lock_dlm.c

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/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright 2004-2011 Red Hat, Inc.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License version 2.
 */

#include <linux/fs.h>
#include <linux/dlm.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/gfs2_ondisk.h>

#include "incore.h"
#include "glock.h"
#include "util.h"
#include "sys.h"
#include "trace_gfs2.h"

extern struct workqueue_struct *gfs2_control_wq;

static inline void gfs2_update_stats(struct gfs2_lkstats *s, unsigned index,
                     s64 sample)
{
    s64 delta = sample - s->stats[index];
    s->stats[index] += (delta >> 3);
    index++;
    s->stats[index] += ((abs64(delta) - s->stats[index]) >> 2);
}

static inline void gfs2_update_reply_times(struct gfs2_glock *gl)
{
    struct gfs2_pcpu_lkstats *lks;
    const unsigned gltype = gl->gl_name.ln_type;
    unsigned index = test_bit(GLF_BLOCKING, &gl->gl_flags) ?
             GFS2_LKS_SRTTB : GFS2_LKS_SRTT;
    s64 rtt;

    preempt_disable();
    rtt = ktime_to_ns(ktime_sub(ktime_get_real(), gl->gl_dstamp));
    lks = this_cpu_ptr(gl->gl_sbd->sd_lkstats);
    gfs2_update_stats(&gl->gl_stats, index, rtt);       /* Local */
    gfs2_update_stats(&lks->lkstats[gltype], index, rtt);   /* Global */
    preempt_enable();

    trace_gfs2_glock_lock_time(gl, rtt);
}

static inline void gfs2_update_request_times(struct gfs2_glock *gl)
{
    struct gfs2_pcpu_lkstats *lks;
    const unsigned gltype = gl->gl_name.ln_type;
    ktime_t dstamp;
    s64 irt;

    preempt_disable();
    dstamp = gl->gl_dstamp;
    gl->gl_dstamp = ktime_get_real();
    irt = ktime_to_ns(ktime_sub(gl->gl_dstamp, dstamp));
    lks = this_cpu_ptr(gl->gl_sbd->sd_lkstats);
    gfs2_update_stats(&gl->gl_stats, GFS2_LKS_SIRT, irt);       /* Local */
    gfs2_update_stats(&lks->lkstats[gltype], GFS2_LKS_SIRT, irt);   /* Global */
    preempt_enable();
}
 
static void gdlm_ast(void *arg)
{
    struct gfs2_glock *gl = arg;
    unsigned ret = gl->gl_state;

    gfs2_update_reply_times(gl);
    BUG_ON(gl->gl_lksb.sb_flags & DLM_SBF_DEMOTED);

    if (gl->gl_lksb.sb_flags & DLM_SBF_VALNOTVALID)
        memset(gl->gl_lvb, 0, GDLM_LVB_SIZE);

    switch (gl->gl_lksb.sb_status) {
    case -DLM_EUNLOCK: /* Unlocked, so glock can be freed */
        gfs2_glock_free(gl);
        return;
    case -DLM_ECANCEL: /* Cancel while getting lock */
        ret |= LM_OUT_CANCELED;
        goto out;
    case -EAGAIN: /* Try lock fails */
    case -EDEADLK: /* Deadlock detected */
        goto out;
    case -ETIMEDOUT: /* Canceled due to timeout */
        ret |= LM_OUT_ERROR;
        goto out;
    case 0: /* Success */
        break;
    default: /* Something unexpected */
        BUG();
    }

    ret = gl->gl_req;
    if (gl->gl_lksb.sb_flags & DLM_SBF_ALTMODE) {
        if (gl->gl_req == LM_ST_SHARED)
            ret = LM_ST_DEFERRED;
        else if (gl->gl_req == LM_ST_DEFERRED)
            ret = LM_ST_SHARED;
        else
            BUG();
    }

    set_bit(GLF_INITIAL, &gl->gl_flags);
    gfs2_glock_complete(gl, ret);
    return;
out:
    if (!test_bit(GLF_INITIAL, &gl->gl_flags))
        gl->gl_lksb.sb_lkid = 0;
    gfs2_glock_complete(gl, ret);
}

static void gdlm_bast(void *arg, int mode)
{
    struct gfs2_glock *gl = arg;

    switch (mode) {
    case DLM_LOCK_EX:
        gfs2_glock_cb(gl, LM_ST_UNLOCKED);
        break;
    case DLM_LOCK_CW:
        gfs2_glock_cb(gl, LM_ST_DEFERRED);
        break;
    case DLM_LOCK_PR:
        gfs2_glock_cb(gl, LM_ST_SHARED);
        break;
    default:
        printk(KERN_ERR "unknown bast mode %d", mode);
        BUG();
    }
}

/* convert gfs lock-state to dlm lock-mode */

static int make_mode(const unsigned int lmstate)
{
    switch (lmstate) {
    case LM_ST_UNLOCKED:
        return DLM_LOCK_NL;
    case LM_ST_EXCLUSIVE:
        return DLM_LOCK_EX;
    case LM_ST_DEFERRED:
        return DLM_LOCK_CW;
    case LM_ST_SHARED:
        return DLM_LOCK_PR;
    }
    printk(KERN_ERR "unknown LM state %d", lmstate);
    BUG();
    return -1;
}

static u32 make_flags(struct gfs2_glock *gl, const unsigned int gfs_flags,
              const int req)
{
    u32 lkf = DLM_LKF_VALBLK;
    u32 lkid = gl->gl_lksb.sb_lkid;

    if (gfs_flags & LM_FLAG_TRY)
        lkf |= DLM_LKF_NOQUEUE;

    if (gfs_flags & LM_FLAG_TRY_1CB) {
        lkf |= DLM_LKF_NOQUEUE;
        lkf |= DLM_LKF_NOQUEUEBAST;
    }

    if (gfs_flags & LM_FLAG_PRIORITY) {
        lkf |= DLM_LKF_NOORDER;
        lkf |= DLM_LKF_HEADQUE;
    }

