Linux-2.6.12-rc2

[mirror_ubuntu-artful-kernel.git] / drivers / md / dm-table.c

/*
 * Copyright (C) 2001 Sistina Software (UK) Limited.
 * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include "dm.h"

#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/namei.h>
#include <linux/ctype.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <asm/atomic.h>

#define MAX_DEPTH 16
#define NODE_SIZE L1_CACHE_BYTES
#define KEYS_PER_NODE (NODE_SIZE / sizeof(sector_t))
#define CHILDREN_PER_NODE (KEYS_PER_NODE + 1)

struct dm_table {
        atomic_t holders;

        /* btree table */
        unsigned int depth;
        unsigned int counts[MAX_DEPTH]; /* in nodes */
        sector_t *index[MAX_DEPTH];

        unsigned int num_targets;
        unsigned int num_allocated;
        sector_t *highs;
        struct dm_target *targets;

        /*
         * Indicates the rw permissions for the new logical
         * device.  This should be a combination of FMODE_READ
         * and FMODE_WRITE.
         */
        int mode;

        /* a list of devices used by this table */
        struct list_head devices;

        /*
         * These are optimistic limits taken from all the
         * targets, some targets will need smaller limits.
         */
        struct io_restrictions limits;

        /* events get handed up using this callback */
        void (*event_fn)(void *);
        void *event_context;
};

/*
 * Similar to ceiling(log_size(n))
 */
static unsigned int int_log(unsigned int n, unsigned int base)
{
        int result = 0;

        while (n > 1) {
                n = dm_div_up(n, base);
                result++;
        }

        return result;
}

/*
 * Returns the minimum that is _not_ zero, unless both are zero.
 */
#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))

/*
 * Combine two io_restrictions, always taking the lower value.
 */
static void combine_restrictions_low(struct io_restrictions *lhs,
                                     struct io_restrictions *rhs)
{
        lhs->max_sectors =
                min_not_zero(lhs->max_sectors, rhs->max_sectors);

        lhs->max_phys_segments =
                min_not_zero(lhs->max_phys_segments, rhs->max_phys_segments);

        lhs->max_hw_segments =
                min_not_zero(lhs->max_hw_segments, rhs->max_hw_segments);

        lhs->hardsect_size = max(lhs->hardsect_size, rhs->hardsect_size);

        lhs->max_segment_size =
                min_not_zero(lhs->max_segment_size, rhs->max_segment_size);

        lhs->seg_boundary_mask =
                min_not_zero(lhs->seg_boundary_mask, rhs->seg_boundary_mask);
}

/*
 * Calculate the index of the child node of the n'th node k'th key.
 */
static inline unsigned int get_child(unsigned int n, unsigned int k)
{
        return (n * CHILDREN_PER_NODE) + k;
}

/*
 * Return the n'th node of level l from table t.
 */
static inline sector_t *get_node(struct dm_table *t,
                                 unsigned int l, unsigned int n)
{
        return t->index[l] + (n * KEYS_PER_NODE);
}

/*
 * Return the highest key that you could lookup from the n'th
 * node on level l of the btree.
 */
static sector_t high(struct dm_table *t, unsigned int l, unsigned int n)
{
        for (; l < t->depth - 1; l++)
                n = get_child(n, CHILDREN_PER_NODE - 1);

        if (n >= t->counts[l])
                return (sector_t) - 1;

        return get_node(t, l, n)[KEYS_PER_NODE - 1];
}

/*
 * Fills in a level of the btree based on the highs of the level
 * below it.
 */
static int setup_btree_index(unsigned int l, struct dm_table *t)
{
        unsigned int n, k;
        sector_t *node;

        for (n = 0U; n < t->counts[l]; n++) {
                node = get_node(t, l, n);

                for (k = 0U; k < KEYS_PER_NODE; k++)
                        node[k] = high(t, l + 1, get_child(n, k));
        }

        return 0;
}

void *dm_vcalloc(unsigned long nmemb, unsigned long elem_size)
{
        unsigned long size;
        void *addr;

