initial commit with v2.6.9

[linux-2.6.9-moxart.git] / drivers / md / dm-io.c

/*
 * Copyright (C) 2003 Sistina Software
 *
 * This file is released under the GPL.
 */

#include "dm-io.h"

#include <linux/bio.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>

#define BIO_POOL_SIZE 256


/*-----------------------------------------------------------------
 * Bio set, move this to bio.c
 *---------------------------------------------------------------*/
#define BV_NAME_SIZE 16
struct biovec_pool {
        int nr_vecs;
        char name[BV_NAME_SIZE];
        kmem_cache_t *slab;
        mempool_t *pool;
        atomic_t allocated;     /* FIXME: debug */
};

#define BIOVEC_NR_POOLS 6
struct bio_set {
        char name[BV_NAME_SIZE];
        kmem_cache_t *bio_slab;
        mempool_t *bio_pool;
        struct biovec_pool pools[BIOVEC_NR_POOLS];
};

static void bio_set_exit(struct bio_set *bs)
{
        unsigned i;
        struct biovec_pool *bp;

        if (bs->bio_pool)
                mempool_destroy(bs->bio_pool);

        if (bs->bio_slab)
                kmem_cache_destroy(bs->bio_slab);

        for (i = 0; i < BIOVEC_NR_POOLS; i++) {
                bp = bs->pools + i;
                if (bp->pool)
                        mempool_destroy(bp->pool);

                if (bp->slab)
                        kmem_cache_destroy(bp->slab);
        }
}

static void mk_name(char *str, size_t len, const char *prefix, unsigned count)
{
        snprintf(str, len, "%s-%u", prefix, count);
}

static int bio_set_init(struct bio_set *bs, const char *slab_prefix,
                         unsigned pool_entries, unsigned scale)
{
        /* FIXME: this must match bvec_index(), why not go the
         * whole hog and have a pool per power of 2 ? */
        static unsigned _vec_lengths[BIOVEC_NR_POOLS] = {
                1, 4, 16, 64, 128, BIO_MAX_PAGES
        };


        unsigned i, size;
        struct biovec_pool *bp;

        /* zero the bs so we can tear down properly on error */
        memset(bs, 0, sizeof(*bs));

        /*
         * Set up the bio pool.
         */
        snprintf(bs->name, sizeof(bs->name), "%s-bio", slab_prefix);

        bs->bio_slab = kmem_cache_create(bs->name, sizeof(struct bio), 0,
                                         SLAB_HWCACHE_ALIGN, NULL, NULL);
        if (!bs->bio_slab) {
                DMWARN("can't init bio slab");
                goto bad;
        }

        bs->bio_pool = mempool_create(pool_entries, mempool_alloc_slab,
                                      mempool_free_slab, bs->bio_slab);
        if (!bs->bio_pool) {
                DMWARN("can't init bio pool");
                goto bad;
        }

        /*
         * Set up the biovec pools.
         */
        for (i = 0; i < BIOVEC_NR_POOLS; i++) {
                bp = bs->pools + i;
                bp->nr_vecs = _vec_lengths[i];
                atomic_set(&bp->allocated, 1); /* FIXME: debug */


                size = bp->nr_vecs * sizeof(struct bio_vec);

                mk_name(bp->name, sizeof(bp->name), slab_prefix, i);
                bp->slab = kmem_cache_create(bp->name, size, 0,
                                             SLAB_HWCACHE_ALIGN, NULL, NULL);
                if (!bp->slab) {
                        DMWARN("can't init biovec slab cache");
                        goto bad;
                }

                if (i >= scale)
                        pool_entries >>= 1;

                bp->pool = mempool_create(pool_entries, mempool_alloc_slab,
                                          mempool_free_slab, bp->slab);
                if (!bp->pool) {
                        DMWARN("can't init biovec mempool");
                        goto bad;
                }
        }

        return 0;

 bad:
        bio_set_exit(bs);
        return -ENOMEM;
}

/* FIXME: blech */
static inline unsigned bvec_index(unsigned nr)
{
        switch (nr) {
        case 1:         return 0;
        case 2 ... 4:   return 1;
        case 5 ... 16:  return 2;
        case 17 ... 64: return 3;
        case 65 ... 128:return 4;
        case 129 ... BIO_MAX_PAGES: return 5;
        }

