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    Subject[PATCH 5/9] fat: Update free_clusters even if it is untrusted
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    Currently, free_clusters is not updated until it is trusted, because
    Windows doesn't update it correctly.

    But if user is using FAT driver of Linux, it updates free_clusters
    correctly. Instead, this updates it even if it's untrusted, so if
    free_clustes is correct, now keep correct value.

    Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
    ---

    fs/fat/fatent.c | 7 +++++--
    fs/fat/inode.c | 7 ++++---
    include/linux/msdos_fs.h | 1 +
    3 files changed, 10 insertions(+), 5 deletions(-)

    diff -puN include/linux/msdos_fs.h~fat_fix-free_clusters-check include/linux/msdos_fs.h
    --- linux-2.6/include/linux/msdos_fs.h~fat_fix-free_clusters-check 2008-03-14 05:38:40.000000000 +0900
    +++ linux-2.6-hirofumi/include/linux/msdos_fs.h 2008-03-14 05:38:40.000000000 +0900
    @@ -233,6 +233,7 @@ struct msdos_sb_info {
    struct mutex fat_lock;
    unsigned int prev_free; /* previously allocated cluster number */
    unsigned int free_clusters; /* -1 if undefined */
    + unsigned int free_clus_valid; /* is free_clusters valid? */
    struct fat_mount_options options;
    struct nls_table *nls_disk; /* Codepage used on disk */
    struct nls_table *nls_io; /* Charset used for input and display */
    diff -puN fs/fat/inode.c~fat_fix-free_clusters-check fs/fat/inode.c
    --- linux-2.6/fs/fat/inode.c~fat_fix-free_clusters-check 2008-03-14 05:38:40.000000000 +0900
    +++ linux-2.6-hirofumi/fs/fat/inode.c 2008-03-14 05:38:40.000000000 +0900
    @@ -537,7 +537,7 @@ static int fat_statfs(struct dentry *den
    struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);

    /* If the count of free cluster is still unknown, counts it here. */
    - if (sbi->free_clusters == -1) {
    + if (sbi->free_clusters == -1 || !sbi->free_clus_valid) {
    int err = fat_count_free_clusters(dentry->d_sb);
    if (err)
    return err;
    @@ -1274,6 +1274,7 @@ int fat_fill_super(struct super_block *s
    sbi->fat_length = le16_to_cpu(b->fat_length);
    sbi->root_cluster = 0;
    sbi->free_clusters = -1; /* Don't know yet */
    + sbi->free_clus_valid = 0;
    sbi->prev_free = FAT_START_ENT;

    if (!sbi->fat_length && b->fat32_length) {
    @@ -1309,8 +1310,8 @@ int fat_fill_super(struct super_block *s
    sbi->fsinfo_sector);
    } else {
    if (sbi->options.usefree)
    - sbi->free_clusters =
    - le32_to_cpu(fsinfo->free_clusters);
    + sbi->free_clus_valid = 1;
    + sbi->free_clusters = le32_to_cpu(fsinfo->free_clusters);
    sbi->prev_free = le32_to_cpu(fsinfo->next_cluster);
    }

    diff -puN fs/fat/fatent.c~fat_fix-free_clusters-check fs/fat/fatent.c
    --- linux-2.6/fs/fat/fatent.c~fat_fix-free_clusters-check 2008-03-14 05:38:40.000000000 +0900
    +++ linux-2.6-hirofumi/fs/fat/fatent.c 2008-03-14 05:38:40.000000000 +0900
    @@ -450,7 +450,8 @@ int fat_alloc_clusters(struct inode *ino
    BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2)); /* fixed limit */

    lock_fat(sbi);
    - if (sbi->free_clusters != -1 && sbi->free_clusters < nr_cluster) {
    + if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
    + sbi->free_clusters < nr_cluster) {
    unlock_fat(sbi);
    return -ENOSPC;
    }
    @@ -504,6 +505,7 @@ int fat_alloc_clusters(struct inode *ino

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

    @@ -615,7 +617,7 @@ int fat_count_free_clusters(struct super
    int err = 0, free;

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

    reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
    @@ -643,6 +645,7 @@ int fat_count_free_clusters(struct super
    } while (fat_ent_next(sbi, &fatent));
    }
    sbi->free_clusters = free;
    + sbi->free_clus_valid = 1;
    sb->s_dirt = 1;
    fatent_brelse(&fatent);
    out:
    _

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