super.c

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/*
 * fs/logfs/super.c
 *
 * As should be obvious for Linux kernel code, license is GPLv2
 *
 * Copyright (c) 2005-2008 Joern Engel <[email protected]>
 *
 * Generally contains mount/umount code and also serves as a dump area for
 * any functions that don't fit elsewhere and neither justify a file of their
 * own.
 */
#include "logfs.h"
#include <linux/bio.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/mtd/mtd.h>
#include <linux/statfs.h>
#include <linux/buffer_head.h>

static DEFINE_MUTEX(emergency_mutex);
static struct page *emergency_page;

struct page *emergency_read_begin(struct address_space *mapping, pgoff_t index)
{
    filler_t *filler = (filler_t *)mapping->a_ops->readpage;
    struct page *page;
    int err;

    page = read_cache_page(mapping, index, filler, NULL);
    if (page)
        return page;

    /* No more pages available, switch to emergency page */
    printk(KERN_INFO"Logfs: Using emergency page\n");
    mutex_lock(&emergency_mutex);
    err = filler(NULL, emergency_page);
    if (err) {
        mutex_unlock(&emergency_mutex);
        printk(KERN_EMERG"Logfs: Error reading emergency page\n");
        return ERR_PTR(err);
    }
    return emergency_page;
}

void emergency_read_end(struct page *page)
{
    if (page == emergency_page)
        mutex_unlock(&emergency_mutex);
    else
        page_cache_release(page);
}

static void dump_segfile(struct super_block *sb)
{
    struct logfs_super *super = logfs_super(sb);
    struct logfs_segment_entry se;
    u32 segno;

    for (segno = 0; segno < super->s_no_segs; segno++) {
        logfs_get_segment_entry(sb, segno, &se);
        printk("%3x: %6x %8x", segno, be32_to_cpu(se.ec_level),
                be32_to_cpu(se.valid));
        if (++segno < super->s_no_segs) {
            logfs_get_segment_entry(sb, segno, &se);
            printk(" %6x %8x", be32_to_cpu(se.ec_level),
                    be32_to_cpu(se.valid));
        }
        if (++segno < super->s_no_segs) {
            logfs_get_segment_entry(sb, segno, &se);
            printk(" %6x %8x", be32_to_cpu(se.ec_level),
                    be32_to_cpu(se.valid));
        }
        if (++segno < super->s_no_segs) {
            logfs_get_segment_entry(sb, segno, &se);
            printk(" %6x %8x", be32_to_cpu(se.ec_level),
                    be32_to_cpu(se.valid));
        }
        printk("\n");
    }
}

/*
 * logfs_crash_dump - dump debug information to device
 *
 * The LogFS superblock only occupies part of a segment.  This function will
 * write as much debug information as it can gather into the spare space.
 */
void logfs_crash_dump(struct super_block *sb)
{
    dump_segfile(sb);
}

/*
 * FIXME: There should be a reserve for root, similar to ext2.
 */
int logfs_statfs(struct dentry *dentry, struct kstatfs *stats)
{
    struct super_block *sb = dentry->d_sb;
    struct logfs_super *super = logfs_super(sb);

    stats->f_type       = LOGFS_MAGIC_U32;
    stats->f_bsize      = sb->s_blocksize;
    stats->f_blocks     = super->s_size >> LOGFS_BLOCK_BITS >> 3;
    stats->f_bfree      = super->s_free_bytes >> sb->s_blocksize_bits;
    stats->f_bavail     = super->s_free_bytes >> sb->s_blocksize_bits;
    stats->f_files      = 0;
    stats->f_ffree      = 0;
    stats->f_namelen    = LOGFS_MAX_NAMELEN;
    return 0;
}

static int logfs_sb_set(struct super_block *sb, void *_super)
{
    struct logfs_super *super = _super;

    sb->s_fs_info = super;
    sb->s_mtd = super->s_mtd;
    sb->s_bdev = super->s_bdev;
#ifdef CONFIG_BLOCK
    if (sb->s_bdev)
        sb->s_bdi = &bdev_get_queue(sb->s_bdev)->backing_dev_info;
#endif
#ifdef CONFIG_MTD
    if (sb->s_mtd)
        sb->s_bdi = sb->s_mtd->backing_dev_info;
#endif
    return 0;
}

