOR_SHIFT));
 
     /* this might happen with very small
      * flexible external meta data device,
      * or with PAGE_SIZE > 4k */
     last_bm_sect = drbd_md_last_bitmap_sector(device->ldev);
     if (first_bm_sect <= on_disk_sector && last_bm_sect >= on_disk_sector) {
         sector_t len_sect = last_bm_sect - on_disk_sector + 1;
         if (len_sect < PAGE_SIZE/SECTOR_SIZE)
             len = (unsigned int)len_sect*SECTOR_SIZE;
         else
             len = PAGE_SIZE;
     } else {
         if (__ratelimit(&drbd_ratelimit_state)) {
             drbd_err(device, "Invalid offset during on-disk bitmap access: "
                  "page idx %u, sector %llu\n", page_nr, on_disk_sector);
         }
         ctx->error = -EIO;
         bm_set_page_io_err(b->bm_pages[page_nr]);
         if (atomic_dec_and_test(&ctx->in_flight)) {
             ctx->done = 1;
             wake_up(&device->misc_wait);
             kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
         }
         return;
     }
 
     /* serialize IO on this page */
     bm_page_lock_io(device, page_nr);
     /* before memcpy and submit,
      * so it can be redirtied any time */
     bm_set_page_unchanged(b->bm_pages[page_nr]);
 
     if (ctx->flags & BM_AIO_COPY_PAGES) {
         page = mempool_alloc(&drbd_md_io_page_pool,
                 GFP_NOIO | __GFP_HIGHMEM);
         copy_highpage(page, b->bm_pages[page_nr]);
         bm_store_page_idx(page, page_nr);
     } else
         page = b->bm_pages[page_nr];
     bio = bio_alloc_bioset(device->ldev->md_bdev, 1, op, GFP_NOIO,
             &drbd_md_io_bio_set);
     bio->bi_iter.bi_sector = on_disk_sector;
     /* bio_add_page of a single page to an empty bio will always succeed,
      * according to api.  Do we want to assert that? */
     bio_add_page(bio, page, len, 0);
     bio->bi_private = ctx;
     bio->bi_end_io = drbd_bm_endio;
 
     if (drbd_insert_fault(device, (op == REQ_OP_WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD)) {
         bio_io_error(bio);
     } else {
         submit_bio(bio);
         /* this should not count as user activity and cause the
          * resync to throttle -- see drbd_rs_should_slow_down(). */
         atomic_add(len >> 9, &device->rs_sect_ev);
     }
 }
 
 /*
  * bm_rw: read/write the whole bitmap from/to its on disk location.
  */
 static int bm_rw(struct drbd_device *device, const unsigned int flags, unsigned lazy_writeout_upper_idx) __must_hold(local)
 {
     struct drbd_bm_aio_ctx *ctx;
     struct drbd_bitmap *b = device->bitmap;
     unsigned int num_pages, i, count = 0;
     unsigned long now;
     char ppb[10];
     int err = 0;
 
     /*
      * We are protected against bitmap disappearing/resizing by holding an
      * ldev reference (caller must have called get_ldev()).
      * For read/write, we are protected against changes to the bitmap by
      * the bitmap lock (see drbd_bitmap_io).
      * For lazy writeout, we don't care for ongoing changes to the bitmap,
      * as we submit copies of pages anyways.
      */
 
     ctx = kmalloc(sizeof(struct drbd_bm_aio_ctx), GFP_NOIO);
     if (!ctx)
         return -ENOMEM;
 
     *ctx = (struct drbd_bm_aio_ctx) {
         .device = device,
         .start_jif = jiffies,
         .in_flight = ATOMIC_INIT(1),
         .done = 0,
         .flags = flags,
         .error = 0,
         .kref = KREF_INIT(2),
     };
 
     if (!get_ldev_if_state(device, D_ATTACHING)) {  /* put is in drbd_bm_aio_ctx_destroy() */
         drbd_err(device, "ASSERT FAILED: get_ldev_if_state() == 1 in bm_rw()\n");
         kfree(ctx);
         return -ENODEV;
     }
     /* Here D_ATTACHING is sufficient since drbd_bm_read() is called only from
        drbd_adm_attach(), after device->ldev was assigned. */
 
     if (0 == (ctx->flags & ~BM_AIO_READ))
         WARN_ON(!(BM_LOCKED_MASK & b->bm_flags));
 
     spin_lock_irq(&device->resource->req_lock);
     list_add_tail(&ctx->list, &device->pending_bitmap_io);
     spin_unlock_irq(&device->resource->req_lock);
 
     num_pages = b->bm_number_of_pages;
 
     now = jiffies;
 