        /*
         * Check that we're not going to overflow.
         */
        if (nmemb > (ULONG_MAX / elem_size))
                return NULL;

        size = nmemb * elem_size;
        addr = vmalloc(size);
        if (addr)
                memset(addr, 0, size);

        return addr;
}

/*
 * highs, and targets are managed as dynamic arrays during a
 * table load.
 */
static int alloc_targets(struct dm_table *t, unsigned int num)
{
        sector_t *n_highs;
        struct dm_target *n_targets;
        int n = t->num_targets;

        /*
         * Allocate both the target array and offset array at once.
         */
        n_highs = (sector_t *) dm_vcalloc(num, sizeof(struct dm_target) +
                                          sizeof(sector_t));
        if (!n_highs)
                return -ENOMEM;

        n_targets = (struct dm_target *) (n_highs + num);

        if (n) {
                memcpy(n_highs, t->highs, sizeof(*n_highs) * n);
                memcpy(n_targets, t->targets, sizeof(*n_targets) * n);
        }

        memset(n_highs + n, -1, sizeof(*n_highs) * (num - n));
        vfree(t->highs);

        t->num_allocated = num;
        t->highs = n_highs;
        t->targets = n_targets;

        return 0;
}

int dm_table_create(struct dm_table **result, int mode, unsigned num_targets)
{
        struct dm_table *t = kmalloc(sizeof(*t), GFP_KERNEL);

        if (!t)
                return -ENOMEM;

        memset(t, 0, sizeof(*t));
        INIT_LIST_HEAD(&t->devices);
        atomic_set(&t->holders, 1);

        if (!num_targets)
                num_targets = KEYS_PER_NODE;

        num_targets = dm_round_up(num_targets, KEYS_PER_NODE);

        if (alloc_targets(t, num_targets)) {
                kfree(t);
                t = NULL;
                return -ENOMEM;
        }

        t->mode = mode;
        *result = t;
        return 0;
}

static void free_devices(struct list_head *devices)
{
        struct list_head *tmp, *next;

        for (tmp = devices->next; tmp != devices; tmp = next) {
                struct dm_dev *dd = list_entry(tmp, struct dm_dev, list);
                next = tmp->next;
                kfree(dd);
        }
}

void table_destroy(struct dm_table *t)
{
        unsigned int i;

        /* free the indexes (see dm_table_complete) */
        if (t->depth >= 2)
                vfree(t->index[t->depth - 2]);

        /* free the targets */
        for (i = 0; i < t->num_targets; i++) {
                struct dm_target *tgt = t->targets + i;

                if (tgt->type->dtr)
                        tgt->type->dtr(tgt);

                dm_put_target_type(tgt->type);
        }

        vfree(t->highs);

        /* free the device list */
        if (t->devices.next != &t->devices) {
                DMWARN("devices still present during destroy: "
                       "dm_table_remove_device calls missing");

                free_devices(&t->devices);
        }

        kfree(t);
}

void dm_table_get(struct dm_table *t)
{
        atomic_inc(&t->holders);
}

void dm_table_put(struct dm_table *t)
{
        if (!t)
                return;

        if (atomic_dec_and_test(&t->holders))
                table_destroy(t);
}

/*
 * Checks to see if we need to extend highs or targets.
 */
static inline int check_space(struct dm_table *t)
{
        if (t->num_targets >= t->num_allocated)
                return alloc_targets(t, t->num_allocated * 2);

        return 0;
}

/*
 * Convert a device path to a dev_t.
 */
static int lookup_device(const char *path, dev_t *dev)
{
        int r;
        struct nameidata nd;
        struct inode *inode;

        if ((r = path_lookup(path, LOOKUP_FOLLOW, &nd)))
                return r;

        inode = nd.dentry->d_inode;
        if (!inode) {
                r = -ENOENT;
                goto out;
        }

        if (!S_ISBLK(inode->i_mode)) {
                r = -ENOTBLK;
                goto out;
        }

