Hopefully get the Kconfig PCI stuff right, finally.

[linux-2.6/linux-mips.git] / drivers / md / dm.c

/*
 * Copyright (C) 2001, 2002 Sistina Software (UK) Limited.
 *
 * This file is released under the GPL.
 */

#include "dm.h"

#include <linux/init.h>
#include <linux/module.h>
#include <linux/blk.h>
#include <linux/blkpg.h>
#include <linux/bio.h>
#include <linux/mempool.h>
#include <linux/slab.h>

static const char *_name = DM_NAME;
#define MAX_DEVICES 1024

static int major = 0;
static int _major = 0;

struct dm_io {
        struct mapped_device *md;
        int error;
        struct bio *bio;
        atomic_t io_count;
};

struct deferred_io {
        struct bio *bio;
        struct deferred_io *next;
};

/*
 * Bits for the md->flags field.
 */
#define DMF_BLOCK_IO 0
#define DMF_SUSPENDED 1

struct mapped_device {
        struct rw_semaphore lock;
        atomic_t holders;

        unsigned long flags;

        request_queue_t queue;
        struct gendisk *disk;

        /*
         * A list of ios that arrived while we were suspended.
         */
        atomic_t pending;
        wait_queue_head_t wait;
        struct deferred_io *deferred;

        /*
         * The current mapping.
         */
        struct dm_table *map;

        /*
         * io objects are allocated from here.
         */
        mempool_t *io_pool;
};

#define MIN_IOS 256
static kmem_cache_t *_io_cache;

static __init int local_init(void)
{
        int r;

        /* allocate a slab for the dm_ios */
        _io_cache = kmem_cache_create("dm io",
                                      sizeof(struct dm_io), 0, 0, NULL, NULL);
        if (!_io_cache)
                return -ENOMEM;

        _major = major;
        r = register_blkdev(_major, _name);
        if (r < 0) {
                kmem_cache_destroy(_io_cache);
                return r;
        }

        if (!_major)
                _major = r;

        return 0;
}

static void local_exit(void)
{
        kmem_cache_destroy(_io_cache);

        if (unregister_blkdev(_major, _name) < 0)
                DMERR("devfs_unregister_blkdev failed");

        _major = 0;

        DMINFO("cleaned up");
}

/*
 * We have a lot of init/exit functions, so it seems easier to
 * store them in an array.  The disposable macro 'xx'
 * expands a prefix into a pair of function names.
 */
static struct {
        int (*init) (void);
        void (*exit) (void);

} _inits[] = {
#define xx(n) {n ## _init, n ## _exit},
        xx(local)
        xx(dm_target)
        xx(dm_linear)
        xx(dm_stripe)
        xx(dm_interface)
#undef xx
};

static int __init dm_init(void)
{
        const int count = ARRAY_SIZE(_inits);

        int r, i;

        for (i = 0; i < count; i++) {
                r = _inits[i].init();
                if (r)
                        goto bad;
        }

        return 0;

      bad:
        while (i--)
                _inits[i].exit();

        return r;
}

static void __exit dm_exit(void)
{
        int i = ARRAY_SIZE(_inits);

        while (i--)
                _inits[i].exit();
}

/*
 * Block device functions
 */
static int dm_blk_open(struct inode *inode, struct file *file)
{
        struct mapped_device *md;

        md = inode->i_bdev->bd_disk->private_data;
        dm_get(md);
        return 0;
}

static int dm_blk_close(struct inode *inode, struct file *file)
{
        struct mapped_device *md;

        md = inode->i_bdev->bd_disk->private_data;
        dm_put(md);
        return 0;
}

static inline struct dm_io *alloc_io(struct mapped_device *md)
{
        return mempool_alloc(md->io_pool, GFP_NOIO);
}

static inline void free_io(struct mapped_device *md, struct dm_io *io)
{
        mempool_free(io, md->io_pool);
}

static inline struct deferred_io *alloc_deferred(void)
{
        return kmalloc(sizeof(struct deferred_io), GFP_NOIO);
}

static inline void free_deferred(struct deferred_io *di)
{
        kfree(di);
}

/*
 * Add the bio to the list of deferred io.
 */
static int queue_io(struct mapped_device *md, struct bio *bio)
{
        struct deferred_io *di;

        di = alloc_deferred();
        if (!di)
                return -ENOMEM;

        down_write(&md->lock);

        if (!test_bit(DMF_BLOCK_IO, &md->flags)) {
                up_write(&md->lock);
                free_deferred(di);
                return 1;
        }

        di->bio = bio;
        di->next = md->deferred;
        md->deferred = di;

        up_write(&md->lock);
        return 0;               /* deferred successfully */
}