    if (gfs_flags & LM_FLAG_ANY) {
        if (req == DLM_LOCK_PR)
            lkf |= DLM_LKF_ALTCW;
        else if (req == DLM_LOCK_CW)
            lkf |= DLM_LKF_ALTPR;
        else
            BUG();
    }

    if (lkid != 0) {
        lkf |= DLM_LKF_CONVERT;
        if (test_bit(GLF_BLOCKING, &gl->gl_flags))
            lkf |= DLM_LKF_QUECVT;
    }

    return lkf;
}

static void gfs2_reverse_hex(char *c, u64 value)
{
    while (value) {
        *c-- = hex_asc[value & 0x0f];
        value >>= 4;
    }
}

static int gdlm_lock(struct gfs2_glock *gl, unsigned int req_state,
             unsigned int flags)
{
    struct lm_lockstruct *ls = &gl->gl_sbd->sd_lockstruct;
    int req;
    u32 lkf;
    char strname[GDLM_STRNAME_BYTES] = "";

    req = make_mode(req_state);
    lkf = make_flags(gl, flags, req);
    gfs2_glstats_inc(gl, GFS2_LKS_DCOUNT);
    gfs2_sbstats_inc(gl, GFS2_LKS_DCOUNT);
    if (gl->gl_lksb.sb_lkid) {
        gfs2_update_request_times(gl);
    } else {
        memset(strname, ' ', GDLM_STRNAME_BYTES - 1);
        strname[GDLM_STRNAME_BYTES - 1] = '\0';
        gfs2_reverse_hex(strname + 7, gl->gl_name.ln_type);
        gfs2_reverse_hex(strname + 23, gl->gl_name.ln_number);
        gl->gl_dstamp = ktime_get_real();
    }
    /*
     * Submit the actual lock request.
     */

    return dlm_lock(ls->ls_dlm, req, &gl->gl_lksb, lkf, strname,
            GDLM_STRNAME_BYTES - 1, 0, gdlm_ast, gl, gdlm_bast);
}

static void gdlm_put_lock(struct gfs2_glock *gl)
{
    struct gfs2_sbd *sdp = gl->gl_sbd;
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    int error;

    if (gl->gl_lksb.sb_lkid == 0) {
        gfs2_glock_free(gl);
        return;
    }

    clear_bit(GLF_BLOCKING, &gl->gl_flags);
    gfs2_glstats_inc(gl, GFS2_LKS_DCOUNT);
    gfs2_sbstats_inc(gl, GFS2_LKS_DCOUNT);
    gfs2_update_request_times(gl);
    error = dlm_unlock(ls->ls_dlm, gl->gl_lksb.sb_lkid, DLM_LKF_VALBLK,
               NULL, gl);
    if (error) {
        printk(KERN_ERR "gdlm_unlock %x,%llx err=%d\n",
               gl->gl_name.ln_type,
               (unsigned long long)gl->gl_name.ln_number, error);
        return;
    }
}

static void gdlm_cancel(struct gfs2_glock *gl)
{
    struct lm_lockstruct *ls = &gl->gl_sbd->sd_lockstruct;
    dlm_unlock(ls->ls_dlm, gl->gl_lksb.sb_lkid, DLM_LKF_CANCEL, NULL, gl);
}

