[thirdparty/mdadm.git] / monitor.c

/*
 * mdmon - monitor external metadata arrays
 *
 * Copyright (C) 2007-2009 Neil Brown <neilb@suse.de>
 * Copyright (C) 2007-2009 Intel Corporation
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "mdadm.h"
#include "mdmon.h"
#include <sys/syscall.h>
#include <sys/select.h>

static char *array_states[] = {
        "clear", "inactive", "suspended", "readonly", "read-auto",
        "clean", "active", "write-pending", "active-idle", "broken", NULL };
static char *sync_actions[] = {
        "idle", "reshape", "resync", "recover", "check", "repair", NULL
};

enum bb_action {
        RECORD_BB = 1,
        COMPARE_BB,
};

static int write_attr(char *attr, int fd)
{
        return write(fd, attr, strlen(attr));
}

static void add_fd(fd_set *fds, int *maxfd, int fd)
{
        struct stat st;
        if (fd < 0)
                return;
        if (fstat(fd, &st) == -1) {
                dprintf("Invalid fd %d\n", fd);
                return;
        }
        if (st.st_nlink == 0) {
                dprintf("fd %d was deleted\n", fd);
                return;
        }
        if (fd > *maxfd)
                *maxfd = fd;
        FD_SET(fd, fds);
}

static int read_attr(char *buf, int len, int fd)
{
        int n;

        if (fd < 0) {
                buf[0] = 0;
                return 0;
        }
        lseek(fd, 0, 0);
        n = read(fd, buf, len - 1);

        if (n <= 0) {
                buf[0] = 0;
                return 0;
        }
        buf[n] = 0;
        if (buf[n-1] == '\n')
                buf[n-1] = 0;
        return n;
}

static void read_resync_start(int fd, unsigned long long *v)
{
        char buf[30];
        int n;

        n = read_attr(buf, 30, fd);
        if (n <= 0) {
                dprintf("Failed to read resync_start (%d)\n", fd);
                return;
        }
        if (strncmp(buf, "none", 4) == 0)
                *v = MaxSector;
        else
                *v = strtoull(buf, NULL, 10);
}

static unsigned long long read_sync_completed(int fd)
{
        unsigned long long val;
        char buf[50];
        int n;
        char *ep;

        n = read_attr(buf, 50, fd);

        if (n <= 0)
                return 0;
        buf[n] = 0;
        val = strtoull(buf, &ep, 0);
        if (ep == buf || (*ep != 0 && *ep != '\n' && *ep != ' '))
                return 0;
        return val;
}

static enum array_state read_state(int fd)
{
        char buf[20];
        int n = read_attr(buf, 20, fd);

        if (n <= 0)
                return bad_word;
        return (enum array_state) sysfs_match_word(buf, array_states);
}

static enum sync_action read_action( int fd)
{
        char buf[20];
        int n = read_attr(buf, 20, fd);

        if (n <= 0)
                return bad_action;
        return (enum sync_action) sysfs_match_word(buf, sync_actions);
}

int read_dev_state(int fd)
{
        char buf[100];
        int n = read_attr(buf, sizeof(buf), fd);
        char *cp;
        int rv = 0;

        if (n <= 0)
                return 0;

        cp = buf;
        while (cp) {
                if (sysfs_attr_match(cp, "faulty"))
                        rv |= DS_FAULTY;
                if (sysfs_attr_match(cp, "in_sync"))
                        rv |= DS_INSYNC;
                if (sysfs_attr_match(cp, "write_mostly"))
                        rv |= DS_WRITE_MOSTLY;
                if (sysfs_attr_match(cp, "spare"))
                        rv |= DS_SPARE;
                if (sysfs_attr_match(cp, "blocked"))
                        rv |= DS_BLOCKED;
                cp = strchr(cp, ',');
                if (cp)
                        cp++;
        }
        return rv;
}

int process_ubb(struct active_array *a, struct mdinfo *mdi, const unsigned long
                long sector, const int length, const char *buf,
                const int buf_len)
{
        struct superswitch *ss = a->container->ss;