static int logfs_sb_test(struct super_block *sb, void *_super)
{
    struct logfs_super *super = _super;
    struct mtd_info *mtd = super->s_mtd;

    if (mtd && sb->s_mtd == mtd)
        return 1;
    if (super->s_bdev && sb->s_bdev == super->s_bdev)
        return 1;
    return 0;
}

static void set_segment_header(struct logfs_segment_header *sh, u8 type,
        u8 level, u32 segno, u32 ec)
{
    sh->pad = 0;
    sh->type = type;
    sh->level = level;
    sh->segno = cpu_to_be32(segno);
    sh->ec = cpu_to_be32(ec);
    sh->gec = cpu_to_be64(segno);
    sh->crc = logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4);
}

static void logfs_write_ds(struct super_block *sb, struct logfs_disk_super *ds,
        u32 segno, u32 ec)
{
    struct logfs_super *super = logfs_super(sb);
    struct logfs_segment_header *sh = &ds->ds_sh;
    int i;

    memset(ds, 0, sizeof(*ds));
    set_segment_header(sh, SEG_SUPER, 0, segno, ec);

    ds->ds_ifile_levels = super->s_ifile_levels;
    ds->ds_iblock_levels    = super->s_iblock_levels;
    ds->ds_data_levels  = super->s_data_levels; /* XXX: Remove */
    ds->ds_segment_shift    = super->s_segshift;
    ds->ds_block_shift  = sb->s_blocksize_bits;
    ds->ds_write_shift  = super->s_writeshift;
    ds->ds_filesystem_size  = cpu_to_be64(super->s_size);
    ds->ds_segment_size = cpu_to_be32(super->s_segsize);
    ds->ds_bad_seg_reserve  = cpu_to_be32(super->s_bad_seg_reserve);
    ds->ds_feature_incompat = cpu_to_be64(super->s_feature_incompat);
    ds->ds_feature_ro_compat= cpu_to_be64(super->s_feature_ro_compat);
    ds->ds_feature_compat   = cpu_to_be64(super->s_feature_compat);
    ds->ds_feature_flags    = cpu_to_be64(super->s_feature_flags);
    ds->ds_root_reserve = cpu_to_be64(super->s_root_reserve);
    ds->ds_speed_reserve    = cpu_to_be64(super->s_speed_reserve);
    journal_for_each(i)
        ds->ds_journal_seg[i] = cpu_to_be32(super->s_journal_seg[i]);
    ds->ds_magic        = cpu_to_be64(LOGFS_MAGIC);
    ds->ds_crc = logfs_crc32(ds, sizeof(*ds),
            LOGFS_SEGMENT_HEADERSIZE + 12);
}

static int write_one_sb(struct super_block *sb,
        struct page *(*find_sb)(struct super_block *sb, u64 *ofs))
{
    struct logfs_super *super = logfs_super(sb);
    struct logfs_disk_super *ds;
    struct logfs_segment_entry se;
    struct page *page;
    u64 ofs;
    u32 ec, segno;
    int err;

    page = find_sb(sb, &ofs);
    if (!page)
        return -EIO;
    ds = page_address(page);
    segno = seg_no(sb, ofs);
    logfs_get_segment_entry(sb, segno, &se);
    ec = be32_to_cpu(se.ec_level) >> 4;
    ec++;
    logfs_set_segment_erased(sb, segno, ec, 0);
    logfs_write_ds(sb, ds, segno, ec);
    err = super->s_devops->write_sb(sb, page);
    page_cache_release(page);
    return err;
}

int logfs_write_sb(struct super_block *sb)
{
    struct logfs_super *super = logfs_super(sb);
    int err;

    /* First superblock */
    err = write_one_sb(sb, super->s_devops->find_first_sb);
    if (err)
        return err;

    /* Last superblock */
    err = write_one_sb(sb, super->s_devops->find_last_sb);
    if (err)
        return err;
    return 0;
}

static int ds_cmp(const void *ds0, const void *ds1)
{
    size_t len = sizeof(struct logfs_disk_super);

    /* We know the segment headers differ, so ignore them */
    len -= LOGFS_SEGMENT_HEADERSIZE;
    ds0 += LOGFS_SEGMENT_HEADERSIZE;
    ds1 += LOGFS_SEGMENT_HEADERSIZE;
    return memcmp(ds0, ds1, len);
}

static int logfs_recover_sb(struct super_block *sb)
{
    struct logfs_super *super = logfs_super(sb);
    struct logfs_disk_super _ds0, *ds0 = &_ds0;
    struct logfs_disk_super _ds1, *ds1 = &_ds1;
    int err, valid0, valid1;

