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Re: [dm-devel] [PATCH] Cluster-aware logging module.



Hi Jonathan,
I'd like to test Your clustered mirror patches, do You have some newer version in the meantime?
Ot is this one the latest one?
thanks a lot in advance!
BR
nik

On Tue, Dec 16, 2008 at 04:10:55PM -0600, Jonathan Brassow wrote:
> Please note that this patch depends on
> "dm-raid1-add-is_remote_recovering-hook-for-clusters.patch", which is
> already listed in agk_'s repository
> (http://www.kernel.org/pub/linux/kernel/people/agk/patches/2.6/editing/).
> 
> I have run the cluster mirrors through a number of tests on the most
> recent kernel.  It still works after the extraction of the region
> hashing code from dm-raid1.c - which was my original concern.
> 
> I'm asking anyone who is willing to test/review cluster mirroring.  You
> will also need the code for userspace daemon.  It is currently located
> in the 'cluster' repository.  Get it by doing:
> 1) git clone git://git.fedorahosted.org/cluster.git
> 2) git branch --track myRHEL5 origin/RHEL5
> 3) git checkout myRHEL5
> 
> I plan on moving the cluster log daemon (clogd) to the LVM2 repository
> soon.  I would certainly appreciate people starting the review now.  In
> the next week or so, I plan to post the patches that would perform this
> move... and later check the code in to LVM2/daemons/clogd.
> 
> As for the kernel patch that I am attaching, I know there is still one
> point of contention.  Agk had brought up the fact that I am currently
> hard-coding the values for the connector interface 'static struct cb_id
> cn_clog_id = { 0x4, 0x1 };'.  I welcome any comments on how to resolve
> this.  Also, I'm wondering if people think the
> include/linux/dm-cluster-log.h:RQ_TYPE macro is bad...
> 
> thanks,
>  brassow
> 
> This patch contains a cluster-aware log module.  When used
> by dm-raid1, device-mapper mirroring can be cluster-aware.
> 
> There is a kernel component (provided in this patch) and a
> user space component.  The kernel component implements the
> logging interface and passes all requests to userspace via
> 'connector' (a netlink wrapper).  The userspace daemon is
> built upon OpenAIS for cluster communication and is fault
> tolerant.
> 
> Signed-off-by: Jonathan Brassow <jbrassow redhat com>
> Index: linux-2.6/drivers/md/dm-clog-tfr.c
> ===================================================================
> --- /dev/null
> +++ linux-2.6/drivers/md/dm-clog-tfr.c
> @@ -0,0 +1,272 @@
> +/*
> + * Copyright (C) 2006-2008 Red Hat, Inc.
> + *
> + * This file is released under the LGPL.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <net/sock.h>
> +#include <linux/workqueue.h>
> +#include <linux/connector.h>
> +#include <linux/device-mapper.h>
> +
> +#include <linux/dm-cluster-log.h>
> +#include "dm-clog-tfr.h"
> +
> +#include <asm/div64.h> /* Unnecessary */
> +
> +#define SHORT_UUID(x) (strlen(x) > 8) ? ((x) + (strlen(x) - 8)) : (x)
> +
> +static uint32_t seq = 0;
> +
> +/*
> + * Pre-allocated space for speed
> + */
> +#define DM_CLOG_PREALLOCED_SIZE 512
> +static struct cn_msg *prealloced_cn_msg = NULL;
> +static struct clog_tfr *prealloced_clog_tfr = NULL;
> +
> +static struct cb_id cn_clog_id = { 0x4, 0x1 };
> +static DEFINE_MUTEX(_lock);
> +
> +struct receiving_pkg {
> +	struct list_head list;
> +	struct completion complete;
> +
> +	uint32_t seq;
> +
> +	int error;
> +	int *data_size;
> +	char *data;
> +};
> +
> +static spinlock_t receiving_list_lock = SPIN_LOCK_UNLOCKED;
> +static struct list_head receiving_list;
> +
> +static int dm_clog_sendto_server(struct clog_tfr *tfr)
> +{
> +	int r;
> +	int size;
> +	struct cn_msg *msg = prealloced_cn_msg;
> +
> +	if (tfr != prealloced_clog_tfr) {
> +		size = sizeof(struct cn_msg) +
> +			sizeof(struct clog_tfr) + tfr->data_size;
> +		msg = kmalloc(size, GFP_NOIO);
> +		if (!msg)
> +			return -ENOMEM;
> +		memcpy((msg + 1), tfr,
> +		       sizeof(struct clog_tfr) + tfr->data_size);
> +	}
> +
> +	memset(msg, 0, sizeof(struct cn_msg));
> +
> +	msg->id.idx = cn_clog_id.idx;
> +	msg->id.val = cn_clog_id.val;
> +	msg->ack = 0;
> +	msg->seq = tfr->seq;
> +	msg->len = sizeof(struct clog_tfr) + tfr->data_size;
> +
> +	r = cn_netlink_send(msg, 0, gfp_any());
> +
> +	if (msg != prealloced_cn_msg)
> +		kfree(msg);
> +
> +	return r;
> +}
> +
> +/*
> + * fill_pkg
> + * @msg
> + * @tfr
> + *
> + * Parameters can be either msg or tfr, but not both.  This
> + * function fills in the reply for a waiting request.  If just
> + * msg is given, then the reply is simply an ACK from userspace
> + * that the request was received.
> + *
> + * Returns: 0 on success, -ENOENT on failure
> + */
> +static int fill_pkg(struct cn_msg *msg, struct clog_tfr *tfr)
> +{
> +	uint32_t rtn_seq = (msg) ? msg->seq : (tfr) ? tfr->seq : 0;
> +	struct receiving_pkg *pkg;
> +
> +	list_for_each_entry(pkg, &receiving_list, list) {
> +		if (rtn_seq != pkg->seq)
> +			continue;
> +
> +		if (msg) {
> +			pkg->error = -msg->ack;
> +			/*
> +			 * If we are trying again, we will need to know our
> +			 * storage capacity.  Otherwise, along with the
> +			 * error code, we make explicit that we have no data.