        /*
         * record bad block in metadata first, then acknowledge it to the driver
         * via sysfs file
         */
        if ((ss->record_bad_block(a, mdi->disk.raid_disk, sector, length)) &&
            (write(mdi->bb_fd, buf, buf_len) == buf_len))
                return 1;

        /*
         * failed to store or acknowledge bad block, switch of bad block support
         * to get it out of blocked state
         */
        sysfs_set_str(&a->info, mdi, "state", "-external_bbl");
        return -1;
}

int compare_bb(struct active_array *a, struct mdinfo *mdi, const unsigned long
               long sector, const unsigned int length, void *arg)
{
        struct superswitch *ss = a->container->ss;
        struct md_bb *bb = (struct md_bb *) arg;
        int record = 1;
        int i;

        for (i = 0; i < bb->count; i++) {
                unsigned long long start = bb->entries[i].sector;
                unsigned long long len = bb->entries[i].length;

                /*
                 * bad block in metadata exactly matches bad block in kernel
                 * list, just remove it from a list
                 */
                if ((start == sector) && (len == length)) {
                        if (i < bb->count - 1)
                                bb->entries[i] = bb->entries[bb->count - 1];
                        bb->count -= 1;
                        record = 0;
                        break;
                }
                /*
                 * bad block in metadata spans bad block in kernel list,
                 * clear it and record new bad block
                 */
                if ((sector >= start) && (sector + length <= start + len)) {
                        ss->clear_bad_block(a, mdi->disk.raid_disk, start, len);
                        break;
                }
        }

        /* record all bad blocks not in metadata list */
        if (record && (ss->record_bad_block(a, mdi->disk.raid_disk, sector,
                                             length) <= 0)) {
                sysfs_set_str(&a->info, mdi, "state", "-external_bbl");
                return -1;
        }

        return 1;
}

static int read_bb_file(int fd, struct active_array *a, struct mdinfo *mdi,
                        enum bb_action action, void *arg)
{
        char buf[30];
        int n = 0;
        int ret = 0;
        int read_again = 0;
        int off = 0;
        int pos = 0;
        int preserve_pos = (action == RECORD_BB ? 0 : 1);

        if (lseek(fd, 0, SEEK_SET) == (off_t) -1)
                return -1;

        do {
                read_again = 0;
                n = read(fd, buf + pos, sizeof(buf) - 1 - pos);
                if (n < 0)
                        return -1;
                n += pos;

                buf[n] = '\0';
                off = 0;

                while (off < n) {
                        unsigned long long sector;
                        int length;
                        char newline;
                        int consumed;
                        int matched;
                        int rc;

                        /* kernel sysfs file format: "sector length\n" */
                        matched = sscanf(buf + off, "%llu %d%c%n", &sector,
                                         &length, &newline, &consumed);
                        if ((matched != 3) && (off > 0)) {
                                /* truncated entry, read again */
                                if (preserve_pos) {
                                        pos = sizeof(buf) - off - 1;
                                        memmove(buf, buf + off, pos);
                                } else {
                                        if (lseek(fd, 0, SEEK_SET) ==
                                            (off_t) -1)
                                                return -1;
                                }
                                read_again = 1;
                                break;
                        }
                        if (matched != 3)
                                return -1;
                        if (newline != '\n')
                                return -1;
                        if (length <= 0)
                                return -1;

                        if (action == RECORD_BB)
                                rc = process_ubb(a, mdi, sector, length,
                                                  buf + off, consumed);
                        else if (action == COMPARE_BB)
                                rc = compare_bb(a, mdi, sector, length, arg);
                        else
                                rc = -1;

                        if (rc < 0)
                                return rc;
                        ret += rc;
                        off += consumed;
                }
        } while (read_again);

        return ret;
}

static int process_dev_ubb(struct active_array *a, struct mdinfo *mdi)
{
        return read_bb_file(mdi->ubb_fd, a, mdi, RECORD_BB, NULL);
}

static int check_for_cleared_bb(struct active_array *a, struct mdinfo *mdi)
{
        struct superswitch *ss = a->container->ss;
        struct md_bb *bb;
        int i;

        if (!ss->get_bad_blocks)
                return -1;

