/*
 * Copyright (C) 2006-2009 Red Hat, Inc.
 *
 * This file is released under the LGPL.
 */

#include <linux/bio.h>
#include <linux/slab.h>
#include <linux/dm-dirty-log.h>
#include <linux/device-mapper.h>
#include <linux/dm-log-userspace.h>
#include <linux/module.h>

#include "dm-log-userspace-transfer.h"

#define DM_LOG_USERSPACE_VSN "1.1.0"

struct flush_entry {
        int type;
        region_t region;
        struct list_head list;
};

/*
 * This limit on the number of mark and clear request is, to a degree,
 * arbitrary.  However, there is some basis for the choice in the limits
 * imposed on the size of data payload by dm-log-userspace-transfer.c:
 * dm_consult_userspace().
 */
#define MAX_FLUSH_GROUP_COUNT 32

struct log_c {
        struct dm_target *ti;
        struct dm_dev *log_dev;
        uint32_t region_size;
        region_t region_count;
        uint64_t luid;
        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;

        /*
         * Mark and clear requests are held until a flush is issued
         * so that we can group, and thereby limit, the amount of
         * network traffic between kernel and userspace.  The 'flush_lock'
         * is used to protect these lists.
         */
        spinlock_t flush_lock;
        struct list_head mark_list;
        struct list_head clear_list;
};

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, lc->luid, 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, lc->luid, 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, lc->luid, 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;
        }

        str_size = sprintf(str, "%llu", (unsigned long long)ti->len);
        for (i = 0; i < argc; i++)
                str_size += sprintf(str + str_size, " %s", argv[i]);

        *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);
        char *devices_rdata = NULL;
        size_t devices_rdata_size = DM_NAME_LEN;

        if (argc < 3) {
                DMWARN("Too few arguments to userspace dirty log");
                return -EINVAL;
        }

        lc = kzalloc(sizeof(*lc), GFP_KERNEL);
        if (!lc) {
                DMWARN("Unable to allocate userspace log context.");
                return -ENOMEM;
        }

        /* The ptr value is sufficient for local unique id */
        lc->luid = (unsigned long)lc;

        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->mark_list);
        INIT_LIST_HEAD(&lc->clear_list);

        str_size = build_constructor_string(ti, argc - 1, argv + 1, &ctr_str);
        if (str_size < 0) {
                kfree(lc);
                return str_size;
        }

        devices_rdata = kzalloc(devices_rdata_size, GFP_KERNEL);
        if (!devices_rdata) {
                DMERR("Failed to allocate memory for device information");
                r = -ENOMEM;
                goto out;
        }

        /*
         * Send table string and get back any opened device.
         */
        r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_CTR,
                                 ctr_str, str_size,
                                 devices_rdata, &devices_rdata_size);

        if (r < 0) {
                if (r == -ESRCH)
                        DMERR("Userspace log server not found");
                else
                        DMERR("Userspace log server failed to create log");
                goto out;
        }

        /* Since the region size does not change, get it now */
        rdata_size = sizeof(rdata);
        r = dm_consult_userspace(lc->uuid, lc->luid, 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);

        if (devices_rdata_size) {
                if (devices_rdata[devices_rdata_size - 1] != '\0') {
                        DMERR("DM_ULOG_CTR device return string not properly terminated");
                        r = -EINVAL;
                        goto out;
                }
                r = dm_get_device(ti, devices_rdata,
                                  dm_table_get_mode(ti->table), &lc->log_dev);
                if (r)
                        DMERR("Failed to register %s with device-mapper",
                              devices_rdata);
        }
out:
        kfree(devices_rdata);
        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)
{
        struct log_c *lc = log->context;

        (void) dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_DTR,
                                 NULL, 0,
                                 NULL, NULL);

        if (lc->log_dev)
                dm_put_device(lc->ti, lc->log_dev);

        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, lc->luid, 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, lc->luid, 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, lc->luid, 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;
}

static int flush_one_by_one(struct log_c *lc, struct list_head *flush_list)
{
        int r = 0;
        struct flush_entry *fe;

        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)
                        break;
        }

        return r;
}

static int flush_by_group(struct log_c *lc, struct list_head *flush_list)
{
        int r = 0;
        int count;
        uint32_t type = 0;
        struct flush_entry *fe, *tmp_fe;
        LIST_HEAD(tmp_list);
        uint64_t group[MAX_FLUSH_GROUP_COUNT];

        /*
         * Group process the requests
         */
        while (!list_empty(flush_list)) {
                count = 0;

                list_for_each_entry_safe(fe, tmp_fe, flush_list, list) {
                        group[count] = fe->region;
                        count++;

                        list_move(&fe->list, &tmp_list);

                        type = fe->type;
                        if (count >= MAX_FLUSH_GROUP_COUNT)
                                break;
                }

                r = userspace_do_request(lc, lc->uuid, type,
                                         (char *)(group),
                                         count * sizeof(uint64_t),
                                         NULL, NULL);
                if (r) {
                        /* Group send failed.  Attempt one-by-one. */
                        list_splice_init(&tmp_list, flush_list);
                        r = flush_one_by_one(lc, flush_list);
                        break;
                }
        }

        /*
         * Must collect flush_entrys that were successfully processed
         * as a group so that they will be free'd by the caller.
         */
        list_splice_init(&tmp_list, flush_list);

        return r;
}

/*
 * 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(mark_list);
        LIST_HEAD(clear_list);
        struct flush_entry *fe, *tmp_fe;

        spin_lock_irqsave(&lc->flush_lock, flags);
        list_splice_init(&lc->mark_list, &mark_list);
        list_splice_init(&lc->clear_list, &clear_list);
        spin_unlock_irqrestore(&lc->flush_lock, flags);

        if (list_empty(&mark_list) && list_empty(&clear_list))
                return 0;

        r = flush_by_group(lc, &mark_list);
        if (r)
                goto fail;

        r = flush_by_group(lc, &clear_list);
        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, &mark_list, list) {
                list_del(&fe->list);
                mempool_free(fe, flush_entry_pool);
        }
        list_for_each_entry_safe(fe, tmp_fe, &clear_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->mark_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->clear_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;
        char *table_args;
        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;
                table_args = strchr(lc->usr_argv_str, ' ');
                BUG_ON(!table_args); /* There will always be a ' ' */
                table_args++;

                DMEMIT("%s %u %s %s ", log->type->name, lc->usr_argc,
                       lc->uuid, table_args);
                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 " DM_LOG_USERSPACE_VSN " 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 " DM_LOG_USERSPACE_VSN " 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");