partition-generic.c

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/*
 *  Code extracted from drivers/block/genhd.c
 *  Copyright (C) 1991-1998  Linus Torvalds
 *  Re-organised Feb 1998 Russell King
 *
 *  We now have independent partition support from the
 *  block drivers, which allows all the partition code to
 *  be grouped in one location, and it to be mostly self
 *  contained.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/ctype.h>
#include <linux/genhd.h>
#include <linux/blktrace_api.h>

#include "partitions/check.h"

#ifdef CONFIG_BLK_DEV_MD
extern void md_autodetect_dev(dev_t dev);
#endif
 
/*
 * disk_name() is used by partition check code and the genhd driver.
 * It formats the devicename of the indicated disk into
 * the supplied buffer (of size at least 32), and returns
 * a pointer to that same buffer (for convenience).
 */

char *disk_name(struct gendisk *hd, int partno, char *buf)
{
    if (!partno)
        snprintf(buf, BDEVNAME_SIZE, "%s", hd->disk_name);
    else if (isdigit(hd->disk_name[strlen(hd->disk_name)-1]))
        snprintf(buf, BDEVNAME_SIZE, "%sp%d", hd->disk_name, partno);
    else
        snprintf(buf, BDEVNAME_SIZE, "%s%d", hd->disk_name, partno);

    return buf;
}

const char *bdevname(struct block_device *bdev, char *buf)
{
    return disk_name(bdev->bd_disk, bdev->bd_part->partno, buf);
}

EXPORT_SYMBOL(bdevname);

/*
 * There's very little reason to use this, you should really
 * have a struct block_device just about everywhere and use
 * bdevname() instead.
 */
const char *__bdevname(dev_t dev, char *buffer)
{
    scnprintf(buffer, BDEVNAME_SIZE, "unknown-block(%u,%u)",
                MAJOR(dev), MINOR(dev));
    return buffer;
}

EXPORT_SYMBOL(__bdevname);

static ssize_t part_partition_show(struct device *dev,
                   struct device_attribute *attr, char *buf)
{
    struct hd_struct *p = dev_to_part(dev);

    return sprintf(buf, "%d\n", p->partno);
}

static ssize_t part_start_show(struct device *dev,
                   struct device_attribute *attr, char *buf)
{
    struct hd_struct *p = dev_to_part(dev);

    return sprintf(buf, "%llu\n",(unsigned long long)p->start_sect);
}

ssize_t part_size_show(struct device *dev,
               struct device_attribute *attr, char *buf)
{
    struct hd_struct *p = dev_to_part(dev);
    return sprintf(buf, "%llu\n",(unsigned long long)part_nr_sects_read(p));
}

static ssize_t part_ro_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
    struct hd_struct *p = dev_to_part(dev);
    return sprintf(buf, "%d\n", p->policy ? 1 : 0);
}

static ssize_t part_alignment_offset_show(struct device *dev,
                      struct device_attribute *attr, char *buf)
{
    struct hd_struct *p = dev_to_part(dev);
    return sprintf(buf, "%llu\n", (unsigned long long)p->alignment_offset);
}

static ssize_t part_discard_alignment_show(struct device *dev,
                       struct device_attribute *attr, char *buf)
{
    struct hd_struct *p = dev_to_part(dev);
    return sprintf(buf, "%u\n", p->discard_alignment);
}

ssize_t part_stat_show(struct device *dev,
               struct device_attribute *attr, char *buf)
{
    struct hd_struct *p = dev_to_part(dev);
    int cpu;

    cpu = part_stat_lock();
    part_round_stats(cpu, p);
    part_stat_unlock();
    return sprintf(buf,
        "%8lu %8lu %8llu %8u "
        "%8lu %8lu %8llu %8u "
        "%8u %8u %8u"
        "\n",
        part_stat_read(p, ios[READ]),
        part_stat_read(p, merges[READ]),
        (unsigned long long)part_stat_read(p, sectors[READ]),
        jiffies_to_msecs(part_stat_read(p, ticks[READ])),
        part_stat_read(p, ios[WRITE]),
        part_stat_read(p, merges[WRITE]),
        (unsigned long long)part_stat_read(p, sectors[WRITE]),
        jiffies_to_msecs(part_stat_read(p, ticks[WRITE])),
        part_in_flight(p),
        jiffies_to_msecs(part_stat_read(p, io_ticks)),
        jiffies_to_msecs(part_stat_read(p, time_in_queue)));
}

ssize_t part_inflight_show(struct device *dev,
            struct device_attribute *attr, char *buf)
{
    struct hd_struct *p = dev_to_part(dev);

    return sprintf(buf, "%8u %8u\n", atomic_read(&p->in_flight[0]),
        atomic_read(&p->in_flight[1]));
}