/*-----------------------------------------------------------------
 * CRUD START:
 *   A more elegant soln is in the works that uses the queue
 *   merge fn, unfortunately there are a couple of changes to
 *   the block layer that I want to make for this.  So in the
 *   interests of getting something for people to use I give
 *   you this clearly demarcated crap.
 *---------------------------------------------------------------*/
static inline sector_t to_sector(unsigned int bytes)
{
        return bytes >> SECTOR_SHIFT;
}

static inline unsigned int to_bytes(sector_t sector)
{
        return sector << SECTOR_SHIFT;
}

/*
 * Decrements the number of outstanding ios that a bio has been
 * cloned into, completing the original io if necc.
 */
static inline void dec_pending(struct dm_io *io, int error)
{
        static spinlock_t _uptodate_lock = SPIN_LOCK_UNLOCKED;
        unsigned long flags;

        if (error) {
                spin_lock_irqsave(&_uptodate_lock, flags);
                io->error = error;
                spin_unlock_irqrestore(&_uptodate_lock, flags);
        }

        if (atomic_dec_and_test(&io->io_count)) {
                if (atomic_dec_and_test(&io->md->pending))
                        /* nudge anyone waiting on suspend queue */
                        wake_up(&io->md->wait);

                bio_endio(io->bio, io->bio->bi_size, io->error);
                free_io(io->md, io);
        }
}

static int clone_endio(struct bio *bio, unsigned int done, int error)
{
        struct dm_io *io = bio->bi_private;

        if (bio->bi_size)
                return 1;

        dec_pending(io, error);
        bio_put(bio);
        return 0;
}


static sector_t max_io_len(struct mapped_device *md,
                           sector_t sector, struct dm_target *ti)
{
        sector_t offset = sector - ti->begin;
        sector_t len = ti->len - offset;

        /* FIXME: obey io_restrictions ! */


        /*
         * Does the target need to split even further ?
         */
        if (ti->split_io) {
                sector_t boundary;
                boundary = dm_round_up(offset + 1, ti->split_io) - offset;

                if (len > boundary)
                        len = boundary;
        }

        return len;
}

static void __map_bio(struct dm_target *ti, struct bio *clone, struct dm_io *io)
{
        int r;

        /*
         * Sanity checks.
         */
        BUG_ON(!clone->bi_size);

        clone->bi_end_io = clone_endio;
        clone->bi_private = io;

        /*
         * Map the clone.  If r == 0 we don't need to do
         * anything, the target has assumed ownership of
         * this io.
         */
        atomic_inc(&io->io_count);
        r = ti->type->map(ti, clone);
        if (r > 0)
                /* the bio has been remapped so dispatch it */
                generic_make_request(clone);

        else if (r < 0)
                /* error the io and bail out */
                dec_pending(io, -EIO);
}

struct clone_info {
        struct mapped_device *md;
        struct bio *bio;
        struct dm_io *io;
        sector_t sector;
        sector_t sector_count;
        unsigned short idx;
};

/*
 * Creates a little bio that is just does part of a bvec.
 */
static struct bio *split_bvec(struct bio *bio, sector_t sector,
                              unsigned short idx, unsigned int offset,
                              unsigned int len)
{
        struct bio *clone;
        struct bio_vec *bv = bio->bi_io_vec + idx;

        clone = bio_alloc(GFP_NOIO, 1);
        memcpy(clone->bi_io_vec, bv, sizeof(*bv));

        clone->bi_sector = sector;
        clone->bi_bdev = bio->bi_bdev;
        clone->bi_rw = bio->bi_rw;
        clone->bi_vcnt = 1;
        clone->bi_size = to_bytes(len);
        clone->bi_io_vec->bv_offset = offset;
        clone->bi_io_vec->bv_len = clone->bi_size;