> +			 */
> +			if (pkg->error != -EAGAIN)
> +				*(pkg->data_size) = 0;
> +		} else if (tfr->data_size > *(pkg->data_size)) {
> +			DMERR("Insufficient space to receive package [%s]::",
> +			      RQ_TYPE(tfr->request_type));
> +			DMERR("  tfr->data_size    = %u", tfr->data_size);
> +			DMERR("  *(pkg->data_size) = %u", *(pkg->data_size));
> +
> +			*(pkg->data_size) = 0;
> +			pkg->error = -ENOSPC;
> +		} else {
> +			pkg->error = tfr->error;
> +			memcpy(pkg->data, tfr->data, tfr->data_size);
> +			*(pkg->data_size) = tfr->data_size;
> +		}
> +		complete(&pkg->complete);
> +		return 0;
> +	}
> +
> +	return -ENOENT;
> +}
> +
> +/*
> + * cn_clog_callback
> + * @data
> + *
> + * This is the connector callback that delivers data
> + * that was sent from userspace.
> + */
> +static void cn_clog_callback(void *data)
> +{
> +	struct cn_msg *msg = (struct cn_msg *)data;
> +	struct clog_tfr *tfr = (struct clog_tfr *)(msg + 1);
> +
> +	spin_lock(&receiving_list_lock);
> +	if (msg->len == 0)
> +		fill_pkg(msg, NULL);
> +	else if (msg->len < sizeof(*tfr))
> +		DMERR("Incomplete message received: [%u]", msg->seq);
> +	else
> +		fill_pkg(NULL, tfr);
> +	spin_unlock(&receiving_list_lock);
> +}
> +
> +/*
> + * dm_clog_consult_server
> + * @uuid: log's uuid (must be DM_UUID_LEN in size)
> + * @request_type:
> + * @data: data to tx to the server
> + * @data_size: size of data in bytes
> + * @rdata: place to put return data from server
> + * @rdata_size: value-result (amount of space given/amount of space used)
> + *
> + * Only one process at a time can communicate with the server.
> + * rdata_size is undefined on failure.
> + *
> + * Returns: 0 on success, -EXXX on failure
> + */
> +int dm_clog_consult_server(const char *uuid, int request_type,
> +			   char *data, int data_size,
> +			   char *rdata, int *rdata_size)
> +{
> +	int r = 0;
> +	int dummy = 0;
> +	int overhead_size = sizeof(struct clog_tfr *) + sizeof(struct cn_msg);
> +	struct clog_tfr *tfr = prealloced_clog_tfr;
> +	struct receiving_pkg pkg;
> +
> +	if (data_size > (DM_CLOG_PREALLOCED_SIZE - overhead_size)) {
> +		DMINFO("Size of tfr exceeds preallocated size");
> +		/* FIXME: is kmalloc sufficient if we need this much space? */
> +		tfr = kzalloc(data_size + sizeof(*tfr), GFP_NOIO);
> +	}
> +
> +	if (!tfr)
> +		return -ENOMEM;
> +
> +	if (!rdata_size)
> +		rdata_size = &dummy;
> +resend:
> +	/*
> +	 * We serialize the sending of requests so we can
> +	 * use the preallocated space.
> +	 */
> +	mutex_lock(&_lock);
> +
> +	memset(tfr, 0, DM_CLOG_PREALLOCED_SIZE - overhead_size);
> +	memcpy(tfr->uuid, uuid, DM_UUID_LEN);
> +	tfr->seq = seq++;
> +	tfr->request_type = request_type;
> +	tfr->data_size = data_size;
> +	if (data && data_size)
> +		memcpy(tfr->data, data, data_size);
> +
> +	memset(&pkg, 0, sizeof(pkg));
> +	init_completion(&pkg.complete);
> +	pkg.seq = tfr->seq;
> +	pkg.data_size = rdata_size;
> +	pkg.data = rdata;
> +	spin_lock(&receiving_list_lock);
> +	list_add(&(pkg.list), &receiving_list);
> +	spin_unlock(&receiving_list_lock);
> +
> +	r = dm_clog_sendto_server(tfr);
> +
> +	mutex_unlock(&_lock);
> +
> +	if (r) {
> +		DMERR("Unable to send cluster log request [%s] to server: %d",
> +		      RQ_TYPE(request_type), r);
> +		spin_lock(&receiving_list_lock);
> +		list_del_init(&(pkg.list));
> +		spin_unlock(&receiving_list_lock);
> +
> +		goto out;
> +	}
> +
> +	r = wait_for_completion_timeout(&(pkg.complete), 15 * HZ);
> +	spin_lock(&receiving_list_lock);
> +	list_del_init(&(pkg.list));
> +	spin_unlock(&receiving_list_lock);
> +	if (!r) {
> +		DMWARN("[%s] Request timed out: [%s/%u] - retrying",
> +		       SHORT_UUID(uuid), RQ_TYPE(request_type), pkg.seq);
> +		goto resend;
> +	}
> +
> +	r = pkg.error;
> +	if (r == -EAGAIN)
> +		goto resend;
> +
> +out:
> +	if (tfr != (struct clog_tfr *)prealloced_clog_tfr)
> +		kfree(tfr);
> +
> +	return r;
> +}
> +
> +int dm_clog_tfr_init(void)
> +{
> +	int r;
> +	void *prealloced;
> +
> +	INIT_LIST_HEAD(&receiving_list);
> +
> +	prealloced = kmalloc(DM_CLOG_PREALLOCED_SIZE, GFP_KERNEL);
> +	if (!prealloced)
> +		return -ENOMEM;
> +
> +	prealloced_cn_msg = prealloced;
> +	prealloced_clog_tfr = prealloced + sizeof(struct cn_msg);
> +
> +	r = cn_add_callback(&cn_clog_id, "clulog", cn_clog_callback);
> +	if (r) {
> +		cn_del_callback(&cn_clog_id);
> +		return r;
> +	}
> +
> +	return 0;
> +}
> +
> +void dm_clog_tfr_exit(void)
> +{
> +	cn_del_callback(&cn_clog_id);
> +	kfree(prealloced_cn_msg);
> +}
> Index: linux-2.6/drivers/md/dm-clog-tfr.h
> ===================================================================
> --- /dev/null
> +++ linux-2.6/drivers/md/dm-clog-tfr.h
> @@ -0,0 +1,18 @@
> +/*
> + * Copyright (C) 2006-2008 Red Hat, Inc.
