5 files changed, 1004 insertions, 0 deletions

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 09f93fa68912..020f9573fd82 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -231,6 +231,17 @@ config DM_MIRROR
          Allow volume managers to mirror logical volumes, also
          needed for live data migration tools such as 'pvmove'.
 
+config DM_LOG_USERSPACE
+        tristate "Mirror userspace logging (EXPERIMENTAL)"
+        depends on DM_MIRROR && EXPERIMENTAL && NET
+        select CONNECTOR
+        ---help---
+          The userspace logging module provides a mechanism for
+          relaying the dm-dirty-log API to userspace.  Log designs
+          which are more suited to userspace implementation (e.g.
+          shared storage logs) or experimental logs can be implemented
+          by leveraging this framework.
+
 config DM_ZERO
         tristate "Zero target"
         depends on BLK_DEV_DM
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index dade52f60733..1dc4185bd781 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -8,6 +8,8 @@ dm-multipath-y	+= dm-path-selector.o dm-mpath.o
 dm-snapshot-y   += dm-snap.o dm-exception-store.o dm-snap-transient.o \
                     dm-snap-persistent.o
 dm-mirror-y     += dm-raid1.o
+dm-log-userspace-y \
+                += dm-log-userspace-base.o dm-log-userspace-transfer.o
 md-mod-y        += md.o bitmap.o
 raid456-y       += raid5.o
 raid6_pq-y      += raid6algos.o raid6recov.o raid6tables.o \
@@ -40,6 +42,7 @@ obj-$(CONFIG_DM_MULTIPATH_QL)	+= dm-queue-length.o
 obj-$(CONFIG_DM_MULTIPATH_ST)   += dm-service-time.o
 obj-$(CONFIG_DM_SNAPSHOT)       += dm-snapshot.o
 obj-$(CONFIG_DM_MIRROR)         += dm-mirror.o dm-log.o dm-region-hash.o
+obj-$(CONFIG_DM_LOG_USERSPACE)  += dm-log-userspace.o
 obj-$(CONFIG_DM_ZERO)           += dm-zero.o
 
 quiet_cmd_unroll = UNROLL  $@
diff --git a/drivers/md/dm-log-userspace-base.c b/drivers/md/dm-log-userspace-base.c
new file mode 100644
index 000000000000..e69b96560997
--- /dev/null
+++ b/drivers/md/dm-log-userspace-base.c
@@ -0,0 +1,696 @@
+/*
+ * Copyright (C) 2006-2009 Red Hat, Inc.
+ *
+ * This file is released under the LGPL.
+ */
+
+#include <linux/bio.h>
+#include <linux/dm-dirty-log.h>
+#include <linux/device-mapper.h>
+#include <linux/dm-log-userspace.h>
+
+#include "dm-log-userspace-transfer.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 *usr_argv_str;
+        uint32_t usr_argc;
+
+        /*
+         * 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 */
+};
+
+static mempool_t *flush_entry_pool;
+
+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);
+}
+
+static int userspace_do_request(struct log_c *lc, const char *uuid,
+                                int request_type, char *data, size_t data_size,
+                                char *rdata, size_t *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_consult_userspace(uuid, request_type, data,
+                                 data_size, rdata, rdata_size);
+
+        if (r != -ESRCH)
+                return r;
+
+        DMERR(" Userspace log server not found.");
+        while (1) {
+                set_current_state(TASK_INTERRUPTIBLE);
+                schedule_timeout(2*HZ);
+                DMWARN("Attempting to contact userspace log server...");
+                r = dm_consult_userspace(uuid, DM_ULOG_CTR, lc->usr_argv_str,
+                                         strlen(lc->usr_argv_str) + 1,
+                                         NULL, NULL);
+                if (!r)
+                        break;
+        }
+        DMINFO("Reconnected to userspace log server... DM_ULOG_CTR complete");
+        r = dm_consult_userspace(uuid, DM_ULOG_RESUME, NULL,
+                                 0, NULL, NULL);
+        if (!r)
+                goto retry;
+
+        DMERR("Error trying to resume userspace log: %d", r);
+
+        return -ESRCH;
+}
+
+static int build_constructor_string(struct dm_target *ti,
+                                    unsigned argc, char **argv,
+                                    char **ctr_str)
+{
+        int i, str_size;
+        char *str = NULL;
+
+        *ctr_str = NULL;
+
+        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 */
+
+        str = kzalloc(str_size, GFP_KERNEL);
+        if (!str) {
+                DMWARN("Unable to allocate memory for constructor string");
+                return -ENOMEM;
+        }
+
+        for (i = 0, str_size = 0; i < argc; i++)
+                str_size += sprintf(str + str_size, "%s ", argv[i]);
+        str_size += sprintf(str + str_size, "%llu",
+                            (unsigned long long)ti->len);
+
+        *ctr_str = str;
+        return str_size;
+}
+
+/*
+ * userspace_ctr
+ *
+ * argv contains:
+ *      <UUID> <other args>
+ * Where 'other args' is the userspace implementation specific log
+ * arguments.  An example might be:
+ *      <UUID> clustered_disk <arg count> <log dev> <region_size> [[no]sync]
+ *
+ * So, this module will strip off the <UUID> for identification purposes
+ * when communicating with userspace about a log; but will pass on everything
+ * else.
