drbd: Add explicit device parameter to D_ASSERT

[deliverable/linux.git] / drivers / block / drbd / drbd_actlog.c

/*
   drbd_actlog.c

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

   Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
   Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
   Copyright (C) 2003-2008, 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/slab.h>
#include <linux/crc32c.h>
#include <linux/drbd.h>
#include <linux/drbd_limits.h>
#include <linux/dynamic_debug.h>
#include "drbd_int.h"
#include "drbd_wrappers.h"


enum al_transaction_types {
        AL_TR_UPDATE = 0,
        AL_TR_INITIALIZED = 0xffff
};
/* all fields on disc in big endian */
struct __packed al_transaction_on_disk {
        /* don't we all like magic */
        __be32  magic;

        /* to identify the most recent transaction block
         * in the on disk ring buffer */
        __be32  tr_number;

        /* checksum on the full 4k block, with this field set to 0. */
        __be32  crc32c;

        /* type of transaction, special transaction types like:
         * purge-all, set-all-idle, set-all-active, ... to-be-defined
         * see also enum al_transaction_types */
        __be16  transaction_type;

        /* we currently allow only a few thousand extents,
         * so 16bit will be enough for the slot number. */

        /* how many updates in this transaction */
        __be16  n_updates;

        /* maximum slot number, "al-extents" in drbd.conf speak.
         * Having this in each transaction should make reconfiguration
         * of that parameter easier. */
        __be16  context_size;

        /* slot number the context starts with */
        __be16  context_start_slot_nr;

        /* Some reserved bytes.  Expected usage is a 64bit counter of
         * sectors-written since device creation, and other data generation tag
         * supporting usage */
        __be32  __reserved[4];

        /* --- 36 byte used --- */

        /* Reserve space for up to AL_UPDATES_PER_TRANSACTION changes
         * in one transaction, then use the remaining byte in the 4k block for
         * context information.  "Flexible" number of updates per transaction
         * does not help, as we have to account for the case when all update
         * slots are used anyways, so it would only complicate code without
         * additional benefit.
         */
        __be16  update_slot_nr[AL_UPDATES_PER_TRANSACTION];

        /* but the extent number is 32bit, which at an extent size of 4 MiB
         * allows to cover device sizes of up to 2**54 Byte (16 PiB) */
        __be32  update_extent_nr[AL_UPDATES_PER_TRANSACTION];

        /* --- 420 bytes used (36 + 64*6) --- */

        /* 4096 - 420 = 3676 = 919 * 4 */
        __be32  context[AL_CONTEXT_PER_TRANSACTION];
};

struct update_odbm_work {
        struct drbd_work w;
        unsigned int enr;
};

struct update_al_work {
        struct drbd_work w;
        struct completion event;
        int err;
};


void *drbd_md_get_buffer(struct drbd_device *device)
{
        int r;

        wait_event(device->misc_wait,
                   (r = atomic_cmpxchg(&device->md_io_in_use, 0, 1)) == 0 ||
                   device->state.disk <= D_FAILED);

        return r ? NULL : page_address(device->md_io_page);
}

void drbd_md_put_buffer(struct drbd_device *device)
{
        if (atomic_dec_and_test(&device->md_io_in_use))
                wake_up(&device->misc_wait);
}

void wait_until_done_or_force_detached(struct drbd_device *device, struct drbd_backing_dev *bdev,
                                     unsigned int *done)
{
        long dt;

        rcu_read_lock();
        dt = rcu_dereference(bdev->disk_conf)->disk_timeout;
        rcu_read_unlock();
        dt = dt * HZ / 10;
        if (dt == 0)
                dt = MAX_SCHEDULE_TIMEOUT;

        dt = wait_event_timeout(device->misc_wait,
                        *done || test_bit(FORCE_DETACH, &device->flags), dt);
        if (dt == 0) {
                drbd_err(device, "meta-data IO operation timed out\n");
                drbd_chk_io_error(device, 1, DRBD_FORCE_DETACH);
        }
}

static int _drbd_md_sync_page_io(struct drbd_device *device,
                                 struct drbd_backing_dev *bdev,
                                 struct page *page, sector_t sector,
                                 int rw, int size)
{
        struct bio *bio;
        int err;

        device->md_io.done = 0;
        device->md_io.error = -ENODEV;

        if ((rw & WRITE) && !test_bit(MD_NO_FUA, &device->flags))
                rw |= REQ_FUA | REQ_FLUSH;
        rw |= REQ_SYNC;

        bio = bio_alloc_drbd(GFP_NOIO);
        bio->bi_bdev = bdev->md_bdev;
        bio->bi_iter.bi_sector = sector;
        err = -EIO;
        if (bio_add_page(bio, page, size, 0) != size)
                goto out;
        bio->bi_private = &device->md_io;
        bio->bi_end_io = drbd_md_io_complete;
        bio->bi_rw = rw;

        if (!(rw & WRITE) && device->state.disk == D_DISKLESS && device->ldev == NULL)
                /* special case, drbd_md_read() during drbd_adm_attach(): no get_ldev */
                ;
        else if (!get_ldev_if_state(device, D_ATTACHING)) {
                /* Corresponding put_ldev in drbd_md_io_complete() */
                drbd_err(device, "ASSERT FAILED: get_ldev_if_state() == 1 in _drbd_md_sync_page_io()\n");
                err = -ENODEV;
                goto out;
        }

        bio_get(bio); /* one bio_put() is in the completion handler */
        atomic_inc(&device->md_io_in_use); /* drbd_md_put_buffer() is in the completion handler */
        if (drbd_insert_fault(device, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD))
                bio_endio(bio, -EIO);
        else
                submit_bio(rw, bio);
        wait_until_done_or_force_detached(device, bdev, &device->md_io.done);
        if (bio_flagged(bio, BIO_UPTODATE))
                err = device->md_io.error;

 out:
        bio_put(bio);
        return err;
}

int drbd_md_sync_page_io(struct drbd_device *device, struct drbd_backing_dev *bdev,
                         sector_t sector, int rw)
{
        int err;
        struct page *iop = device->md_io_page;