> + *
> + * This file is released under the LGPL.
> + */
> +
> +#ifndef __DM_CLOG_TFR_H__
> +#define __DM_CLOG_TFR_H__
> +
> +#define DM_MSG_PREFIX "dm-log-clustered"
> +
> +int dm_clog_tfr_init(void);
> +void dm_clog_tfr_exit(void);
> +int dm_clog_consult_server(const char *uuid, int request_type,
> +			   char *data, int data_size,
> +			   char *rdata, int *rdata_size);
> +
> +#endif /* __DM_CLOG_TFR_H__ */
> Index: linux-2.6/drivers/md/dm-clog.c
> ===================================================================
> --- /dev/null
> +++ linux-2.6/drivers/md/dm-clog.c
> @@ -0,0 +1,786 @@
> +/*
> + * Copyright (C) 2006-2008 Red Hat, Inc.
> + *
> + * This file is released under the LGPL.
> + */
> +
> +#include <linux/blkdev.h> /* for sector_div, which is used in dm-dirty-log.h */
> +#include <linux/bio.h>
> +#include <linux/dm-dirty-log.h>
> +#include <linux/device-mapper.h>
> +
> +#include <linux/dm-cluster-log.h>
> +#include "dm-clog-tfr.h"
> +
> +struct flush_entry {
> +	int type;
> +	region_t region;
> +	struct list_head list;
> +};
> +
> +struct log_c {
> +	struct dm_target *ti;
> +	uint32_t region_size;
> +	region_t region_count;
> +	char uuid[DM_UUID_LEN];
> +
> +	char *ctr_str; /* Gives ability to restart if userspace dies */
> +	uint32_t ctr_size;
> +
> +	/*
> +	 * in_sync_hint gets set when doing is_remote_recovering.  It
> +	 * represents the first region that needs recovery.  IOW, the
> +	 * first zero bit of sync_bits.  This can be useful for to limit
> +	 * traffic for calls like is_remote_recovering and get_resync_work,
> +	 * but be take care in its use for anything else.
> +	 */
> +	uint64_t in_sync_hint;
> +
> +	spinlock_t flush_lock;
> +	struct list_head flush_list;  /* only for clear and mark requests */
> +
> +	struct dm_dev *disk_log;
> +};
> +
> +static mempool_t *flush_entry_pool = NULL;
> +
> +static void *flush_entry_alloc(gfp_t gfp_mask, void *pool_data)
> +{
> +	return kmalloc(sizeof(struct flush_entry), gfp_mask);
> +}
> +
> +static void flush_entry_free(void *element, void *pool_data)
> +{
> +	kfree(element);
> +}
> +
> +int cluster_do_request(struct log_c *lc, const char *uuid, int request_type,
> +		       char *data, int data_size, char *rdata, int *rdata_size)
> +{
> +	int r;
> +
> +	/*
> +	 * If the server isn't there, -ESRCH is returned,
> +	 * and we must keep trying until the server is
> +	 * restored.
> +	 */
> +retry:
> +	r = dm_clog_consult_server(uuid, request_type, data,
> +				   data_size, rdata, rdata_size);
> +
> +	if (r != -ESRCH)
> +		return r;
> +
> +	DMERR(" Userspace cluster log server not found.");
> +	while (1) {
> +		set_current_state(TASK_INTERRUPTIBLE);
> +		schedule_timeout(2*HZ);
> +		DMWARN("Attempting to contact cluster log server...");
> +		r = dm_clog_consult_server(uuid, DM_CLOG_CTR, lc->ctr_str,
> +					   lc->ctr_size, NULL, NULL);
> +		if (!r)
> +			break;
> +	}
> +	DMINFO("Reconnected to cluster log server... CTR complete");
> +	r = dm_clog_consult_server(uuid, DM_CLOG_RESUME, NULL,
> +				   0, NULL, NULL);
> +	if (!r)
> +		goto retry;
> +
> +	DMERR("Error trying to resume cluster log: %d", r);
> +
> +	return -ESRCH;
> +}
> +
> +static int cluster_ctr(struct dm_dirty_log *log, struct dm_target *ti,
> +		       unsigned int argc, char **argv,
> +		       struct dm_dev *disk_log)
> +{
> +	int i;
> +	int r = 0;
> +	int str_size;
> +	int offset = (disk_log) ? 1 : 0;
> +	char *ctr_str = NULL;
> +	struct log_c *lc = NULL;
> +	uint32_t region_size;
> +	region_t region_count;
> +
> +	/* Already checked argument count */
> +
> +	if (sscanf(argv[offset], "%u", &region_size) != 1) {
> +		DMWARN("Invalid region size string");
> +		return -EINVAL;
> +	}
> +
> +	region_count = dm_sector_div_up(ti->len, region_size);
> +
> +	lc = kmalloc(sizeof(*lc), GFP_KERNEL);
> +	if (!lc) {
> +		DMWARN("Unable to allocate cluster log context.");
> +		return -ENOMEM;
> +	}
> +
> +	lc->ti = ti;
> +	lc->region_size = region_size;
> +	lc->region_count = region_count;
> +	lc->disk_log = disk_log;
> +
> +	/* FIXME: Need to check size of uuid arg */
> +	memcpy(lc->uuid, argv[1 + offset], DM_UUID_LEN);