/*
 * dlm/gfs2 recovery coordination using dlm_recover callbacks
 *
 *  1. dlm_controld sees lockspace members change
 *  2. dlm_controld blocks dlm-kernel locking activity
 *  3. dlm_controld within dlm-kernel notifies gfs2 (recover_prep)
 *  4. dlm_controld starts and finishes its own user level recovery
 *  5. dlm_controld starts dlm-kernel dlm_recoverd to do kernel recovery
 *  6. dlm_recoverd notifies gfs2 of failed nodes (recover_slot)
 *  7. dlm_recoverd does its own lock recovery
 *  8. dlm_recoverd unblocks dlm-kernel locking activity
 *  9. dlm_recoverd notifies gfs2 when done (recover_done with new generation)
 * 10. gfs2_control updates control_lock lvb with new generation and jid bits
 * 11. gfs2_control enqueues journals for gfs2_recover to recover (maybe none)
 * 12. gfs2_recover dequeues and recovers journals of failed nodes
 * 13. gfs2_recover provides recovery results to gfs2_control (recovery_result)
 * 14. gfs2_control updates control_lock lvb jid bits for recovered journals
 * 15. gfs2_control unblocks normal locking when all journals are recovered
 *
 * - failures during recovery
 *
 * recover_prep() may set BLOCK_LOCKS (step 3) again before gfs2_control
 * clears BLOCK_LOCKS (step 15), e.g. another node fails while still
 * recovering for a prior failure.  gfs2_control needs a way to detect
 * this so it can leave BLOCK_LOCKS set in step 15.  This is managed using
 * the recover_block and recover_start values.
 *
 * recover_done() provides a new lockspace generation number each time it
 * is called (step 9).  This generation number is saved as recover_start.
 * When recover_prep() is called, it sets BLOCK_LOCKS and sets
 * recover_block = recover_start.  So, while recover_block is equal to
 * recover_start, BLOCK_LOCKS should remain set.  (recover_spin must
 * be held around the BLOCK_LOCKS/recover_block/recover_start logic.)
 *
 * - more specific gfs2 steps in sequence above
 *
 *  3. recover_prep sets BLOCK_LOCKS and sets recover_block = recover_start
 *  6. recover_slot records any failed jids (maybe none)
 *  9. recover_done sets recover_start = new generation number
 * 10. gfs2_control sets control_lock lvb = new gen + bits for failed jids
 * 12. gfs2_recover does journal recoveries for failed jids identified above
 * 14. gfs2_control clears control_lock lvb bits for recovered jids
 * 15. gfs2_control checks if recover_block == recover_start (step 3 occured
 *     again) then do nothing, otherwise if recover_start > recover_block
 *     then clear BLOCK_LOCKS.
 *
 * - parallel recovery steps across all nodes
 *
 * All nodes attempt to update the control_lock lvb with the new generation
 * number and jid bits, but only the first to get the control_lock EX will
 * do so; others will see that it's already done (lvb already contains new
 * generation number.)
 *
 * . All nodes get the same recover_prep/recover_slot/recover_done callbacks
 * . All nodes attempt to set control_lock lvb gen + bits for the new gen
 * . One node gets control_lock first and writes the lvb, others see it's done
 * . All nodes attempt to recover jids for which they see control_lock bits set
 * . One node succeeds for a jid, and that one clears the jid bit in the lvb
 * . All nodes will eventually see all lvb bits clear and unblock locks
 *
 * - is there a problem with clearing an lvb bit that should be set
 *   and missing a journal recovery?
 *
 * 1. jid fails
 * 2. lvb bit set for step 1
 * 3. jid recovered for step 1
 * 4. jid taken again (new mount)
 * 5. jid fails (for step 4)
 * 6. lvb bit set for step 5 (will already be set)
 * 7. lvb bit cleared for step 3
 *
 * This is not a problem because the failure in step 5 does not
 * require recovery, because the mount in step 4 could not have
 * progressed far enough to unblock locks and access the fs.  The
 * control_mount() function waits for all recoveries to be complete
 * for the latest lockspace generation before ever unblocking locks
 * and returning.  The mount in step 4 waits until the recovery in
 * step 1 is done.
 *
 * - special case of first mounter: first node to mount the fs
 *
 * The first node to mount a gfs2 fs needs to check all the journals
 * and recover any that need recovery before other nodes are allowed
 * to mount the fs.  (Others may begin mounting, but they must wait
 * for the first mounter to be done before taking locks on the fs
 * or accessing the fs.)  This has two parts:
 *
 * 1. The mounted_lock tells a node it's the first to mount the fs.
 * Each node holds the mounted_lock in PR while it's mounted.
 * Each node tries to acquire the mounted_lock in EX when it mounts.
 * If a node is granted the mounted_lock EX it means there are no
 * other mounted nodes (no PR locks exist), and it is the first mounter.
 * The mounted_lock is demoted to PR when first recovery is done, so
 * others will fail to get an EX lock, but will get a PR lock.
 *
 * 2. The control_lock blocks others in control_mount() while the first
 * mounter is doing first mount recovery of all journals.
 * A mounting node needs to acquire control_lock in EX mode before
 * it can proceed.  The first mounter holds control_lock in EX while doing
 * the first mount recovery, blocking mounts from other nodes, then demotes
 * control_lock to NL when it's done (others_may_mount/first_done),
 * allowing other nodes to continue mounting.
 *
 * first mounter:
 * control_lock EX/NOQUEUE success
 * mounted_lock EX/NOQUEUE success (no other PR, so no other mounters)
 * set first=1
 * do first mounter recovery
 * mounted_lock EX->PR
 * control_lock EX->NL, write lvb generation
 *
 * other mounter:
 * control_lock EX/NOQUEUE success (if fail -EAGAIN, retry)
 * mounted_lock EX/NOQUEUE fail -EAGAIN (expected due to other mounters PR)
 * mounted_lock PR/NOQUEUE success
 * read lvb generation
 * control_lock EX->NL
 * set first=0
 *
 * - mount during recovery
 *
 * If a node mounts while others are doing recovery (not first mounter),
 * the mounting node will get its initial recover_done() callback without
 * having seen any previous failures/callbacks.
 *
 * It must wait for all recoveries preceding its mount to be finished
 * before it unblocks locks.  It does this by repeating the "other mounter"
 * steps above until the lvb generation number is >= its mount generation
 * number (from initial recover_done) and all lvb bits are clear.
 *
 * - control_lock lvb format
 *
 * 4 bytes generation number: the latest dlm lockspace generation number
 * from recover_done callback.  Indicates the jid bitmap has been updated
 * to reflect all slot failures through that generation.
 * 4 bytes unused.
 * GDLM_LVB_SIZE-8 bytes of jid bit map. If bit N is set, it indicates
 * that jid N needs recovery.
 */

#define JID_BITMAP_OFFSET 8 /* 4 byte generation number + 4 byte unused */

static void control_lvb_read(struct lm_lockstruct *ls, uint32_t *lvb_gen,
                 char *lvb_bits)
{
    uint32_t gen;
    memcpy(lvb_bits, ls->ls_control_lvb, GDLM_LVB_SIZE);
    memcpy(&gen, lvb_bits, sizeof(uint32_t));
    *lvb_gen = le32_to_cpu(gen);
}

static void control_lvb_write(struct lm_lockstruct *ls, uint32_t lvb_gen,
                  char *lvb_bits)
{
    uint32_t gen;
    memcpy(ls->ls_control_lvb, lvb_bits, GDLM_LVB_SIZE);
    gen = cpu_to_le32(lvb_gen);
    memcpy(ls->ls_control_lvb, &gen, sizeof(uint32_t));
}

static int all_jid_bits_clear(char *lvb)
{
    int i;
    for (i = JID_BITMAP_OFFSET; i < GDLM_LVB_SIZE; i++) {
        if (lvb[i])
            return 0;
    }
    return 1;
}

static void sync_wait_cb(void *arg)
{
    struct lm_lockstruct *ls = arg;
    complete(&ls->ls_sync_wait);
}

static int sync_unlock(struct gfs2_sbd *sdp, struct dlm_lksb *lksb, char *name)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    int error;

    error = dlm_unlock(ls->ls_dlm, lksb->sb_lkid, 0, lksb, ls);
    if (error) {
        fs_err(sdp, "%s lkid %x error %d\n",
               name, lksb->sb_lkid, error);
        return error;
    }