    /* read first superblock */
    err = wbuf_read(sb, super->s_sb_ofs[0], sizeof(*ds0), ds0);
    if (err)
        return err;
    /* read last superblock */
    err = wbuf_read(sb, super->s_sb_ofs[1], sizeof(*ds1), ds1);
    if (err)
        return err;
    valid0 = logfs_check_ds(ds0) == 0;
    valid1 = logfs_check_ds(ds1) == 0;

    if (!valid0 && valid1) {
        printk(KERN_INFO"First superblock is invalid - fixing.\n");
        return write_one_sb(sb, super->s_devops->find_first_sb);
    }
    if (valid0 && !valid1) {
        printk(KERN_INFO"Last superblock is invalid - fixing.\n");
        return write_one_sb(sb, super->s_devops->find_last_sb);
    }
    if (valid0 && valid1 && ds_cmp(ds0, ds1)) {
        printk(KERN_INFO"Superblocks don't match - fixing.\n");
        return logfs_write_sb(sb);
    }
    /* If neither is valid now, something's wrong.  Didn't we properly
     * check them before?!? */
    BUG_ON(!valid0 && !valid1);
    return 0;
}

static int logfs_make_writeable(struct super_block *sb)
{
    int err;

    err = logfs_open_segfile(sb);
    if (err)
        return err;

    /* Repair any broken superblock copies */
    err = logfs_recover_sb(sb);
    if (err)
        return err;

    /* Check areas for trailing unaccounted data */
    err = logfs_check_areas(sb);
    if (err)
        return err;

    /* Do one GC pass before any data gets dirtied */
    logfs_gc_pass(sb);

    /* after all initializations are done, replay the journal
     * for rw-mounts, if necessary */
    err = logfs_replay_journal(sb);
    if (err)
        return err;

    return 0;
}

static int logfs_get_sb_final(struct super_block *sb)
{
    struct logfs_super *super = logfs_super(sb);
    struct inode *rootdir;
    int err;

    /* root dir */
    rootdir = logfs_iget(sb, LOGFS_INO_ROOT);
    if (IS_ERR(rootdir))
        goto fail;

    sb->s_root = d_make_root(rootdir);
    if (!sb->s_root)
        goto fail;

    /* at that point we know that ->put_super() will be called */
    super->s_erase_page = alloc_pages(GFP_KERNEL, 0);
    if (!super->s_erase_page)
        return -ENOMEM;
    memset(page_address(super->s_erase_page), 0xFF, PAGE_SIZE);

    /* FIXME: check for read-only mounts */
    err = logfs_make_writeable(sb);
    if (err) {
        __free_page(super->s_erase_page);
        return err;
    }

    log_super("LogFS: Finished mounting\n");
    return 0;

fail:
    iput(super->s_master_inode);
    iput(super->s_segfile_inode);
    iput(super->s_mapping_inode);
    return -EIO;
}

int logfs_check_ds(struct logfs_disk_super *ds)
{
    struct logfs_segment_header *sh = &ds->ds_sh;

    if (ds->ds_magic != cpu_to_be64(LOGFS_MAGIC))
        return -EINVAL;
    if (sh->crc != logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4))
        return -EINVAL;
    if (ds->ds_crc != logfs_crc32(ds, sizeof(*ds),
                LOGFS_SEGMENT_HEADERSIZE + 12))
        return -EINVAL;
    return 0;
}

static struct page *find_super_block(struct super_block *sb)
{
    struct logfs_super *super = logfs_super(sb);
    struct page *first, *last;

    first = super->s_devops->find_first_sb(sb, &super->s_sb_ofs[0]);
    if (!first || IS_ERR(first))
        return NULL;
    last = super->s_devops->find_last_sb(sb, &super->s_sb_ofs[1]);
    if (!last || IS_ERR(last)) {
        page_cache_release(first);
        return NULL;
    }

    if (!logfs_check_ds(page_address(first))) {
        page_cache_release(last);
        return first;
    }

    /* First one didn't work, try the second superblock */
    if (!logfs_check_ds(page_address(last))) {
        page_cache_release(first);
        return last;
    }