> +	spin_lock_init(&lc->flush_lock);
> +	INIT_LIST_HEAD(&lc->flush_list);
> +
> +	for (i = 0, str_size = 0; i < argc; i++)
> +		str_size += strlen(argv[i]) + 1; /* +1 for space between args */
> +
> +	str_size += 20; /* Max number of chars in a printed u64 number */
> +
> +	ctr_str = kzalloc(str_size, GFP_KERNEL);
> +	if (!ctr_str) {
> +		DMWARN("Unable to allocate memory for constructor string");
> +		kfree(lc);
> +		return -ENOMEM;
> +	}
> +
> +	for (i = 0, str_size = 0; i < argc; i++)
> +		str_size += sprintf(ctr_str + str_size, "%s ", argv[i]);
> +	str_size += sprintf(ctr_str + str_size, "%llu",
> +			    (unsigned long long)ti->len);
> +
> +	/* Send table string */
> +	r = dm_clog_consult_server(lc->uuid, DM_CLOG_CTR,
> +				   ctr_str, str_size, NULL, NULL);
> +
> +	if (r == -ESRCH)
> +		DMERR(" Userspace cluster log server not found");
> +
> +	if (r) {
> +		kfree(lc);
> +		kfree(ctr_str);
> +	} else {
> +		lc->ctr_str = ctr_str;
> +		lc->ctr_size = str_size;
> +		log->context = lc;
> +	}
> +
> +	return r;
> +}
> +
> +/*
> + * cluster_core_ctr
> + * @log
> + * @ti
> + * @argc
> + * @argv
> + *
> + * argv contains:
> + *   <region_size> <uuid> [[no]sync]
> + *
> + * Returns: 0 on success, -XXX on failure
> + */
> +static int cluster_core_ctr(struct dm_dirty_log *log, struct dm_target *ti,
> +			    unsigned int argc, char **argv)
> +{
> +	int i, r;
> +	if ((argc < 2) || (argc > 3)) {
> +		DMERR("Too %s arguments to clustered-core mirror log type.",
> +		      (argc < 2) ? "few" : "many");
> +		DMERR("  %d arguments supplied:", argc);
> +		for (i = 0; i < argc; i++)
> +			DMERR("    %s", argv[i]);
> +		return -EINVAL;
> +	}
> +
> +	r = cluster_ctr(log, ti, argc, argv, NULL);
> +
> +	return r;
> +}
> +
> +
> +/*
> + * cluster_core_ctr
> + * @log
> + * @ti
> + * @argc
> + * @argv
> + *
> + * argv contains:
> + *   <disk> <region_size> <uuid> [[no]sync]
> + *
> + * Returns: 0 on success, -XXX on failure
> + */
> +static int cluster_disk_ctr(struct dm_dirty_log *log, struct dm_target *ti,
> +			    unsigned int argc, char **argv)
> +{
> +	int r, i;
> +	struct dm_dev *dev;
> +
> +	if ((argc < 3) || (argc > 4)) {
> +		DMERR("Too %s arguments to clustered-disk mirror log type.",
> +		      (argc < 3) ? "few" : "many");
> +		DMERR("  %d arguments supplied:", argc);
> +		for (i = 0; i < argc; i++)
> +			DMERR("    %s", argv[i]);
> +		return -EINVAL;
> +	}
> +
> +	r = dm_get_device(ti, argv[0], 0, 0, FMODE_READ | FMODE_WRITE, &dev);
> +	if (r)
> +		return r;
> +
> +	r = cluster_ctr(log, ti, argc, argv, dev);
> +	if (r)
> +		dm_put_device(ti, dev);
> +
> +	return r;
> +}
> +
> +/*
> + * cluster_dtr
> + * @log
> + */
> +static void cluster_dtr(struct dm_dirty_log *log)
> +{
> +	int r;
> +	struct log_c *lc = (struct log_c *)log->context;
> +
> +	r = dm_clog_consult_server(lc->uuid, DM_CLOG_DTR,
> +				   NULL, 0,
> +				   NULL, NULL);
> +
> +	if (lc->disk_log)
> +		dm_put_device(lc->ti, lc->disk_log);
> +	kfree(lc->ctr_str);
> +	kfree(lc);
> +
> +	return;
> +}
> +
> +/*
> + * cluster_presuspend
> + * @log
> + */
> +static int cluster_presuspend(struct dm_dirty_log *log)
> +{
> +	int r;
> +	struct log_c *lc = (struct log_c *)log->context;
> +
> +	r = dm_clog_consult_server(lc->uuid, DM_CLOG_PRESUSPEND,
> +				   NULL, 0,
> +				   NULL, NULL);
> +
> +	return r;
> +}
> +
> +/*
> + * cluster_postsuspend
> + * @log
> + */
> +static int cluster_postsuspend(struct dm_dirty_log *log)
> +{
> +	int r;
> +	struct log_c *lc = (struct log_c *)log->context;
> +
> +	r = dm_clog_consult_server(lc->uuid, DM_CLOG_POSTSUSPEND,
> +				   NULL, 0,
> +				   NULL, NULL);
> +
> +	return r;
> +}
> +
> +/*
> + * cluster_resume
> + * @log
> + */
> +static int cluster_resume(struct dm_dirty_log *log)
> +{
> +	int r;
> +	struct log_c *lc = (struct log_c *)log->context;
> +
> +	lc->in_sync_hint = 0;
> +	r = dm_clog_consult_server(lc->uuid, DM_CLOG_RESUME,
> +				   NULL, 0,
> +				   NULL, NULL);
> +
> +	return r;
> +}
> +
> +/*
> + * cluster_get_region_size
> + * @log
> + *
> + * Only called during mirror construction, ok to block.