     /* let the layers below us try to merge these bios... */
 
     if (flags & BM_AIO_READ) {
         for (i = 0; i < num_pages; i++) {
             atomic_inc(&ctx->in_flight);
             bm_page_io_async(ctx, i);
             ++count;
             cond_resched();
         }
     } else if (flags & BM_AIO_WRITE_HINTED) {
         /* ASSERT: BM_AIO_WRITE_ALL_PAGES is not set. */
         unsigned int hint;
         for (hint = 0; hint < b->n_bitmap_hints; hint++) {
             i = b->al_bitmap_hints[hint];
             if (i >= num_pages) /* == -1U: no hint here. */
                 continue;
             /* Several AL-extents may point to the same page. */
             if (!test_and_clear_bit(BM_PAGE_HINT_WRITEOUT,
                 &page_private(b->bm_pages[i])))
                 continue;
             /* Has it even changed? */
             if (bm_test_page_unchanged(b->bm_pages[i]))
                 continue;
             atomic_inc(&ctx->in_flight);
             bm_page_io_async(ctx, i);
             ++count;
         }
     } else {
         for (i = 0; i < num_pages; i++) {
             /* ignore completely unchanged pages */
             if (lazy_writeout_upper_idx && i == lazy_writeout_upper_idx)
                 break;
             if (!(flags & BM_AIO_WRITE_ALL_PAGES) &&
                 bm_test_page_unchanged(b->bm_pages[i])) {
                 dynamic_drbd_dbg(device, "skipped bm write for idx %u\n", i);
                 continue;
             }
             /* during lazy writeout,
              * ignore those pages not marked for lazy writeout. */
             if (lazy_writeout_upper_idx &&
                 !bm_test_page_lazy_writeout(b->bm_pages[i])) {
                 dynamic_drbd_dbg(device, "skipped bm lazy write for idx %u\n", i);
                 continue;
             }
             atomic_inc(&ctx->in_flight);
             bm_page_io_async(ctx, i);
             ++count;
             cond_resched();
         }
     }
 
     /*
      * We initialize ctx->in_flight to one to make sure drbd_bm_endio
      * will not set ctx->done early, and decrement / test it here.  If there
      * are still some bios in flight, we need to wait for them here.
      * If all IO is done already (or nothing had been submitted), there is
      * no need to wait.  Still, we need to put the kref associated with the
      * "in_flight reached zero, all done" event.
      */
     if (!atomic_dec_and_test(&ctx->in_flight))
         wait_until_done_or_force_detached(device, device->ldev, &ctx->done);
     else
         kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
 
     /* summary for global bitmap IO */
     if (flags == 0) {
         unsigned int ms = jiffies_to_msecs(jiffies - now);
         if (ms > 5) {
             drbd_info(device, "bitmap %s of %u pages took %u ms\n",
                  (flags & BM_AIO_READ) ? "READ" : "WRITE",
                  count, ms);
         }
     }
 
     if (ctx->error) {
         drbd_alert(device, "we had at least one MD IO ERROR during bitmap IO\n");
         drbd_chk_io_error(device, 1, DRBD_META_IO_ERROR);
         err = -EIO; /* ctx->error ? */
     }
 
     if (atomic_read(&ctx->in_flight))
         err = -EIO; /* Disk timeout/force-detach during IO... */
 
     now = jiffies;
     if (flags & BM_AIO_READ) {
         b->bm_set = bm_count_bits(b);
         drbd_info(device, "recounting of set bits took additional %lu jiffies\n",
              jiffies - now);
     }
     now = b->bm_set;
 
     if ((flags & ~BM_AIO_READ) == 0)
         drbd_info(device, "%s (%lu bits) marked out-of-sync by on disk bit-map.\n",
              ppsize(ppb, now << (BM_BLOCK_SHIFT-10)), now);
 
     kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
     return err;
 }
 
 /**
  * drbd_bm_read() - Read the whole bitmap from its on disk location.
  * @device: DRBD device.
  */
 int drbd_bm_read(struct drbd_device *device) __must_hold(local)
 {
     return bm_rw(device, BM_AIO_READ, 0);
 }
 