        BUG();
        return 0;
}

static inline void bs_bio_init(struct bio *bio)
{
        bio->bi_next = NULL;
        bio->bi_flags = 1 << BIO_UPTODATE;
        bio->bi_rw = 0;
        bio->bi_vcnt = 0;
        bio->bi_idx = 0;
        bio->bi_phys_segments = 0;
        bio->bi_hw_segments = 0;
        bio->bi_size = 0;
        bio->bi_max_vecs = 0;
        bio->bi_end_io = NULL;
        atomic_set(&bio->bi_cnt, 1);
        bio->bi_private = NULL;
}

static unsigned _bio_count = 0;
struct bio *bio_set_alloc(struct bio_set *bs, int gfp_mask, int nr_iovecs)
{
        struct biovec_pool *bp;
        struct bio_vec *bv = NULL;
        unsigned long idx;
        struct bio *bio;

        bio = mempool_alloc(bs->bio_pool, gfp_mask);
        if (unlikely(!bio))
                return NULL;

        bio_init(bio);

        if (likely(nr_iovecs)) {
                idx = bvec_index(nr_iovecs);
                bp = bs->pools + idx;
                bv = mempool_alloc(bp->pool, gfp_mask);
                if (!bv) {
                        mempool_free(bio, bs->bio_pool);
                        return NULL;
                }

                memset(bv, 0, bp->nr_vecs * sizeof(*bv));
                bio->bi_flags |= idx << BIO_POOL_OFFSET;
                bio->bi_max_vecs = bp->nr_vecs;
                atomic_inc(&bp->allocated);
        }

        bio->bi_io_vec = bv;
        return bio;
}

static void bio_set_free(struct bio_set *bs, struct bio *bio)
{
        struct biovec_pool *bp = bs->pools + BIO_POOL_IDX(bio);

        if (atomic_dec_and_test(&bp->allocated))
                BUG();

        mempool_free(bio->bi_io_vec, bp->pool);
        mempool_free(bio, bs->bio_pool);
}

/*-----------------------------------------------------------------
 * dm-io proper
 *---------------------------------------------------------------*/
static struct bio_set _bios;

/* FIXME: can we shrink this ? */
struct io {
        unsigned long error;
        atomic_t count;
        struct task_struct *sleeper;
        io_notify_fn callback;
        void *context;
};

/*
 * io contexts are only dynamically allocated for asynchronous
 * io.  Since async io is likely to be the majority of io we'll
 * have the same number of io contexts as buffer heads ! (FIXME:
 * must reduce this).
 */
static unsigned _num_ios;
static mempool_t *_io_pool;

static void *alloc_io(int gfp_mask, void *pool_data)
{
        return kmalloc(sizeof(struct io), gfp_mask);
}

static void free_io(void *element, void *pool_data)
{
        kfree(element);
}

static unsigned int pages_to_ios(unsigned int pages)
{
        return 4 * pages;       /* too many ? */
}

static int resize_pool(unsigned int new_ios)
{
        int r = 0;

        if (_io_pool) {
                if (new_ios == 0) {
                        /* free off the pool */
                        mempool_destroy(_io_pool);
                        _io_pool = NULL;
                        bio_set_exit(&_bios);

                } else {
                        /* resize the pool */
                        r = mempool_resize(_io_pool, new_ios, GFP_KERNEL);
                }

        } else {
                /* create new pool */
                _io_pool = mempool_create(new_ios, alloc_io, free_io, NULL);
                if (!_io_pool)
                        r = -ENOMEM;

                r = bio_set_init(&_bios, "dm-io", 512, 1);
                if (r) {
                        mempool_destroy(_io_pool);
                        _io_pool = NULL;
                }
        }

        if (!r)
                _num_ios = new_ios;

        return r;
}

int dm_io_get(unsigned int num_pages)
{
        return resize_pool(_num_ios + pages_to_ios(num_pages));
}

void dm_io_put(unsigned int num_pages)
{
        resize_pool(_num_ios - pages_to_ios(num_pages));
}

/*-----------------------------------------------------------------
 * We need to keep track of which region a bio is doing io for.
 * In order to save a memory allocation we store this the last
 * bvec which we know is unused (blech).
 *---------------------------------------------------------------*/
static inline void bio_set_region(struct bio *bio, unsigned region)
{
        bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len = region;
}

static inline unsigned bio_get_region(struct bio *bio)
{
        return bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len;
}

/*-----------------------------------------------------------------
 * We need an io object to keep track of the number of bios that
 * have been dispatched for a particular io.
 *---------------------------------------------------------------*/
static void dec_count(struct io *io, unsigned int region, int error)
{
        if (error)
                set_bit(region, &io->error);

        if (atomic_dec_and_test(&io->count)) {
                if (io->sleeper)
                        wake_up_process(io->sleeper);

                else {
                        int r = io->error;
                        io_notify_fn fn = io->callback;
                        void *context = io->context;

