fatent.c

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/*
 * Copyright (C) 2004, OGAWA Hirofumi
 * Released under GPL v2.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/msdos_fs.h>
#include <linux/blkdev.h>
#include "fat.h"

struct fatent_operations {
    void (*ent_blocknr)(struct super_block *, int, int *, sector_t *);
    void (*ent_set_ptr)(struct fat_entry *, int);
    int (*ent_bread)(struct super_block *, struct fat_entry *,
             int, sector_t);
    int (*ent_get)(struct fat_entry *);
    void (*ent_put)(struct fat_entry *, int);
    int (*ent_next)(struct fat_entry *);
};

static DEFINE_SPINLOCK(fat12_entry_lock);

static void fat12_ent_blocknr(struct super_block *sb, int entry,
                  int *offset, sector_t *blocknr)
{
    struct msdos_sb_info *sbi = MSDOS_SB(sb);
    int bytes = entry + (entry >> 1);
    WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
    *offset = bytes & (sb->s_blocksize - 1);
    *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
}

static void fat_ent_blocknr(struct super_block *sb, int entry,
                int *offset, sector_t *blocknr)
{
    struct msdos_sb_info *sbi = MSDOS_SB(sb);
    int bytes = (entry << sbi->fatent_shift);
    WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
    *offset = bytes & (sb->s_blocksize - 1);
    *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
}

static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
{
    struct buffer_head **bhs = fatent->bhs;
    if (fatent->nr_bhs == 1) {
        WARN_ON(offset >= (bhs[0]->b_size - 1));
        fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
        fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
    } else {
        WARN_ON(offset != (bhs[0]->b_size - 1));
        fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
        fatent->u.ent12_p[1] = bhs[1]->b_data;
    }
}

static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
{
    WARN_ON(offset & (2 - 1));
    fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
}

static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
{
    WARN_ON(offset & (4 - 1));
    fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
}

static int fat12_ent_bread(struct super_block *sb, struct fat_entry *fatent,
               int offset, sector_t blocknr)
{
    struct buffer_head **bhs = fatent->bhs;

    WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
    fatent->fat_inode = MSDOS_SB(sb)->fat_inode;

    bhs[0] = sb_bread(sb, blocknr);
    if (!bhs[0])
        goto err;

    if ((offset + 1) < sb->s_blocksize)
        fatent->nr_bhs = 1;
    else {
        /* This entry is block boundary, it needs the next block */
        blocknr++;
        bhs[1] = sb_bread(sb, blocknr);
        if (!bhs[1])
            goto err_brelse;
        fatent->nr_bhs = 2;
    }
    fat12_ent_set_ptr(fatent, offset);
    return 0;

err_brelse:
    brelse(bhs[0]);
err:
    fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", (llu)blocknr);
    return -EIO;
}

static int fat_ent_bread(struct super_block *sb, struct fat_entry *fatent,
             int offset, sector_t blocknr)
{
    struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;

    WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
    fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
    fatent->bhs[0] = sb_bread(sb, blocknr);
    if (!fatent->bhs[0]) {
        fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
               (llu)blocknr);
        return -EIO;
    }
    fatent->nr_bhs = 1;
    ops->ent_set_ptr(fatent, offset);
    return 0;
}

static int fat12_ent_get(struct fat_entry *fatent)
{
    u8 **ent12_p = fatent->u.ent12_p;
    int next;

    spin_lock(&fat12_entry_lock);
    if (fatent->entry & 1)
        next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4);
    else
        next = (*ent12_p[1] << 8) | *ent12_p[0];
    spin_unlock(&fat12_entry_lock);

    next &= 0x0fff;
    if (next >= BAD_FAT12)
        next = FAT_ENT_EOF;
    return next;
}

static int fat16_ent_get(struct fat_entry *fatent)
{
    int next = le16_to_cpu(*fatent->u.ent16_p);
    WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1));
    if (next >= BAD_FAT16)
        next = FAT_ENT_EOF;
    return next;
}

