/* Copyright (c) 2013 Coraid, Inc.  See COPYING for GPL terms. */
/*
 * aoedev.c
 * AoE device utility functions; maintains device list.
 */

#include <linux/hdreg.h>
#include <linux/blkdev.h>
#include <linux/netdevice.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/bitmap.h>
#include <linux/kdev_t.h>
#include <linux/moduleparam.h>
#include <linux/string.h>
#include "aoe.h"

static void freetgt(struct aoedev *d, struct aoetgt *t);
static void skbpoolfree(struct aoedev *d);

static int aoe_dyndevs = 1;
module_param(aoe_dyndevs, int, 0644);
MODULE_PARM_DESC(aoe_dyndevs, "Use dynamic minor numbers for devices.");

static struct aoedev *devlist;
static DEFINE_SPINLOCK(devlist_lock);

/* Because some systems will have one, many, or no
 *   - partitions,
 *   - slots per shelf,
 *   - or shelves,
 * we need some flexibility in the way the minor numbers
 * are allocated.  So they are dynamic.
 */
#define N_DEVS ((1U<<MINORBITS)/AOE_PARTITIONS)

static DEFINE_SPINLOCK(used_minors_lock);
static DECLARE_BITMAP(used_minors, N_DEVS);

static int
minor_get_dyn(ulong *sysminor)
{
        ulong flags;
        ulong n;
        int error = 0;

        spin_lock_irqsave(&used_minors_lock, flags);
        n = find_first_zero_bit(used_minors, N_DEVS);
        if (n < N_DEVS)
                set_bit(n, used_minors);
        else
                error = -1;
        spin_unlock_irqrestore(&used_minors_lock, flags);

        *sysminor = n * AOE_PARTITIONS;
        return error;
}

static int
minor_get_static(ulong *sysminor, ulong aoemaj, int aoemin)
{
        ulong flags;
        ulong n;
        int error = 0;
        enum {
                /* for backwards compatibility when !aoe_dyndevs,
                 * a static number of supported slots per shelf */
                NPERSHELF = 16,
        };

        if (aoemin >= NPERSHELF) {
                pr_err("aoe: %s %d slots per shelf\n",
                        "static minor device numbers support only",
                        NPERSHELF);
                error = -1;
                goto out;
        }

        n = aoemaj * NPERSHELF + aoemin;
        if (n >= N_DEVS) {
                pr_err("aoe: %s with e%ld.%d\n",
                        "cannot use static minor device numbers",
                        aoemaj, aoemin);
                error = -1;
                goto out;
        }

        spin_lock_irqsave(&used_minors_lock, flags);
        if (test_bit(n, used_minors)) {
                pr_err("aoe: %s %lu\n",
                        "existing device already has static minor number",
                        n);
                error = -1;
        } else
                set_bit(n, used_minors);
        spin_unlock_irqrestore(&used_minors_lock, flags);
        *sysminor = n * AOE_PARTITIONS;
out:
        return error;
}

static int
minor_get(ulong *sysminor, ulong aoemaj, int aoemin)
{
        if (aoe_dyndevs)
                return minor_get_dyn(sysminor);
        else
                return minor_get_static(sysminor, aoemaj, aoemin);
}

static void
minor_free(ulong minor)
{
        ulong flags;

        minor /= AOE_PARTITIONS;
        BUG_ON(minor >= N_DEVS);

        spin_lock_irqsave(&used_minors_lock, flags);
        BUG_ON(!test_bit(minor, used_minors));
        clear_bit(minor, used_minors);
        spin_unlock_irqrestore(&used_minors_lock, flags);
}

/*
 * Users who grab a pointer to the device with aoedev_by_aoeaddr
 * automatically get a reference count and must be responsible
 * for performing a aoedev_put.  With the addition of async
 * kthread processing I'm no longer confident that we can
 * guarantee consistency in the face of device flushes.
 *
 * For the time being, we only bother to add extra references for
 * frames sitting on the iocq.  When the kthreads finish processing
 * these frames, they will aoedev_put the device.
 */

void
aoedev_put(struct aoedev *d)
{
        ulong flags;

        spin_lock_irqsave(&devlist_lock, flags);
        d->ref--;
        spin_unlock_irqrestore(&devlist_lock, flags);
}

static void
dummy_timer(struct timer_list *t)
{
        struct aoedev *d;

        d = from_timer(d, t, timer);
        if (d->flags & DEVFL_TKILL)
                return;
        d->timer.expires = jiffies + HZ;
        add_timer(&d->timer);
}

static void
aoe_failip(struct aoedev *d)
{
        struct request *rq;
        struct bio *bio;
        unsigned long n;

        aoe_failbuf(d, d->ip.buf);

        rq = d->ip.rq;
        if (rq == NULL)
                return;
        while ((bio = d->ip.nxbio)) {
                bio->bi_status = BLK_STS_IOERR;
                d->ip.nxbio = bio->bi_next;
                n = (unsigned long) rq->special;
                rq->special = (void *) --n;
        }
        if ((unsigned long) rq->special == 0)
                aoe_end_request(d, rq, 0);
}

static void
downdev_frame(struct list_head *pos)
{
        struct frame *f;

        f = list_entry(pos, struct frame, head);
        list_del(pos);
        if (f->buf) {
                f->buf->nframesout--;
                aoe_failbuf(f->t->d, f->buf);
        }
        aoe_freetframe(f);
}

void
aoedev_downdev(struct aoedev *d)
{
        struct aoetgt *t, **tt, **te;
        struct list_head *head, *pos, *nx;
        struct request *rq;
        int i;

        d->flags &= ~DEVFL_UP;