        *dev = inode->i_rdev;

 out:
        path_release(&nd);
        return r;
}

/*
 * See if we've already got a device in the list.
 */
static struct dm_dev *find_device(struct list_head *l, dev_t dev)
{
        struct dm_dev *dd;

        list_for_each_entry (dd, l, list)
                if (dd->bdev->bd_dev == dev)
                        return dd;

        return NULL;
}

/*
 * Open a device so we can use it as a map destination.
 */
static int open_dev(struct dm_dev *d, dev_t dev)
{
        static char *_claim_ptr = "I belong to device-mapper";
        struct block_device *bdev;

        int r;

        if (d->bdev)
                BUG();

        bdev = open_by_devnum(dev, d->mode);
        if (IS_ERR(bdev))
                return PTR_ERR(bdev);
        r = bd_claim(bdev, _claim_ptr);
        if (r)
                blkdev_put(bdev);
        else
                d->bdev = bdev;
        return r;
}

/*
 * Close a device that we've been using.
 */
static void close_dev(struct dm_dev *d)
{
        if (!d->bdev)
                return;

        bd_release(d->bdev);
        blkdev_put(d->bdev);
        d->bdev = NULL;
}

/*
 * If possible (ie. blk_size[major] is set), this checks an area
 * of a destination device is valid.
 */
static int check_device_area(struct dm_dev *dd, sector_t start, sector_t len)
{
        sector_t dev_size;
        dev_size = dd->bdev->bd_inode->i_size >> SECTOR_SHIFT;
        return ((start < dev_size) && (len <= (dev_size - start)));
}

/*
 * This upgrades the mode on an already open dm_dev.  Being
 * careful to leave things as they were if we fail to reopen the
 * device.
 */
static int upgrade_mode(struct dm_dev *dd, int new_mode)
{
        int r;
        struct dm_dev dd_copy;
        dev_t dev = dd->bdev->bd_dev;

        dd_copy = *dd;

        dd->mode |= new_mode;
        dd->bdev = NULL;
        r = open_dev(dd, dev);
        if (!r)
                close_dev(&dd_copy);
        else
                *dd = dd_copy;

        return r;
}

/*
 * Add a device to the list, or just increment the usage count if
 * it's already present.
 */
static int __table_get_device(struct dm_table *t, struct dm_target *ti,
                              const char *path, sector_t start, sector_t len,
                              int mode, struct dm_dev **result)
{
        int r;
        dev_t dev;
        struct dm_dev *dd;
        unsigned int major, minor;

        if (!t)
                BUG();

        if (sscanf(path, "%u:%u", &major, &minor) == 2) {
                /* Extract the major/minor numbers */
                dev = MKDEV(major, minor);
                if (MAJOR(dev) != major || MINOR(dev) != minor)
                        return -EOVERFLOW;
        } else {
                /* convert the path to a device */
                if ((r = lookup_device(path, &dev)))
                        return r;
        }

        dd = find_device(&t->devices, dev);
        if (!dd) {
                dd = kmalloc(sizeof(*dd), GFP_KERNEL);
                if (!dd)
                        return -ENOMEM;

                dd->mode = mode;
                dd->bdev = NULL;

                if ((r = open_dev(dd, dev))) {
                        kfree(dd);
                        return r;
                }

                format_dev_t(dd->name, dev);

                atomic_set(&dd->count, 0);
                list_add(&dd->list, &t->devices);

        } else if (dd->mode != (mode | dd->mode)) {
                r = upgrade_mode(dd, mode);
                if (r)
                        return r;
        }
        atomic_inc(&dd->count);

        if (!check_device_area(dd, start, len)) {
                DMWARN("device %s too small for target", path);
                dm_put_device(ti, dd);
                return -EINVAL;
        }

        *result = dd;

        return 0;
}


int dm_get_device(struct dm_target *ti, const char *path, sector_t start,
                  sector_t len, int mode, struct dm_dev **result)
{
        int r = __table_get_device(ti->table, ti, path,
                                   start, len, mode, result);
        if (!r) {
                request_queue_t *q = bdev_get_queue((*result)->bdev);
                struct io_restrictions *rs = &ti->limits;

                /*
                 * Combine the device limits low.
                 *
                 * FIXME: if we move an io_restriction struct
                 *        into q this would just be a call to
                 *        combine_restrictions_low()
                 */
                rs->max_sectors =
                        min_not_zero(rs->max_sectors, q->max_sectors);