        /*
         * Get a list of bad blocks for an array, then read list of
         * acknowledged bad blocks from kernel and compare it against metadata
         * list, clear all bad blocks remaining in metadata list
         */
        bb = ss->get_bad_blocks(a, mdi->disk.raid_disk);
        if (!bb)
                return -1;

        if (read_bb_file(mdi->bb_fd, a, mdi, COMPARE_BB, bb) < 0)
                return -1;

        for (i = 0; i < bb->count; i++) {
                unsigned long long sector = bb->entries[i].sector;
                int length = bb->entries[i].length;

                ss->clear_bad_block(a, mdi->disk.raid_disk, sector, length);
        }

        return 0;
}

static void signal_manager(void)
{
        /* tgkill(getpid(), mon_tid, SIGUSR1); */
        int pid = getpid();
        syscall(SYS_tgkill, pid, mgr_tid, SIGUSR1);
}

/* Monitor a set of active md arrays - all of which share the
 * same metadata - and respond to events that require
 * metadata update.
 *
 * New arrays are detected by another thread which allocates
 * required memory and attaches the data structure to our list.
 *
 * Events:
 *  Array stops.
 *    This is detected by array_state going to 'clear' or 'inactive'.
 *    while we thought it was active.
 *    Response is to mark metadata as clean and 'clear' the array(??)
 *  write-pending
 *    array_state if 'write-pending'
 *    We mark metadata as 'dirty' then set array to 'active'.
 *  active_idle
 *    Either ignore, or mark clean, then mark metadata as clean.
 *
 *  device fails
 *    detected by rd-N/state reporting "faulty"
 *    mark device as 'failed' in metadata, let the kernel release the
 *    device by writing '-blocked' to rd/state, and finally write 'remove' to
 *    rd/state.  Before a disk can be replaced it must be failed and removed
 *    from all container members, this will be preemptive for the other
 *    arrays... safe?
 *
 *  sync completes
 *    sync_action was 'resync' and becomes 'idle' and resync_start becomes
 *    MaxSector
 *    Notify metadata that sync is complete.
 *
 *  recovery completes
 *    sync_action changes from 'recover' to 'idle'
 *    Check each device state and mark metadata if 'faulty' or 'in_sync'.
 *
 *  deal with resync
 *    This only happens on finding a new array... mdadm will have set
 *    'resync_start' to the correct value.  If 'resync_start' indicates that an
 *    resync needs to occur set the array to the 'active' state rather than the
 *    initial read-auto state.
 *
 *
 *
 * We wait for a change (poll/select) on array_state, sync_action, and
 * each rd-X/state file.
 * When we get any change, we check everything.  So read each state file,
 * then decide what to do.
 *
 * The core action is to write new metadata to all devices in the array.
 * This is done at most once on any wakeup.
 * After that we might:
 *   - update the array_state
 *   - set the role of some devices.
 *   - request a sync_action
 *
 */

#define ARRAY_DIRTY 1
#define ARRAY_BUSY 2
static int read_and_act(struct active_array *a, fd_set *fds)
{
        unsigned long long sync_completed;
        int check_degraded = 0;
        int check_reshape = 0;
        int deactivate = 0;
        struct mdinfo *mdi;
        int ret = 0;
        int count = 0;
        struct timeval tv;

        a->next_state = bad_word;
        a->next_action = bad_action;

