/* 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 . Copyright (C) 2004-2008, Lars Ellenberg . 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 #include #include #include #include #include #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; /* 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)); } /** * 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 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]; set_bit(BM_PAGE_HINT_WRITEOUT, &page_private(page)); } static int bm_test_page_unchanged(struct page *page) { volatile const unsigned long *addr = &page_private(page); return (*addr & ((1UL<> 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]) { 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_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_HIGHMEM | __GFP_ZERO, PAGE_KERNEL); if (!new_pages) return NULL; vmalloced = 1; } 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, vmalloced); 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); */ } if (vmalloced) b->bm_flags |= BM_P_VMALLOCED; else b->bm_flags &= ~BM_P_VMALLOCED; return new_pages; } /* * called on driver init only. TODO call when a device is created. * 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, (BM_P_VMALLOCED & device->bitmap->bm_flags)); 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. */ #define BITS_PER_PAGE (1UL << (PAGE_SHIFT + 3)) #define BITS_PER_PAGE_MASK (BITS_PER_PAGE - 1) #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, i, last_word; /* all but last page */ for (idx = 0; idx < b->bm_number_of_pages - 1; idx++) { p_addr = __bm_map_pidx(b, idx); for (i = 0; i < LWPP; i++) bits += hweight_long(p_addr[i]); __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); for (i = 0; i < last_word; i++) bits += hweight_long(p_addr[i]); p_addr[last_word] &= cpu_to_lel(mask); bits += hweight_long(p_addr[last_word]); /* 32bit arch, may have an unused padding long */ if (BITS_PER_LONG == 32 && (last_word & 1) == 0) p_addr[last_word+1] = 0; __bm_unmap(p_addr); 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) { 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; 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) { printk(KERN_ALERT "drbd: 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, growing; int opages_vmalloced; 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; opages_vmalloced = (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(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 = ALIGN(words*sizeof(long), PAGE_SIZE) >> PAGE_SHIFT; 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, opages_vmalloced); 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); } struct bm_aio_ctx { struct drbd_device *device; atomic_t in_flight; unsigned int done; unsigned flags; #define BM_AIO_COPY_PAGES 1 #define BM_AIO_WRITE_HINTED 2 #define BM_WRITE_ALL_PAGES 4 int error; struct kref kref; }; static void bm_aio_ctx_destroy(struct kref *kref) { struct bm_aio_ctx *ctx = container_of(kref, struct bm_aio_ctx, kref); put_ldev(ctx->device); kfree(ctx); } /* bv_page may be a copy, or may be the original */ static void bm_async_io_complete(struct bio *bio, int error) { struct 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->bi_io_vec[0].bv_page); 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 ((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 (error) { /* ctx error will hold the completed-last non-zero error code, * in case error codes differ. */ ctx->error = error; 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", error, 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, &bm_aio_ctx_destroy); } } static void bm_page_io_async(struct bm_aio_ctx *ctx, int page_nr, int rw) __must_hold(local) { struct bio *bio = bio_alloc_drbd(GFP_NOIO); struct drbd_device *device = ctx->device; struct drbd_bitmap *b = device->bitmap; struct page *page; unsigned int len; sector_t on_disk_sector = device->ldev->md.md_offset + device->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, * or with PAGE_SIZE > 4k */ len = min_t(unsigned int, PAGE_SIZE, (drbd_md_last_sector(device->ldev) - on_disk_sector + 1)<<9); /* 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_HIGHMEM|__GFP_WAIT); copy_highpage(page, b->bm_pages[page_nr]); bm_store_page_idx(page, page_nr); } else page = b->bm_pages[page_nr]; bio->bi_bdev = device->ldev->md_bdev; 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 = bm_async_io_complete; if (drbd_insert_fault(device, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD)) { bio->bi_rw |= rw; bio_endio(bio, -EIO); } else { submit_bio(rw, 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, int rw, unsigned flags, unsigned lazy_writeout_upper_idx) __must_hold(local) { struct bm_aio_ctx *ctx; struct drbd_bitmap *b = device->bitmap; 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 bm_aio_ctx), GFP_NOIO); if (!ctx) return -ENOMEM; *ctx = (struct bm_aio_ctx) { .device = device, .in_flight = ATOMIC_INIT(1), .done = 0, .flags = flags, .error = 0, .kref = { ATOMIC_INIT(2) }, }; if (!get_ldev_if_state(device, D_ATTACHING)) { /* put is in 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 (!ctx->flags) WARN_ON(!(BM_LOCKED_MASK & b->bm_flags)); num_pages = b->bm_number_of_pages; now = jiffies; /* let the layers below us try to merge these bios... */ for (i = 0; i < num_pages; i++) { /* ignore completely unchanged pages */ if (lazy_writeout_upper_idx && i == lazy_writeout_upper_idx) break; if (rw & WRITE) { if ((flags & BM_AIO_WRITE_HINTED) && !test_and_clear_bit(BM_PAGE_HINT_WRITEOUT, &page_private(b->bm_pages[i]))) continue; if (!(flags & BM_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, rw); ++count; cond_resched(); } /* * We initialize ctx->in_flight to one to make sure bm_async_io_complete * 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, &bm_aio_ctx_destroy); /* summary for global bitmap IO */ if (flags == 0) drbd_info(device, "bitmap %s of %u pages took %lu jiffies\n", rw == WRITE ? "WRITE" : "READ", count, jiffies - now); 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 (rw == WRITE) { drbd_md_flush(device); } else /* rw == 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 == 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, &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, READ, 0, 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, WRITE, 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, WRITE, BM_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, WRITE, 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, WRITE, 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]); 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); while (n--) count += hweight_long(*bm++); 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; }