        D_ASSERT(device, atomic_read(&device->md_io_in_use) == 1);

        BUG_ON(!bdev->md_bdev);

        drbd_dbg(device, "meta_data io: %s [%d]:%s(,%llus,%s) %pS\n",
             current->comm, current->pid, __func__,
             (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ",
             (void*)_RET_IP_ );

        if (sector < drbd_md_first_sector(bdev) ||
            sector + 7 > drbd_md_last_sector(bdev))
                drbd_alert(device, "%s [%d]:%s(,%llus,%s) out of range md access!\n",
                     current->comm, current->pid, __func__,
                     (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");

        /* we do all our meta data IO in aligned 4k blocks. */
        err = _drbd_md_sync_page_io(device, bdev, iop, sector, rw, 4096);
        if (err) {
                drbd_err(device, "drbd_md_sync_page_io(,%llus,%s) failed with error %d\n",
                    (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ", err);
        }
        return err;
}

static struct bm_extent *find_active_resync_extent(struct drbd_device *device, unsigned int enr)
{
        struct lc_element *tmp;
        tmp = lc_find(device->resync, enr/AL_EXT_PER_BM_SECT);
        if (unlikely(tmp != NULL)) {
                struct bm_extent  *bm_ext = lc_entry(tmp, struct bm_extent, lce);
                if (test_bit(BME_NO_WRITES, &bm_ext->flags))
                        return bm_ext;
        }
        return NULL;
}

static struct lc_element *_al_get(struct drbd_device *device, unsigned int enr, bool nonblock)
{
        struct lc_element *al_ext;
        struct bm_extent *bm_ext;
        int wake;

        spin_lock_irq(&device->al_lock);
        bm_ext = find_active_resync_extent(device, enr);
        if (bm_ext) {
                wake = !test_and_set_bit(BME_PRIORITY, &bm_ext->flags);
                spin_unlock_irq(&device->al_lock);
                if (wake)
                        wake_up(&device->al_wait);
                return NULL;
        }
        if (nonblock)
                al_ext = lc_try_get(device->act_log, enr);
        else
                al_ext = lc_get(device->act_log, enr);
        spin_unlock_irq(&device->al_lock);
        return al_ext;
}

bool drbd_al_begin_io_fastpath(struct drbd_device *device, struct drbd_interval *i)
{
        /* for bios crossing activity log extent boundaries,
         * we may need to activate two extents in one go */
        unsigned first = i->sector >> (AL_EXTENT_SHIFT-9);
        unsigned last = i->size == 0 ? first : (i->sector + (i->size >> 9) - 1) >> (AL_EXTENT_SHIFT-9);

        D_ASSERT(device, (unsigned)(last - first) <= 1);
        D_ASSERT(device, atomic_read(&device->local_cnt) > 0);

        /* FIXME figure out a fast path for bios crossing AL extent boundaries */
        if (first != last)
                return false;

        return _al_get(device, first, true);
}

static
bool drbd_al_begin_io_prepare(struct drbd_device *device, struct drbd_interval *i)
{
        /* for bios crossing activity log extent boundaries,
         * we may need to activate two extents in one go */
        unsigned first = i->sector >> (AL_EXTENT_SHIFT-9);
        unsigned last = i->size == 0 ? first : (i->sector + (i->size >> 9) - 1) >> (AL_EXTENT_SHIFT-9);
        unsigned enr;
        bool need_transaction = false;

        D_ASSERT(device, first <= last);
        D_ASSERT(device, atomic_read(&device->local_cnt) > 0);

        for (enr = first; enr <= last; enr++) {
                struct lc_element *al_ext;
                wait_event(device->al_wait,
                                (al_ext = _al_get(device, enr, false)) != NULL);
                if (al_ext->lc_number != enr)
                        need_transaction = true;
        }
        return need_transaction;
}

static int al_write_transaction(struct drbd_device *device, bool delegate);

/* When called through generic_make_request(), we must delegate
 * activity log I/O to the worker thread: a further request
 * submitted via generic_make_request() within the same task
 * would be queued on current->bio_list, and would only start
 * after this function returns (see generic_make_request()).
 *
 * However, if we *are* the worker, we must not delegate to ourselves.
 */

/*
 * @delegate:   delegate activity log I/O to the worker thread
 */
void drbd_al_begin_io_commit(struct drbd_device *device, bool delegate)
{
        bool locked = false;

        BUG_ON(delegate && current == first_peer_device(device)->connection->worker.task);

        /* Serialize multiple transactions.
         * This uses test_and_set_bit, memory barrier is implicit.
         */
        wait_event(device->al_wait,
                        device->act_log->pending_changes == 0 ||
                        (locked = lc_try_lock_for_transaction(device->act_log)));

        if (locked) {
                /* Double check: it may have been committed by someone else,
                 * while we have been waiting for the lock. */
                if (device->act_log->pending_changes) {
                        bool write_al_updates;

                        rcu_read_lock();
                        write_al_updates = rcu_dereference(device->ldev->disk_conf)->al_updates;
                        rcu_read_unlock();

                        if (write_al_updates)
                                al_write_transaction(device, delegate);
                        spin_lock_irq(&device->al_lock);
                        /* FIXME
                        if (err)
                                we need an "lc_cancel" here;
                        */
                        lc_committed(device->act_log);
                        spin_unlock_irq(&device->al_lock);
                }
                lc_unlock(device->act_log);
                wake_up(&device->al_wait);
        }
}