        a->curr_state = read_state(a->info.state_fd);
        a->curr_action = read_action(a->action_fd);
        if (a->curr_state != clear)
                /*
                 * In "clear" state, resync_start may wrongly be set to "0"
                 * when the kernel called md_clean but didn't remove the
                 * sysfs attributes yet
                 */
                read_resync_start(a->resync_start_fd, &a->info.resync_start);
        sync_completed = read_sync_completed(a->sync_completed_fd);
        for (mdi = a->info.devs; mdi ; mdi = mdi->next) {
                mdi->next_state = 0;
                mdi->curr_state = 0;
                if (mdi->state_fd >= 0) {
                        read_resync_start(mdi->recovery_fd,
                                          &mdi->recovery_start);
                        mdi->curr_state = read_dev_state(mdi->state_fd);
                }
                /*
                 * If array is blocked and metadata handler is able to handle
                 * BB, check if you can acknowledge them to md driver. If
                 * successful, clear faulty state and unblock the array.
                 */
                if ((mdi->curr_state & DS_BLOCKED) &&
                    a->container->ss->record_bad_block &&
                    (process_dev_ubb(a, mdi) > 0)) {
                        mdi->next_state |= DS_UNBLOCK;
                }
                if (FD_ISSET(mdi->bb_fd, fds))
                        check_for_cleared_bb(a, mdi);
        }

        gettimeofday(&tv, NULL);
        dprintf("(%d): %ld.%06ld state:%s prev:%s action:%s prev: %s start:%llu\n",
                a->info.container_member,
                tv.tv_sec, tv.tv_usec,
                array_states[a->curr_state],
                array_states[a->prev_state],
                sync_actions[a->curr_action],
                sync_actions[a->prev_action],
                a->info.resync_start
                );

        if ((a->curr_state == bad_word || a->curr_state <= inactive) &&
            a->prev_state > inactive) {
                /* array has been stopped */
                a->container->ss->set_array_state(a, 1);
                a->next_state = clear;
                deactivate = 1;
        }
        if (a->curr_state == write_pending) {
                a->container->ss->set_array_state(a, 0);
                a->next_state = active;
                ret |= ARRAY_DIRTY;
        }
        if (a->curr_state == active_idle) {
                /* Set array to 'clean' FIRST, then mark clean
                 * in the metadata
                 */
                a->next_state = clean;
                ret |= ARRAY_DIRTY;
        }
        if ((a->curr_state == clean) || (a->curr_state == broken)) {
                a->container->ss->set_array_state(a, 1);
        }
        if (a->curr_state == active ||
            a->curr_state == suspended)
                ret |= ARRAY_DIRTY;
        if (a->curr_state == readonly) {
                /* Well, I'm ready to handle things.  If readonly
                 * wasn't requested, transition to read-auto.
                 */
                char buf[64];
                read_attr(buf, sizeof(buf), a->metadata_fd);
                if (strncmp(buf, "external:-", 10) == 0) {
                        /* explicit request for readonly array.  Leave it alone */
                        ;
                } else {
                        if (a->container->ss->set_array_state(a, 2))
                                a->next_state = read_auto; /* array is clean */
                        else {
                                a->next_state = active; /* Now active for recovery etc */
                                ret |= ARRAY_DIRTY;
                        }
                }
        }

        if (!deactivate &&
            a->curr_action == idle &&
            a->prev_action == resync) {
                /* A resync has finished.  The endpoint is recorded in
                 * 'sync_start'.  We don't update the metadata
                 * until the array goes inactive or readonly though.
                 * Just check if we need to fiddle spares.
                 */
                a->container->ss->set_array_state(a, a->curr_state <= clean);
                check_degraded = 1;
        }

        if (!deactivate &&
            a->curr_action == idle &&
            a->prev_action == recover) {
                /* A recovery has finished.  Some disks may be in sync now,
                 * and the array may no longer be degraded
                 */
                for (mdi = a->info.devs ; mdi ; mdi = mdi->next) {
                        a->container->ss->set_disk(a, mdi->disk.raid_disk,
                                                   mdi->curr_state);
                        if (! (mdi->curr_state & DS_INSYNC))
                                check_degraded = 1;
                        count++;
                }
                if (count != a->info.array.raid_disks)
                        check_degraded = 1;
        }

        if (!deactivate &&
            a->curr_action == reshape &&
            a->prev_action != reshape)
                /* reshape was requested by mdadm.  Need to see if
                 * new devices have been added.  Manager does that
                 * when it sees check_reshape
                 */
                check_reshape = 1;