    wait_for_completion(&ls->ls_sync_wait);

    if (lksb->sb_status != -DLM_EUNLOCK) {
        fs_err(sdp, "%s lkid %x status %d\n",
               name, lksb->sb_lkid, lksb->sb_status);
        return -1;
    }
    return 0;
}

static int sync_lock(struct gfs2_sbd *sdp, int mode, uint32_t flags,
             unsigned int num, struct dlm_lksb *lksb, char *name)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    char strname[GDLM_STRNAME_BYTES];
    int error, status;

    memset(strname, 0, GDLM_STRNAME_BYTES);
    snprintf(strname, GDLM_STRNAME_BYTES, "%8x%16x", LM_TYPE_NONDISK, num);

    error = dlm_lock(ls->ls_dlm, mode, lksb, flags,
             strname, GDLM_STRNAME_BYTES - 1,
             0, sync_wait_cb, ls, NULL);
    if (error) {
        fs_err(sdp, "%s lkid %x flags %x mode %d error %d\n",
               name, lksb->sb_lkid, flags, mode, error);
        return error;
    }

    wait_for_completion(&ls->ls_sync_wait);

    status = lksb->sb_status;

    if (status && status != -EAGAIN) {
        fs_err(sdp, "%s lkid %x flags %x mode %d status %d\n",
               name, lksb->sb_lkid, flags, mode, status);
    }

    return status;
}

static int mounted_unlock(struct gfs2_sbd *sdp)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    return sync_unlock(sdp, &ls->ls_mounted_lksb, "mounted_lock");
}

static int mounted_lock(struct gfs2_sbd *sdp, int mode, uint32_t flags)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    return sync_lock(sdp, mode, flags, GFS2_MOUNTED_LOCK,
             &ls->ls_mounted_lksb, "mounted_lock");
}

static int control_unlock(struct gfs2_sbd *sdp)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    return sync_unlock(sdp, &ls->ls_control_lksb, "control_lock");
}

static int control_lock(struct gfs2_sbd *sdp, int mode, uint32_t flags)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    return sync_lock(sdp, mode, flags, GFS2_CONTROL_LOCK,
             &ls->ls_control_lksb, "control_lock");
}

static void gfs2_control_func(struct work_struct *work)
{
    struct gfs2_sbd *sdp = container_of(work, struct gfs2_sbd, sd_control_work.work);
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    char lvb_bits[GDLM_LVB_SIZE];
    uint32_t block_gen, start_gen, lvb_gen, flags;
    int recover_set = 0;
    int write_lvb = 0;
    int recover_size;
    int i, error;

    spin_lock(&ls->ls_recover_spin);
    /*
     * No MOUNT_DONE means we're still mounting; control_mount()
     * will set this flag, after which this thread will take over
     * all further clearing of BLOCK_LOCKS.
     *
     * FIRST_MOUNT means this node is doing first mounter recovery,
     * for which recovery control is handled by
     * control_mount()/control_first_done(), not this thread.
     */
    if (!test_bit(DFL_MOUNT_DONE, &ls->ls_recover_flags) ||
         test_bit(DFL_FIRST_MOUNT, &ls->ls_recover_flags)) {
        spin_unlock(&ls->ls_recover_spin);
        return;
    }
    block_gen = ls->ls_recover_block;
    start_gen = ls->ls_recover_start;
    spin_unlock(&ls->ls_recover_spin);

    /*
     * Equal block_gen and start_gen implies we are between
     * recover_prep and recover_done callbacks, which means
     * dlm recovery is in progress and dlm locking is blocked.
     * There's no point trying to do any work until recover_done.
     */

    if (block_gen == start_gen)
        return;

    /*
     * Propagate recover_submit[] and recover_result[] to lvb:
     * dlm_recoverd adds to recover_submit[] jids needing recovery
     * gfs2_recover adds to recover_result[] journal recovery results
     *
     * set lvb bit for jids in recover_submit[] if the lvb has not
     * yet been updated for the generation of the failure
     *
     * clear lvb bit for jids in recover_result[] if the result of
     * the journal recovery is SUCCESS
     */

    error = control_lock(sdp, DLM_LOCK_EX, DLM_LKF_CONVERT|DLM_LKF_VALBLK);
    if (error) {
        fs_err(sdp, "control lock EX error %d\n", error);
        return;
    }

    control_lvb_read(ls, &lvb_gen, lvb_bits);

    spin_lock(&ls->ls_recover_spin);
    if (block_gen != ls->ls_recover_block ||
        start_gen != ls->ls_recover_start) {
        fs_info(sdp, "recover generation %u block1 %u %u\n",
            start_gen, block_gen, ls->ls_recover_block);
        spin_unlock(&ls->ls_recover_spin);
        control_lock(sdp, DLM_LOCK_NL, DLM_LKF_CONVERT);
        return;
    }

    recover_size = ls->ls_recover_size;

    if (lvb_gen <= start_gen) {
        /*
         * Clear lvb bits for jids we've successfully recovered.
         * Because all nodes attempt to recover failed journals,
         * a journal can be recovered multiple times successfully
         * in succession.  Only the first will really do recovery,
         * the others find it clean, but still report a successful
         * recovery.  So, another node may have already recovered
         * the jid and cleared the lvb bit for it.
         */
        for (i = 0; i < recover_size; i++) {
            if (ls->ls_recover_result[i] != LM_RD_SUCCESS)
                continue;

            ls->ls_recover_result[i] = 0;

            if (!test_bit_le(i, lvb_bits + JID_BITMAP_OFFSET))
                continue;