 /**
  * drbd_bm_write() - Write the whole bitmap to its on disk location.
  * @device: DRBD device.
  *
  * Will only write pages that have changed since last IO.
  */
 int drbd_bm_write(struct drbd_device *device) __must_hold(local)
 {
     return bm_rw(device, 0, 0);
 }
 
 /**
  * drbd_bm_write_all() - Write the whole bitmap to its on disk location.
  * @device: DRBD device.
  *
  * Will write all pages.
  */
 int drbd_bm_write_all(struct drbd_device *device) __must_hold(local)
 {
     return bm_rw(device, BM_AIO_WRITE_ALL_PAGES, 0);
 }
 
 /**
  * drbd_bm_write_lazy() - Write bitmap pages 0 to @upper_idx-1, if they have changed.
  * @device: DRBD device.
  * @upper_idx:  0: write all changed pages; +ve: page index to stop scanning for changed pages
  */
 int drbd_bm_write_lazy(struct drbd_device *device, unsigned upper_idx) __must_hold(local)
 {
     return bm_rw(device, BM_AIO_COPY_PAGES, upper_idx);
 }
 
 /**
  * drbd_bm_write_copy_pages() - Write the whole bitmap to its on disk location.
  * @device: DRBD device.
  *
  * Will only write pages that have changed since last IO.
  * In contrast to drbd_bm_write(), this will copy the bitmap pages
  * to temporary writeout pages. It is intended to trigger a full write-out
  * while still allowing the bitmap to change, for example if a resync or online
  * verify is aborted due to a failed peer disk, while local IO continues, or
  * pending resync acks are still being processed.
  */
 int drbd_bm_write_copy_pages(struct drbd_device *device) __must_hold(local)
 {
     return bm_rw(device, BM_AIO_COPY_PAGES, 0);
 }
 
 /**
  * drbd_bm_write_hinted() - Write bitmap pages with "hint" marks, if they have changed.
  * @device: DRBD device.
  */
 int drbd_bm_write_hinted(struct drbd_device *device) __must_hold(local)
 {
     return bm_rw(device, BM_AIO_WRITE_HINTED | BM_AIO_COPY_PAGES, 0);
 }
 
 /* NOTE
  * find_first_bit returns int, we return unsigned long.
  * 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!
  */
 static unsigned long __bm_find_next(struct drbd_device *device, unsigned long bm_fo,
     const int find_zero_bit)
 {
     struct drbd_bitmap *b = device->bitmap;
     unsigned long *p_addr;
     unsigned long bit_offset;
     unsigned i;
 
 
     if (bm_fo > b->bm_bits) {
         drbd_err(device, "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 & ~BITS_PER_PAGE_MASK;
             p_addr = __bm_map_pidx(b, bm_bit_to_page_idx(b, bm_fo));
 
             if (find_zero_bit)
                 i = find_next_zero_bit_le(p_addr,
                         PAGE_SIZE*8, bm_fo & BITS_PER_PAGE_MASK);
             else
                 i = find_next_bit_le(p_addr,
                         PAGE_SIZE*8, bm_fo & BITS_PER_PAGE_MASK);
 
             __bm_unmap(p_addr);
             if (i < PAGE_SIZE*8) {
                 bm_fo = bit_offset + i;
                 if (bm_fo >= b->bm_bits)
                     break;
                 goto found;
             }
             bm_fo = bit_offset + PAGE_SIZE*8;
         }
         bm_fo = DRBD_END_OF_BITMAP;
     }
  found:
     return bm_fo;
 }
 
 static unsigned long bm_find_next(struct drbd_device *device,
     unsigned long bm_fo, const int find_zero_bit)
 {
     struct drbd_bitmap *b = device->bitmap;
     unsigned long i = DRBD_END_OF_BITMAP;
 
     if (!expect(b))
         return i;
     if (!expect(b->bm_pages))
         return i;
 
     spin_lock_irq(&b->bm_lock);
     if (BM_DONT_TEST & b->bm_flags)
         bm_print_lock_info(device);
 
     i = __bm_find_next(device, bm_fo, find_zero_bit);
 
     spin_unlock_irq(&b->bm_lock);
     return i;
 }
 
 unsigned long drbd_bm_find_next(struct drbd_device *device, unsigned long bm_fo)
 {
     return bm_find_next(device, bm_fo, 0);
 }
 