#ifdef CONFIG_FAIL_MAKE_REQUEST
ssize_t part_fail_show(struct device *dev,
               struct device_attribute *attr, char *buf)
{
    struct hd_struct *p = dev_to_part(dev);

    return sprintf(buf, "%d\n", p->make_it_fail);
}

ssize_t part_fail_store(struct device *dev,
            struct device_attribute *attr,
            const char *buf, size_t count)
{
    struct hd_struct *p = dev_to_part(dev);
    int i;

    if (count > 0 && sscanf(buf, "%d", &i) > 0)
        p->make_it_fail = (i == 0) ? 0 : 1;

    return count;
}
#endif

static DEVICE_ATTR(partition, S_IRUGO, part_partition_show, NULL);
static DEVICE_ATTR(start, S_IRUGO, part_start_show, NULL);
static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
static DEVICE_ATTR(ro, S_IRUGO, part_ro_show, NULL);
static DEVICE_ATTR(alignment_offset, S_IRUGO, part_alignment_offset_show, NULL);
static DEVICE_ATTR(discard_alignment, S_IRUGO, part_discard_alignment_show,
           NULL);
static DEVICE_ATTR(stat, S_IRUGO, part_stat_show, NULL);
static DEVICE_ATTR(inflight, S_IRUGO, part_inflight_show, NULL);
#ifdef CONFIG_FAIL_MAKE_REQUEST
static struct device_attribute dev_attr_fail =
    __ATTR(make-it-fail, S_IRUGO|S_IWUSR, part_fail_show, part_fail_store);
#endif

static struct attribute *part_attrs[] = {
    &dev_attr_partition.attr,
    &dev_attr_start.attr,
    &dev_attr_size.attr,
    &dev_attr_ro.attr,
    &dev_attr_alignment_offset.attr,
    &dev_attr_discard_alignment.attr,
    &dev_attr_stat.attr,
    &dev_attr_inflight.attr,
#ifdef CONFIG_FAIL_MAKE_REQUEST
    &dev_attr_fail.attr,
#endif
    NULL
};

static struct attribute_group part_attr_group = {
    .attrs = part_attrs,
};

static const struct attribute_group *part_attr_groups[] = {
    &part_attr_group,
#ifdef CONFIG_BLK_DEV_IO_TRACE
    &blk_trace_attr_group,
#endif
    NULL
};

static void part_release(struct device *dev)
{
    struct hd_struct *p = dev_to_part(dev);
    free_part_stats(p);
    free_part_info(p);
    kfree(p);
}

struct device_type part_type = {
    .name       = "partition",
    .groups     = part_attr_groups,
    .release    = part_release,
};

static void delete_partition_rcu_cb(struct rcu_head *head)
{
    struct hd_struct *part = container_of(head, struct hd_struct, rcu_head);

    part->start_sect = 0;
    part->nr_sects = 0;
    part_stat_set_all(part, 0);
    put_device(part_to_dev(part));
}

void __delete_partition(struct hd_struct *part)
{
    call_rcu(&part->rcu_head, delete_partition_rcu_cb);
}

void delete_partition(struct gendisk *disk, int partno)
{
    struct disk_part_tbl *ptbl = disk->part_tbl;
    struct hd_struct *part;

    if (partno >= ptbl->len)
        return;

    part = ptbl->part[partno];
    if (!part)
        return;

    blk_free_devt(part_devt(part));
    rcu_assign_pointer(ptbl->part[partno], NULL);
    rcu_assign_pointer(ptbl->last_lookup, NULL);
    kobject_put(part->holder_dir);
    device_del(part_to_dev(part));

    hd_struct_put(part);
}

static ssize_t whole_disk_show(struct device *dev,
                   struct device_attribute *attr, char *buf)
{
    return 0;
}
static DEVICE_ATTR(whole_disk, S_IRUSR | S_IRGRP | S_IROTH,
           whole_disk_show, NULL);