        /* Check for failures and if found:
         * 1/ Record the failure in the metadata and unblock the device.
         *    FIXME update the kernel to stop notifying on failed drives when
         *    the array is readonly and we have cleared 'blocked'
         * 2/ Try to remove the device if the array is writable, or can be
         *    made writable.
         */
        for (mdi = a->info.devs ; mdi ; mdi = mdi->next) {
                if (mdi->curr_state & DS_FAULTY) {
                        a->container->ss->set_disk(a, mdi->disk.raid_disk,
                                                   mdi->curr_state);
                        check_degraded = 1;
                        if (mdi->curr_state & DS_BLOCKED)
                                mdi->next_state |= DS_UNBLOCK;
                        if (a->curr_state == read_auto) {
                                a->container->ss->set_array_state(a, 0);
                                a->next_state = active;
                        }
                        if (a->curr_state > readonly)
                                mdi->next_state |= DS_REMOVE;
                }
        }

        /* Check for recovery checkpoint notifications.  We need to be a
         * minimum distance away from the last checkpoint to prevent
         * over checkpointing.  Note reshape checkpointing is handled
         * in the second branch.
         */
        if (sync_completed > a->last_checkpoint &&
            sync_completed - a->last_checkpoint > a->info.component_size >> 4 &&
            a->curr_action > reshape) {
                /* A (non-reshape) sync_action has reached a checkpoint.
                 * Record the updated position in the metadata
                 */
                a->last_checkpoint = sync_completed;
                a->container->ss->set_array_state(a, a->curr_state <= clean);
        } else if ((a->curr_action == idle && a->prev_action == reshape) ||
                   (a->curr_action == reshape &&
                    sync_completed > a->last_checkpoint)) {
                /* Reshape has progressed or completed so we need to
                 * update the array state - and possibly the array size
                 */
                if (sync_completed != 0)
                        a->last_checkpoint = sync_completed;
                /* We might need to update last_checkpoint depending on
                 * the reason that reshape finished.
                 * if array reshape is really finished:
                 *        set check point to the end, this allows
                 *        set_array_state() to finalize reshape in metadata
                 * if reshape if broken: do not set checkpoint to the end
                 *        this allows for reshape restart from checkpoint
                 */
                if ((a->curr_action != reshape) &&
                    (a->prev_action == reshape)) {
                        char buf[40];
                        if ((sysfs_get_str(&a->info, NULL,
                                          "reshape_position",
                                          buf,
                                          sizeof(buf)) >= 0) &&
                             strncmp(buf, "none", 4) == 0)
                                a->last_checkpoint = a->info.component_size;
                }
                a->container->ss->set_array_state(a, a->curr_state <= clean);
                a->last_checkpoint = sync_completed;
        }

        if (sync_completed > a->last_checkpoint)
                a->last_checkpoint = sync_completed;

        if (sync_completed >= a->info.component_size)
                a->last_checkpoint = 0;

        a->container->ss->sync_metadata(a->container);
        dprintf("(%d): state:%s action:%s next(", a->info.container_member,
                array_states[a->curr_state], sync_actions[a->curr_action]);

        /* Effect state changes in the array */
        if (a->next_state != bad_word) {
                dprintf_cont(" state:%s", array_states[a->next_state]);
                write_attr(array_states[a->next_state], a->info.state_fd);
        }
        if (a->next_action != bad_action) {
                write_attr(sync_actions[a->next_action], a->action_fd);
                dprintf_cont(" action:%s", sync_actions[a->next_action]);
        }
        for (mdi = a->info.devs; mdi ; mdi = mdi->next) {
                if (mdi->next_state & DS_UNBLOCK) {
                        dprintf_cont(" %d:-blocked", mdi->disk.raid_disk);
                        write_attr("-blocked", mdi->state_fd);
                }

                if ((mdi->next_state & DS_REMOVE) && mdi->state_fd >= 0) {
                        int remove_result;