> + *
> + * Returns: region size (doesn't fail)
> + */
> +static uint32_t cluster_get_region_size(struct dm_dirty_log *log)
> +{
> +	struct log_c *lc = (struct log_c *)log->context;
> +
> +	return lc->region_size;
> +}
> +
> +/*
> + * cluster_is_clean
> + * @log
> + * @region
> + *
> + * Check whether a region is clean.  If there is any sort of
> + * failure when consulting the server, we return not clean.
> + *
> + * Returns: 1 if clean, 0 otherwise
> + */
> +static int cluster_is_clean(struct dm_dirty_log *log, region_t region)
> +{
> +	int r;
> +	int is_clean;
> +	int rdata_size;
> +	struct log_c *lc = (struct log_c *)log->context;
> +
> +	rdata_size = sizeof(is_clean);
> +	r = cluster_do_request(lc, lc->uuid, DM_CLOG_IS_CLEAN,
> +			       (char *)&region, sizeof(region),
> +			       (char *)&is_clean, &rdata_size);
> +
> +	return (r) ? 0 : is_clean;
> +}
> +
> +/*
> + * cluster_in_sync
> + * @log
> + * @region
> + * @can_block: if set, return immediately
> + *
> + * Check if the region is in-sync.  If there is any sort
> + * of failure when consulting the server, we assume that
> + * the region is not in sync.
> + *
> + * Returns: 1 if in-sync, 0 if not-in-sync, -EWOULDBLOCK
> + */
> +static int cluster_in_sync(struct dm_dirty_log *log, region_t region, int can_block)
> +{
> +	int r;
> +	int in_sync;
> +	int rdata_size;
> +	struct log_c *lc = (struct log_c *)log->context;
> +
> +	/*
> +	 * We can never respond directly - even if in_sync_hint is
> +	 * set.  This is because another machine could see a device
> +	 * failure and mark the region out-of-sync.  If we don't go
> +	 * to userspace to ask, we might think the region is in-sync
> +	 * and allow a read to pick up data that is stale.  (This is
> +	 * very unlikely if a device actually fails; but it is very
> +	 * likely if a connection to one device from one machine fails.)
> +	 *
> +	 * There still might be a problem if the mirror caches the region
> +	 * state as in-sync... but then this call would not be made.  So,
> +	 * that is a mirror problem.
> +	 */
> +	if (!can_block)
> +		return -EWOULDBLOCK;
> +
> +	rdata_size = sizeof(in_sync);
> +	r = cluster_do_request(lc, lc->uuid, DM_CLOG_IN_SYNC,
> +			       (char *)&region, sizeof(region),
> +			       (char *)&in_sync, &rdata_size);
> +	return (r) ? 0 : in_sync;
> +}
> +
> +/*
> + * cluster_flush
> + * @log
> + *
> + * This function is ok to block.
> + * The flush happens in two stages.  First, it sends all
> + * clear/mark requests that are on the list.  Then it
> + * tells the server to commit them.  This gives the
> + * server a chance to optimise the commit to the cluster
> + * and/or disk, instead of doing it for every request.
> + *
> + * Additionally, we could implement another thread that
> + * sends the requests up to the server - reducing the
> + * load on flush.  Then the flush would have less in
> + * the list and be responsible for the finishing commit.
> + *
> + * Returns: 0 on success, < 0 on failure
> + */
> +static int cluster_flush(struct dm_dirty_log *log)
> +{
> +	int r = 0;
> +	unsigned long flags;
> +	struct log_c *lc = (struct log_c *)log->context;
> +	LIST_HEAD(flush_list);
> +	struct flush_entry *fe, *tmp_fe;
> +
> +	spin_lock_irqsave(&lc->flush_lock, flags);
> +	list_splice_init(&lc->flush_list, &flush_list);
> +	spin_unlock_irqrestore(&lc->flush_lock, flags);
> +
> +	if (list_empty(&flush_list))
> +		return 0;
> +
> +	/*
> +	 * FIXME: Count up requests, group request types,
> +	 * allocate memory to stick all requests in and
> +	 * send to server in one go.  Failing the allocation,
> +	 * do it one by one.
> +	 */
> +
> +	list_for_each_entry(fe, &flush_list, list) {
> +		r = cluster_do_request(lc, lc->uuid, fe->type,
> +				       (char *)&fe->region,
> +				       sizeof(fe->region),
> +				       NULL, NULL);
> +		if (r)
> +			goto fail;
> +	}
> +
> +	r = cluster_do_request(lc, lc->uuid, DM_CLOG_FLUSH,
> +			       NULL, 0, NULL, NULL);
> +
> +fail:
> +	/*
> +	 * We can safely remove these entries, even if failure.
> +	 * Calling code will receive an error and will know that
> +	 * the log facility has failed.
> +	 */
> +	list_for_each_entry_safe(fe, tmp_fe, &flush_list, list) {
> +		list_del(&fe->list);
> +		mempool_free(fe, flush_entry_pool);
> +	}
> +
> +	if (r)
> +		dm_table_event(lc->ti->table);
> +
> +	return r;
> +}
> +
> +/*
> + * cluster_mark_region
> + * @log
> + * @region
> + *
> + * This function should avoid blocking unless absolutely required.
> + * (Memory allocation is valid for blocking.)
> + */
> +static void cluster_mark_region(struct dm_dirty_log *log, region_t region)
> +{
> +	unsigned long flags;
> +	struct log_c *lc = (struct log_c *)log->context;
> +	struct flush_entry *fe;
> +
> +	/* Wait for an allocation, but _never_ fail */
> +	fe = mempool_alloc(flush_entry_pool, GFP_NOIO);
> +	BUG_ON(!fe);
> +
> +	spin_lock_irqsave(&lc->flush_lock, flags);
> +	fe->type = DM_CLOG_MARK_REGION;
> +	fe->region = region;
> +	list_add(&fe->list, &lc->flush_list);
> +	spin_unlock_irqrestore(&lc->flush_lock, flags);
> +
> +	return;
> +}
> +
> +/*
> + * cluster_clear_region
> + * @log
> + * @region
> + *
> + * This function must not block.