struct hd_struct *add_partition(struct gendisk *disk, int partno,
                sector_t start, sector_t len, int flags,
                struct partition_meta_info *info)
{
    struct hd_struct *p;
    dev_t devt = MKDEV(0, 0);
    struct device *ddev = disk_to_dev(disk);
    struct device *pdev;
    struct disk_part_tbl *ptbl;
    const char *dname;
    int err;

    err = disk_expand_part_tbl(disk, partno);
    if (err)
        return ERR_PTR(err);
    ptbl = disk->part_tbl;

    if (ptbl->part[partno])
        return ERR_PTR(-EBUSY);

    p = kzalloc(sizeof(*p), GFP_KERNEL);
    if (!p)
        return ERR_PTR(-EBUSY);

    if (!init_part_stats(p)) {
        err = -ENOMEM;
        goto out_free;
    }

    seqcount_init(&p->nr_sects_seq);
    pdev = part_to_dev(p);

    p->start_sect = start;
    p->alignment_offset =
        queue_limit_alignment_offset(&disk->queue->limits, start);
    p->discard_alignment =
        queue_limit_discard_alignment(&disk->queue->limits, start);
    p->nr_sects = len;
    p->partno = partno;
    p->policy = get_disk_ro(disk);

    if (info) {
        struct partition_meta_info *pinfo = alloc_part_info(disk);
        if (!pinfo)
            goto out_free_stats;
        memcpy(pinfo, info, sizeof(*info));
        p->info = pinfo;
    }

    dname = dev_name(ddev);
    if (isdigit(dname[strlen(dname) - 1]))
        dev_set_name(pdev, "%sp%d", dname, partno);
    else
        dev_set_name(pdev, "%s%d", dname, partno);

    device_initialize(pdev);
    pdev->class = &block_class;
    pdev->type = &part_type;
    pdev->parent = ddev;

    err = blk_alloc_devt(p, &devt);
    if (err)
        goto out_free_info;
    pdev->devt = devt;

    /* delay uevent until 'holders' subdir is created */
    dev_set_uevent_suppress(pdev, 1);
    err = device_add(pdev);
    if (err)
        goto out_put;

    err = -ENOMEM;
    p->holder_dir = kobject_create_and_add("holders", &pdev->kobj);
    if (!p->holder_dir)
        goto out_del;

    dev_set_uevent_suppress(pdev, 0);
    if (flags & ADDPART_FLAG_WHOLEDISK) {
        err = device_create_file(pdev, &dev_attr_whole_disk);
        if (err)
            goto out_del;
    }

    /* everything is up and running, commence */
    rcu_assign_pointer(ptbl->part[partno], p);

    /* suppress uevent if the disk suppresses it */
    if (!dev_get_uevent_suppress(ddev))
        kobject_uevent(&pdev->kobj, KOBJ_ADD);

    hd_ref_init(p);
    return p;

out_free_info:
    free_part_info(p);
out_free_stats:
    free_part_stats(p);
out_free:
    kfree(p);
    return ERR_PTR(err);
out_del:
    kobject_put(p->holder_dir);
    device_del(pdev);
out_put:
    put_device(pdev);
    blk_free_devt(devt);
    return ERR_PTR(err);
}

static bool disk_unlock_native_capacity(struct gendisk *disk)
{
    const struct block_device_operations *bdops = disk->fops;

    if (bdops->unlock_native_capacity &&
        !(disk->flags & GENHD_FL_NATIVE_CAPACITY)) {
        printk(KERN_CONT "enabling native capacity\n");
        bdops->unlock_native_capacity(disk);
        disk->flags |= GENHD_FL_NATIVE_CAPACITY;
        return true;
    } else {
        printk(KERN_CONT "truncated\n");
        return false;
    }
}

static int drop_partitions(struct gendisk *disk, struct block_device *bdev)
{
    struct disk_part_iter piter;
    struct hd_struct *part;
    int res;

    if (bdev->bd_part_count)
        return -EBUSY;
    res = invalidate_partition(disk, 0);
    if (res)
        return res;

    disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);
    while ((part = disk_part_iter_next(&piter)))
        delete_partition(disk, part->partno);
    disk_part_iter_exit(&piter);

    return 0;
}

int rescan_partitions(struct gendisk *disk, struct block_device *bdev)
{
    struct parsed_partitions *state = NULL;
    struct hd_struct *part;
    int p, highest, res;
rescan:
    if (state && !IS_ERR(state)) {
        kfree(state);
        state = NULL;
    }