static int fat32_ent_get(struct fat_entry *fatent)
{
    int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
    WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
    if (next >= BAD_FAT32)
        next = FAT_ENT_EOF;
    return next;
}

static void fat12_ent_put(struct fat_entry *fatent, int new)
{
    u8 **ent12_p = fatent->u.ent12_p;

    if (new == FAT_ENT_EOF)
        new = EOF_FAT12;

    spin_lock(&fat12_entry_lock);
    if (fatent->entry & 1) {
        *ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f);
        *ent12_p[1] = new >> 4;
    } else {
        *ent12_p[0] = new & 0xff;
        *ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8);
    }
    spin_unlock(&fat12_entry_lock);

    mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
    if (fatent->nr_bhs == 2)
        mark_buffer_dirty_inode(fatent->bhs[1], fatent->fat_inode);
}

static void fat16_ent_put(struct fat_entry *fatent, int new)
{
    if (new == FAT_ENT_EOF)
        new = EOF_FAT16;

    *fatent->u.ent16_p = cpu_to_le16(new);
    mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
}

static void fat32_ent_put(struct fat_entry *fatent, int new)
{
    WARN_ON(new & 0xf0000000);
    new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
    *fatent->u.ent32_p = cpu_to_le32(new);
    mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
}

static int fat12_ent_next(struct fat_entry *fatent)
{
    u8 **ent12_p = fatent->u.ent12_p;
    struct buffer_head **bhs = fatent->bhs;
    u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);

    fatent->entry++;
    if (fatent->nr_bhs == 1) {
        WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data +
                            (bhs[0]->b_size - 2)));
        WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data +
                            (bhs[0]->b_size - 1)));
        if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
            ent12_p[0] = nextp - 1;
            ent12_p[1] = nextp;
            return 1;
        }
    } else {
        WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data +
                            (bhs[0]->b_size - 1)));
        WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data);
        ent12_p[0] = nextp - 1;
        ent12_p[1] = nextp;
        brelse(bhs[0]);
        bhs[0] = bhs[1];
        fatent->nr_bhs = 1;
        return 1;
    }
    ent12_p[0] = NULL;
    ent12_p[1] = NULL;
    return 0;
}

static int fat16_ent_next(struct fat_entry *fatent)
{
    const struct buffer_head *bh = fatent->bhs[0];
    fatent->entry++;
    if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) {
        fatent->u.ent16_p++;
        return 1;
    }
    fatent->u.ent16_p = NULL;
    return 0;
}

static int fat32_ent_next(struct fat_entry *fatent)
{
    const struct buffer_head *bh = fatent->bhs[0];
    fatent->entry++;
    if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) {
        fatent->u.ent32_p++;
        return 1;
    }
    fatent->u.ent32_p = NULL;
    return 0;
}

static struct fatent_operations fat12_ops = {
    .ent_blocknr    = fat12_ent_blocknr,
    .ent_set_ptr    = fat12_ent_set_ptr,
    .ent_bread  = fat12_ent_bread,
    .ent_get    = fat12_ent_get,
    .ent_put    = fat12_ent_put,
    .ent_next   = fat12_ent_next,
};

static struct fatent_operations fat16_ops = {
    .ent_blocknr    = fat_ent_blocknr,
    .ent_set_ptr    = fat16_ent_set_ptr,
    .ent_bread  = fat_ent_bread,
    .ent_get    = fat16_ent_get,
    .ent_put    = fat16_ent_put,
    .ent_next   = fat16_ent_next,
};

static struct fatent_operations fat32_ops = {
    .ent_blocknr    = fat_ent_blocknr,
    .ent_set_ptr    = fat32_ent_set_ptr,
    .ent_bread  = fat_ent_bread,
    .ent_get    = fat32_ent_get,
    .ent_put    = fat32_ent_put,
    .ent_next   = fat32_ent_next,
};

