Date:	Tue, 2 Oct 2012 05:30:18 -0500
From:	Ed Cashin <ecashin@...aid.com>
To:	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
CC:	Ed Cashin <ecashin@...aid.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/7] aoe: support more AoE addresses with dynamic block
 device minor numbers

I should have mentioned that these seven patches were made for linux-next/akpm, which contains the last 14-patch series for aoe.

On Oct 1, 2012, at 9:59 PM, "Ed Cashin" <ecashin@...aid.com> wrote:

> The ATA over Ethernet protocol uses a major (shelf) and
> minor (slot) address to identify a particular storage target.
> These changes remove an artificial limitation the aoe driver
> imposes on the use of AoE addresses.  For example, without these
> changes, the slot address has a maximum of 15, but users commonly
> use slot numbers much greater than that.
> 
> The AoE shelf and slot address space is often used sparsely.
> Instead of using a static mapping between AoE addresses and the
> block device minor number, the block device minor numbers are now
> allocated on demand.
> 
> Signed-off-by: Ed Cashin <ecashin@...aid.com>
> ---
> drivers/block/aoe/aoe.h    |    6 ++--
> drivers/block/aoe/aoeblk.c |    2 +-
> drivers/block/aoe/aoechr.c |    2 +-
> drivers/block/aoe/aoecmd.c |   25 ++++---------
> drivers/block/aoe/aoedev.c |   86 ++++++++++++++++++++++++++++++--------------
> 5 files changed, 72 insertions(+), 49 deletions(-)
> 
> diff --git a/drivers/block/aoe/aoe.h b/drivers/block/aoe/aoe.h
> index 27d0a21..7b694f7 100644
> --- a/drivers/block/aoe/aoe.h
> +++ b/drivers/block/aoe/aoe.h
> @@ -49,6 +49,8 @@ struct aoe_hdr {
>    __be32 tag;
> };
> 
> +#define AOE_MAXSHELF (0xffff-1)    /* one less than the broadcast shelf address */
> +
> struct aoe_atahdr {
>    unsigned char aflags;
>    unsigned char errfeat;
> @@ -211,8 +213,7 @@ void aoe_ktstop(struct ktstate *k);
> 
> int aoedev_init(void);
> void aoedev_exit(void);
> -struct aoedev *aoedev_by_aoeaddr(int maj, int min);
> -struct aoedev *aoedev_by_sysminor_m(ulong sysminor);
> +struct aoedev *aoedev_by_aoeaddr(ulong maj, int min, int do_alloc);
> void aoedev_downdev(struct aoedev *d);
> int aoedev_flush(const char __user *str, size_t size);
> void aoe_failbuf(struct aoedev *, struct buf *);
> @@ -223,4 +224,3 @@ void aoenet_exit(void);
> void aoenet_xmit(struct sk_buff_head *);
> int is_aoe_netif(struct net_device *ifp);
> int set_aoe_iflist(const char __user *str, size_t size);
> -
> diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
> index 83160ab..00dfc50 100644
> --- a/drivers/block/aoe/aoeblk.c
> +++ b/drivers/block/aoe/aoeblk.c
> @@ -249,7 +249,7 @@ aoeblk_gdalloc(void *vp)
>    q->queuedata = d;
>    d->gd = gd;
>    gd->major = AOE_MAJOR;
> -    gd->first_minor = d->sysminor * AOE_PARTITIONS;
> +    gd->first_minor = d->sysminor;
>    gd->fops = &aoe_bdops;
>    gd->private_data = d;
>    set_capacity(gd, d->ssize);
> diff --git a/drivers/block/aoe/aoechr.c b/drivers/block/aoe/aoechr.c
> index deb30c1..ed57a89 100644
> --- a/drivers/block/aoe/aoechr.c
> +++ b/drivers/block/aoe/aoechr.c
> @@ -91,7 +91,7 @@ revalidate(const char __user *str, size_t size)
>        pr_err("aoe: invalid device specification %s\n", buf);
>        return -EINVAL;
>    }
> -    d = aoedev_by_aoeaddr(major, minor);
> +    d = aoedev_by_aoeaddr(major, minor, 0);
>    if (!d)
>        return -EINVAL;
>    spin_lock_irqsave(&d->lock, flags);
> diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
> index 39dacdb..94e810c 100644
> --- a/drivers/block/aoe/aoecmd.c
> +++ b/drivers/block/aoe/aoecmd.c
> @@ -1149,7 +1149,7 @@ aoecmd_ata_rsp(struct sk_buff *skb)
> 
>    h = (struct aoe_hdr *) skb->data;
>    aoemajor = be16_to_cpu(get_unaligned(&h->major));
> -    d = aoedev_by_aoeaddr(aoemajor, h->minor);
> +    d = aoedev_by_aoeaddr(aoemajor, h->minor, 0);
>    if (d == NULL) {
>        snprintf(ebuf, sizeof ebuf, "aoecmd_ata_rsp: ata response "
>            "for unknown device %d.%d\n",
> @@ -1330,7 +1330,7 @@ aoecmd_cfg_rsp(struct sk_buff *skb)
>    struct aoe_hdr *h;
>    struct aoe_cfghdr *ch;
>    struct aoetgt *t;
> -    ulong flags, sysminor, aoemajor;
> +    ulong flags, aoemajor;
>    struct sk_buff *sl;
>    struct sk_buff_head queue;
>    u16 n;