/*
 * @delegate:   delegate activity log I/O to the worker thread
 */
void drbd_al_begin_io(struct drbd_device *device, struct drbd_interval *i, bool delegate)
{
        BUG_ON(delegate && current == first_peer_device(device)->connection->worker.task);

        if (drbd_al_begin_io_prepare(device, i))
                drbd_al_begin_io_commit(device, delegate);
}

int drbd_al_begin_io_nonblock(struct drbd_device *device, struct drbd_interval *i)
{
        struct lru_cache *al = device->act_log;
        /* for bios crossing activity log extent boundaries,
         * we may need to activate two extents in one go */
        unsigned first = i->sector >> (AL_EXTENT_SHIFT-9);
        unsigned last = i->size == 0 ? first : (i->sector + (i->size >> 9) - 1) >> (AL_EXTENT_SHIFT-9);
        unsigned nr_al_extents;
        unsigned available_update_slots;
        unsigned enr;

        D_ASSERT(device, first <= last);

        nr_al_extents = 1 + last - first; /* worst case: all touched extends are cold. */
        available_update_slots = min(al->nr_elements - al->used,
                                al->max_pending_changes - al->pending_changes);

        /* We want all necessary updates for a given request within the same transaction
         * We could first check how many updates are *actually* needed,
         * and use that instead of the worst-case nr_al_extents */
        if (available_update_slots < nr_al_extents)
                return -EWOULDBLOCK;

        /* Is resync active in this area? */
        for (enr = first; enr <= last; enr++) {
                struct lc_element *tmp;
                tmp = lc_find(device->resync, enr/AL_EXT_PER_BM_SECT);
                if (unlikely(tmp != NULL)) {
                        struct bm_extent  *bm_ext = lc_entry(tmp, struct bm_extent, lce);
                        if (test_bit(BME_NO_WRITES, &bm_ext->flags)) {
                                if (!test_and_set_bit(BME_PRIORITY, &bm_ext->flags))
                                        return -EBUSY;
                                return -EWOULDBLOCK;
                        }
                }
        }

        /* Checkout the refcounts.
         * Given that we checked for available elements and update slots above,
         * this has to be successful. */
        for (enr = first; enr <= last; enr++) {
                struct lc_element *al_ext;
                al_ext = lc_get_cumulative(device->act_log, enr);
                if (!al_ext)
                        drbd_info(device, "LOGIC BUG for enr=%u\n", enr);
        }
        return 0;
}

void drbd_al_complete_io(struct drbd_device *device, struct drbd_interval *i)
{
        /* for bios crossing activity log extent boundaries,
         * we may need to activate two extents in one go */
        unsigned first = i->sector >> (AL_EXTENT_SHIFT-9);
        unsigned last = i->size == 0 ? first : (i->sector + (i->size >> 9) - 1) >> (AL_EXTENT_SHIFT-9);
        unsigned enr;
        struct lc_element *extent;
        unsigned long flags;

        D_ASSERT(device, first <= last);
        spin_lock_irqsave(&device->al_lock, flags);

        for (enr = first; enr <= last; enr++) {
                extent = lc_find(device->act_log, enr);
                if (!extent) {
                        drbd_err(device, "al_complete_io() called on inactive extent %u\n", enr);
                        continue;
                }
                lc_put(device->act_log, extent);
        }
        spin_unlock_irqrestore(&device->al_lock, flags);
        wake_up(&device->al_wait);
}

#if (PAGE_SHIFT + 3) < (AL_EXTENT_SHIFT - BM_BLOCK_SHIFT)
/* Currently BM_BLOCK_SHIFT, BM_EXT_SHIFT and AL_EXTENT_SHIFT
 * are still coupled, or assume too much about their relation.
 * Code below will not work if this is violated.
 * Will be cleaned up with some followup patch.
 */
# error FIXME
#endif

static unsigned int al_extent_to_bm_page(unsigned int al_enr)
{
        return al_enr >>
                /* bit to page */
                ((PAGE_SHIFT + 3) -
                /* al extent number to bit */
                 (AL_EXTENT_SHIFT - BM_BLOCK_SHIFT));
}

static unsigned int rs_extent_to_bm_page(unsigned int rs_enr)
{
        return rs_enr >>
                /* bit to page */
                ((PAGE_SHIFT + 3) -
                /* resync extent number to bit */
                 (BM_EXT_SHIFT - BM_BLOCK_SHIFT));
}

static sector_t al_tr_number_to_on_disk_sector(struct drbd_device *device)
{
        const unsigned int stripes = device->ldev->md.al_stripes;
        const unsigned int stripe_size_4kB = device->ldev->md.al_stripe_size_4k;

        /* transaction number, modulo on-disk ring buffer wrap around */
        unsigned int t = device->al_tr_number % (device->ldev->md.al_size_4k);

        /* ... to aligned 4k on disk block */
        t = ((t % stripes) * stripe_size_4kB) + t/stripes;

        /* ... to 512 byte sector in activity log */
        t *= 8;

        /* ... plus offset to the on disk position */
        return device->ldev->md.md_offset + device->ldev->md.al_offset + t;
}

static int
_al_write_transaction(struct drbd_device *device)
{
        struct al_transaction_on_disk *buffer;
        struct lc_element *e;
        sector_t sector;
        int i, mx;
        unsigned extent_nr;
        unsigned crc = 0;
        int err = 0;

        if (!get_ldev(device)) {
                drbd_err(device, "disk is %s, cannot start al transaction\n",
                        drbd_disk_str(device->state.disk));
                return -EIO;
        }

        /* The bitmap write may have failed, causing a state change. */
        if (device->state.disk < D_INCONSISTENT) {
                drbd_err(device,
                        "disk is %s, cannot write al transaction\n",
                        drbd_disk_str(device->state.disk));
                put_ldev(device);
                return -EIO;
        }

        buffer = drbd_md_get_buffer(device); /* protects md_io_buffer, al_tr_cycle, ... */
        if (!buffer) {
                drbd_err(device, "disk failed while waiting for md_io buffer\n");
                put_ldev(device);
                return -ENODEV;
        }

        memset(buffer, 0, sizeof(*buffer));
        buffer->magic = cpu_to_be32(DRBD_AL_MAGIC);
        buffer->tr_number = cpu_to_be32(device->al_tr_number);

        i = 0;