        /* clean out active and to-be-retransmitted buffers */
        for (i = 0; i < NFACTIVE; i++) {
                head = &d->factive[i];
                list_for_each_safe(pos, nx, head)
                        downdev_frame(pos);
        }
        head = &d->rexmitq;
        list_for_each_safe(pos, nx, head)
                downdev_frame(pos);

        /* reset window dressings */
        tt = d->targets;
        te = tt + d->ntargets;
        for (; tt < te && (t = *tt); tt++) {
                aoecmd_wreset(t);
                t->nout = 0;
        }

        /* clean out the in-process request (if any) */
        aoe_failip(d);

        /* fast fail all pending I/O */
        if (d->blkq) {
                while ((rq = blk_peek_request(d->blkq))) {
                        blk_start_request(rq);
                        aoe_end_request(d, rq, 1);
                }
        }

        if (d->gd)
                set_capacity(d->gd, 0);
}

/* return whether the user asked for this particular
 * device to be flushed
 */
static int
user_req(char *s, size_t slen, struct aoedev *d)
{
        const char *p;
        size_t lim;

        if (!d->gd)
                return 0;
        p = kbasename(d->gd->disk_name);
        lim = sizeof(d->gd->disk_name);
        lim -= p - d->gd->disk_name;
        if (slen < lim)
                lim = slen;

        return !strncmp(s, p, lim);
}

static void
freedev(struct aoedev *d)
{
        struct aoetgt **t, **e;
        int freeing = 0;
        unsigned long flags;

        spin_lock_irqsave(&d->lock, flags);
        if (d->flags & DEVFL_TKILL
        && !(d->flags & DEVFL_FREEING)) {
                d->flags |= DEVFL_FREEING;
                freeing = 1;
        }
        spin_unlock_irqrestore(&d->lock, flags);
        if (!freeing)
                return;

        del_timer_sync(&d->timer);
        if (d->gd) {
                aoedisk_rm_debugfs(d);
                aoedisk_rm_sysfs(d);
                del_gendisk(d->gd);
                put_disk(d->gd);
                blk_cleanup_queue(d->blkq);
        }
        t = d->targets;
        e = t + d->ntargets;
        for (; t < e && *t; t++)
                freetgt(d, *t);
        if (d->bufpool)
                mempool_destroy(d->bufpool);
        skbpoolfree(d);
        minor_free(d->sysminor);

        spin_lock_irqsave(&d->lock, flags);
        d->flags |= DEVFL_FREED;
        spin_unlock_irqrestore(&d->lock, flags);
}

enum flush_parms {
        NOT_EXITING = 0,
        EXITING = 1,
};

static int
flush(const char __user *str, size_t cnt, int exiting)
{
        ulong flags;
        struct aoedev *d, **dd;
        char buf[16];
        int all = 0;
        int specified = 0;      /* flush a specific device */
        unsigned int skipflags;

        skipflags = DEVFL_GDALLOC | DEVFL_NEWSIZE | DEVFL_TKILL;

        if (!exiting && cnt >= 3) {
                if (cnt > sizeof buf)
                        cnt = sizeof buf;
                if (copy_from_user(buf, str, cnt))
                        return -EFAULT;
                all = !strncmp(buf, "all", 3);
                if (!all)
                        specified = 1;
        }

        flush_scheduled_work();
        /* pass one: without sleeping, do aoedev_downdev */
        spin_lock_irqsave(&devlist_lock, flags);
        for (d = devlist; d; d = d->next) {
                spin_lock(&d->lock);
                if (exiting) {
                        /* unconditionally take each device down */
                } else if (specified) {
                        if (!user_req(buf, cnt, d))
                                goto cont;
                } else if ((!all && (d->flags & DEVFL_UP))
                || d->flags & skipflags
                || d->nopen
                || d->ref)
                        goto cont;

                aoedev_downdev(d);
                d->flags |= DEVFL_TKILL;
cont:
                spin_unlock(&d->lock);
        }
        spin_unlock_irqrestore(&devlist_lock, flags);

        /* pass two: call freedev, which might sleep,
         * for aoedevs marked with DEVFL_TKILL
         */
restart:
        spin_lock_irqsave(&devlist_lock, flags);
        for (d = devlist; d; d = d->next) {
                spin_lock(&d->lock);
                if (d->flags & DEVFL_TKILL
                && !(d->flags & DEVFL_FREEING)) {
                        spin_unlock(&d->lock);
                        spin_unlock_irqrestore(&devlist_lock, flags);
                        freedev(d);
                        goto restart;
                }
                spin_unlock(&d->lock);
        }