            __clear_bit_le(i, lvb_bits + JID_BITMAP_OFFSET);
            write_lvb = 1;
        }
    }

    if (lvb_gen == start_gen) {
        /*
         * Failed slots before start_gen are already set in lvb.
         */
        for (i = 0; i < recover_size; i++) {
            if (!ls->ls_recover_submit[i])
                continue;
            if (ls->ls_recover_submit[i] < lvb_gen)
                ls->ls_recover_submit[i] = 0;
        }
    } else if (lvb_gen < start_gen) {
        /*
         * Failed slots before start_gen are not yet set in lvb.
         */
        for (i = 0; i < recover_size; i++) {
            if (!ls->ls_recover_submit[i])
                continue;
            if (ls->ls_recover_submit[i] < start_gen) {
                ls->ls_recover_submit[i] = 0;
                __set_bit_le(i, lvb_bits + JID_BITMAP_OFFSET);
            }
        }
        /* even if there are no bits to set, we need to write the
           latest generation to the lvb */
        write_lvb = 1;
    } else {
        /*
         * we should be getting a recover_done() for lvb_gen soon
         */
    }
    spin_unlock(&ls->ls_recover_spin);

    if (write_lvb) {
        control_lvb_write(ls, start_gen, lvb_bits);
        flags = DLM_LKF_CONVERT | DLM_LKF_VALBLK;
    } else {
        flags = DLM_LKF_CONVERT;
    }

    error = control_lock(sdp, DLM_LOCK_NL, flags);
    if (error) {
        fs_err(sdp, "control lock NL error %d\n", error);
        return;
    }

    /*
     * Everyone will see jid bits set in the lvb, run gfs2_recover_set(),
     * and clear a jid bit in the lvb if the recovery is a success.
     * Eventually all journals will be recovered, all jid bits will
     * be cleared in the lvb, and everyone will clear BLOCK_LOCKS.
     */

    for (i = 0; i < recover_size; i++) {
        if (test_bit_le(i, lvb_bits + JID_BITMAP_OFFSET)) {
            fs_info(sdp, "recover generation %u jid %d\n",
                start_gen, i);
            gfs2_recover_set(sdp, i);
            recover_set++;
        }
    }
    if (recover_set)
        return;

    /*
     * No more jid bits set in lvb, all recovery is done, unblock locks
     * (unless a new recover_prep callback has occured blocking locks
     * again while working above)
     */

    spin_lock(&ls->ls_recover_spin);
    if (ls->ls_recover_block == block_gen &&
        ls->ls_recover_start == start_gen) {
        clear_bit(DFL_BLOCK_LOCKS, &ls->ls_recover_flags);
        spin_unlock(&ls->ls_recover_spin);
        fs_info(sdp, "recover generation %u done\n", start_gen);
        gfs2_glock_thaw(sdp);
    } else {
        fs_info(sdp, "recover generation %u block2 %u %u\n",
            start_gen, block_gen, ls->ls_recover_block);
        spin_unlock(&ls->ls_recover_spin);
    }
}

static int control_mount(struct gfs2_sbd *sdp)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    char lvb_bits[GDLM_LVB_SIZE];
    uint32_t start_gen, block_gen, mount_gen, lvb_gen;
    int mounted_mode;
    int retries = 0;
    int error;

    memset(&ls->ls_mounted_lksb, 0, sizeof(struct dlm_lksb));
    memset(&ls->ls_control_lksb, 0, sizeof(struct dlm_lksb));
    memset(&ls->ls_control_lvb, 0, GDLM_LVB_SIZE);
    ls->ls_control_lksb.sb_lvbptr = ls->ls_control_lvb;
    init_completion(&ls->ls_sync_wait);

    set_bit(DFL_BLOCK_LOCKS, &ls->ls_recover_flags);

    error = control_lock(sdp, DLM_LOCK_NL, DLM_LKF_VALBLK);
    if (error) {
        fs_err(sdp, "control_mount control_lock NL error %d\n", error);
        return error;
    }

    error = mounted_lock(sdp, DLM_LOCK_NL, 0);
    if (error) {
        fs_err(sdp, "control_mount mounted_lock NL error %d\n", error);
        control_unlock(sdp);
        return error;
    }
    mounted_mode = DLM_LOCK_NL;

restart:
    if (retries++ && signal_pending(current)) {
        error = -EINTR;
        goto fail;
    }

    /*
     * We always start with both locks in NL. control_lock is
     * demoted to NL below so we don't need to do it here.
     */

    if (mounted_mode != DLM_LOCK_NL) {
        error = mounted_lock(sdp, DLM_LOCK_NL, DLM_LKF_CONVERT);
        if (error)
            goto fail;
        mounted_mode = DLM_LOCK_NL;
    }

    /*
     * Other nodes need to do some work in dlm recovery and gfs2_control
     * before the recover_done and control_lock will be ready for us below.
     * A delay here is not required but often avoids having to retry.
     */

    msleep_interruptible(500);

    /*
     * Acquire control_lock in EX and mounted_lock in either EX or PR.
     * control_lock lvb keeps track of any pending journal recoveries.
     * mounted_lock indicates if any other nodes have the fs mounted.
     */

    error = control_lock(sdp, DLM_LOCK_EX, DLM_LKF_CONVERT|DLM_LKF_NOQUEUE|DLM_LKF_VALBLK);
    if (error == -EAGAIN) {
        goto restart;
    } else if (error) {
        fs_err(sdp, "control_mount control_lock EX error %d\n", error);
        goto fail;
    }

    error = mounted_lock(sdp, DLM_LOCK_EX, DLM_LKF_CONVERT|DLM_LKF_NOQUEUE);
    if (!error) {
        mounted_mode = DLM_LOCK_EX;
        goto locks_done;
    } else if (error != -EAGAIN) {
        fs_err(sdp, "control_mount mounted_lock EX error %d\n", error);
        goto fail;
    }

    error = mounted_lock(sdp, DLM_LOCK_PR, DLM_LKF_CONVERT|DLM_LKF_NOQUEUE);
    if (!error) {
        mounted_mode = DLM_LOCK_PR;
        goto locks_done;
    } else {
        /* not even -EAGAIN should happen here */
        fs_err(sdp, "control_mount mounted_lock PR error %d\n", error);
        goto fail;
    }