        /* Even though no one can start to change this list
         * once we set the LC_LOCKED -- from drbd_al_begin_io(),
         * lc_try_lock_for_transaction() --, someone may still
         * be in the process of changing it. */
        spin_lock_irq(&device->al_lock);
        list_for_each_entry(e, &device->act_log->to_be_changed, list) {
                if (i == AL_UPDATES_PER_TRANSACTION) {
                        i++;
                        break;
                }
                buffer->update_slot_nr[i] = cpu_to_be16(e->lc_index);
                buffer->update_extent_nr[i] = cpu_to_be32(e->lc_new_number);
                if (e->lc_number != LC_FREE)
                        drbd_bm_mark_for_writeout(device,
                                        al_extent_to_bm_page(e->lc_number));
                i++;
        }
        spin_unlock_irq(&device->al_lock);
        BUG_ON(i > AL_UPDATES_PER_TRANSACTION);

        buffer->n_updates = cpu_to_be16(i);
        for ( ; i < AL_UPDATES_PER_TRANSACTION; i++) {
                buffer->update_slot_nr[i] = cpu_to_be16(-1);
                buffer->update_extent_nr[i] = cpu_to_be32(LC_FREE);
        }

        buffer->context_size = cpu_to_be16(device->act_log->nr_elements);
        buffer->context_start_slot_nr = cpu_to_be16(device->al_tr_cycle);

        mx = min_t(int, AL_CONTEXT_PER_TRANSACTION,
                   device->act_log->nr_elements - device->al_tr_cycle);
        for (i = 0; i < mx; i++) {
                unsigned idx = device->al_tr_cycle + i;
                extent_nr = lc_element_by_index(device->act_log, idx)->lc_number;
                buffer->context[i] = cpu_to_be32(extent_nr);
        }
        for (; i < AL_CONTEXT_PER_TRANSACTION; i++)
                buffer->context[i] = cpu_to_be32(LC_FREE);

        device->al_tr_cycle += AL_CONTEXT_PER_TRANSACTION;
        if (device->al_tr_cycle >= device->act_log->nr_elements)
                device->al_tr_cycle = 0;

        sector = al_tr_number_to_on_disk_sector(device);

        crc = crc32c(0, buffer, 4096);
        buffer->crc32c = cpu_to_be32(crc);

        if (drbd_bm_write_hinted(device))
                err = -EIO;
        else {
                bool write_al_updates;
                rcu_read_lock();
                write_al_updates = rcu_dereference(device->ldev->disk_conf)->al_updates;
                rcu_read_unlock();
                if (write_al_updates) {
                        if (drbd_md_sync_page_io(device, device->ldev, sector, WRITE)) {
                                err = -EIO;
                                drbd_chk_io_error(device, 1, DRBD_META_IO_ERROR);
                        } else {
                                device->al_tr_number++;
                                device->al_writ_cnt++;
                        }
                }
        }

        drbd_md_put_buffer(device);
        put_ldev(device);

        return err;
}


static int w_al_write_transaction(struct drbd_work *w, int unused)
{
        struct update_al_work *aw = container_of(w, struct update_al_work, w);
        struct drbd_device *device = w->device;
        int err;

        err = _al_write_transaction(device);
        aw->err = err;
        complete(&aw->event);

        return err != -EIO ? err : 0;
}

/* Calls from worker context (see w_restart_disk_io()) need to write the
   transaction directly. Others came through generic_make_request(),
   those need to delegate it to the worker. */
static int al_write_transaction(struct drbd_device *device, bool delegate)
{
        if (delegate) {
                struct update_al_work al_work;
                init_completion(&al_work.event);
                al_work.w.cb = w_al_write_transaction;
                al_work.w.device = device;
                drbd_queue_work_front(&first_peer_device(device)->connection->sender_work, &al_work.w);
                wait_for_completion(&al_work.event);
                return al_work.err;
        } else
                return _al_write_transaction(device);
}

static int _try_lc_del(struct drbd_device *device, struct lc_element *al_ext)
{
        int rv;

        spin_lock_irq(&device->al_lock);
        rv = (al_ext->refcnt == 0);
        if (likely(rv))
                lc_del(device->act_log, al_ext);
        spin_unlock_irq(&device->al_lock);

        return rv;
}

/**
 * drbd_al_shrink() - Removes all active extents form the activity log
 * @device:     DRBD device.
 *
 * Removes all active extents form the activity log, waiting until
 * the reference count of each entry dropped to 0 first, of course.
 *
 * You need to lock device->act_log with lc_try_lock() / lc_unlock()
 */
void drbd_al_shrink(struct drbd_device *device)
{
        struct lc_element *al_ext;
        int i;

        D_ASSERT(device, test_bit(__LC_LOCKED, &device->act_log->flags));

        for (i = 0; i < device->act_log->nr_elements; i++) {
                al_ext = lc_element_by_index(device->act_log, i);
                if (al_ext->lc_number == LC_FREE)
                        continue;
                wait_event(device->al_wait, _try_lc_del(device, al_ext));
        }

        wake_up(&device->al_wait);
}

int drbd_initialize_al(struct drbd_device *device, void *buffer)
{
        struct al_transaction_on_disk *al = buffer;
        struct drbd_md *md = &device->ldev->md;
        sector_t al_base = md->md_offset + md->al_offset;
        int al_size_4k = md->al_stripes * md->al_stripe_size_4k;
        int i;

        memset(al, 0, 4096);
        al->magic = cpu_to_be32(DRBD_AL_MAGIC);
        al->transaction_type = cpu_to_be16(AL_TR_INITIALIZED);
        al->crc32c = cpu_to_be32(crc32c(0, al, 4096));

        for (i = 0; i < al_size_4k; i++) {
                int err = drbd_md_sync_page_io(device, device->ldev, al_base + i * 8, WRITE);
                if (err)
                        return err;
        }
        return 0;
}

static int w_update_odbm(struct drbd_work *w, int unused)
{
        struct update_odbm_work *udw = container_of(w, struct update_odbm_work, w);
        struct drbd_device *device = w->device;
        struct sib_info sib = { .sib_reason = SIB_SYNC_PROGRESS, };