                /* FIXME: Device-Mapper on top of RAID-0 breaks because DM
                 *        currently doesn't honor MD's merge_bvec_fn routine.
                 *        In this case, we'll force DM to use PAGE_SIZE or
                 *        smaller I/O, just to be safe. A better fix is in the
                 *        works, but add this for the time being so it will at
                 *        least operate correctly.
                 */
                if (q->merge_bvec_fn)
                        rs->max_sectors =
                                min_not_zero(rs->max_sectors,
                                             (unsigned short)(PAGE_SIZE >> 9));

                rs->max_phys_segments =
                        min_not_zero(rs->max_phys_segments,
                                     q->max_phys_segments);

                rs->max_hw_segments =
                        min_not_zero(rs->max_hw_segments, q->max_hw_segments);

                rs->hardsect_size = max(rs->hardsect_size, q->hardsect_size);

                rs->max_segment_size =
                        min_not_zero(rs->max_segment_size, q->max_segment_size);

                rs->seg_boundary_mask =
                        min_not_zero(rs->seg_boundary_mask,
                                     q->seg_boundary_mask);
        }

        return r;
}

/*
 * Decrement a devices use count and remove it if necessary.
 */
void dm_put_device(struct dm_target *ti, struct dm_dev *dd)
{
        if (atomic_dec_and_test(&dd->count)) {
                close_dev(dd);
                list_del(&dd->list);
                kfree(dd);
        }
}

/*
 * Checks to see if the target joins onto the end of the table.
 */
static int adjoin(struct dm_table *table, struct dm_target *ti)
{
        struct dm_target *prev;

        if (!table->num_targets)
                return !ti->begin;

        prev = &table->targets[table->num_targets - 1];
        return (ti->begin == (prev->begin + prev->len));
}

/*
 * Used to dynamically allocate the arg array.
 */
static char **realloc_argv(unsigned *array_size, char **old_argv)
{
        char **argv;
        unsigned new_size;

        new_size = *array_size ? *array_size * 2 : 64;
        argv = kmalloc(new_size * sizeof(*argv), GFP_KERNEL);
        if (argv) {
                memcpy(argv, old_argv, *array_size * sizeof(*argv));
                *array_size = new_size;
        }

        kfree(old_argv);
        return argv;
}

/*
 * Destructively splits up the argument list to pass to ctr.
 */
int dm_split_args(int *argc, char ***argvp, char *input)
{
        char *start, *end = input, *out, **argv = NULL;
        unsigned array_size = 0;

        *argc = 0;
        argv = realloc_argv(&array_size, argv);
        if (!argv)
                return -ENOMEM;

        while (1) {
                start = end;

                /* Skip whitespace */
                while (*start && isspace(*start))
                        start++;

                if (!*start)
                        break;  /* success, we hit the end */

                /* 'out' is used to remove any back-quotes */
                end = out = start;
                while (*end) {
                        /* Everything apart from '\0' can be quoted */
                        if (*end == '\\' && *(end + 1)) {
                                *out++ = *(end + 1);
                                end += 2;
                                continue;
                        }

                        if (isspace(*end))
                                break;  /* end of token */

                        *out++ = *end++;
                }

                /* have we already filled the array ? */
                if ((*argc + 1) > array_size) {
                        argv = realloc_argv(&array_size, argv);
                        if (!argv)
                                return -ENOMEM;
                }

                /* we know this is whitespace */
                if (*end)
                        end++;

                /* terminate the string and put it in the array */
                *out = '\0';
                argv[*argc] = start;
                (*argc)++;
        }