+ */
+static int userspace_ctr(struct dm_dirty_log *log, struct dm_target *ti,
+                         unsigned argc, char **argv)
+{
+        int r = 0;
+        int str_size;
+        char *ctr_str = NULL;
+        struct log_c *lc = NULL;
+        uint64_t rdata;
+        size_t rdata_size = sizeof(rdata);
+
+        if (argc < 3) {
+                DMWARN("Too few arguments to userspace dirty log");
+                return -EINVAL;
+        }
+
+        lc = kmalloc(sizeof(*lc), GFP_KERNEL);
+        if (!lc) {
+                DMWARN("Unable to allocate userspace log context.");
+                return -ENOMEM;
+        }
+
+        lc->ti = ti;
+
+        if (strlen(argv[0]) > (DM_UUID_LEN - 1)) {
+                DMWARN("UUID argument too long.");
+                kfree(lc);
+                return -EINVAL;
+        }
+
+        strncpy(lc->uuid, argv[0], DM_UUID_LEN);
+        spin_lock_init(&lc->flush_lock);
+        INIT_LIST_HEAD(&lc->flush_list);
+
+        str_size = build_constructor_string(ti, argc - 1, argv + 1, &ctr_str);
+        if (str_size < 0) {
+                kfree(lc);
+                return str_size;
+        }
+
+        /* Send table string */
+        r = dm_consult_userspace(lc->uuid, DM_ULOG_CTR,
+                                 ctr_str, str_size, NULL, NULL);
+
+        if (r == -ESRCH) {
+                DMERR("Userspace log server not found");
+                goto out;
+        }
+
+        /* Since the region size does not change, get it now */
+        rdata_size = sizeof(rdata);
+        r = dm_consult_userspace(lc->uuid, DM_ULOG_GET_REGION_SIZE,
+                                 NULL, 0, (char *)&rdata, &rdata_size);
+
+        if (r) {
+                DMERR("Failed to get region size of dirty log");
+                goto out;
+        }
+
+        lc->region_size = (uint32_t)rdata;
+        lc->region_count = dm_sector_div_up(ti->len, lc->region_size);
+
+out:
+        if (r) {
+                kfree(lc);
+                kfree(ctr_str);
+        } else {
+                lc->usr_argv_str = ctr_str;
+                lc->usr_argc = argc;
+                log->context = lc;
+        }
+
+        return r;
+}
+
+static void userspace_dtr(struct dm_dirty_log *log)
+{
+        int r;
+        struct log_c *lc = log->context;
+
+        r = dm_consult_userspace(lc->uuid, DM_ULOG_DTR,
+                                 NULL, 0,
+                                 NULL, NULL);
+
+        kfree(lc->usr_argv_str);
+        kfree(lc);
+
+        return;
+}
+
+static int userspace_presuspend(struct dm_dirty_log *log)
+{
+        int r;
+        struct log_c *lc = log->context;
+
+        r = dm_consult_userspace(lc->uuid, DM_ULOG_PRESUSPEND,
+                                 NULL, 0,
+                                 NULL, NULL);
+
+        return r;
+}
+
+static int userspace_postsuspend(struct dm_dirty_log *log)
+{
+        int r;
+        struct log_c *lc = log->context;
+
+        r = dm_consult_userspace(lc->uuid, DM_ULOG_POSTSUSPEND,
+                                 NULL, 0,
+                                 NULL, NULL);
+
+        return r;
+}
+
+static int userspace_resume(struct dm_dirty_log *log)
+{
+        int r;
+        struct log_c *lc = log->context;
+
+        lc->in_sync_hint = 0;
+        r = dm_consult_userspace(lc->uuid, DM_ULOG_RESUME,
+                                 NULL, 0,
+                                 NULL, NULL);
+
+        return r;
+}
+
+static uint32_t userspace_get_region_size(struct dm_dirty_log *log)
+{
+        struct log_c *lc = log->context;
+
+        return lc->region_size;
+}
+
+/*
+ * userspace_is_clean
+ *
+ * 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 userspace_is_clean(struct dm_dirty_log *log, region_t region)