        if (!get_ldev(device)) {
                if (__ratelimit(&drbd_ratelimit_state))
                        drbd_warn(device, "Can not update on disk bitmap, local IO disabled.\n");
                kfree(udw);
                return 0;
        }

        drbd_bm_write_page(device, rs_extent_to_bm_page(udw->enr));
        put_ldev(device);

        kfree(udw);

        if (drbd_bm_total_weight(device) <= device->rs_failed) {
                switch (device->state.conn) {
                case C_SYNC_SOURCE:  case C_SYNC_TARGET:
                case C_PAUSED_SYNC_S: case C_PAUSED_SYNC_T:
                        drbd_resync_finished(device);
                default:
                        /* nothing to do */
                        break;
                }
        }
        drbd_bcast_event(device, &sib);

        return 0;
}


/* ATTENTION. The AL's extents are 4MB each, while the extents in the
 * resync LRU-cache are 16MB each.
 * The caller of this function has to hold an get_ldev() reference.
 *
 * TODO will be obsoleted once we have a caching lru of the on disk bitmap
 */
static void drbd_try_clear_on_disk_bm(struct drbd_device *device, sector_t sector,
                                      int count, int success)
{
        struct lc_element *e;
        struct update_odbm_work *udw;

        unsigned int enr;

        D_ASSERT(device, atomic_read(&device->local_cnt));

        /* I simply assume that a sector/size pair never crosses
         * a 16 MB extent border. (Currently this is true...) */
        enr = BM_SECT_TO_EXT(sector);

        e = lc_get(device->resync, enr);
        if (e) {
                struct bm_extent *ext = lc_entry(e, struct bm_extent, lce);
                if (ext->lce.lc_number == enr) {
                        if (success)
                                ext->rs_left -= count;
                        else
                                ext->rs_failed += count;
                        if (ext->rs_left < ext->rs_failed) {
                                drbd_warn(device, "BAD! sector=%llus enr=%u rs_left=%d "
                                    "rs_failed=%d count=%d cstate=%s\n",
                                     (unsigned long long)sector,
                                     ext->lce.lc_number, ext->rs_left,
                                     ext->rs_failed, count,
                                     drbd_conn_str(device->state.conn));

                                /* We don't expect to be able to clear more bits
                                 * than have been set when we originally counted
                                 * the set bits to cache that value in ext->rs_left.
                                 * Whatever the reason (disconnect during resync,
                                 * delayed local completion of an application write),
                                 * try to fix it up by recounting here. */
                                ext->rs_left = drbd_bm_e_weight(device, enr);
                        }
                } else {
                        /* Normally this element should be in the cache,
                         * since drbd_rs_begin_io() pulled it already in.
                         *
                         * But maybe an application write finished, and we set
                         * something outside the resync lru_cache in sync.
                         */
                        int rs_left = drbd_bm_e_weight(device, enr);
                        if (ext->flags != 0) {
                                drbd_warn(device, "changing resync lce: %d[%u;%02lx]"
                                     " -> %d[%u;00]\n",
                                     ext->lce.lc_number, ext->rs_left,
                                     ext->flags, enr, rs_left);
                                ext->flags = 0;
                        }
                        if (ext->rs_failed) {
                                drbd_warn(device, "Kicking resync_lru element enr=%u "
                                     "out with rs_failed=%d\n",
                                     ext->lce.lc_number, ext->rs_failed);
                        }
                        ext->rs_left = rs_left;
                        ext->rs_failed = success ? 0 : count;
                        /* we don't keep a persistent log of the resync lru,
                         * we can commit any change right away. */
                        lc_committed(device->resync);
                }
                lc_put(device->resync, &ext->lce);
                /* no race, we are within the al_lock! */

                if (ext->rs_left == ext->rs_failed) {
                        ext->rs_failed = 0;

                        udw = kmalloc(sizeof(*udw), GFP_ATOMIC);
                        if (udw) {
                                udw->enr = ext->lce.lc_number;
                                udw->w.cb = w_update_odbm;
                                udw->w.device = device;
                                drbd_queue_work_front(&first_peer_device(device)->connection->sender_work, &udw->w);
                        } else {
                                drbd_warn(device, "Could not kmalloc an udw\n");
                        }
                }
        } else {
                drbd_err(device, "lc_get() failed! locked=%d/%d flags=%lu\n",
                    device->resync_locked,
                    device->resync->nr_elements,
                    device->resync->flags);
        }
}

void drbd_advance_rs_marks(struct drbd_device *device, unsigned long still_to_go)
{
        unsigned long now = jiffies;
        unsigned long last = device->rs_mark_time[device->rs_last_mark];
        int next = (device->rs_last_mark + 1) % DRBD_SYNC_MARKS;
        if (time_after_eq(now, last + DRBD_SYNC_MARK_STEP)) {
                if (device->rs_mark_left[device->rs_last_mark] != still_to_go &&
                    device->state.conn != C_PAUSED_SYNC_T &&
                    device->state.conn != C_PAUSED_SYNC_S) {
                        device->rs_mark_time[next] = now;
                        device->rs_mark_left[next] = still_to_go;
                        device->rs_last_mark = next;
                }
        }
}

/* clear the bit corresponding to the piece of storage in question:
 * size byte of data starting from sector.  Only clear a bits of the affected
 * one ore more _aligned_ BM_BLOCK_SIZE blocks.
 *
 * called by worker on C_SYNC_TARGET and receiver on SyncSource.
 *
 */
void __drbd_set_in_sync(struct drbd_device *device, sector_t sector, int size,
                       const char *file, const unsigned int line)
{
        /* Is called from worker and receiver context _only_ */
        unsigned long sbnr, ebnr, lbnr;
        unsigned long count = 0;
        sector_t esector, nr_sectors;
        int wake_up = 0;
        unsigned long flags;

        if (size <= 0 || !IS_ALIGNED(size, 512) || size > DRBD_MAX_BIO_SIZE) {
                drbd_err(device, "drbd_set_in_sync: sector=%llus size=%d nonsense!\n",
                                (unsigned long long)sector, size);
                return;
        }

        if (!get_ldev(device))
                return; /* no disk, no metadata, no bitmap to clear bits in */

        nr_sectors = drbd_get_capacity(device->this_bdev);
        esector = sector + (size >> 9) - 1;

        if (!expect(sector < nr_sectors))
                goto out;
        if (!expect(esector < nr_sectors))
                esector = nr_sectors - 1;

        lbnr = BM_SECT_TO_BIT(nr_sectors-1);