        return clone;
}

/*
 * Creates a bio that consists of range of complete bvecs.
 */
static struct bio *clone_bio(struct bio *bio, sector_t sector,
                             unsigned short idx, unsigned short bv_count,
                             unsigned int len)
{
        struct bio *clone;

        clone = bio_clone(bio, GFP_NOIO);
        clone->bi_sector = sector;
        clone->bi_idx = idx;
        clone->bi_vcnt = idx + bv_count;
        clone->bi_size = to_bytes(len);

        return clone;
}

static void __clone_and_map(struct clone_info *ci)
{
        struct bio *clone, *bio = ci->bio;
        struct dm_target *ti = dm_table_find_target(ci->md->map, ci->sector);
        sector_t len = 0, max = max_io_len(ci->md, ci->sector, ti);

        if (ci->sector_count <= max) {
                /*
                 * Optimise for the simple case where we can do all of
                 * the remaining io with a single clone.
                 */
                clone = clone_bio(bio, ci->sector, ci->idx,
                                  bio->bi_vcnt - ci->idx, ci->sector_count);
                __map_bio(ti, clone, ci->io);
                ci->sector_count = 0;

        } else if (to_sector(bio->bi_io_vec[ci->idx].bv_len) <= max) {
                /*
                 * There are some bvecs that don't span targets.
                 * Do as many of these as possible.
                 */
                int i;
                sector_t remaining = max;
                sector_t bv_len;

                for (i = ci->idx; remaining && (i < bio->bi_vcnt); i++) {
                        bv_len = to_sector(bio->bi_io_vec[i].bv_len);

                        if (bv_len > remaining)
                                break;

                        remaining -= bv_len;
                        len += bv_len;
                }

                clone = clone_bio(bio, ci->sector, ci->idx, i - ci->idx, len);
                __map_bio(ti, clone, ci->io);

                ci->sector += len;
                ci->sector_count -= len;
                ci->idx = i;

        } else {
                /*
                 * Create two copy bios to deal with io that has
                 * been split across a target.
                 */
                struct bio_vec *bv = bio->bi_io_vec + ci->idx;

                clone = split_bvec(bio, ci->sector, ci->idx,
                                   bv->bv_offset, max);
                __map_bio(ti, clone, ci->io);

                ci->sector += max;
                ci->sector_count -= max;
                ti = dm_table_find_target(ci->md->map, ci->sector);

                len = to_sector(bv->bv_len) - max;
                clone = split_bvec(bio, ci->sector, ci->idx,
                                   bv->bv_offset + to_bytes(max), len);
                __map_bio(ti, clone, ci->io);

                ci->sector += len;
                ci->sector_count -= len;
                ci->idx++;
        }
}

/*
 * Split the bio into several clones.
 */
static void __split_bio(struct mapped_device *md, struct bio *bio)
{
        struct clone_info ci;

        ci.md = md;
        ci.bio = bio;
        ci.io = alloc_io(md);
        ci.io->error = 0;
        atomic_set(&ci.io->io_count, 1);
        ci.io->bio = bio;
        ci.io->md = md;
        ci.sector = bio->bi_sector;
        ci.sector_count = bio_sectors(bio);
        ci.idx = bio->bi_idx;

        atomic_inc(&md->pending);
        while (ci.sector_count)
                __clone_and_map(&ci);

        /* drop the extra reference count */
        dec_pending(ci.io, 0);
}
/*-----------------------------------------------------------------
 * CRUD END
 *---------------------------------------------------------------*/


/*
 * The request function that just remaps the bio built up by
 * dm_merge_bvec.
 */
static int dm_request(request_queue_t *q, struct bio *bio)
{
        int r;
        struct mapped_device *md = q->queuedata;

        down_read(&md->lock);

        /*
         * If we're suspended we have to queue
         * this io for later.
         */
        while (test_bit(DMF_BLOCK_IO, &md->flags)) {
                up_read(&md->lock);

                if (bio_rw(bio) == READA) {
                        bio_io_error(bio, bio->bi_size);
                        return 0;
                }

                r = queue_io(md, bio);
                if (r < 0) {
                        bio_io_error(bio, bio->bi_size);
                        return 0;