 #if 0
 /* not yet needed for anything. */
 unsigned long drbd_bm_find_next_zero(struct drbd_device *device, unsigned long bm_fo)
 {
     return bm_find_next(device, bm_fo, 1);
 }
 #endif
 
 /* does not spin_lock_irqsave.
  * you must take drbd_bm_lock() first */
 unsigned long _drbd_bm_find_next(struct drbd_device *device, unsigned long bm_fo)
 {
     /* WARN_ON(!(BM_DONT_SET & device->b->bm_flags)); */
     return __bm_find_next(device, bm_fo, 0);
 }
 
 unsigned long _drbd_bm_find_next_zero(struct drbd_device *device, unsigned long bm_fo)
 {
     /* WARN_ON(!(BM_DONT_SET & device->b->bm_flags)); */
     return __bm_find_next(device, bm_fo, 1);
 }
 
 /* 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. */
 static int __bm_change_bits_to(struct drbd_device *device, const unsigned long s,
     unsigned long e, int val)
 {
     struct drbd_bitmap *b = device->bitmap;
     unsigned long *p_addr = NULL;
     unsigned long bitnr;
     unsigned int last_page_nr = -1U;
     int c = 0;
     int changed_total = 0;
 
     if (e >= b->bm_bits) {
         drbd_err(device, "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 int page_nr = bm_bit_to_page_idx(b, bitnr);
         if (page_nr != last_page_nr) {
             if (p_addr)
                 __bm_unmap(p_addr);
             if (c < 0)
                 bm_set_page_lazy_writeout(b->bm_pages[last_page_nr]);
             else if (c > 0)
                 bm_set_page_need_writeout(b->bm_pages[last_page_nr]);
             changed_total += c;
             c = 0;
             p_addr = __bm_map_pidx(b, page_nr);
             last_page_nr = page_nr;
         }
         if (val)
             c += (0 == __test_and_set_bit_le(bitnr & BITS_PER_PAGE_MASK, p_addr));
         else
             c -= (0 != __test_and_clear_bit_le(bitnr & BITS_PER_PAGE_MASK, p_addr));
     }
     if (p_addr)
         __bm_unmap(p_addr);
     if (c < 0)
         bm_set_page_lazy_writeout(b->bm_pages[last_page_nr]);
     else if (c > 0)
         bm_set_page_need_writeout(b->bm_pages[last_page_nr]);
     changed_total += c;
     b->bm_set += changed_total;
     return changed_total;
 }
 
 /* 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 */
 static int bm_change_bits_to(struct drbd_device *device, const unsigned long s,
     const unsigned long e, int val)
 {
     unsigned long flags;
     struct drbd_bitmap *b = device->bitmap;
     int c = 0;
 
     if (!expect(b))
         return 1;
     if (!expect(b->bm_pages))
         return 0;
 
     spin_lock_irqsave(&b->bm_lock, flags);
     if ((val ? BM_DONT_SET : BM_DONT_CLEAR) & b->bm_flags)
         bm_print_lock_info(device);
 
     c = __bm_change_bits_to(device, s, e, val);
 
     spin_unlock_irqrestore(&b->bm_lock, flags);
     return c;
 }
 
 /* returns number of bits changed 0 -> 1 */
 int drbd_bm_set_bits(struct drbd_device *device, const unsigned long s, const unsigned long e)
 {
     return bm_change_bits_to(device, s, e, 1);
 }
 
 /* returns number of bits changed 1 -> 0 */
 int drbd_bm_clear_bits(struct drbd_device *device, const unsigned long s, const unsigned long e)
 {
     return -bm_change_bits_to(device, 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;
     int changed = 0;
     unsigned long *paddr = kmap_atomic(b->bm_pages[page_nr]);
 
     /* I think it is more cache line friendly to hweight_long then set to ~0UL,
      * than to first bitmap_weight() all words, then bitmap_fill() all words */
     for (i = first_word; i < last_word; i++) {
         bits = hweight_long(paddr[i]);
         paddr[i] = ~0UL;
         changed += BITS_PER_LONG - bits;
     }
     kunmap_atomic(paddr);
     if (changed) {
         /* We only need lazy writeout, the information is still in the
          * remote bitmap as well, and is reconstructed during the next
          * bitmap exchange, if lost locally due to a crash. */
         bm_set_page_lazy_writeout(b->bm_pages[page_nr]);
         b->bm_set += changed;
     }
 }
 