        /* we clear it (in sync).
         * round up start sector, round down end sector.  we make sure we only
         * clear full, aligned, BM_BLOCK_SIZE (4K) blocks */
        if (unlikely(esector < BM_SECT_PER_BIT-1))
                goto out;
        if (unlikely(esector == (nr_sectors-1)))
                ebnr = lbnr;
        else
                ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
        sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);

        if (sbnr > ebnr)
                goto out;

        /*
         * ok, (capacity & 7) != 0 sometimes, but who cares...
         * we count rs_{total,left} in bits, not sectors.
         */
        count = drbd_bm_clear_bits(device, sbnr, ebnr);
        if (count) {
                drbd_advance_rs_marks(device, drbd_bm_total_weight(device));
                spin_lock_irqsave(&device->al_lock, flags);
                drbd_try_clear_on_disk_bm(device, sector, count, true);
                spin_unlock_irqrestore(&device->al_lock, flags);

                /* just wake_up unconditional now, various lc_chaged(),
                 * lc_put() in drbd_try_clear_on_disk_bm(). */
                wake_up = 1;
        }
out:
        put_ldev(device);
        if (wake_up)
                wake_up(&device->al_wait);
}

/*
 * this is intended to set one request worth of data out of sync.
 * affects at least 1 bit,
 * and at most 1+DRBD_MAX_BIO_SIZE/BM_BLOCK_SIZE bits.
 *
 * called by tl_clear and drbd_send_dblock (==drbd_make_request).
 * so this can be _any_ process.
 */
int __drbd_set_out_of_sync(struct drbd_device *device, sector_t sector, int size,
                            const char *file, const unsigned int line)
{
        unsigned long sbnr, ebnr, flags;
        sector_t esector, nr_sectors;
        unsigned int enr, count = 0;
        struct lc_element *e;

        /* this should be an empty REQ_FLUSH */
        if (size == 0)
                return 0;

        if (size < 0 || !IS_ALIGNED(size, 512) || size > DRBD_MAX_BIO_SIZE) {
                drbd_err(device, "sector: %llus, size: %d\n",
                        (unsigned long long)sector, size);
                return 0;
        }

        if (!get_ldev(device))
                return 0; /* no disk, no metadata, no bitmap to set bits in */

        nr_sectors = drbd_get_capacity(device->this_bdev);
        esector = sector + (size >> 9) - 1;

        if (!expect(sector < nr_sectors))
                goto out;
        if (!expect(esector < nr_sectors))
                esector = nr_sectors - 1;

        /* we set it out of sync,
         * we do not need to round anything here */
        sbnr = BM_SECT_TO_BIT(sector);
        ebnr = BM_SECT_TO_BIT(esector);

        /* ok, (capacity & 7) != 0 sometimes, but who cares...
         * we count rs_{total,left} in bits, not sectors.  */
        spin_lock_irqsave(&device->al_lock, flags);
        count = drbd_bm_set_bits(device, sbnr, ebnr);

        enr = BM_SECT_TO_EXT(sector);
        e = lc_find(device->resync, enr);
        if (e)
                lc_entry(e, struct bm_extent, lce)->rs_left += count;
        spin_unlock_irqrestore(&device->al_lock, flags);

out:
        put_ldev(device);

        return count;
}

static
struct bm_extent *_bme_get(struct drbd_device *device, unsigned int enr)
{
        struct lc_element *e;
        struct bm_extent *bm_ext;
        int wakeup = 0;
        unsigned long rs_flags;

        spin_lock_irq(&device->al_lock);
        if (device->resync_locked > device->resync->nr_elements/2) {
                spin_unlock_irq(&device->al_lock);
                return NULL;
        }
        e = lc_get(device->resync, enr);
        bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
        if (bm_ext) {
                if (bm_ext->lce.lc_number != enr) {
                        bm_ext->rs_left = drbd_bm_e_weight(device, enr);
                        bm_ext->rs_failed = 0;
                        lc_committed(device->resync);
                        wakeup = 1;
                }
                if (bm_ext->lce.refcnt == 1)
                        device->resync_locked++;
                set_bit(BME_NO_WRITES, &bm_ext->flags);
        }
        rs_flags = device->resync->flags;
        spin_unlock_irq(&device->al_lock);
        if (wakeup)
                wake_up(&device->al_wait);

        if (!bm_ext) {
                if (rs_flags & LC_STARVING)
                        drbd_warn(device, "Have to wait for element"
                             " (resync LRU too small?)\n");
                BUG_ON(rs_flags & LC_LOCKED);
        }

        return bm_ext;
}

static int _is_in_al(struct drbd_device *device, unsigned int enr)
{
        int rv;

        spin_lock_irq(&device->al_lock);
        rv = lc_is_used(device->act_log, enr);
        spin_unlock_irq(&device->al_lock);

        return rv;
}

/**
 * drbd_rs_begin_io() - Gets an extent in the resync LRU cache and sets it to BME_LOCKED
 * @device:     DRBD device.
 * @sector:     The sector number.
 *
 * This functions sleeps on al_wait. Returns 0 on success, -EINTR if interrupted.
 */
int drbd_rs_begin_io(struct drbd_device *device, sector_t sector)
{
        unsigned int enr = BM_SECT_TO_EXT(sector);
        struct bm_extent *bm_ext;
        int i, sig;
        int sa = 200; /* Step aside 200 times, then grab the extent and let app-IO wait.
                         200 times -> 20 seconds. */