                } else if (r == 0)
                        return 0;       /* deferred successfully */

                /*
                 * We're in a while loop, because someone could suspend
                 * before we get to the following read lock.
                 */
                down_read(&md->lock);
        }

        __split_bio(md, bio);
        up_read(&md->lock);
        return 0;
}

/*-----------------------------------------------------------------
 * A bitset is used to keep track of allocated minor numbers.
 *---------------------------------------------------------------*/
static spinlock_t _minor_lock = SPIN_LOCK_UNLOCKED;
static unsigned long _minor_bits[MAX_DEVICES / BITS_PER_LONG];

static void free_minor(int minor)
{
        spin_lock(&_minor_lock);
        clear_bit(minor, _minor_bits);
        spin_unlock(&_minor_lock);
}

/*
 * See if the device with a specific minor # is free.
 */
static int specific_minor(int minor)
{
        int r = -EBUSY;

        if (minor >= MAX_DEVICES) {
                DMWARN("request for a mapped_device beyond MAX_DEVICES (%d)",
                       MAX_DEVICES);
                return -EINVAL;
        }

        spin_lock(&_minor_lock);
        if (!test_and_set_bit(minor, _minor_bits))
                r = minor;
        spin_unlock(&_minor_lock);

        return r;
}

static int next_free_minor(void)
{
        int minor, r = -EBUSY;

        spin_lock(&_minor_lock);
        minor = find_first_zero_bit(_minor_bits, MAX_DEVICES);
        if (minor != MAX_DEVICES) {
                set_bit(minor, _minor_bits);
                r = minor;
        }
        spin_unlock(&_minor_lock);

        return r;
}

/*
 * Allocate and initialise a blank device with a given minor.
 */
static struct mapped_device *alloc_dev(int minor)
{
        struct mapped_device *md = kmalloc(sizeof(*md), GFP_KERNEL);

        if (!md) {
                DMWARN("unable to allocate device, out of memory.");
                return NULL;
        }

        /* get a minor number for the dev */
        minor = (minor < 0) ? next_free_minor() : specific_minor(minor);
        if (minor < 0) {
                kfree(md);
                return NULL;
        }

        DMWARN("allocating minor %d.", minor);
        memset(md, 0, sizeof(*md));
        init_rwsem(&md->lock);
        atomic_set(&md->holders, 1);

        md->queue.queuedata = md;
        blk_queue_make_request(&md->queue, dm_request);

        md->io_pool = mempool_create(MIN_IOS, mempool_alloc_slab,
                                     mempool_free_slab, _io_cache);
        if (!md->io_pool) {
                free_minor(md->disk->first_minor);
                kfree(md);
                return NULL;
        }

        md->disk = alloc_disk(1);
        if (!md->disk) {
                mempool_destroy(md->io_pool);
                free_minor(md->disk->first_minor);
                kfree(md);
                return NULL;
        }

        md->disk->major = _major;
        md->disk->first_minor = minor;
        md->disk->fops = &dm_blk_dops;
        md->disk->queue = &md->queue;
        md->disk->private_data = md;
        sprintf(md->disk->disk_name, "dm-%d", minor);
        add_disk(md->disk);

        atomic_set(&md->pending, 0);
        init_waitqueue_head(&md->wait);
        return md;
}

static void free_dev(struct mapped_device *md)
{
        free_minor(md->disk->first_minor);
        mempool_destroy(md->io_pool);
        del_gendisk(md->disk);
        put_disk(md->disk);
        kfree(md);
}

/*
 * Bind a table to the device.
 */
static int __bind(struct mapped_device *md, struct dm_table *t)
{
        request_queue_t *q = &md->queue;
        sector_t size;
        md->map = t;

        size = dm_table_get_size(t);
        set_capacity(md->disk, size);
        if (size == 0)
                return 0;

        dm_table_get(t);
        dm_table_set_restrictions(t, q);
        return 0;
}

static void __unbind(struct mapped_device *md)
{
        dm_table_put(md->map);
        md->map = NULL;
        set_capacity(md->disk, 0);
}