locks_done:
    /*
     * If we got both locks above in EX, then we're the first mounter.
     * If not, then we need to wait for the control_lock lvb to be
     * updated by other mounted nodes to reflect our mount generation.
     *
     * In simple first mounter cases, first mounter will see zero lvb_gen,
     * but in cases where all existing nodes leave/fail before mounting
     * nodes finish control_mount, then all nodes will be mounting and
     * lvb_gen will be non-zero.
     */

    control_lvb_read(ls, &lvb_gen, lvb_bits);

    if (lvb_gen == 0xFFFFFFFF) {
        /* special value to force mount attempts to fail */
        fs_err(sdp, "control_mount control_lock disabled\n");
        error = -EINVAL;
        goto fail;
    }

    if (mounted_mode == DLM_LOCK_EX) {
        /* first mounter, keep both EX while doing first recovery */
        spin_lock(&ls->ls_recover_spin);
        clear_bit(DFL_BLOCK_LOCKS, &ls->ls_recover_flags);
        set_bit(DFL_MOUNT_DONE, &ls->ls_recover_flags);
        set_bit(DFL_FIRST_MOUNT, &ls->ls_recover_flags);
        spin_unlock(&ls->ls_recover_spin);
        fs_info(sdp, "first mounter control generation %u\n", lvb_gen);
        return 0;
    }

    error = control_lock(sdp, DLM_LOCK_NL, DLM_LKF_CONVERT);
    if (error)
        goto fail;

    /*
     * We are not first mounter, now we need to wait for the control_lock
     * lvb generation to be >= the generation from our first recover_done
     * and all lvb bits to be clear (no pending journal recoveries.)
     */

    if (!all_jid_bits_clear(lvb_bits)) {
        /* journals need recovery, wait until all are clear */
        fs_info(sdp, "control_mount wait for journal recovery\n");
        goto restart;
    }

    spin_lock(&ls->ls_recover_spin);
    block_gen = ls->ls_recover_block;
    start_gen = ls->ls_recover_start;
    mount_gen = ls->ls_recover_mount;

    if (lvb_gen < mount_gen) {
        /* wait for mounted nodes to update control_lock lvb to our
           generation, which might include new recovery bits set */
        fs_info(sdp, "control_mount wait1 block %u start %u mount %u "
            "lvb %u flags %lx\n", block_gen, start_gen, mount_gen,
            lvb_gen, ls->ls_recover_flags);
        spin_unlock(&ls->ls_recover_spin);
        goto restart;
    }

    if (lvb_gen != start_gen) {
        /* wait for mounted nodes to update control_lock lvb to the
           latest recovery generation */
        fs_info(sdp, "control_mount wait2 block %u start %u mount %u "
            "lvb %u flags %lx\n", block_gen, start_gen, mount_gen,
            lvb_gen, ls->ls_recover_flags);
        spin_unlock(&ls->ls_recover_spin);
        goto restart;
    }

    if (block_gen == start_gen) {
        /* dlm recovery in progress, wait for it to finish */
        fs_info(sdp, "control_mount wait3 block %u start %u mount %u "
            "lvb %u flags %lx\n", block_gen, start_gen, mount_gen,
            lvb_gen, ls->ls_recover_flags);
        spin_unlock(&ls->ls_recover_spin);
        goto restart;
    }

    clear_bit(DFL_BLOCK_LOCKS, &ls->ls_recover_flags);
    set_bit(DFL_MOUNT_DONE, &ls->ls_recover_flags);
    memset(ls->ls_recover_submit, 0, ls->ls_recover_size*sizeof(uint32_t));
    memset(ls->ls_recover_result, 0, ls->ls_recover_size*sizeof(uint32_t));
    spin_unlock(&ls->ls_recover_spin);
    return 0;

fail:
    mounted_unlock(sdp);
    control_unlock(sdp);
    return error;
}

static int dlm_recovery_wait(void *word)
{
    schedule();
    return 0;
}

static int control_first_done(struct gfs2_sbd *sdp)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    char lvb_bits[GDLM_LVB_SIZE];
    uint32_t start_gen, block_gen;
    int error;

restart:
    spin_lock(&ls->ls_recover_spin);
    start_gen = ls->ls_recover_start;
    block_gen = ls->ls_recover_block;

    if (test_bit(DFL_BLOCK_LOCKS, &ls->ls_recover_flags) ||
        !test_bit(DFL_MOUNT_DONE, &ls->ls_recover_flags) ||
        !test_bit(DFL_FIRST_MOUNT, &ls->ls_recover_flags)) {
        /* sanity check, should not happen */
        fs_err(sdp, "control_first_done start %u block %u flags %lx\n",
               start_gen, block_gen, ls->ls_recover_flags);
        spin_unlock(&ls->ls_recover_spin);
        control_unlock(sdp);
        return -1;
    }

    if (start_gen == block_gen) {
        /*
         * Wait for the end of a dlm recovery cycle to switch from
         * first mounter recovery.  We can ignore any recover_slot
         * callbacks between the recover_prep and next recover_done
         * because we are still the first mounter and any failed nodes
         * have not fully mounted, so they don't need recovery.
         */
        spin_unlock(&ls->ls_recover_spin);
        fs_info(sdp, "control_first_done wait gen %u\n", start_gen);

        wait_on_bit(&ls->ls_recover_flags, DFL_DLM_RECOVERY,
                dlm_recovery_wait, TASK_UNINTERRUPTIBLE);
        goto restart;
    }

    clear_bit(DFL_FIRST_MOUNT, &ls->ls_recover_flags);
    set_bit(DFL_FIRST_MOUNT_DONE, &ls->ls_recover_flags);
    memset(ls->ls_recover_submit, 0, ls->ls_recover_size*sizeof(uint32_t));
    memset(ls->ls_recover_result, 0, ls->ls_recover_size*sizeof(uint32_t));
    spin_unlock(&ls->ls_recover_spin);

    memset(lvb_bits, 0, sizeof(lvb_bits));
    control_lvb_write(ls, start_gen, lvb_bits);

    error = mounted_lock(sdp, DLM_LOCK_PR, DLM_LKF_CONVERT);
    if (error)
        fs_err(sdp, "control_first_done mounted PR error %d\n", error);

    error = control_lock(sdp, DLM_LOCK_NL, DLM_LKF_CONVERT|DLM_LKF_VALBLK);
    if (error)
        fs_err(sdp, "control_first_done control NL error %d\n", error);

    return error;
}

/*
 * Expand static jid arrays if necessary (by increments of RECOVER_SIZE_INC)
 * to accomodate the largest slot number.  (NB dlm slot numbers start at 1,
 * gfs2 jids start at 0, so jid = slot - 1)
 */