static inline void lock_fat(struct msdos_sb_info *sbi)
{
    mutex_lock(&sbi->fat_lock);
}

static inline void unlock_fat(struct msdos_sb_info *sbi)
{
    mutex_unlock(&sbi->fat_lock);
}

void fat_ent_access_init(struct super_block *sb)
{
    struct msdos_sb_info *sbi = MSDOS_SB(sb);

    mutex_init(&sbi->fat_lock);

    switch (sbi->fat_bits) {
    case 32:
        sbi->fatent_shift = 2;
        sbi->fatent_ops = &fat32_ops;
        break;
    case 16:
        sbi->fatent_shift = 1;
        sbi->fatent_ops = &fat16_ops;
        break;
    case 12:
        sbi->fatent_shift = -1;
        sbi->fatent_ops = &fat12_ops;
        break;
    }
}

static void mark_fsinfo_dirty(struct super_block *sb)
{
    struct msdos_sb_info *sbi = MSDOS_SB(sb);

    if (sb->s_flags & MS_RDONLY || sbi->fat_bits != 32)
        return;

    __mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
}

static inline int fat_ent_update_ptr(struct super_block *sb,
                     struct fat_entry *fatent,
                     int offset, sector_t blocknr)
{
    struct msdos_sb_info *sbi = MSDOS_SB(sb);
    struct fatent_operations *ops = sbi->fatent_ops;
    struct buffer_head **bhs = fatent->bhs;

    /* Is this fatent's blocks including this entry? */
    if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
        return 0;
    if (sbi->fat_bits == 12) {
        if ((offset + 1) < sb->s_blocksize) {
            /* This entry is on bhs[0]. */
            if (fatent->nr_bhs == 2) {
                brelse(bhs[1]);
                fatent->nr_bhs = 1;
            }
        } else {
            /* This entry needs the next block. */
            if (fatent->nr_bhs != 2)
                return 0;
            if (bhs[1]->b_blocknr != (blocknr + 1))
                return 0;
        }
    }
    ops->ent_set_ptr(fatent, offset);
    return 1;
}

int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
{
    struct super_block *sb = inode->i_sb;
    struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
    struct fatent_operations *ops = sbi->fatent_ops;
    int err, offset;
    sector_t blocknr;

    if (entry < FAT_START_ENT || sbi->max_cluster <= entry) {
        fatent_brelse(fatent);
        fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
        return -EIO;
    }

    fatent_set_entry(fatent, entry);
    ops->ent_blocknr(sb, entry, &offset, &blocknr);

    if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
        fatent_brelse(fatent);
        err = ops->ent_bread(sb, fatent, offset, blocknr);
        if (err)
            return err;
    }
    return ops->ent_get(fatent);
}

/* FIXME: We can write the blocks as more big chunk. */
static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
              int nr_bhs)
{
    struct msdos_sb_info *sbi = MSDOS_SB(sb);
    struct buffer_head *c_bh;
    int err, n, copy;

    err = 0;
    for (copy = 1; copy < sbi->fats; copy++) {
        sector_t backup_fat = sbi->fat_length * copy;

        for (n = 0; n < nr_bhs; n++) {
            c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
            if (!c_bh) {
                err = -ENOMEM;
                goto error;
            }
            memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
            set_buffer_uptodate(c_bh);
            mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
            if (sb->s_flags & MS_SYNCHRONOUS)
                err = sync_dirty_buffer(c_bh);
            brelse(c_bh);
            if (err)
                goto error;
        }
    }
error:
    return err;
}

int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
          int new, int wait)
{
    struct super_block *sb = inode->i_sb;
    struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
    int err;

    ops->ent_put(fatent, new);
    if (wait) {
        err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
        if (err)
            return err;
    }
    return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
}

static inline int fat_ent_next(struct msdos_sb_info *sbi,
                   struct fat_entry *fatent)
{
    if (sbi->fatent_ops->ent_next(fatent)) {
        if (fatent->entry < sbi->max_cluster)
            return 1;
    }
    return 0;
}