> @@ -1349,18 +1349,15 @@ aoecmd_cfg_rsp(struct sk_buff *skb)
>            "Check shelf dip switches.\n");
>        return;
>    }
> -    if (h->minor >= NPERSHELF) {
> -        pr_err("aoe: e%ld.%d %s, %d\n",
> -            aoemajor, h->minor,
> -            "slot number larger than the maximum",
> -            NPERSHELF-1);
> +    if (aoemajor > AOE_MAXSHELF) {
> +        pr_info("aoe: e%ld.%d: shelf number too large\n",
> +            aoemajor, (int) h->minor);
>        return;
>    }
> 
> -    sysminor = SYSMINOR(aoemajor, h->minor);
> -    if (sysminor * AOE_PARTITIONS + AOE_PARTITIONS > MINORMASK) {
> -        printk(KERN_INFO "aoe: e%ld.%d: minor number too large\n",
> -            aoemajor, (int) h->minor);
> +    d = aoedev_by_aoeaddr(aoemajor, h->minor, 1);
> +    if (d == NULL) {
> +        pr_info("aoe: device allocation failure\n");
>        return;
>    }
> 
> @@ -1368,12 +1365,6 @@ aoecmd_cfg_rsp(struct sk_buff *skb)
>    if (n > aoe_maxout)    /* keep it reasonable */
>        n = aoe_maxout;
> 
> -    d = aoedev_by_sysminor_m(sysminor);
> -    if (d == NULL) {
> -        printk(KERN_INFO "aoe: device sysminor_m failure\n");
> -        return;
> -    }
> -
>    spin_lock_irqsave(&d->lock, flags);
> 
>    t = gettgt(d, h->src);
> diff --git a/drivers/block/aoe/aoedev.c b/drivers/block/aoe/aoedev.c
> index ccaecff..68a7a5a 100644
> --- a/drivers/block/aoe/aoedev.c
> +++ b/drivers/block/aoe/aoedev.c
> @@ -9,6 +9,8 @@
> #include <linux/netdevice.h>
> #include <linux/delay.h>
> #include <linux/slab.h>
> +#include <linux/bitmap.h>
> +#include <linux/kdev_t.h>
> #include "aoe.h"
> 
> static void dummy_timer(ulong);
> @@ -19,35 +21,63 @@ static void skbpoolfree(struct aoedev *d);
> static struct aoedev *devlist;
> static DEFINE_SPINLOCK(devlist_lock);
> 
> -/*
> - * Users who grab a pointer to the device with aoedev_by_aoeaddr or
> - * aoedev_by_sysminor_m 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.
> +/* 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.
>  */
> -struct aoedev *
> -aoedev_by_aoeaddr(int maj, int min)
> +#define N_DEVS ((1U<<MINORBITS)/AOE_PARTITIONS)
> +
> +static DEFINE_SPINLOCK(used_minors_lock);
> +static DECLARE_BITMAP(used_minors, N_DEVS);
> +
> +static int
> +minor_get(ulong *minor)
> {
> -    struct aoedev *d;
>    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);
> +
> +    *minor = n * AOE_PARTITIONS;
> +    return error;
> +}
> 
> -    spin_lock_irqsave(&devlist_lock, flags);
> +static void
> +minor_free(ulong minor)
> +{
> +    ulong flags;
> 
> -    for (d=devlist; d; d=d->next)
> -        if (d->aoemajor == maj && d->aoeminor == min) {
> -            d->ref++;
> -            break;
> -        }
> +    minor /= AOE_PARTITIONS;
> +    BUG_ON(minor >= N_DEVS);
> 
> -    spin_unlock_irqrestore(&devlist_lock, flags);
> -    return d;
> +    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)
> {
> @@ -159,6 +189,7 @@ aoedev_freedev(struct aoedev *d)
>    if (d->bufpool)
>        mempool_destroy(d->bufpool);
>    skbpoolfree(d);
> +    minor_free(d->sysminor);
>    kfree(d);
> }
> 
> @@ -246,22 +277,23 @@ skbpoolfree(struct aoedev *d)
>    __skb_queue_head_init(&d->skbpool);
> }
> 
> -/* find it or malloc it */
> +/* find it or allocate it */
> struct aoedev *
> -aoedev_by_sysminor_m(ulong sysminor)
> +aoedev_by_aoeaddr(ulong maj, int min, int do_alloc)
> {
>    struct aoedev *d;
>    int i;
>    ulong flags;
> +    ulong sysminor;
> 
>    spin_lock_irqsave(&devlist_lock, flags);
> 
>    for (d=devlist; d; d=d->next)
> -        if (d->sysminor == sysminor) {
> +        if (d->aoemajor == maj && d->aoeminor == min) {
>            d->ref++;
>            break;
>        }
> -    if (d)
> +    if (d || !do_alloc || minor_get(&sysminor) < 0)
>        goto out;
>    d = kcalloc(1, sizeof *d, GFP_ATOMIC);
>    if (!d)
> @@ -280,8 +312,8 @@ aoedev_by_sysminor_m(ulong sysminor)
>    for (i = 0; i < NFACTIVE; i++)
>        INIT_LIST_HEAD(&d->factive[i]);
>    d->sysminor = sysminor;
> -    d->aoemajor = AOEMAJOR(sysminor);
> -    d->aoeminor = AOEMINOR(sysminor);
> +    d->aoemajor = maj;
> +    d->aoeminor = min;
>    d->mintimer = MINTIMER;
>    d->next = devlist;
>    devlist = d;
> -- 
> 1.7.1
> 
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