retry:
        sig = wait_event_interruptible(device->al_wait,
                        (bm_ext = _bme_get(device, enr)));
        if (sig)
                return -EINTR;

        if (test_bit(BME_LOCKED, &bm_ext->flags))
                return 0;

        for (i = 0; i < AL_EXT_PER_BM_SECT; i++) {
                sig = wait_event_interruptible(device->al_wait,
                                               !_is_in_al(device, enr * AL_EXT_PER_BM_SECT + i) ||
                                               test_bit(BME_PRIORITY, &bm_ext->flags));

                if (sig || (test_bit(BME_PRIORITY, &bm_ext->flags) && sa)) {
                        spin_lock_irq(&device->al_lock);
                        if (lc_put(device->resync, &bm_ext->lce) == 0) {
                                bm_ext->flags = 0; /* clears BME_NO_WRITES and eventually BME_PRIORITY */
                                device->resync_locked--;
                                wake_up(&device->al_wait);
                        }
                        spin_unlock_irq(&device->al_lock);
                        if (sig)
                                return -EINTR;
                        if (schedule_timeout_interruptible(HZ/10))
                                return -EINTR;
                        if (sa && --sa == 0)
                                drbd_warn(device, "drbd_rs_begin_io() stepped aside for 20sec."
                                         "Resync stalled?\n");
                        goto retry;
                }
        }
        set_bit(BME_LOCKED, &bm_ext->flags);
        return 0;
}

/**
 * drbd_try_rs_begin_io() - Gets an extent in the resync LRU cache, does not sleep
 * @device:     DRBD device.
 * @sector:     The sector number.
 *
 * Gets an extent in the resync LRU cache, sets it to BME_NO_WRITES, then
 * tries to set it to BME_LOCKED. Returns 0 upon success, and -EAGAIN
 * if there is still application IO going on in this area.
 */
int drbd_try_rs_begin_io(struct drbd_device *device, sector_t sector)
{
        unsigned int enr = BM_SECT_TO_EXT(sector);
        const unsigned int al_enr = enr*AL_EXT_PER_BM_SECT;
        struct lc_element *e;
        struct bm_extent *bm_ext;
        int i;

        spin_lock_irq(&device->al_lock);
        if (device->resync_wenr != LC_FREE && device->resync_wenr != enr) {
                /* in case you have very heavy scattered io, it may
                 * stall the syncer undefined if we give up the ref count
                 * when we try again and requeue.
                 *
                 * if we don't give up the refcount, but the next time
                 * we are scheduled this extent has been "synced" by new
                 * application writes, we'd miss the lc_put on the
                 * extent we keep the refcount on.
                 * so we remembered which extent we had to try again, and
                 * if the next requested one is something else, we do
                 * the lc_put here...
                 * we also have to wake_up
                 */
                e = lc_find(device->resync, device->resync_wenr);
                bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
                if (bm_ext) {
                        D_ASSERT(device, !test_bit(BME_LOCKED, &bm_ext->flags));
                        D_ASSERT(device, test_bit(BME_NO_WRITES, &bm_ext->flags));
                        clear_bit(BME_NO_WRITES, &bm_ext->flags);
                        device->resync_wenr = LC_FREE;
                        if (lc_put(device->resync, &bm_ext->lce) == 0)
                                device->resync_locked--;
                        wake_up(&device->al_wait);
                } else {
                        drbd_alert(device, "LOGIC BUG\n");
                }
        }
        /* TRY. */
        e = lc_try_get(device->resync, enr);
        bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
        if (bm_ext) {
                if (test_bit(BME_LOCKED, &bm_ext->flags))
                        goto proceed;
                if (!test_and_set_bit(BME_NO_WRITES, &bm_ext->flags)) {
                        device->resync_locked++;
                } else {
                        /* we did set the BME_NO_WRITES,
                         * but then could not set BME_LOCKED,
                         * so we tried again.
                         * drop the extra reference. */
                        bm_ext->lce.refcnt--;
                        D_ASSERT(device, bm_ext->lce.refcnt > 0);
                }
                goto check_al;
        } else {
                /* do we rather want to try later? */
                if (device->resync_locked > device->resync->nr_elements-3)
                        goto try_again;
                /* Do or do not. There is no try. -- Yoda */
                e = lc_get(device->resync, enr);
                bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
                if (!bm_ext) {
                        const unsigned long rs_flags = device->resync->flags;
                        if (rs_flags & LC_STARVING)
                                drbd_warn(device, "Have to wait for element"
                                     " (resync LRU too small?)\n");
                        BUG_ON(rs_flags & LC_LOCKED);
                        goto try_again;
                }
                if (bm_ext->lce.lc_number != enr) {
                        bm_ext->rs_left = drbd_bm_e_weight(device, enr);
                        bm_ext->rs_failed = 0;
                        lc_committed(device->resync);
                        wake_up(&device->al_wait);
                        D_ASSERT(device, test_bit(BME_LOCKED, &bm_ext->flags) == 0);
                }
                set_bit(BME_NO_WRITES, &bm_ext->flags);
                D_ASSERT(device, bm_ext->lce.refcnt == 1);
                device->resync_locked++;
                goto check_al;
        }
check_al:
        for (i = 0; i < AL_EXT_PER_BM_SECT; i++) {
                if (lc_is_used(device->act_log, al_enr+i))
                        goto try_again;
        }
        set_bit(BME_LOCKED, &bm_ext->flags);
proceed:
        device->resync_wenr = LC_FREE;
        spin_unlock_irq(&device->al_lock);
        return 0;

try_again:
        if (bm_ext)
                device->resync_wenr = enr;
        spin_unlock_irq(&device->al_lock);
        return -EAGAIN;
}

void drbd_rs_complete_io(struct drbd_device *device, sector_t sector)
{
        unsigned int enr = BM_SECT_TO_EXT(sector);
        struct lc_element *e;
        struct bm_extent *bm_ext;
        unsigned long flags;