    res = drop_partitions(disk, bdev);
    if (res)
        return res;

    if (disk->fops->revalidate_disk)
        disk->fops->revalidate_disk(disk);
    check_disk_size_change(disk, bdev);
    bdev->bd_invalidated = 0;
    if (!get_capacity(disk) || !(state = check_partition(disk, bdev)))
        return 0;
    if (IS_ERR(state)) {
        /*
         * I/O error reading the partition table.  If any
         * partition code tried to read beyond EOD, retry
         * after unlocking native capacity.
         */
        if (PTR_ERR(state) == -ENOSPC) {
            printk(KERN_WARNING "%s: partition table beyond EOD, ",
                   disk->disk_name);
            if (disk_unlock_native_capacity(disk))
                goto rescan;
        }
        return -EIO;
    }
    /*
     * If any partition code tried to read beyond EOD, try
     * unlocking native capacity even if partition table is
     * successfully read as we could be missing some partitions.
     */
    if (state->access_beyond_eod) {
        printk(KERN_WARNING
               "%s: partition table partially beyond EOD, ",
               disk->disk_name);
        if (disk_unlock_native_capacity(disk))
            goto rescan;
    }

    /* tell userspace that the media / partition table may have changed */
    kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);

    /* Detect the highest partition number and preallocate
     * disk->part_tbl.  This is an optimization and not strictly
     * necessary.
     */
    for (p = 1, highest = 0; p < state->limit; p++)
        if (state->parts[p].size)
            highest = p;

    disk_expand_part_tbl(disk, highest);

    /* add partitions */
    for (p = 1; p < state->limit; p++) {
        sector_t size, from;
        struct partition_meta_info *info = NULL;

        size = state->parts[p].size;
        if (!size)
            continue;

        from = state->parts[p].from;
        if (from >= get_capacity(disk)) {
            printk(KERN_WARNING
                   "%s: p%d start %llu is beyond EOD, ",
                   disk->disk_name, p, (unsigned long long) from);
            if (disk_unlock_native_capacity(disk))
                goto rescan;
            continue;
        }

        if (from + size > get_capacity(disk)) {
            printk(KERN_WARNING
                   "%s: p%d size %llu extends beyond EOD, ",
                   disk->disk_name, p, (unsigned long long) size);

            if (disk_unlock_native_capacity(disk)) {
                /* free state and restart */
                goto rescan;
            } else {
                /*
                 * we can not ignore partitions of broken tables
                 * created by for example camera firmware, but
                 * we limit them to the end of the disk to avoid
                 * creating invalid block devices
                 */
                size = get_capacity(disk) - from;
            }
        }

        if (state->parts[p].has_info)
            info = &state->parts[p].info;
        part = add_partition(disk, p, from, size,
                     state->parts[p].flags,
                     &state->parts[p].info);
        if (IS_ERR(part)) {
            printk(KERN_ERR " %s: p%d could not be added: %ld\n",
                   disk->disk_name, p, -PTR_ERR(part));
            continue;
        }
#ifdef CONFIG_BLK_DEV_MD
        if (state->parts[p].flags & ADDPART_FLAG_RAID)
            md_autodetect_dev(part_to_dev(part)->devt);
#endif
    }
    kfree(state);
    return 0;
}

int invalidate_partitions(struct gendisk *disk, struct block_device *bdev)
{
    int res;

    if (!bdev->bd_invalidated)
        return 0;

    res = drop_partitions(disk, bdev);
    if (res)
        return res;

    set_capacity(disk, 0);
    check_disk_size_change(disk, bdev);
    bdev->bd_invalidated = 0;
    /* tell userspace that the media / partition table may have changed */
    kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);

    return 0;
}

unsigned char *read_dev_sector(struct block_device *bdev, sector_t n, Sector *p)
{
    struct address_space *mapping = bdev->bd_inode->i_mapping;
    struct page *page;

    page = read_mapping_page(mapping, (pgoff_t)(n >> (PAGE_CACHE_SHIFT-9)),
                 NULL);
    if (!IS_ERR(page)) {
        if (PageError(page))
            goto fail;
        p->v = page;
        return (unsigned char *)page_address(page) +  ((n & ((1 << (PAGE_CACHE_SHIFT - 9)) - 1)) << 9);
fail:
        page_cache_release(page);
    }
    p->v = NULL;
    return NULL;
}

EXPORT_SYMBOL(read_dev_sector);