path: root/drivers/block/drbd/drbd_bitmap.c

/*
   drbd_bitmap.c

   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.

   Copyright (C) 2004-2008, LINBIT Information Technologies GmbH.
   Copyright (C) 2004-2008, Philipp Reisner <philipp.reisner@linbit.com>.
   Copyright (C) 2004-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.

   drbd is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   drbd is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with drbd; see the file COPYING.  If not, write to
   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/bitops.h>
#include <linux/vmalloc.h>
#include <linux/string.h>
#include <linux/drbd.h>
#include <linux/slab.h>
#include <asm/kmap_types.h>
#include "drbd_int.h"

/* OPAQUE outside this file!
 * interface defined in drbd_int.h

 * convention:
 * function name drbd_bm_... => used elsewhere, "public".
 * function name      bm_... => internal to implementation, "private".

 * Note that since find_first_bit returns int, at the current granularity of
 * the bitmap (4KB per byte), this implementation "only" supports up to
 * 1<<(32+12) == 16 TB...
 */

/*
 * NOTE
 *  Access to the *bm_pages is protected by bm_lock.
 *  It is safe to read the other members within the lock.
 *
 *  drbd_bm_set_bits is called from bio_endio callbacks,
 *  We may be called with irq already disabled,
 *  so we need spin_lock_irqsave().
 *  And we need the kmap_atomic.
 */
struct drbd_bitmap {
	struct page **bm_pages;
	spinlock_t bm_lock;
	/* WARNING unsigned long bm_*:
	 * 32bit number of bit offset is just enough for 512 MB bitmap.
	 * it will blow up if we make the bitmap bigger...
	 * not that it makes much sense to have a bitmap that large,
	 * rather change the granularity to 16k or 64k or something.
	 * (that implies other problems, however...)
	 */
	unsigned long bm_set;       /* nr of set bits; THINK maybe atomic_t? */
	unsigned long bm_bits;
	size_t   bm_words;
	size_t   bm_number_of_pages;
	sector_t bm_dev_capacity;
	struct mutex bm_change; /* serializes resize operations */

	atomic_t bm_async_io;
	wait_queue_head_t bm_io_wait;

	unsigned long  bm_flags;

	/* debugging aid, in case we are still racy somewhere */
	char          *bm_why;
	struct task_struct *bm_task;
};

/* definition of bits in bm_flags */
#define BM_LOCKED       0
#define BM_MD_IO_ERROR  1
#define BM_P_VMALLOCED  2

static int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
			       unsigned long e, int val, const enum km_type km);

static int bm_is_locked(struct drbd_bitmap *b)
{
	return test_bit(BM_LOCKED, &b->bm_flags);
}

#define bm_print_lock_info(m) __bm_print_lock_info(m, __func__)
static void __bm_print_lock_info(struct drbd_conf *mdev, const char *func)
{
	struct drbd_bitmap *b = mdev->bitmap;
	if (!__ratelimit(&drbd_ratelimit_state))
		return;
	dev_err(DEV, "FIXME %s in %s, bitmap locked for '%s' by %s\n",
	    current == mdev->receiver.task ?