+{
+        int r;
+        uint64_t region64 = (uint64_t)region;
+        int64_t is_clean;
+        size_t rdata_size;
+        struct log_c *lc = log->context;
+
+        rdata_size = sizeof(is_clean);
+        r = userspace_do_request(lc, lc->uuid, DM_ULOG_IS_CLEAN,
+                                 (char *)&region64, sizeof(region64),
+                                 (char *)&is_clean, &rdata_size);
+
+        return (r) ? 0 : (int)is_clean;
+}
+
+/*
+ * userspace_in_sync
+ *
+ * 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.
+ *
+ * If 'can_block' is set, return immediately
+ *
+ * Returns: 1 if in-sync, 0 if not-in-sync, -EWOULDBLOCK
+ */
+static int userspace_in_sync(struct dm_dirty_log *log, region_t region,
+                             int can_block)
+{
+        int r;
+        uint64_t region64 = region;
+        int64_t in_sync;
+        size_t rdata_size;
+        struct log_c *lc = 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 = userspace_do_request(lc, lc->uuid, DM_ULOG_IN_SYNC,
+                                 (char *)&region64, sizeof(region64),
+                                 (char *)&in_sync, &rdata_size);
+        return (r) ? 0 : (int)in_sync;
+}
+
+/*
+ * userspace_flush
+ *
+ * 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, 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 userspace_flush(struct dm_dirty_log *log)
+{
+        int r = 0;
+        unsigned long flags;
+        struct log_c *lc = 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 = userspace_do_request(lc, lc->uuid, fe->type,
+                                         (char *)&fe->region,
+                                         sizeof(fe->region),
+                                         NULL, NULL);
+                if (r)
+                        goto fail;
+        }
+
+        r = userspace_do_request(lc, lc->uuid, DM_ULOG_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;
+}
+
+/*
+ * userspace_mark_region
+ *
+ * This function should avoid blocking unless absolutely required.
+ * (Memory allocation is valid for blocking.)
+ */
+static void userspace_mark_region(struct dm_dirty_log *log, region_t region)
+{
+        unsigned long flags;
+        struct log_c *lc = 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_ULOG_MARK_REGION;
+        fe->region = region;
+        list_add(&fe->list, &lc->flush_list);
+        spin_unlock_irqrestore(&lc->flush_lock, flags);
+
+        return;
+}
+
+/*
+ * userspace_clear_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 userspace_clear_region(struct dm_dirty_log *log, region_t region)
+{
+        unsigned long flags;
+        struct log_c *lc = 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_ULOG_CLEAR_REGION;
+        fe->region = region;
+        list_add(&fe->list, &lc->flush_list);
+        spin_unlock_irqrestore(&lc->flush_lock, flags);
+
+        return;
+}
+
+/*
+ * userspace_get_resync_work
+ *
+ * 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 userspace_get_resync_work(struct dm_dirty_log *log, region_t *region)
+{
+        int r;
+        size_t rdata_size;
+        struct log_c *lc = log->context;
+        struct {
+                int64_t i; /* 64-bit for mix arch compatibility */
+                region_t r;
+        } pkg;
+
+        if (lc->in_sync_hint >= lc->region_count)
+                return 0;
+
+        rdata_size = sizeof(pkg);
+        r = userspace_do_request(lc, lc->uuid, DM_ULOG_GET_RESYNC_WORK,
+                                 NULL, 0,
+                                 (char *)&pkg, &rdata_size);
+
+        *region = pkg.r;
+        return (r) ? r : (int)pkg.i;
+}
+
+/*
+ * userspace_set_region_sync
+ *
+ * Set the sync status of a given region.  This function
+ * must not fail.