                        mempool_free(io, _io_pool);
                        fn(r, context);
                }
        }
}

/* FIXME Move this to bio.h? */
static void zero_fill_bio(struct bio *bio)
{
        unsigned long flags;
        struct bio_vec *bv;
        int i;

        bio_for_each_segment(bv, bio, i) {
                char *data = bvec_kmap_irq(bv, &flags);
                memset(data, 0, bv->bv_len);
                flush_dcache_page(bv->bv_page);
                bvec_kunmap_irq(data, &flags);
        }
}

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

        /* keep going until we've finished */
        if (bio->bi_size)
                return 1;

        if (error && bio_data_dir(bio) == READ)
                zero_fill_bio(bio);

        dec_count(io, bio_get_region(bio), error);
        bio_put(bio);

        return 0;
}

static void bio_dtr(struct bio *bio)
{
        _bio_count--;
        bio_set_free(&_bios, bio);
}

/*-----------------------------------------------------------------
 * These little objects provide an abstraction for getting a new
 * destination page for io.
 *---------------------------------------------------------------*/
struct dpages {
        void (*get_page)(struct dpages *dp,
                         struct page **p, unsigned long *len, unsigned *offset);
        void (*next_page)(struct dpages *dp);

        unsigned context_u;
        void *context_ptr;
};

/*
 * Functions for getting the pages from a list.
 */
static void list_get_page(struct dpages *dp,
                  struct page **p, unsigned long *len, unsigned *offset)
{
        unsigned o = dp->context_u;
        struct page_list *pl = (struct page_list *) dp->context_ptr;

        *p = pl->page;
        *len = PAGE_SIZE - o;
        *offset = o;
}

static void list_next_page(struct dpages *dp)
{
        struct page_list *pl = (struct page_list *) dp->context_ptr;
        dp->context_ptr = pl->next;
        dp->context_u = 0;
}

static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
{
        dp->get_page = list_get_page;
        dp->next_page = list_next_page;
        dp->context_u = offset;
        dp->context_ptr = pl;
}

/*
 * Functions for getting the pages from a bvec.
 */
static void bvec_get_page(struct dpages *dp,
                  struct page **p, unsigned long *len, unsigned *offset)
{
        struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
        *p = bvec->bv_page;
        *len = bvec->bv_len;
        *offset = bvec->bv_offset;
}

static void bvec_next_page(struct dpages *dp)
{
        struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
        dp->context_ptr = bvec + 1;
}

static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
{
        dp->get_page = bvec_get_page;
        dp->next_page = bvec_next_page;
        dp->context_ptr = bvec;
}

static void vm_get_page(struct dpages *dp,
                 struct page **p, unsigned long *len, unsigned *offset)
{
        *p = vmalloc_to_page(dp->context_ptr);
        *offset = dp->context_u;
        *len = PAGE_SIZE - dp->context_u;
}

static void vm_next_page(struct dpages *dp)
{
        dp->context_ptr += PAGE_SIZE - dp->context_u;
        dp->context_u = 0;
}

static void vm_dp_init(struct dpages *dp, void *data)
{
        dp->get_page = vm_get_page;
        dp->next_page = vm_next_page;
        dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
        dp->context_ptr = data;
}

/*-----------------------------------------------------------------
 * IO routines that accept a list of pages.
 *---------------------------------------------------------------*/
static void do_region(int rw, unsigned int region, struct io_region *where,
                      struct dpages *dp, struct io *io)
{
        struct bio *bio;
        struct page *page;
        unsigned long len;
        unsigned offset;
        unsigned num_bvecs;
        sector_t remaining = where->count;

        while (remaining) {
                /*
                 * Allocate a suitably sized bio, we add an extra
                 * bvec for bio_get/set_region().
                 */
                num_bvecs = (remaining / (PAGE_SIZE >> 9)) + 2;
                _bio_count++;
                bio = bio_set_alloc(&_bios, GFP_NOIO, num_bvecs);
                bio->bi_sector = where->sector + (where->count - remaining);
                bio->bi_bdev = where->bdev;
                bio->bi_end_io = endio;
                bio->bi_private = io;
                bio->bi_destructor = bio_dtr;
                bio_set_region(bio, region);