> + * So, the alloc can't block.  In the worst case, it is ok to
> + * fail.  It would simply mean we can't clear the region.
> + * Does nothing to current sync context, but does mean
> + * the region will be re-sync'ed on a reload of the mirror
> + * even though it is in-sync.
> + */
> +static void cluster_clear_region(struct dm_dirty_log *log, region_t region)
> +{
> +	unsigned long flags;
> +	struct log_c *lc = (struct log_c *)log->context;
> +	struct flush_entry *fe;
> +
> +	/*
> +	 * If we fail to allocate, we skip the clearing of
> +	 * the region.  This doesn't hurt us in any way, except
> +	 * to cause the region to be resync'ed when the
> +	 * device is activated next time.
> +	 */
> +	fe = mempool_alloc(flush_entry_pool, GFP_ATOMIC);
> +	if (!fe) {
> +		DMERR("Failed to allocate memory to clear region.");
> +		return;
> +	}
> +
> +	spin_lock_irqsave(&lc->flush_lock, flags);
> +	fe->type = DM_CLOG_CLEAR_REGION;
> +	fe->region = region;
> +	list_add(&fe->list, &lc->flush_list);
> +	spin_unlock_irqrestore(&lc->flush_lock, flags);
> +
> +	return;
> +}
> +
> +/*
> + * cluster_get_resync_work
> + * @log
> + * @region
> + *
> + * Get a region that needs recovery.  It is valid to return
> + * an error for this function.
> + *
> + * Returns: 1 if region filled, 0 if no work, <0 on error
> + */
> +static int cluster_get_resync_work(struct dm_dirty_log *log, region_t *region)
> +{
> +	int r;
> +	int rdata_size;
> +	struct log_c *lc = (struct log_c *)log->context;
> +	struct { int i; region_t r; } pkg;
> +
> +	if (lc->in_sync_hint >= lc->region_count)
> +		return 0;
> +
> +	rdata_size = sizeof(pkg);
> +	r = cluster_do_request(lc, lc->uuid, DM_CLOG_GET_RESYNC_WORK,
> +			       NULL, 0,
> +			       (char *)&pkg, &rdata_size);
> +
> +	*region = pkg.r;
> +	return (r) ? r : pkg.i;
> +}
> +
> +/*
> + * cluster_set_region_sync
> + * @log
> + * @region
> + * @in_sync
> + *
> + * Set the sync status of a given region.  This function
> + * must not fail.
> + */
> +static void cluster_set_region_sync(struct dm_dirty_log *log,
> +				    region_t region, int in_sync)
> +{
> +	int r;
> +	struct log_c *lc = (struct log_c *)log->context;
> +	struct { region_t r; int i; } pkg;
> +
> +	pkg.r = region;
> +	pkg.i = in_sync;
> +
> +	r = cluster_do_request(lc, lc->uuid, DM_CLOG_SET_REGION_SYNC,
> +			       (char *)&pkg, sizeof(pkg),
> +			       NULL, NULL);
> +
> +	/*
> +	 * It would be nice to be able to report failures.
> +	 * However, it is easy emough to detect and resolve.
> +	 */
> +	return;
> +}
> +
> +/*
> + * cluster_get_sync_count
> + * @log
> + *
> + * If there is any sort of failure when consulting the server,
> + * we assume that the sync count is zero.
> + *
> + * Returns: sync count on success, 0 on failure
> + */
> +static region_t cluster_get_sync_count(struct dm_dirty_log *log)
> +{
> +	int r;
> +	int rdata_size;
> +	region_t sync_count;
> +	struct log_c *lc = (struct log_c *)log->context;
> +
> +	rdata_size = sizeof(sync_count);
> +	r = cluster_do_request(lc, lc->uuid, DM_CLOG_GET_SYNC_COUNT,
> +			       NULL, 0,
> +			       (char *)&sync_count, &rdata_size);
> +
> +	if (r)
> +		return 0;
> +
> +	if (sync_count >= lc->region_count)
> +		lc->in_sync_hint = lc->region_count;
> +
> +	return sync_count;
> +}
> +
> +/*
> + * cluster_status
> + * @log
> + * @status_type
> + * @result
> + * @maxlen
> + *
> + * Returns: amount of space consumed
> + */
> +static int cluster_status(struct dm_dirty_log *log, status_type_t status_type,
> +			  char *result, unsigned int maxlen)
> +{
> +	int r = 0;
> +	unsigned int sz = maxlen;
> +	struct log_c *lc = (struct log_c *)log->context;
> +
> +	switch(status_type) {
> +	case STATUSTYPE_INFO:
> +		r = cluster_do_request(lc, lc->uuid, DM_CLOG_STATUS_INFO,
> +				       NULL, 0,
> +				       result, &sz);
> +		/*
> +		 * FIXME: If we fail to contact server, we should still
> +		 * populate this with parsible results
> +		 */
> +		break;
> +	case STATUSTYPE_TABLE:
> +		r = cluster_do_request(lc, lc->uuid, DM_CLOG_STATUS_TABLE,
> +				       NULL, 0,
> +				       result, &sz);
> +		break;
> +	}
> +	return (r) ? 0: sz;
> +}
> +
> +/*
> + * cluster_is_remote_recovering
> + * @log
> + * @region
> + *
> + * Returns: 1 if region recovering, 0 otherwise
> + */
> +static int cluster_is_remote_recovering(struct dm_dirty_log *log,
> +					region_t region)
> +{
> +	int r;
> +	struct log_c *lc = (struct log_c *)log->context;
> +	static unsigned long long limit = 0;
> +	struct { int is_recovering; uint64_t in_sync_hint; } pkg;
> +	int rdata_size = sizeof(pkg);
> +
> +	/*
> +	 * Once the mirror has been reported to be in-sync,
> +	 * it will never again ask for recovery work.  So,
> +	 * we can safely say there is not a remote machine
> +	 * recovering if the device is in-sync.  (in_sync_hint
> +	 * must be reset at resume time.)