+ */
+static void userspace_set_region_sync(struct dm_dirty_log *log,
+                                      region_t region, int in_sync)
+{
+        int r;
+        struct log_c *lc = log->context;
+        struct {
+                region_t r;
+                int64_t i;
+        } pkg;
+
+        pkg.r = region;
+        pkg.i = (int64_t)in_sync;
+
+        r = userspace_do_request(lc, lc->uuid, DM_ULOG_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;
+}
+
+/*
+ * userspace_get_sync_count
+ *
+ * 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 userspace_get_sync_count(struct dm_dirty_log *log)
+{
+        int r;
+        size_t rdata_size;
+        uint64_t sync_count;
+        struct log_c *lc = log->context;
+
+        rdata_size = sizeof(sync_count);
+        r = userspace_do_request(lc, lc->uuid, DM_ULOG_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 (region_t)sync_count;
+}
+
+/*
+ * userspace_status
+ *
+ * Returns: amount of space consumed
+ */
+static int userspace_status(struct dm_dirty_log *log, status_type_t status_type,
+                            char *result, unsigned maxlen)
+{
+        int r = 0;
+        size_t sz = (size_t)maxlen;
+        struct log_c *lc = log->context;
+
+        switch (status_type) {
+        case STATUSTYPE_INFO:
+                r = userspace_do_request(lc, lc->uuid, DM_ULOG_STATUS_INFO,
+                                         NULL, 0,
+                                         result, &sz);
+
+                if (r) {
+                        sz = 0;
+                        DMEMIT("%s 1 COM_FAILURE", log->type->name);
+                }
+                break;
+        case STATUSTYPE_TABLE:
+                sz = 0;
+                DMEMIT("%s %u %s %s", log->type->name, lc->usr_argc + 1,
+                       lc->uuid, lc->usr_argv_str);
+                break;
+        }
+        return (r) ? 0 : (int)sz;
+}
+
+/*
+ * userspace_is_remote_recovering
+ *
+ * Returns: 1 if region recovering, 0 otherwise
+ */
+static int userspace_is_remote_recovering(struct dm_dirty_log *log,
+                                          region_t region)
+{
+        int r;
+        uint64_t region64 = region;
+        struct log_c *lc = log->context;
+        static unsigned long long limit;
+        struct {
+                int64_t is_recovering;
+                uint64_t in_sync_hint;
+        } pkg;
+        size_t 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 = userspace_do_request(lc, lc->uuid, DM_ULOG_IS_REMOTE_RECOVERING,
+                                 (char *)&region64, sizeof(region64),
+                                 (char *)&pkg, &rdata_size);
+        if (r)
+                return 1;
+
+        lc->in_sync_hint = pkg.in_sync_hint;
+
+        return (int)pkg.is_recovering;
+}
+
+static struct dm_dirty_log_type _userspace_type = {
+        .name = "userspace",
+        .module = THIS_MODULE,
+        .ctr = userspace_ctr,
+        .dtr = userspace_dtr,
+        .presuspend = userspace_presuspend,
+        .postsuspend = userspace_postsuspend,
+        .resume = userspace_resume,
+        .get_region_size = userspace_get_region_size,
+        .is_clean = userspace_is_clean,
+        .in_sync = userspace_in_sync,
+        .flush = userspace_flush,
+        .mark_region = userspace_mark_region,
+        .clear_region = userspace_clear_region,
+        .get_resync_work = userspace_get_resync_work,
+        .set_region_sync = userspace_set_region_sync,
+        .get_sync_count = userspace_get_sync_count,
+        .status = userspace_status,
+        .is_remote_recovering = userspace_is_remote_recovering,
+};
+
+static int __init userspace_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_ulog_tfr_init();
+        if (r) {
+                DMWARN("Unable to initialize userspace log communications");
+                mempool_destroy(flush_entry_pool);
+                return r;
+        }
+
+        r = dm_dirty_log_type_register(&_userspace_type);
+        if (r) {
+                DMWARN("Couldn't register userspace dirty log type");
+                dm_ulog_tfr_exit();