 /* Same thing as drbd_bm_set_bits,
  * but more efficient for a large bit range.
  * 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_device *device, 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.
      */
     struct drbd_bitmap *b = device->bitmap;
     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. */
         spin_lock_irq(&b->bm_lock);
         __bm_change_bits_to(device, s, e, 1);
         spin_unlock_irq(&b->bm_lock);
         return;
     }
 
     /* difference is large enough that we can trust sl and el */
 
     spin_lock_irq(&b->bm_lock);
 
     /* bits filling the current long */
     if (sl)
         __bm_change_bits_to(device, s, sl-1, 1);
 
     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(device->bitmap, page_nr, first_word, last_word);
         spin_unlock_irq(&b->bm_lock);
         cond_resched();
         first_word = 0;
         spin_lock_irq(&b->bm_lock);
     }
     /* last page (respectively only page, for first page == last page) */
     last_word = MLPP(el >> LN2_BPL);
 
     /* consider bitmap->bm_bits = 32768, bitmap->bm_number_of_pages = 1. (or multiples).
      * ==> e = 32767, el = 32768, last_page = 2,
      * and now last_word = 0.
      * We do not want to touch last_page in this case,
      * as we did not allocate it, it is not present in bitmap->bm_pages.
      */
     if (last_word)
         bm_set_full_words_within_one_page(device->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(device, el, e, 1);
     spin_unlock_irq(&b->bm_lock);
 }
 
 /* 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_device *device, const unsigned long bitnr)
 {
     unsigned long flags;
     struct drbd_bitmap *b = device->bitmap;
     unsigned long *p_addr;
     int i;
 
     if (!expect(b))
         return 0;
     if (!expect(b->bm_pages))
         return 0;
 
     spin_lock_irqsave(&b->bm_lock, flags);
     if (BM_DONT_TEST & b->bm_flags)
         bm_print_lock_info(device);
     if (bitnr < b->bm_bits) {
         p_addr = bm_map_pidx(b, bm_bit_to_page_idx(b, bitnr));
         i = test_bit_le(bitnr & BITS_PER_PAGE_MASK, p_addr) ? 1 : 0;
         bm_unmap(p_addr);
     } else if (bitnr == b->bm_bits) {
         i = -1;
     } else { /* (bitnr > b->bm_bits) */
         drbd_err(device, "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_device *device, const unsigned long s, const unsigned long e)
 {
     unsigned long flags;
     struct drbd_bitmap *b = device->bitmap;
     unsigned long *p_addr = NULL;
     unsigned long bitnr;
     unsigned int page_nr = -1U;
     int c = 0;
 
     /* 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) */
     if (!expect(b))
         return 1;
     if (!expect(b->bm_pages))
         return 1;
 
     spin_lock_irqsave(&b->bm_lock, flags);
     if (BM_DONT_TEST & b->bm_flags)
         bm_print_lock_info(device);
     for (bitnr = s; bitnr <= e; bitnr++) {
         unsigned int idx = bm_bit_to_page_idx(b, bitnr);
         if (page_nr != idx) {
             page_nr = idx;
             if (p_addr)
                 bm_unmap(p_addr);
             p_addr = bm_map_pidx(b, idx);
         }
         if (expect(bitnr < b->bm_bits))
             c += (0 != test_bit_le(bitnr - (page_nr << (PAGE_SHIFT+3)), p_addr));
         else
             drbd_err(device, "bitnr=%lu bm_bits=%lu\n", bitnr, b->bm_bits);
     }
     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_device *device, unsigned long enr)
 {
     struct drbd_bitmap *b = device->bitmap;
     int count, s, e;
     unsigned long flags;
     unsigned long *p_addr, *bm;
 
     if (!expect(b))
         return 0;
     if (!expect(b->bm_pages))
         return 0;
 
     spin_lock_irqsave(&b->bm_lock, flags);
     if (BM_DONT_TEST & b->bm_flags)
         bm_print_lock_info(device);
 
     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_pidx(b, bm_word_to_page_idx(b, s));
         bm = p_addr + MLPP(s);
         count += bitmap_weight(bm, n * BITS_PER_LONG);
         bm_unmap(p_addr);
     } else {
         drbd_err(device, "start offset (%d) too large in drbd_bm_e_weight\n", s);
     }
     spin_unlock_irqrestore(&b->bm_lock, flags);
     return count;
 }

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