#define RECOVER_SIZE_INC 16

static int set_recover_size(struct gfs2_sbd *sdp, struct dlm_slot *slots,
                int num_slots)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    uint32_t *submit = NULL;
    uint32_t *result = NULL;
    uint32_t old_size, new_size;
    int i, max_jid;

    max_jid = 0;
    for (i = 0; i < num_slots; i++) {
        if (max_jid < slots[i].slot - 1)
            max_jid = slots[i].slot - 1;
    }

    old_size = ls->ls_recover_size;

    if (old_size >= max_jid + 1)
        return 0;

    new_size = old_size + RECOVER_SIZE_INC;

    submit = kzalloc(new_size * sizeof(uint32_t), GFP_NOFS);
    result = kzalloc(new_size * sizeof(uint32_t), GFP_NOFS);
    if (!submit || !result) {
        kfree(submit);
        kfree(result);
        return -ENOMEM;
    }

    spin_lock(&ls->ls_recover_spin);
    memcpy(submit, ls->ls_recover_submit, old_size * sizeof(uint32_t));
    memcpy(result, ls->ls_recover_result, old_size * sizeof(uint32_t));
    kfree(ls->ls_recover_submit);
    kfree(ls->ls_recover_result);
    ls->ls_recover_submit = submit;
    ls->ls_recover_result = result;
    ls->ls_recover_size = new_size;
    spin_unlock(&ls->ls_recover_spin);
    return 0;
}

static void free_recover_size(struct lm_lockstruct *ls)
{
    kfree(ls->ls_recover_submit);
    kfree(ls->ls_recover_result);
    ls->ls_recover_submit = NULL;
    ls->ls_recover_result = NULL;
    ls->ls_recover_size = 0;
}

/* dlm calls before it does lock recovery */

static void gdlm_recover_prep(void *arg)
{
    struct gfs2_sbd *sdp = arg;
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;

    spin_lock(&ls->ls_recover_spin);
    ls->ls_recover_block = ls->ls_recover_start;
    set_bit(DFL_DLM_RECOVERY, &ls->ls_recover_flags);

    if (!test_bit(DFL_MOUNT_DONE, &ls->ls_recover_flags) ||
         test_bit(DFL_FIRST_MOUNT, &ls->ls_recover_flags)) {
        spin_unlock(&ls->ls_recover_spin);
        return;
    }
    set_bit(DFL_BLOCK_LOCKS, &ls->ls_recover_flags);
    spin_unlock(&ls->ls_recover_spin);
}

/* dlm calls after recover_prep has been completed on all lockspace members;
   identifies slot/jid of failed member */

static void gdlm_recover_slot(void *arg, struct dlm_slot *slot)
{
    struct gfs2_sbd *sdp = arg;
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    int jid = slot->slot - 1;

    spin_lock(&ls->ls_recover_spin);
    if (ls->ls_recover_size < jid + 1) {
        fs_err(sdp, "recover_slot jid %d gen %u short size %d",
               jid, ls->ls_recover_block, ls->ls_recover_size);
        spin_unlock(&ls->ls_recover_spin);
        return;
    }

    if (ls->ls_recover_submit[jid]) {
        fs_info(sdp, "recover_slot jid %d gen %u prev %u",
            jid, ls->ls_recover_block, ls->ls_recover_submit[jid]);
    }
    ls->ls_recover_submit[jid] = ls->ls_recover_block;
    spin_unlock(&ls->ls_recover_spin);
}

/* dlm calls after recover_slot and after it completes lock recovery */

static void gdlm_recover_done(void *arg, struct dlm_slot *slots, int num_slots,
                  int our_slot, uint32_t generation)
{
    struct gfs2_sbd *sdp = arg;
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;

    /* ensure the ls jid arrays are large enough */
    set_recover_size(sdp, slots, num_slots);

    spin_lock(&ls->ls_recover_spin);
    ls->ls_recover_start = generation;

    if (!ls->ls_recover_mount) {
        ls->ls_recover_mount = generation;
        ls->ls_jid = our_slot - 1;
    }

    if (!test_bit(DFL_UNMOUNT, &ls->ls_recover_flags))
        queue_delayed_work(gfs2_control_wq, &sdp->sd_control_work, 0);

    clear_bit(DFL_DLM_RECOVERY, &ls->ls_recover_flags);
    smp_mb__after_clear_bit();
    wake_up_bit(&ls->ls_recover_flags, DFL_DLM_RECOVERY);
    spin_unlock(&ls->ls_recover_spin);
}

/* gfs2_recover thread has a journal recovery result */

static void gdlm_recovery_result(struct gfs2_sbd *sdp, unsigned int jid,
                 unsigned int result)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;

    if (test_bit(DFL_NO_DLM_OPS, &ls->ls_recover_flags))
        return;