+                mempool_destroy(flush_entry_pool);
+                return r;
+        }
+
+        DMINFO("version 1.0.0 loaded");
+        return 0;
+}
+
+static void __exit userspace_dirty_log_exit(void)
+{
+        dm_dirty_log_type_unregister(&_userspace_type);
+        dm_ulog_tfr_exit();
+        mempool_destroy(flush_entry_pool);
+
+        DMINFO("version 1.0.0 unloaded");
+        return;
+}
+
+module_init(userspace_dirty_log_init);
+module_exit(userspace_dirty_log_exit);
+
+MODULE_DESCRIPTION(DM_NAME " userspace dirty log link");
+MODULE_AUTHOR("Jonathan Brassow <dm-devel@redhat.com>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/md/dm-log-userspace-transfer.c b/drivers/md/dm-log-userspace-transfer.c
new file mode 100644
index 000000000000..0ca1ee768a1f
--- /dev/null
+++ b/drivers/md/dm-log-userspace-transfer.c
@@ -0,0 +1,276 @@
+/*
+ * Copyright (C) 2006-2009 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-log-userspace.h>
+
+#include "dm-log-userspace-transfer.h"
+
+static uint32_t dm_ulog_seq;
+
+/*
+ * Netlink/Connector is an unreliable protocol.  How long should
+ * we wait for a response before assuming it was lost and retrying?
+ * (If we do receive a response after this time, it will be discarded
+ * and the response to the resent request will be waited for.
+ */
+#define DM_ULOG_RETRY_TIMEOUT (15 * HZ)
+
+/*
+ * Pre-allocated space for speed
+ */
+#define DM_ULOG_PREALLOCED_SIZE 512
+static struct cn_msg *prealloced_cn_msg;
+static struct dm_ulog_request *prealloced_ulog_tfr;
+
+static struct cb_id ulog_cn_id = {
+        .idx = CN_IDX_DM,
+        .val = CN_VAL_DM_USERSPACE_LOG
+};
+
+static DEFINE_MUTEX(dm_ulog_lock);
+
+struct receiving_pkg {
+        struct list_head list;
+        struct completion complete;
+
+        uint32_t seq;
+
+        int error;
+        size_t *data_size;
+        char *data;
+};
+
+static DEFINE_SPINLOCK(receiving_list_lock);
+static struct list_head receiving_list;
+
+static int dm_ulog_sendto_server(struct dm_ulog_request *tfr)
+{
+        int r;
+        struct cn_msg *msg = prealloced_cn_msg;
+
+        memset(msg, 0, sizeof(struct cn_msg));
+
+        msg->id.idx = ulog_cn_id.idx;
+        msg->id.val = ulog_cn_id.val;
+        msg->ack = 0;
+        msg->seq = tfr->seq;
+        msg->len = sizeof(struct dm_ulog_request) + tfr->data_size;
+
+        r = cn_netlink_send(msg, 0, gfp_any());
+
+        return r;
+}
+
+/*
+ * Parameters for this function 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 dm_ulog_request *tfr)
+{
+        uint32_t rtn_seq = (msg) ? msg->seq : (tfr) ? tfr->seq : 0;
+        struct receiving_pkg *pkg;
+
+        /*
+         * The 'receiving_pkg' entries in this list are statically
+         * allocated on the stack in 'dm_consult_userspace'.
+         * Each process that is waiting for a reply from the user
+         * space server will have an entry in this list.
+         *
+         * We are safe to do it this way because the stack space
+         * is unique to each process, but still addressable by
+         * other processes.
+         */
+        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 [%u] "
+                              "(%u vs %lu)", tfr->request_type,
+                              tfr->data_size, *(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;
+}
+
+/*
+ * This is the connector callback that delivers data
+ * that was sent from userspace.
+ */
+static void cn_ulog_callback(void *data)
+{
+        struct cn_msg *msg = (struct cn_msg *)data;
+        struct dm_ulog_request *tfr = (struct dm_ulog_request *)(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 (expected %u, got %u): [%u]",
+                      (unsigned)sizeof(*tfr), msg->len, msg->seq);
+        else
+                fill_pkg(NULL, tfr);
+        spin_unlock(&receiving_list_lock);
+}
+
+/**
+ * dm_consult_userspace
+ * @uuid: log's uuid (must be DM_UUID_LEN in size)
+ * @request_type:  found in include/linux/dm-log-userspace.h
+ * @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)
+ *
+ * rdata_size is undefined on failure.