    /* Neither worked, sorry folks */
    page_cache_release(first);
    page_cache_release(last);
    return NULL;
}

static int __logfs_read_sb(struct super_block *sb)
{
    struct logfs_super *super = logfs_super(sb);
    struct page *page;
    struct logfs_disk_super *ds;
    int i;

    page = find_super_block(sb);
    if (!page)
        return -EINVAL;

    ds = page_address(page);
    super->s_size = be64_to_cpu(ds->ds_filesystem_size);
    super->s_root_reserve = be64_to_cpu(ds->ds_root_reserve);
    super->s_speed_reserve = be64_to_cpu(ds->ds_speed_reserve);
    super->s_bad_seg_reserve = be32_to_cpu(ds->ds_bad_seg_reserve);
    super->s_segsize = 1 << ds->ds_segment_shift;
    super->s_segmask = (1 << ds->ds_segment_shift) - 1;
    super->s_segshift = ds->ds_segment_shift;
    sb->s_blocksize = 1 << ds->ds_block_shift;
    sb->s_blocksize_bits = ds->ds_block_shift;
    super->s_writesize = 1 << ds->ds_write_shift;
    super->s_writeshift = ds->ds_write_shift;
    super->s_no_segs = super->s_size >> super->s_segshift;
    super->s_no_blocks = super->s_segsize >> sb->s_blocksize_bits;
    super->s_feature_incompat = be64_to_cpu(ds->ds_feature_incompat);
    super->s_feature_ro_compat = be64_to_cpu(ds->ds_feature_ro_compat);
    super->s_feature_compat = be64_to_cpu(ds->ds_feature_compat);
    super->s_feature_flags = be64_to_cpu(ds->ds_feature_flags);

    journal_for_each(i)
        super->s_journal_seg[i] = be32_to_cpu(ds->ds_journal_seg[i]);

    super->s_ifile_levels = ds->ds_ifile_levels;
    super->s_iblock_levels = ds->ds_iblock_levels;
    super->s_data_levels = ds->ds_data_levels;
    super->s_total_levels = super->s_ifile_levels + super->s_iblock_levels
        + super->s_data_levels;
    page_cache_release(page);
    return 0;
}

static int logfs_read_sb(struct super_block *sb, int read_only)
{
    struct logfs_super *super = logfs_super(sb);
    int ret;

    super->s_btree_pool = mempool_create(32, btree_alloc, btree_free, NULL);
    if (!super->s_btree_pool)
        return -ENOMEM;

    btree_init_mempool64(&super->s_shadow_tree.new, super->s_btree_pool);
    btree_init_mempool64(&super->s_shadow_tree.old, super->s_btree_pool);
    btree_init_mempool32(&super->s_shadow_tree.segment_map,
            super->s_btree_pool);

    ret = logfs_init_mapping(sb);
    if (ret)
        return ret;

    ret = __logfs_read_sb(sb);
    if (ret)
        return ret;

    if (super->s_feature_incompat & ~LOGFS_FEATURES_INCOMPAT)
        return -EIO;
    if ((super->s_feature_ro_compat & ~LOGFS_FEATURES_RO_COMPAT) &&
            !read_only)
        return -EIO;

    ret = logfs_init_rw(sb);
    if (ret)
        return ret;

    ret = logfs_init_areas(sb);
    if (ret)
        return ret;

    ret = logfs_init_gc(sb);
    if (ret)
        return ret;

    ret = logfs_init_journal(sb);
    if (ret)
        return ret;

    return 0;
}

static void logfs_kill_sb(struct super_block *sb)
{
    struct logfs_super *super = logfs_super(sb);

    log_super("LogFS: Start unmounting\n");
    /* Alias entries slow down mount, so evict as many as possible */
    sync_filesystem(sb);
    logfs_write_anchor(sb);
    free_areas(sb);

    /*
     * From this point on alias entries are simply dropped - and any
     * writes to the object store are considered bugs.
     */
    log_super("LogFS: Now in shutdown\n");
    generic_shutdown_super(sb);
    super->s_flags |= LOGFS_SB_FLAG_SHUTDOWN;