> +	 */
> +	if (region < lc->in_sync_hint)
> +		return 0;
> +	else if (jiffies < limit)
> +		return 1;
> +
> +	limit = jiffies + (HZ / 4);
> +	r = cluster_do_request(lc, lc->uuid, DM_CLOG_IS_REMOTE_RECOVERING,
> +			       (char *)&region, sizeof(region),
> +			       (char *)&pkg, &rdata_size);
> +	if (r)
> +		return 1;
> +
> +	lc->in_sync_hint = pkg.in_sync_hint;
> +
> +	return pkg.is_recovering;
> +}
> +
> +static struct dm_dirty_log_type _clustered_core_type = {
> +	.name = "clustered-core",
> +	.module = THIS_MODULE,
> +	.ctr = cluster_core_ctr,
> +	.dtr = cluster_dtr,
> +	.presuspend = cluster_presuspend,
> +	.postsuspend = cluster_postsuspend,
> +	.resume = cluster_resume,
> +	.get_region_size = cluster_get_region_size,
> +	.is_clean = cluster_is_clean,
> +	.in_sync = cluster_in_sync,
> +	.flush = cluster_flush,
> +	.mark_region = cluster_mark_region,
> +	.clear_region = cluster_clear_region,
> +	.get_resync_work = cluster_get_resync_work,
> +	.set_region_sync = cluster_set_region_sync,
> +	.get_sync_count = cluster_get_sync_count,
> +	.status = cluster_status,
> +	.is_remote_recovering = cluster_is_remote_recovering,
> +};
> +
> +static struct dm_dirty_log_type _clustered_disk_type = {
> +	.name = "clustered-disk",
> +	.module = THIS_MODULE,
> +	.ctr = cluster_disk_ctr,
> +	.dtr = cluster_dtr,
> +	.presuspend = cluster_presuspend,
> +	.postsuspend = cluster_postsuspend,
> +	.resume = cluster_resume,
> +	.get_region_size = cluster_get_region_size,
> +	.is_clean = cluster_is_clean,
> +	.in_sync = cluster_in_sync,
> +	.flush = cluster_flush,
> +	.mark_region = cluster_mark_region,
> +	.clear_region = cluster_clear_region,
> +	.get_resync_work = cluster_get_resync_work,
> +	.set_region_sync = cluster_set_region_sync,
> +	.get_sync_count = cluster_get_sync_count,
> +	.status = cluster_status,
> +	.is_remote_recovering = cluster_is_remote_recovering,
> +};
> +
> +static int __init cluster_dirty_log_init(void)
> +{
> +	int r = 0;
> +
> +	flush_entry_pool = mempool_create(100, flush_entry_alloc,
> +					  flush_entry_free, NULL);
> +
> +	if (!flush_entry_pool) {
> +		DMWARN("Unable to create flush_entry_pool:  No memory.");
> +		return -ENOMEM;
> +	}
> +
> +	r = dm_clog_tfr_init();
> +	if (r) {
> +		DMWARN("Unable to initialize cluster log communications");
> +		mempool_destroy(flush_entry_pool);
> +		return r;
> +	}
> +
> +	r = dm_dirty_log_type_register(&_clustered_core_type);
> +	if (r) {
> +		DMWARN("Couldn't register clustered-core dirty log type");
> +		dm_clog_tfr_exit();
> +		mempool_destroy(flush_entry_pool);
> +		return r;
> +	}
> +
> +	r = dm_dirty_log_type_register(&_clustered_disk_type);
> +	if (r) {
> +		DMWARN("Couldn't register clustered-disk dirty log type");
> +		dm_dirty_log_type_unregister(&_clustered_core_type);
> +		dm_clog_tfr_exit();
> +		mempool_destroy(flush_entry_pool);
> +		return r;
> +	}
> +
> +	DMINFO("(built %s %s) installed", __DATE__, __TIME__);
> +	return 0;
> +}
> +
> +static void __exit cluster_dirty_log_exit(void)
> +{
> +	dm_dirty_log_type_unregister(&_clustered_disk_type);
> +	dm_dirty_log_type_unregister(&_clustered_core_type);
> +	dm_clog_tfr_exit();
> +	mempool_destroy(flush_entry_pool);
> +	DMINFO("(built %s %s) removed", __DATE__, __TIME__);
> +	return;
> +}
> +
> +module_init(cluster_dirty_log_init);
> +module_exit(cluster_dirty_log_exit);
> +
> +MODULE_DESCRIPTION(DM_NAME " cluster-aware dirty log");
> +MODULE_AUTHOR("Jonathan Brassow <dm-devel redhat com>");
> +MODULE_LICENSE("GPL");
> Index: linux-2.6/drivers/md/Kconfig
> ===================================================================
> --- linux-2.6.orig/drivers/md/Kconfig
> +++ linux-2.6/drivers/md/Kconfig
> @@ -256,6 +256,15 @@ config DM_MIRROR
>           Allow volume managers to mirror logical volumes, also
>           needed for live data migration tools such as 'pvmove'.
>  
> +config DM_CLOG
> +       tristate "Mirror cluster logging (EXPERIMENTAL)"
> +       depends on DM_MIRROR && EXPERIMENTAL
> +       ---help---
> +         Cluster logging allows device-mapper mirroring to be
> +         cluster-aware.  Mirror devices can be used by multiple
> +         machines at the same time.  Note: this will not make
> +         your applications cluster-aware.
