Adding upstream version 4.2.upstream/4.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 909 insertions, 0 deletions

diff --git a/monitor.c b/monitor.c
new file mode 100644
index 0000000..e0d3be6
--- /dev/null
+++ b/monitor.c
@@ -0,0 +1,909 @@
+/*
+ * 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>
+#include <signal.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;
+
+	/*
+	 * 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);
+}