    BUG_ON(super->s_dirty_used_bytes || super->s_dirty_free_bytes);

    logfs_cleanup_gc(sb);
    logfs_cleanup_journal(sb);
    logfs_cleanup_areas(sb);
    logfs_cleanup_rw(sb);
    if (super->s_erase_page)
        __free_page(super->s_erase_page);
    super->s_devops->put_device(super);
    logfs_mempool_destroy(super->s_btree_pool);
    logfs_mempool_destroy(super->s_alias_pool);
    kfree(super);
    log_super("LogFS: Finished unmounting\n");
}

static struct dentry *logfs_get_sb_device(struct logfs_super *super,
        struct file_system_type *type, int flags)
{
    struct super_block *sb;
    int err = -ENOMEM;
    static int mount_count;

    log_super("LogFS: Start mount %x\n", mount_count++);

    err = -EINVAL;
    sb = sget(type, logfs_sb_test, logfs_sb_set, flags | MS_NOATIME, super);
    if (IS_ERR(sb)) {
        super->s_devops->put_device(super);
        kfree(super);
        return ERR_CAST(sb);
    }

    if (sb->s_root) {
        /* Device is already in use */
        super->s_devops->put_device(super);
        kfree(super);
        return dget(sb->s_root);
    }

    /*
     * sb->s_maxbytes is limited to 8TB.  On 32bit systems, the page cache
     * only covers 16TB and the upper 8TB are used for indirect blocks.
     * On 64bit system we could bump up the limit, but that would make
     * the filesystem incompatible with 32bit systems.
     */
    sb->s_maxbytes  = (1ull << 43) - 1;
    sb->s_max_links = LOGFS_LINK_MAX;
    sb->s_op    = &logfs_super_operations;

    err = logfs_read_sb(sb, sb->s_flags & MS_RDONLY);
    if (err)
        goto err1;

    sb->s_flags |= MS_ACTIVE;
    err = logfs_get_sb_final(sb);
    if (err) {
        deactivate_locked_super(sb);
        return ERR_PTR(err);
    }
    return dget(sb->s_root);

err1:
    /* no ->s_root, no ->put_super() */
    iput(super->s_master_inode);
    iput(super->s_segfile_inode);
    iput(super->s_mapping_inode);
    deactivate_locked_super(sb);
    return ERR_PTR(err);
}

static struct dentry *logfs_mount(struct file_system_type *type, int flags,
        const char *devname, void *data)
{
    ulong mtdnr;
    struct logfs_super *super;
    int err;

    super = kzalloc(sizeof(*super), GFP_KERNEL);
    if (!super)
        return ERR_PTR(-ENOMEM);

    mutex_init(&super->s_dirop_mutex);
    mutex_init(&super->s_object_alias_mutex);
    INIT_LIST_HEAD(&super->s_freeing_list);

    if (!devname)
        err = logfs_get_sb_bdev(super, type, devname);
    else if (strncmp(devname, "mtd", 3))
        err = logfs_get_sb_bdev(super, type, devname);
    else {
        char *garbage;
        mtdnr = simple_strtoul(devname+3, &garbage, 0);
        if (*garbage)
            err = -EINVAL;
        else
            err = logfs_get_sb_mtd(super, mtdnr);
    }

    if (err) {
        kfree(super);
        return ERR_PTR(err);
    }

    return logfs_get_sb_device(super, type, flags);
}

static struct file_system_type logfs_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "logfs",
    .mount      = logfs_mount,
    .kill_sb    = logfs_kill_sb,
    .fs_flags   = FS_REQUIRES_DEV,

};

static int __init logfs_init(void)
{
    int ret;

    emergency_page = alloc_pages(GFP_KERNEL, 0);
    if (!emergency_page)
        return -ENOMEM;

    ret = logfs_compr_init();
    if (ret)
        goto out1;

    ret = logfs_init_inode_cache();
    if (ret)
        goto out2;

    ret = register_filesystem(&logfs_fs_type);
    if (!ret)
        return 0;
    logfs_destroy_inode_cache();
out2:
    logfs_compr_exit();
out1:
    __free_pages(emergency_page, 0);
    return ret;
}

static void __exit logfs_exit(void)
{
    unregister_filesystem(&logfs_fs_type);
    logfs_destroy_inode_cache();
    logfs_compr_exit();
    __free_pages(emergency_page, 0);
}

module_init(logfs_init);
module_exit(logfs_exit);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Joern Engel <[email protected]>");
MODULE_DESCRIPTION("scalable flash filesystem");