        *argvp = argv;
        return 0;
}

static void check_for_valid_limits(struct io_restrictions *rs)
{
        if (!rs->max_sectors)
                rs->max_sectors = MAX_SECTORS;
        if (!rs->max_phys_segments)
                rs->max_phys_segments = MAX_PHYS_SEGMENTS;
        if (!rs->max_hw_segments)
                rs->max_hw_segments = MAX_HW_SEGMENTS;
        if (!rs->hardsect_size)
                rs->hardsect_size = 1 << SECTOR_SHIFT;
        if (!rs->max_segment_size)
                rs->max_segment_size = MAX_SEGMENT_SIZE;
        if (!rs->seg_boundary_mask)
                rs->seg_boundary_mask = -1;
}

int dm_table_add_target(struct dm_table *t, const char *type,
                        sector_t start, sector_t len, char *params)
{
        int r = -EINVAL, argc;
        char **argv;
        struct dm_target *tgt;

        if ((r = check_space(t)))
                return r;

        tgt = t->targets + t->num_targets;
        memset(tgt, 0, sizeof(*tgt));

        if (!len) {
                tgt->error = "zero-length target";
                DMERR("%s", tgt->error);
                return -EINVAL;
        }

        tgt->type = dm_get_target_type(type);
        if (!tgt->type) {
                tgt->error = "unknown target type";
                DMERR("%s", tgt->error);
                return -EINVAL;
        }

        tgt->table = t;
        tgt->begin = start;
        tgt->len = len;
        tgt->error = "Unknown error";

        /*
         * Does this target adjoin the previous one ?
         */
        if (!adjoin(t, tgt)) {
                tgt->error = "Gap in table";
                r = -EINVAL;
                goto bad;
        }

        r = dm_split_args(&argc, &argv, params);
        if (r) {
                tgt->error = "couldn't split parameters (insufficient memory)";
                goto bad;
        }

        r = tgt->type->ctr(tgt, argc, argv);
        kfree(argv);
        if (r)
                goto bad;

        t->highs[t->num_targets++] = tgt->begin + tgt->len - 1;

        /* FIXME: the plan is to combine high here and then have
         * the merge fn apply the target level restrictions. */
        combine_restrictions_low(&t->limits, &tgt->limits);
        return 0;

 bad:
        DMERR("%s", tgt->error);
        dm_put_target_type(tgt->type);
        return r;
}

static int setup_indexes(struct dm_table *t)
{
        int i;
        unsigned int total = 0;
        sector_t *indexes;

        /* allocate the space for *all* the indexes */
        for (i = t->depth - 2; i >= 0; i--) {
                t->counts[i] = dm_div_up(t->counts[i + 1], CHILDREN_PER_NODE);
                total += t->counts[i];
        }

        indexes = (sector_t *) dm_vcalloc(total, (unsigned long) NODE_SIZE);
        if (!indexes)
                return -ENOMEM;

        /* set up internal nodes, bottom-up */
        for (i = t->depth - 2, total = 0; i >= 0; i--) {
                t->index[i] = indexes;
                indexes += (KEYS_PER_NODE * t->counts[i]);
                setup_btree_index(i, t);
        }

        return 0;
}

/*
 * Builds the btree to index the map.
 */
int dm_table_complete(struct dm_table *t)
{
        int r = 0;
        unsigned int leaf_nodes;

        check_for_valid_limits(&t->limits);

        /* how many indexes will the btree have ? */
        leaf_nodes = dm_div_up(t->num_targets, KEYS_PER_NODE);
        t->depth = 1 + int_log(leaf_nodes, CHILDREN_PER_NODE);

        /* leaf layer has already been set up */
        t->counts[t->depth - 1] = leaf_nodes;
        t->index[t->depth - 1] = t->highs;

        if (t->depth >= 2)
                r = setup_indexes(t);

        return r;
}

static DECLARE_MUTEX(_event_lock);
void dm_table_event_callback(struct dm_table *t,
                             void (*fn)(void *), void *context)
{
        down(&_event_lock);
        t->event_fn = fn;
        t->event_context = context;
        up(&_event_lock);
}

void dm_table_event(struct dm_table *t)
{
        /*
         * You can no longer call dm_table_event() from interrupt
         * context, use a bottom half instead.
         */
        BUG_ON(in_interrupt());

        down(&_event_lock);
        if (t->event_fn)
                t->event_fn(t->event_context);
        up(&_event_lock);
}

sector_t dm_table_get_size(struct dm_table *t)
{
        return t->num_targets ? (t->highs[t->num_targets - 1] + 1) : 0;
}

struct dm_target *dm_table_get_target(struct dm_table *t, unsigned int index)
{
        if (index > t->num_targets)
                return NULL;