                        /* The kernel may not be able to immediately remove the
                         * disk.  In that case we wait a little while and
                         * try again.
                         */
                        remove_result = write_attr("remove", mdi->state_fd);
                        if (remove_result > 0) {
                                dprintf_cont(" %d:removed", mdi->disk.raid_disk);
                                close(mdi->state_fd);
                                close(mdi->recovery_fd);
                                close(mdi->bb_fd);
                                close(mdi->ubb_fd);
                                mdi->state_fd = -1;
                        } else
                                ret |= ARRAY_BUSY;
                }
                if (mdi->next_state & DS_INSYNC) {
                        write_attr("+in_sync", mdi->state_fd);
                        dprintf_cont(" %d:+in_sync", mdi->disk.raid_disk);
                }
        }
        dprintf_cont(" )\n");

        /* move curr_ to prev_ */
        a->prev_state = a->curr_state;

        a->prev_action = a->curr_action;

        for (mdi = a->info.devs; mdi ; mdi = mdi->next) {
                mdi->prev_state = mdi->curr_state;
                mdi->next_state = 0;
        }

        if (check_degraded || check_reshape) {
                /* manager will do the actual check */
                if (check_degraded)
                        a->check_degraded = 1;
                if (check_reshape)
                        a->check_reshape = 1;
                signal_manager();
        }

        if (deactivate)
                a->container = NULL;

        return ret;
}

static struct mdinfo *
find_device(struct active_array *a, int major, int minor)
{
        struct mdinfo *mdi;

        for (mdi = a->info.devs ; mdi ; mdi = mdi->next)
                if (mdi->disk.major == major && mdi->disk.minor == minor)
                        return mdi;

        return NULL;
}

static void reconcile_failed(struct active_array *aa, struct mdinfo *failed)
{
        struct active_array *a;
        struct mdinfo *victim;

        for (a = aa; a; a = a->next) {
                if (!a->container || a->to_remove)
                        continue;
                victim = find_device(a, failed->disk.major, failed->disk.minor);
                if (!victim)
                        continue;

                if (!(victim->curr_state & DS_FAULTY))
                        write_attr("faulty", victim->state_fd);
        }
}

#ifdef DEBUG
static void dprint_wake_reasons(fd_set *fds)
{
        int i;
        char proc_path[256];
        char link[256];
        char *basename;
        int rv;

        fprintf(stderr, "monitor: wake ( ");
        for (i = 0; i < FD_SETSIZE; i++) {
                if (FD_ISSET(i, fds)) {
                        sprintf(proc_path, "/proc/%d/fd/%d",
                                (int) getpid(), i);

                        rv = readlink(proc_path, link, sizeof(link) - 1);
                        if (rv < 0) {
                                fprintf(stderr, "%d:unknown ", i);
                                continue;
                        }
                        link[rv] = '\0';
                        basename = strrchr(link, '/');
                        fprintf(stderr, "%d:%s ",
                                i, basename ? ++basename : link);
                }
        }
        fprintf(stderr, ")\n");
}
#endif

int monitor_loop_cnt;

static int wait_and_act(struct supertype *container, int nowait)
{
        fd_set rfds;
        int maxfd = 0;
        struct active_array **aap = &container->arrays;
        struct active_array *a, **ap;
        int rv;
        struct mdinfo *mdi;
        static unsigned int dirty_arrays = ~0; /* start at some non-zero value */

        FD_ZERO(&rfds);

        for (ap = aap ; *ap ;) {
                a = *ap;
                /* once an array has been deactivated we want to
                 * ask the manager to discard it.
                 */
                if (!a->container || a->to_remove) {
                        if (discard_this) {
                                ap = &(*ap)->next;
                                continue;
                        }
                        *ap = a->next;
                        a->next = NULL;
                        discard_this = a;
                        signal_manager();
                        continue;
                }

                add_fd(&rfds, &maxfd, a->info.state_fd);
                add_fd(&rfds, &maxfd, a->action_fd);
                add_fd(&rfds, &maxfd, a->sync_completed_fd);
                for (mdi = a->info.devs ; mdi ; mdi = mdi->next) {
                        add_fd(&rfds, &maxfd, mdi->state_fd);
                        add_fd(&rfds, &maxfd, mdi->bb_fd);
                        add_fd(&rfds, &maxfd, mdi->ubb_fd);
                }