+ *
+ * Memory used to communicate with userspace is zero'ed
+ * before populating to ensure that no unwanted bits leak
+ * from kernel space to user-space.  All userspace log communications
+ * between kernel and user space go through this function.
+ *
+ * Returns: 0 on success, -EXXX on failure
+ **/
+int dm_consult_userspace(const char *uuid, int request_type,
+                         char *data, size_t data_size,
+                         char *rdata, size_t *rdata_size)
+{
+        int r = 0;
+        size_t dummy = 0;
+        int overhead_size =
+                sizeof(struct dm_ulog_request *) + sizeof(struct cn_msg);
+        struct dm_ulog_request *tfr = prealloced_ulog_tfr;
+        struct receiving_pkg pkg;
+
+        if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) {
+                DMINFO("Size of tfr exceeds preallocated size");
+                return -EINVAL;
+        }
+
+        if (!rdata_size)
+                rdata_size = &dummy;
+resend:
+        /*
+         * We serialize the sending of requests so we can
+         * use the preallocated space.
+         */
+        mutex_lock(&dm_ulog_lock);
+
+        memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - overhead_size);
+        memcpy(tfr->uuid, uuid, DM_UUID_LEN);
+        tfr->seq = dm_ulog_seq++;
+
+        /*
+         * Must be valid request type (all other bits set to
+         * zero).  This reserves other bits for possible future
+         * use.
+         */
+        tfr->request_type = request_type & DM_ULOG_REQUEST_MASK;
+
+        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_ulog_sendto_server(tfr);
+
+        mutex_unlock(&dm_ulog_lock);
+
+        if (r) {
+                DMERR("Unable to send log request [%u] to userspace: %d",
+                      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), DM_ULOG_RETRY_TIMEOUT);
+        spin_lock(&receiving_list_lock);
+        list_del_init(&(pkg.list));
+        spin_unlock(&receiving_list_lock);
+        if (!r) {
+                DMWARN("[%s] Request timed out: [%u/%u] - retrying",
+                       (strlen(uuid) > 8) ?
+                       (uuid + (strlen(uuid) - 8)) : (uuid),
+                       request_type, pkg.seq);
+                goto resend;
+        }
+
+        r = pkg.error;
+        if (r == -EAGAIN)
+                goto resend;
+
+out:
+        return r;
+}
+
+int dm_ulog_tfr_init(void)
+{
+        int r;
+        void *prealloced;
+
+        INIT_LIST_HEAD(&receiving_list);
+
+        prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL);
+        if (!prealloced)
+                return -ENOMEM;
+
+        prealloced_cn_msg = prealloced;
+        prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg);
+
+        r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback);
+        if (r) {
+                cn_del_callback(&ulog_cn_id);
+                return r;
+        }
+
+        return 0;
+}
+
+void dm_ulog_tfr_exit(void)
+{
+        cn_del_callback(&ulog_cn_id);
+        kfree(prealloced_cn_msg);
+}
diff --git a/drivers/md/dm-log-userspace-transfer.h b/drivers/md/dm-log-userspace-transfer.h
new file mode 100644
index 000000000000..c26d8e4e2710
--- /dev/null
+++ b/drivers/md/dm-log-userspace-transfer.h
@@ -0,0 +1,18 @@
+/*
+ * Copyright (C) 2006-2009 Red Hat, Inc.
+ *
+ * This file is released under the LGPL.
+ */
+
+#ifndef __DM_LOG_USERSPACE_TRANSFER_H__
+#define __DM_LOG_USERSPACE_TRANSFER_H__
+
+#define DM_MSG_PREFIX "dm-log-userspace"
+
+int dm_ulog_tfr_init(void);
+void dm_ulog_tfr_exit(void);
+int dm_consult_userspace(const char *uuid, int request_type,
+                         char *data, size_t data_size,
+                         char *rdata, size_t *rdata_size);
+
+#endif /* __DM_LOG_USERSPACE_TRANSFER_H__ */