static inline int fat_ent_read_block(struct super_block *sb,
                     struct fat_entry *fatent)
{
    struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
    sector_t blocknr;
    int offset;

    fatent_brelse(fatent);
    ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
    return ops->ent_bread(sb, fatent, offset, blocknr);
}

static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
                struct fat_entry *fatent)
{
    int n, i;

    for (n = 0; n < fatent->nr_bhs; n++) {
        for (i = 0; i < *nr_bhs; i++) {
            if (fatent->bhs[n] == bhs[i])
                break;
        }
        if (i == *nr_bhs) {
            get_bh(fatent->bhs[n]);
            bhs[i] = fatent->bhs[n];
            (*nr_bhs)++;
        }
    }
}

int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
{
    struct super_block *sb = inode->i_sb;
    struct msdos_sb_info *sbi = MSDOS_SB(sb);
    struct fatent_operations *ops = sbi->fatent_ops;
    struct fat_entry fatent, prev_ent;
    struct buffer_head *bhs[MAX_BUF_PER_PAGE];
    int i, count, err, nr_bhs, idx_clus;

    BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));    /* fixed limit */

    lock_fat(sbi);
    if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
        sbi->free_clusters < nr_cluster) {
        unlock_fat(sbi);
        return -ENOSPC;
    }

    err = nr_bhs = idx_clus = 0;
    count = FAT_START_ENT;
    fatent_init(&prev_ent);
    fatent_init(&fatent);
    fatent_set_entry(&fatent, sbi->prev_free + 1);
    while (count < sbi->max_cluster) {
        if (fatent.entry >= sbi->max_cluster)
            fatent.entry = FAT_START_ENT;
        fatent_set_entry(&fatent, fatent.entry);
        err = fat_ent_read_block(sb, &fatent);
        if (err)
            goto out;

        /* Find the free entries in a block */
        do {
            if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
                int entry = fatent.entry;

                /* make the cluster chain */
                ops->ent_put(&fatent, FAT_ENT_EOF);
                if (prev_ent.nr_bhs)
                    ops->ent_put(&prev_ent, entry);

                fat_collect_bhs(bhs, &nr_bhs, &fatent);

                sbi->prev_free = entry;
                if (sbi->free_clusters != -1)
                    sbi->free_clusters--;

                cluster[idx_clus] = entry;
                idx_clus++;
                if (idx_clus == nr_cluster)
                    goto out;

                /*
                 * fat_collect_bhs() gets ref-count of bhs,
                 * so we can still use the prev_ent.
                 */
                prev_ent = fatent;
            }
            count++;
            if (count == sbi->max_cluster)
                break;
        } while (fat_ent_next(sbi, &fatent));
    }

    /* Couldn't allocate the free entries */
    sbi->free_clusters = 0;
    sbi->free_clus_valid = 1;
    err = -ENOSPC;

out:
    unlock_fat(sbi);
    mark_fsinfo_dirty(sb);
    fatent_brelse(&fatent);
    if (!err) {
        if (inode_needs_sync(inode))
            err = fat_sync_bhs(bhs, nr_bhs);
        if (!err)
            err = fat_mirror_bhs(sb, bhs, nr_bhs);
    }
    for (i = 0; i < nr_bhs; i++)
        brelse(bhs[i]);

    if (err && idx_clus)
        fat_free_clusters(inode, cluster[0]);

    return err;
}

int fat_free_clusters(struct inode *inode, int cluster)
{
    struct super_block *sb = inode->i_sb;
    struct msdos_sb_info *sbi = MSDOS_SB(sb);
    struct fatent_operations *ops = sbi->fatent_ops;
    struct fat_entry fatent;
    struct buffer_head *bhs[MAX_BUF_PER_PAGE];
    int i, err, nr_bhs;
    int first_cl = cluster, dirty_fsinfo = 0;