                ap = &(*ap)->next;
        }

        if (manager_ready && (*aap == NULL || (sigterm && !dirty_arrays))) {
                /* No interesting arrays, or we have been told to
                 * terminate and everything is clean.  Lets see about
                 * exiting.  Note that blocking at this point is not a
                 * problem as there are no active arrays, there is
                 * nothing that we need to be ready to do.
                 */
                int fd;
                if (sigterm)
                        fd = open_dev_excl(container->devnm);
                else
                        fd = open_dev_flags(container->devnm, O_RDONLY|O_EXCL);
                if (fd >= 0 || errno != EBUSY) {
                        /* OK, we are safe to leave */
                        if (sigterm && !dirty_arrays)
                                dprintf("caught sigterm, all clean... exiting\n");
                        else
                                dprintf("no arrays to monitor... exiting\n");
                        if (!sigterm)
                                /* On SIGTERM, someone (the take-over mdmon) will
                                 * clean up
                                 */
                                remove_pidfile(container->devnm);
                        exit_now = 1;
                        signal_manager();
                        close(fd);
                        exit(0);
                }
        }

        if (!nowait) {
                sigset_t set;
                struct timespec ts;
                ts.tv_sec = 24*3600;
                ts.tv_nsec = 0;
                if (*aap == NULL || container->retry_soon) {
                        /* just waiting to get O_EXCL access */
                        ts.tv_sec = 0;
                        ts.tv_nsec = 20000000ULL;
                }
                sigprocmask(SIG_UNBLOCK, NULL, &set);
                sigdelset(&set, SIGUSR1);
                monitor_loop_cnt |= 1;
                rv = pselect(maxfd+1, NULL, NULL, &rfds, &ts, &set);
                monitor_loop_cnt += 1;
                if (rv == -1) {
                        if (errno == EINTR) {
                                rv = 0;
                                FD_ZERO(&rfds);
                                dprintf("monitor: caught signal\n");
                        } else
                                dprintf("monitor: error %d in pselect\n",
                                        errno);
                }
                #ifdef DEBUG
                else
                        dprint_wake_reasons(&rfds);
                #endif
                container->retry_soon = 0;
        }

        if (update_queue) {
                struct metadata_update *this;

                for (this = update_queue; this ; this = this->next)
                        container->ss->process_update(container, this);

                update_queue_handled = update_queue;
                update_queue = NULL;
                signal_manager();
                container->ss->sync_metadata(container);
        }

        rv = 0;
        dirty_arrays = 0;
        for (a = *aap; a ; a = a->next) {

                if (a->replaces && !discard_this) {
                        struct active_array **ap;
                        for (ap = &a->next; *ap && *ap != a->replaces;
                             ap = & (*ap)->next)
                                ;
                        if (*ap)
                                *ap = (*ap)->next;
                        discard_this = a->replaces;
                        a->replaces = NULL;
                        /* FIXME check if device->state_fd need to be cleared?*/
                        signal_manager();
                }
                if (a->container && !a->to_remove) {
                        int ret = read_and_act(a, &rfds);
                        rv |= 1;
                        dirty_arrays += !!(ret & ARRAY_DIRTY);
                        /* when terminating stop manipulating the array after it
                         * is clean, but make sure read_and_act() is given a
                         * chance to handle 'active_idle'
                         */
                        if (sigterm && !(ret & ARRAY_DIRTY))
                                a->container = NULL; /* stop touching this array */
                        if (ret & ARRAY_BUSY)
                                container->retry_soon = 1;
                }
        }

        /* propagate failures across container members */
        for (a = *aap; a ; a = a->next) {
                if (!a->container || a->to_remove)
                        continue;
                for (mdi = a->info.devs ; mdi ; mdi = mdi->next)
                        if (mdi->curr_state & DS_FAULTY)
                                reconcile_failed(*aap, mdi);
        }

        return rv;
}

void do_monitor(struct supertype *container)
{
        int rv;
        int first = 1;
        do {
                rv = wait_and_act(container, first);
                first = 0;
        } while (rv >= 0);
}