        return t->targets + index;
}

/*
 * Search the btree for the correct target.
 */
struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector)
{
        unsigned int l, n = 0, k = 0;
        sector_t *node;

        for (l = 0; l < t->depth; l++) {
                n = get_child(n, k);
                node = get_node(t, l, n);

                for (k = 0; k < KEYS_PER_NODE; k++)
                        if (node[k] >= sector)
                                break;
        }

        return &t->targets[(KEYS_PER_NODE * n) + k];
}

void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q)
{
        /*
         * Make sure we obey the optimistic sub devices
         * restrictions.
         */
        blk_queue_max_sectors(q, t->limits.max_sectors);
        q->max_phys_segments = t->limits.max_phys_segments;
        q->max_hw_segments = t->limits.max_hw_segments;
        q->hardsect_size = t->limits.hardsect_size;
        q->max_segment_size = t->limits.max_segment_size;
        q->seg_boundary_mask = t->limits.seg_boundary_mask;
}

unsigned int dm_table_get_num_targets(struct dm_table *t)
{
        return t->num_targets;
}

struct list_head *dm_table_get_devices(struct dm_table *t)
{
        return &t->devices;
}

int dm_table_get_mode(struct dm_table *t)
{
        return t->mode;
}

static void suspend_targets(struct dm_table *t, unsigned postsuspend)
{
        int i = t->num_targets;
        struct dm_target *ti = t->targets;

        while (i--) {
                if (postsuspend) {
                        if (ti->type->postsuspend)
                                ti->type->postsuspend(ti);
                } else if (ti->type->presuspend)
                        ti->type->presuspend(ti);

                ti++;
        }
}

void dm_table_presuspend_targets(struct dm_table *t)
{
        return suspend_targets(t, 0);
}

void dm_table_postsuspend_targets(struct dm_table *t)
{
        return suspend_targets(t, 1);
}

void dm_table_resume_targets(struct dm_table *t)
{
        int i;

        for (i = 0; i < t->num_targets; i++) {
                struct dm_target *ti = t->targets + i;

                if (ti->type->resume)
                        ti->type->resume(ti);
        }
}

int dm_table_any_congested(struct dm_table *t, int bdi_bits)
{
        struct list_head *d, *devices;
        int r = 0;

        devices = dm_table_get_devices(t);
        for (d = devices->next; d != devices; d = d->next) {
                struct dm_dev *dd = list_entry(d, struct dm_dev, list);
                request_queue_t *q = bdev_get_queue(dd->bdev);
                r |= bdi_congested(&q->backing_dev_info, bdi_bits);
        }

        return r;
}

void dm_table_unplug_all(struct dm_table *t)
{
        struct list_head *d, *devices = dm_table_get_devices(t);

        for (d = devices->next; d != devices; d = d->next) {
                struct dm_dev *dd = list_entry(d, struct dm_dev, list);
                request_queue_t *q = bdev_get_queue(dd->bdev);

                if (q->unplug_fn)
                        q->unplug_fn(q);
        }
}

int dm_table_flush_all(struct dm_table *t)
{
        struct list_head *d, *devices = dm_table_get_devices(t);
        int ret = 0;

        for (d = devices->next; d != devices; d = d->next) {
                struct dm_dev *dd = list_entry(d, struct dm_dev, list);
                request_queue_t *q = bdev_get_queue(dd->bdev);
                int err;

                if (!q->issue_flush_fn)
                        err = -EOPNOTSUPP;
                else
                        err = q->issue_flush_fn(q, dd->bdev->bd_disk, NULL);

                if (!ret)
                        ret = err;
        }

        return ret;
}

EXPORT_SYMBOL(dm_vcalloc);
EXPORT_SYMBOL(dm_get_device);
EXPORT_SYMBOL(dm_put_device);
EXPORT_SYMBOL(dm_table_event);
EXPORT_SYMBOL(dm_table_get_mode);
EXPORT_SYMBOL(dm_table_put);
EXPORT_SYMBOL(dm_table_get);
EXPORT_SYMBOL(dm_table_unplug_all);
EXPORT_SYMBOL(dm_table_flush_all);