    nr_bhs = 0;
    fatent_init(&fatent);
    lock_fat(sbi);
    do {
        cluster = fat_ent_read(inode, &fatent, cluster);
        if (cluster < 0) {
            err = cluster;
            goto error;
        } else if (cluster == FAT_ENT_FREE) {
            fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
                     __func__);
            err = -EIO;
            goto error;
        }

        if (sbi->options.discard) {
            /*
             * Issue discard for the sectors we no longer
             * care about, batching contiguous clusters
             * into one request
             */
            if (cluster != fatent.entry + 1) {
                int nr_clus = fatent.entry - first_cl + 1;

                sb_issue_discard(sb,
                    fat_clus_to_blknr(sbi, first_cl),
                    nr_clus * sbi->sec_per_clus,
                    GFP_NOFS, 0);

                first_cl = cluster;
            }
        }

        ops->ent_put(&fatent, FAT_ENT_FREE);
        if (sbi->free_clusters != -1) {
            sbi->free_clusters++;
            dirty_fsinfo = 1;
        }

        if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
            if (sb->s_flags & MS_SYNCHRONOUS) {
                err = fat_sync_bhs(bhs, nr_bhs);
                if (err)
                    goto error;
            }
            err = fat_mirror_bhs(sb, bhs, nr_bhs);
            if (err)
                goto error;
            for (i = 0; i < nr_bhs; i++)
                brelse(bhs[i]);
            nr_bhs = 0;
        }
        fat_collect_bhs(bhs, &nr_bhs, &fatent);
    } while (cluster != FAT_ENT_EOF);

    if (sb->s_flags & MS_SYNCHRONOUS) {
        err = fat_sync_bhs(bhs, nr_bhs);
        if (err)
            goto error;
    }
    err = fat_mirror_bhs(sb, bhs, nr_bhs);
error:
    fatent_brelse(&fatent);
    for (i = 0; i < nr_bhs; i++)
        brelse(bhs[i]);
    unlock_fat(sbi);
    if (dirty_fsinfo)
        mark_fsinfo_dirty(sb);

    return err;
}
EXPORT_SYMBOL_GPL(fat_free_clusters);

/* 128kb is the whole sectors for FAT12 and FAT16 */
#define FAT_READA_SIZE      (128 * 1024)

static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent,
              unsigned long reada_blocks)
{
    struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
    sector_t blocknr;
    int i, offset;

    ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);

    for (i = 0; i < reada_blocks; i++)
        sb_breadahead(sb, blocknr + i);
}

int fat_count_free_clusters(struct super_block *sb)
{
    struct msdos_sb_info *sbi = MSDOS_SB(sb);
    struct fatent_operations *ops = sbi->fatent_ops;
    struct fat_entry fatent;
    unsigned long reada_blocks, reada_mask, cur_block;
    int err = 0, free;

    lock_fat(sbi);
    if (sbi->free_clusters != -1 && sbi->free_clus_valid)
        goto out;

    reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
    reada_mask = reada_blocks - 1;
    cur_block = 0;

    free = 0;
    fatent_init(&fatent);
    fatent_set_entry(&fatent, FAT_START_ENT);
    while (fatent.entry < sbi->max_cluster) {
        /* readahead of fat blocks */
        if ((cur_block & reada_mask) == 0) {
            unsigned long rest = sbi->fat_length - cur_block;
            fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
        }
        cur_block++;

        err = fat_ent_read_block(sb, &fatent);
        if (err)
            goto out;

        do {
            if (ops->ent_get(&fatent) == FAT_ENT_FREE)
                free++;
        } while (fat_ent_next(sbi, &fatent));
    }
    sbi->free_clusters = free;
    sbi->free_clus_valid = 1;
    mark_fsinfo_dirty(sb);
    fatent_brelse(&fatent);
out:
    unlock_fat(sbi);
    return err;
}