    /* don't care about the recovery of own journal during mount */
    if (jid == ls->ls_jid)
        return;

    spin_lock(&ls->ls_recover_spin);
    if (test_bit(DFL_FIRST_MOUNT, &ls->ls_recover_flags)) {
        spin_unlock(&ls->ls_recover_spin);
        return;
    }
    if (ls->ls_recover_size < jid + 1) {
        fs_err(sdp, "recovery_result jid %d short size %d",
               jid, ls->ls_recover_size);
        spin_unlock(&ls->ls_recover_spin);
        return;
    }

    fs_info(sdp, "recover jid %d result %s\n", jid,
        result == LM_RD_GAVEUP ? "busy" : "success");

    ls->ls_recover_result[jid] = result;

    /* GAVEUP means another node is recovering the journal; delay our
       next attempt to recover it, to give the other node a chance to
       finish before trying again */

    if (!test_bit(DFL_UNMOUNT, &ls->ls_recover_flags))
        queue_delayed_work(gfs2_control_wq, &sdp->sd_control_work,
                   result == LM_RD_GAVEUP ? HZ : 0);
    spin_unlock(&ls->ls_recover_spin);
}

const struct dlm_lockspace_ops gdlm_lockspace_ops = {
    .recover_prep = gdlm_recover_prep,
    .recover_slot = gdlm_recover_slot,
    .recover_done = gdlm_recover_done,
};

static int gdlm_mount(struct gfs2_sbd *sdp, const char *table)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    char cluster[GFS2_LOCKNAME_LEN];
    const char *fsname;
    uint32_t flags;
    int error, ops_result;

    /*
     * initialize everything
     */

    INIT_DELAYED_WORK(&sdp->sd_control_work, gfs2_control_func);
    spin_lock_init(&ls->ls_recover_spin);
    ls->ls_recover_flags = 0;
    ls->ls_recover_mount = 0;
    ls->ls_recover_start = 0;
    ls->ls_recover_block = 0;
    ls->ls_recover_size = 0;
    ls->ls_recover_submit = NULL;
    ls->ls_recover_result = NULL;

    error = set_recover_size(sdp, NULL, 0);
    if (error)
        goto fail;

    /*
     * prepare dlm_new_lockspace args
     */

    fsname = strchr(table, ':');
    if (!fsname) {
        fs_info(sdp, "no fsname found\n");
        error = -EINVAL;
        goto fail_free;
    }
    memset(cluster, 0, sizeof(cluster));
    memcpy(cluster, table, strlen(table) - strlen(fsname));
    fsname++;

    flags = DLM_LSFL_FS | DLM_LSFL_NEWEXCL;

    /*
     * create/join lockspace
     */

    error = dlm_new_lockspace(fsname, cluster, flags, GDLM_LVB_SIZE,
                  &gdlm_lockspace_ops, sdp, &ops_result,
                  &ls->ls_dlm);
    if (error) {
        fs_err(sdp, "dlm_new_lockspace error %d\n", error);
        goto fail_free;
    }

    if (ops_result < 0) {
        /*
         * dlm does not support ops callbacks,
         * old dlm_controld/gfs_controld are used, try without ops.
         */
        fs_info(sdp, "dlm lockspace ops not used\n");
        free_recover_size(ls);
        set_bit(DFL_NO_DLM_OPS, &ls->ls_recover_flags);
        return 0;
    }

    if (!test_bit(SDF_NOJOURNALID, &sdp->sd_flags)) {
        fs_err(sdp, "dlm lockspace ops disallow jid preset\n");
        error = -EINVAL;
        goto fail_release;
    }

    /*
     * control_mount() uses control_lock to determine first mounter,
     * and for later mounts, waits for any recoveries to be cleared.
     */

    error = control_mount(sdp);
    if (error) {
        fs_err(sdp, "mount control error %d\n", error);
        goto fail_release;
    }

    ls->ls_first = !!test_bit(DFL_FIRST_MOUNT, &ls->ls_recover_flags);
    clear_bit(SDF_NOJOURNALID, &sdp->sd_flags);
    smp_mb__after_clear_bit();
    wake_up_bit(&sdp->sd_flags, SDF_NOJOURNALID);
    return 0;

fail_release:
    dlm_release_lockspace(ls->ls_dlm, 2);
fail_free:
    free_recover_size(ls);
fail:
    return error;
}

static void gdlm_first_done(struct gfs2_sbd *sdp)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;
    int error;

    if (test_bit(DFL_NO_DLM_OPS, &ls->ls_recover_flags))
        return;

    error = control_first_done(sdp);
    if (error)
        fs_err(sdp, "mount first_done error %d\n", error);
}

static void gdlm_unmount(struct gfs2_sbd *sdp)
{
    struct lm_lockstruct *ls = &sdp->sd_lockstruct;

    if (test_bit(DFL_NO_DLM_OPS, &ls->ls_recover_flags))
        goto release;

    /* wait for gfs2_control_wq to be done with this mount */

    spin_lock(&ls->ls_recover_spin);
    set_bit(DFL_UNMOUNT, &ls->ls_recover_flags);
    spin_unlock(&ls->ls_recover_spin);
    flush_delayed_work(&sdp->sd_control_work);

    /* mounted_lock and control_lock will be purged in dlm recovery */
release:
    if (ls->ls_dlm) {
        dlm_release_lockspace(ls->ls_dlm, 2);
        ls->ls_dlm = NULL;
    }

    free_recover_size(ls);
}

static const match_table_t dlm_tokens = {
    { Opt_jid, "jid=%d"},
    { Opt_id, "id=%d"},
    { Opt_first, "first=%d"},
    { Opt_nodir, "nodir=%d"},
    { Opt_err, NULL },
};

const struct lm_lockops gfs2_dlm_ops = {
    .lm_proto_name = "lock_dlm",
    .lm_mount = gdlm_mount,
    .lm_first_done = gdlm_first_done,
    .lm_recovery_result = gdlm_recovery_result,
    .lm_unmount = gdlm_unmount,
    .lm_put_lock = gdlm_put_lock,
    .lm_lock = gdlm_lock,
    .lm_cancel = gdlm_cancel,
    .lm_tokens = &dlm_tokens,
};