        /* pass three: remove aoedevs marked with DEVFL_FREED */
        for (dd = &devlist, d = *dd; d; d = *dd) {
                struct aoedev *doomed = NULL;

                spin_lock(&d->lock);
                if (d->flags & DEVFL_FREED) {
                        *dd = d->next;
                        doomed = d;
                } else {
                        dd = &d->next;
                }
                spin_unlock(&d->lock);
                if (doomed)
                        kfree(doomed->targets);
                kfree(doomed);
        }
        spin_unlock_irqrestore(&devlist_lock, flags);

        return 0;
}

int
aoedev_flush(const char __user *str, size_t cnt)
{
        return flush(str, cnt, NOT_EXITING);
}

/* This has been confirmed to occur once with Tms=3*1000 due to the
 * driver changing link and not processing its transmit ring.  The
 * problem is hard enough to solve by returning an error that I'm
 * still punting on "solving" this.
 */
static void
skbfree(struct sk_buff *skb)
{
        enum { Sms = 250, Tms = 30 * 1000};
        int i = Tms / Sms;

        if (skb == NULL)
                return;
        while (atomic_read(&skb_shinfo(skb)->dataref) != 1 && i-- > 0)
                msleep(Sms);
        if (i < 0) {
                printk(KERN_ERR
                        "aoe: %s holds ref: %s\n",
                        skb->dev ? skb->dev->name : "netif",
                        "cannot free skb -- memory leaked.");
                return;
        }
        skb->truesize -= skb->data_len;
        skb_shinfo(skb)->nr_frags = skb->data_len = 0;
        skb_trim(skb, 0);
        dev_kfree_skb(skb);
}

static void
skbpoolfree(struct aoedev *d)
{
        struct sk_buff *skb, *tmp;

        skb_queue_walk_safe(&d->skbpool, skb, tmp)
                skbfree(skb);

        __skb_queue_head_init(&d->skbpool);
}

/* find it or allocate it */
struct aoedev *
aoedev_by_aoeaddr(ulong maj, int min, int do_alloc)
{
        struct aoedev *d;
        int i;
        ulong flags;
        ulong sysminor = 0;

        spin_lock_irqsave(&devlist_lock, flags);

        for (d=devlist; d; d=d->next)
                if (d->aoemajor == maj && d->aoeminor == min) {
                        spin_lock(&d->lock);
                        if (d->flags & DEVFL_TKILL) {
                                spin_unlock(&d->lock);
                                d = NULL;
                                goto out;
                        }
                        d->ref++;
                        spin_unlock(&d->lock);
                        break;
                }
        if (d || !do_alloc || minor_get(&sysminor, maj, min) < 0)
                goto out;
        d = kcalloc(1, sizeof *d, GFP_ATOMIC);
        if (!d)
                goto out;
        d->targets = kcalloc(NTARGETS, sizeof(*d->targets), GFP_ATOMIC);
        if (!d->targets) {
                kfree(d);
                d = NULL;
                goto out;
        }
        d->ntargets = NTARGETS;
        INIT_WORK(&d->work, aoecmd_sleepwork);
        spin_lock_init(&d->lock);
        skb_queue_head_init(&d->skbpool);
        timer_setup(&d->timer, dummy_timer, 0);
        d->timer.expires = jiffies + HZ;
        add_timer(&d->timer);
        d->bufpool = NULL;      /* defer to aoeblk_gdalloc */
        d->tgt = d->targets;
        d->ref = 1;
        for (i = 0; i < NFACTIVE; i++)
                INIT_LIST_HEAD(&d->factive[i]);
        INIT_LIST_HEAD(&d->rexmitq);
        d->sysminor = sysminor;
        d->aoemajor = maj;
        d->aoeminor = min;
        d->rttavg = RTTAVG_INIT;
        d->rttdev = RTTDEV_INIT;
        d->next = devlist;
        devlist = d;
 out:
        spin_unlock_irqrestore(&devlist_lock, flags);
        return d;
}

static void
freetgt(struct aoedev *d, struct aoetgt *t)
{
        struct frame *f;
        struct list_head *pos, *nx, *head;
        struct aoeif *ifp;

        for (ifp = t->ifs; ifp < &t->ifs[NAOEIFS]; ++ifp) {
                if (!ifp->nd)
                        break;
                dev_put(ifp->nd);
        }

        head = &t->ffree;
        list_for_each_safe(pos, nx, head) {
                list_del(pos);
                f = list_entry(pos, struct frame, head);
                skbfree(f->skb);
                kfree(f);
        }
        kfree(t);
}

void
aoedev_exit(void)
{
        flush_scheduled_work();
        flush(NULL, 0, EXITING);
}

int __init
aoedev_init(void)
{
        return 0;
}