                /*
                 * Try and add as many pages as possible.
                 */
                while (remaining) {
                        dp->get_page(dp, &page, &len, &offset);
                        len = min(len, to_bytes(remaining));
                        if (!bio_add_page(bio, page, len, offset))
                                break;

                        offset = 0;
                        remaining -= to_sector(len);
                        dp->next_page(dp);
                }

                atomic_inc(&io->count);
                submit_bio(rw, bio);
        }
}

static void dispatch_io(int rw, unsigned int num_regions,
                        struct io_region *where, struct dpages *dp,
                        struct io *io, int sync)
{
        int i;
        struct dpages old_pages = *dp;

        if (sync)
                rw |= (1 << BIO_RW_SYNC);

        /*
         * For multiple regions we need to be careful to rewind
         * the dp object for each call to do_region.
         */
        for (i = 0; i < num_regions; i++) {
                *dp = old_pages;
                if (where[i].count)
                        do_region(rw, i, where + i, dp, io);
        }

        /*
         * Drop the extra refence that we were holding to avoid
         * the io being completed too early.
         */
        dec_count(io, 0, 0);
}

static int sync_io(unsigned int num_regions, struct io_region *where,
            int rw, struct dpages *dp, unsigned long *error_bits)
{
        struct io io;

        if (num_regions > 1 && rw != WRITE) {
                WARN_ON(1);
                return -EIO;
        }

        io.error = 0;
        atomic_set(&io.count, 1); /* see dispatch_io() */
        io.sleeper = current;

        dispatch_io(rw, num_regions, where, dp, &io, 1);

        while (1) {
                set_current_state(TASK_UNINTERRUPTIBLE);

                if (!atomic_read(&io.count) || signal_pending(current))
                        break;

                io_schedule();
        }
        set_current_state(TASK_RUNNING);

        if (atomic_read(&io.count))
                return -EINTR;

        *error_bits = io.error;
        return io.error ? -EIO : 0;
}

static int async_io(unsigned int num_regions, struct io_region *where, int rw,
             struct dpages *dp, io_notify_fn fn, void *context)
{
        struct io *io;

        if (num_regions > 1 && rw != WRITE) {
                WARN_ON(1);
                fn(1, context);
                return -EIO;
        }

        io = mempool_alloc(_io_pool, GFP_NOIO);
        io->error = 0;
        atomic_set(&io->count, 1); /* see dispatch_io() */
        io->sleeper = NULL;
        io->callback = fn;
        io->context = context;

        dispatch_io(rw, num_regions, where, dp, io, 0);
        return 0;
}

int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw,
               struct page_list *pl, unsigned int offset,
               unsigned long *error_bits)
{
        struct dpages dp;
        list_dp_init(&dp, pl, offset);
        return sync_io(num_regions, where, rw, &dp, error_bits);
}

int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where, int rw,
                    struct bio_vec *bvec, unsigned long *error_bits)
{
        struct dpages dp;
        bvec_dp_init(&dp, bvec);
        return sync_io(num_regions, where, rw, &dp, error_bits);
}

int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw,
                  void *data, unsigned long *error_bits)
{
        struct dpages dp;
        vm_dp_init(&dp, data);
        return sync_io(num_regions, where, rw, &dp, error_bits);
}

int dm_io_async(unsigned int num_regions, struct io_region *where, int rw,
                struct page_list *pl, unsigned int offset,
                io_notify_fn fn, void *context)
{
        struct dpages dp;
        list_dp_init(&dp, pl, offset);
        return async_io(num_regions, where, rw, &dp, fn, context);
}

int dm_io_async_bvec(unsigned int num_regions, struct io_region *where, int rw,
                     struct bio_vec *bvec, io_notify_fn fn, void *context)
{
        struct dpages dp;
        bvec_dp_init(&dp, bvec);
        return async_io(num_regions, where, rw, &dp, fn, context);
}

int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw,
                   void *data, io_notify_fn fn, void *context)
{
        struct dpages dp;
        vm_dp_init(&dp, data);
        return async_io(num_regions, where, rw, &dp, fn, context);
}

EXPORT_SYMBOL(dm_io_get);
EXPORT_SYMBOL(dm_io_put);
EXPORT_SYMBOL(dm_io_sync);
EXPORT_SYMBOL(dm_io_async);
EXPORT_SYMBOL(dm_io_sync_bvec);
EXPORT_SYMBOL(dm_io_async_bvec);
EXPORT_SYMBOL(dm_io_sync_vm);
EXPORT_SYMBOL(dm_io_async_vm);