/*
 * Constructor for a new device.
 */
int dm_create(int minor, struct dm_table *table, struct mapped_device **result)
{
        int r;
        struct mapped_device *md;

        md = alloc_dev(minor);
        if (!md)
                return -ENXIO;

        r = __bind(md, table);
        if (r) {
                free_dev(md);
                return r;
        }

        *result = md;
        return 0;
}

void dm_get(struct mapped_device *md)
{
        atomic_inc(&md->holders);
}

void dm_put(struct mapped_device *md)
{
        if (atomic_dec_and_test(&md->holders)) {
                DMWARN("destroying md");
                __unbind(md);
                free_dev(md);
        }
}

/*
 * Requeue the deferred bios by calling generic_make_request.
 */
static void flush_deferred_io(struct deferred_io *c)
{
        struct deferred_io *n;

        while (c) {
                n = c->next;
                generic_make_request(c->bio);
                free_deferred(c);
                c = n;
        }
}

/*
 * Swap in a new table (destroying old one).
 */
int dm_swap_table(struct mapped_device *md, struct dm_table *table)
{
        int r;

        down_write(&md->lock);

        /* device must be suspended */
        if (!test_bit(DMF_SUSPENDED, &md->flags)) {
                up_write(&md->lock);
                return -EPERM;
        }

        __unbind(md);
        r = __bind(md, table);
        if (r)
                return r;

        up_write(&md->lock);
        return 0;
}

/*
 * We need to be able to change a mapping table under a mounted
 * filesystem.  For example we might want to move some data in
 * the background.  Before the table can be swapped with
 * dm_bind_table, dm_suspend must be called to flush any in
 * flight bios and ensure that any further io gets deferred.
 */
int dm_suspend(struct mapped_device *md)
{
        DECLARE_WAITQUEUE(wait, current);

        down_write(&md->lock);

        /*
         * First we set the BLOCK_IO flag so no more ios will be
         * mapped.
         */
        if (test_bit(DMF_BLOCK_IO, &md->flags)) {
                up_write(&md->lock);
                return -EINVAL;
        }

        set_bit(DMF_BLOCK_IO, &md->flags);
        add_wait_queue(&md->wait, &wait);
        up_write(&md->lock);

        /*
         * Then we wait for the already mapped ios to
         * complete.
         */
        blk_run_queues();
        while (1) {
                set_current_state(TASK_INTERRUPTIBLE);

                if (!atomic_read(&md->pending))
                        break;

                yield();
        }

        current->state = TASK_RUNNING;

        down_write(&md->lock);
        remove_wait_queue(&md->wait, &wait);
        set_bit(DMF_SUSPENDED, &md->flags);
        up_write(&md->lock);

        return 0;
}

int dm_resume(struct mapped_device *md)
{
        struct deferred_io *def;

        down_write(&md->lock);
        if (!test_bit(DMF_SUSPENDED, &md->flags) ||
            !dm_table_get_size(md->map)) {
                up_write(&md->lock);
                return -EINVAL;
        }

        clear_bit(DMF_SUSPENDED, &md->flags);
        clear_bit(DMF_BLOCK_IO, &md->flags);
        def = md->deferred;
        md->deferred = NULL;
        up_write(&md->lock);

        flush_deferred_io(def);
        blk_run_queues();

        return 0;
}

/*
 * The gendisk is only valid as long as you have a reference
 * count on 'md'.
 */
struct gendisk *dm_disk(struct mapped_device *md)
{
        return md->disk;
}

struct dm_table *dm_get_table(struct mapped_device *md)
{
        struct dm_table *t;

        down_read(&md->lock);
        t = md->map;
        dm_table_get(t);
        up_read(&md->lock);

        return t;
}

int dm_suspended(struct mapped_device *md)
{
        return test_bit(DMF_SUSPENDED, &md->flags);
}

struct block_device_operations dm_blk_dops = {
        .open = dm_blk_open,
        .release = dm_blk_close,
        .owner = THIS_MODULE
};

/*
 * module hooks
 */
module_init(dm_init);
module_exit(dm_exit);

MODULE_PARM(major, "i");
MODULE_PARM_DESC(major, "The major number of the device mapper");
MODULE_DESCRIPTION(DM_NAME " driver");
MODULE_AUTHOR("Joe Thornber <thornber@sistina.com>");
MODULE_LICENSE("GPL");