> +
>  config DM_ZERO
>  	tristate "Zero target"
>  	depends on BLK_DEV_DM
> Index: linux-2.6/drivers/md/Makefile
> ===================================================================
> --- linux-2.6.orig/drivers/md/Makefile
> +++ linux-2.6/drivers/md/Makefile
> @@ -7,6 +7,7 @@ dm-mod-objs	:= dm.o dm-table.o dm-target
>  dm-multipath-objs := dm-path-selector.o dm-mpath.o
>  dm-snapshot-objs := dm-snap.o dm-exception-store.o
>  dm-mirror-objs	:= dm-raid1.o
> +dm-log-clustered-objs  := dm-clog.o dm-clog-tfr.o
>  md-mod-objs     := md.o bitmap.o
>  raid456-objs	:= raid5.o raid6algos.o raid6recov.o raid6tables.o \
>  		   raid6int1.o raid6int2.o raid6int4.o \
> @@ -35,6 +36,7 @@ obj-$(CONFIG_DM_DELAY)		+= dm-delay.o
>  obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipath.o dm-round-robin.o
>  obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
>  obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o dm-log.o dm-region-hash.o
> +obj-$(CONFIG_DM_CLOG)		+= dm-log-clustered.o
>  obj-$(CONFIG_DM_ZERO)		+= dm-zero.o
>  
>  quiet_cmd_unroll = UNROLL  $@
> Index: linux-2.6/include/linux/dm-cluster-log.h
> ===================================================================
> --- /dev/null
> +++ linux-2.6/include/linux/dm-cluster-log.h
> @@ -0,0 +1,66 @@
> +/*
> + * Copyright (C) 2006-2008 Red Hat, Inc.
> + *
> + * This file is released under the LGPL.
> + */
> +
> +#ifndef __DM_CLUSTER_LOG_H__
> +#define __DM_CLUSTER_LOG_H__
> +
> +#include <linux/dm-ioctl.h> /* For DM_UUID_LEN */
> +
> +#define DM_CLOG_TFR_SIZE 1024
> +
> +#define DM_CLOG_CTR                    1
> +#define DM_CLOG_DTR                    2
> +#define DM_CLOG_PRESUSPEND             3
> +#define DM_CLOG_POSTSUSPEND            4
> +#define DM_CLOG_RESUME                 5
> +#define DM_CLOG_GET_REGION_SIZE        6
> +#define DM_CLOG_IS_CLEAN               7
> +#define DM_CLOG_IN_SYNC                8
> +#define DM_CLOG_FLUSH                  9
> +#define DM_CLOG_MARK_REGION           10
> +#define DM_CLOG_CLEAR_REGION          11
> +#define DM_CLOG_GET_RESYNC_WORK       12
> +#define DM_CLOG_SET_REGION_SYNC       13
> +#define DM_CLOG_GET_SYNC_COUNT        14
> +#define DM_CLOG_STATUS_INFO           15
> +#define DM_CLOG_STATUS_TABLE          16
> +#define DM_CLOG_IS_REMOTE_RECOVERING  17
> +
> +#define RQ_TYPE(x) \
> +	((x) == DM_CLOG_CTR) ? "DM_CLOG_CTR" : \
> +	((x) == DM_CLOG_DTR) ? "DM_CLOG_DTR" : \
> +	((x) == DM_CLOG_PRESUSPEND) ? "DM_CLOG_PRESUSPEND" : \
> +	((x) == DM_CLOG_POSTSUSPEND) ? "DM_CLOG_POSTSUSPEND" : \
> +	((x) == DM_CLOG_RESUME) ? "DM_CLOG_RESUME" : \
> +	((x) == DM_CLOG_GET_REGION_SIZE) ? "DM_CLOG_GET_REGION_SIZE" : \
> +	((x) == DM_CLOG_IS_CLEAN) ? "DM_CLOG_IS_CLEAN" : \
> +	((x) == DM_CLOG_IN_SYNC) ? "DM_CLOG_IN_SYNC" : \
> +	((x) == DM_CLOG_FLUSH) ? "DM_CLOG_FLUSH" : \
> +	((x) == DM_CLOG_MARK_REGION) ? "DM_CLOG_MARK_REGION" : \
> +	((x) == DM_CLOG_CLEAR_REGION) ? "DM_CLOG_CLEAR_REGION" : \
> +	((x) == DM_CLOG_GET_RESYNC_WORK) ? "DM_CLOG_GET_RESYNC_WORK" : \
> +	((x) == DM_CLOG_SET_REGION_SYNC) ? "DM_CLOG_SET_REGION_SYNC" : \
> +	((x) == DM_CLOG_GET_SYNC_COUNT) ? "DM_CLOG_GET_SYNC_COUNT" : \
> +	((x) == DM_CLOG_STATUS_INFO) ? "DM_CLOG_STATUS_INFO" : \
> +	((x) == DM_CLOG_STATUS_TABLE) ? "DM_CLOG_STATUS_TABLE" : \
> +	((x) == DM_CLOG_IS_REMOTE_RECOVERING) ? \
> +	"DM_CLOG_IS_REMOTE_RECOVERING" : NULL
> +
> +struct clog_tfr {
> +	uint64_t private[2];
> +	char uuid[DM_UUID_LEN]; /* Ties a request to a specific mirror log */
> +
> +	int error;              /* Used by server to inform of errors */
> +	uint32_t originator;    /* Cluster ID of this machine */
> +
> +	uint32_t seq;           /* Sequence number for request */
> +	uint32_t request_type;  /* DM_CLOG_* */
> +	uint32_t data_size;     /* How much data (not including this struct) */
> +
> +	char data[0];
> +};
> +
> +#endif /* __DM_CLUSTER_LOG_H__ */
> 
> 
> 
> --
> dm-devel mailing list
> dm-devel redhat com
> https://www.redhat.com/mailman/listinfo/dm-devel
> 

-- 
-------------------------------------
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