        spin_lock_irqsave(&device->al_lock, flags);
        e = lc_find(device->resync, enr);
        bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
        if (!bm_ext) {
                spin_unlock_irqrestore(&device->al_lock, flags);
                if (__ratelimit(&drbd_ratelimit_state))
                        drbd_err(device, "drbd_rs_complete_io() called, but extent not found\n");
                return;
        }

        if (bm_ext->lce.refcnt == 0) {
                spin_unlock_irqrestore(&device->al_lock, flags);
                drbd_err(device, "drbd_rs_complete_io(,%llu [=%u]) called, "
                    "but refcnt is 0!?\n",
                    (unsigned long long)sector, enr);
                return;
        }

        if (lc_put(device->resync, &bm_ext->lce) == 0) {
                bm_ext->flags = 0; /* clear BME_LOCKED, BME_NO_WRITES and BME_PRIORITY */
                device->resync_locked--;
                wake_up(&device->al_wait);
        }

        spin_unlock_irqrestore(&device->al_lock, flags);
}

/**
 * drbd_rs_cancel_all() - Removes all extents from the resync LRU (even BME_LOCKED)
 * @device:     DRBD device.
 */
void drbd_rs_cancel_all(struct drbd_device *device)
{
        spin_lock_irq(&device->al_lock);

        if (get_ldev_if_state(device, D_FAILED)) { /* Makes sure ->resync is there. */
                lc_reset(device->resync);
                put_ldev(device);
        }
        device->resync_locked = 0;
        device->resync_wenr = LC_FREE;
        spin_unlock_irq(&device->al_lock);
        wake_up(&device->al_wait);
}

/**
 * drbd_rs_del_all() - Gracefully remove all extents from the resync LRU
 * @device:     DRBD device.
 *
 * Returns 0 upon success, -EAGAIN if at least one reference count was
 * not zero.
 */
int drbd_rs_del_all(struct drbd_device *device)
{
        struct lc_element *e;
        struct bm_extent *bm_ext;
        int i;

        spin_lock_irq(&device->al_lock);

        if (get_ldev_if_state(device, D_FAILED)) {
                /* ok, ->resync is there. */
                for (i = 0; i < device->resync->nr_elements; i++) {
                        e = lc_element_by_index(device->resync, i);
                        bm_ext = lc_entry(e, struct bm_extent, lce);
                        if (bm_ext->lce.lc_number == LC_FREE)
                                continue;
                        if (bm_ext->lce.lc_number == device->resync_wenr) {
                                drbd_info(device, "dropping %u in drbd_rs_del_all, apparently"
                                     " got 'synced' by application io\n",
                                     device->resync_wenr);
                                D_ASSERT(device, !test_bit(BME_LOCKED, &bm_ext->flags));
                                D_ASSERT(device, test_bit(BME_NO_WRITES, &bm_ext->flags));
                                clear_bit(BME_NO_WRITES, &bm_ext->flags);
                                device->resync_wenr = LC_FREE;
                                lc_put(device->resync, &bm_ext->lce);
                        }
                        if (bm_ext->lce.refcnt != 0) {
                                drbd_info(device, "Retrying drbd_rs_del_all() later. "
                                     "refcnt=%d\n", bm_ext->lce.refcnt);
                                put_ldev(device);
                                spin_unlock_irq(&device->al_lock);
                                return -EAGAIN;
                        }
                        D_ASSERT(device, !test_bit(BME_LOCKED, &bm_ext->flags));
                        D_ASSERT(device, !test_bit(BME_NO_WRITES, &bm_ext->flags));
                        lc_del(device->resync, &bm_ext->lce);
                }
                D_ASSERT(device, device->resync->used == 0);
                put_ldev(device);
        }
        spin_unlock_irq(&device->al_lock);
        wake_up(&device->al_wait);

        return 0;
}

/**
 * drbd_rs_failed_io() - Record information on a failure to resync the specified blocks
 * @device:     DRBD device.
 * @sector:     The sector number.
 * @size:       Size of failed IO operation, in byte.
 */
void drbd_rs_failed_io(struct drbd_device *device, sector_t sector, int size)
{
        /* Is called from worker and receiver context _only_ */
        unsigned long sbnr, ebnr, lbnr;
        unsigned long count;
        sector_t esector, nr_sectors;
        int wake_up = 0;

        if (size <= 0 || !IS_ALIGNED(size, 512) || size > DRBD_MAX_BIO_SIZE) {
                drbd_err(device, "drbd_rs_failed_io: sector=%llus size=%d nonsense!\n",
                                (unsigned long long)sector, size);
                return;
        }
        nr_sectors = drbd_get_capacity(device->this_bdev);
        esector = sector + (size >> 9) - 1;

        if (!expect(sector < nr_sectors))
                return;
        if (!expect(esector < nr_sectors))
                esector = nr_sectors - 1;

        lbnr = BM_SECT_TO_BIT(nr_sectors-1);

        /*
         * round up start sector, round down end sector.  we make sure we only
         * handle full, aligned, BM_BLOCK_SIZE (4K) blocks */
        if (unlikely(esector < BM_SECT_PER_BIT-1))
                return;
        if (unlikely(esector == (nr_sectors-1)))
                ebnr = lbnr;
        else
                ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
        sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);

        if (sbnr > ebnr)
                return;

        /*
         * ok, (capacity & 7) != 0 sometimes, but who cares...
         * we count rs_{total,left} in bits, not sectors.
         */
        spin_lock_irq(&device->al_lock);
        count = drbd_bm_count_bits(device, sbnr, ebnr);
        if (count) {
                device->rs_failed += count;

                if (get_ldev(device)) {
                        drbd_try_clear_on_disk_bm(device, sector, count, false);
                        put_ldev(device);
                }

                /* just wake_up unconditional now, various lc_chaged(),
                 * lc_put() in drbd_try_clear_on_disk_bm(). */
                wake_up = 1;
        }
        spin_unlock_irq(&device->al_lock);
        if (wake_up)
                wake_up(&device->al_wait);
}