RE: [PATCH 1/4 v3] exfat: redefine PBR as boot_sector

From: Sungjong Seo
Date: Mon Jun 01 2020 - 08:18:39 EST

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> Aggregate PBR related definitions and redefine as "boot_sector" to comply
> with the exFAT specification.
> And, rename variable names including 'pbr'.
>
> Signed-off-by: Tetsuhiro Kohada <kohada.t2@xxxxxxxxx>

Reviewed-by: Sungjong Seo <sj1557.seo@xxxxxxxxxxx>

> ---
> Changes in v2:
> - rebase with patch 'optimize dir-cache' applied Changes in v3:
> - rename BOOTSEC_OEM_NAME_LEN to BOOTSEC_FS_NAME_LEN
> - rename oem_name to fs_name in struct boot_sector
>
> fs/exfat/exfat_fs.h | 2 +-
> fs/exfat/exfat_raw.h | 79 +++++++++++++++--------------------------
> fs/exfat/super.c | 84 ++++++++++++++++++++++----------------------
> 3 files changed, 72 insertions(+), 93 deletions(-)
>
> diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h index
> 5caad1380818..9673e2d31045 100644
> --- a/fs/exfat/exfat_fs.h
> +++ b/fs/exfat/exfat_fs.h
> @@ -227,7 +227,7 @@ struct exfat_sb_info {
> unsigned int root_dir; /* root dir cluster */
> unsigned int dentries_per_clu; /* num of dentries per cluster */
> unsigned int vol_flag; /* volume dirty flag */
> - struct buffer_head *pbr_bh; /* buffer_head of PBR sector */
> + struct buffer_head *boot_bh; /* buffer_head of BOOT sector */
>
> unsigned int map_clu; /* allocation bitmap start cluster */
> unsigned int map_sectors; /* num of allocation bitmap sectors */
> diff --git a/fs/exfat/exfat_raw.h b/fs/exfat/exfat_raw.h index
> 8d6c64a7546d..07f74190df44 100644
> --- a/fs/exfat/exfat_raw.h
> +++ b/fs/exfat/exfat_raw.h
> @@ -8,7 +8,8 @@
>
> #include <linux/types.h>
>
> -#define PBR_SIGNATURE 0xAA55
> +#define BOOT_SIGNATURE 0xAA55
> +#define EXBOOT_SIGNATURE 0xAA550000
>
> #define EXFAT_MAX_FILE_LEN 255
>
> @@ -55,7 +56,7 @@
>
> /* checksum types */
> #define CS_DIR_ENTRY 0
> -#define CS_PBR_SECTOR 1
> +#define CS_BOOT_SECTOR 1
> #define CS_DEFAULT 2
>
> /* file attributes */
> @@ -69,57 +70,35 @@
> #define ATTR_RWMASK (ATTR_HIDDEN | ATTR_SYSTEM | ATTR_VOLUME
> | \
> ATTR_SUBDIR | ATTR_ARCHIVE)
>
> -#define PBR64_JUMP_BOOT_LEN 3
> -#define PBR64_OEM_NAME_LEN 8
> -#define PBR64_RESERVED_LEN 53
> +#define BOOTSEC_JUMP_BOOT_LEN 3
> +#define BOOTSEC_FS_NAME_LEN 8
> +#define BOOTSEC_OLDBPB_LEN 53
>
> #define EXFAT_FILE_NAME_LEN 15
>
> -/* EXFAT BIOS parameter block (64 bytes) */ -struct bpb64 {
> - __u8 jmp_boot[PBR64_JUMP_BOOT_LEN];
> - __u8 oem_name[PBR64_OEM_NAME_LEN];
> - __u8 res_zero[PBR64_RESERVED_LEN];
> -} __packed;
> -
> -/* EXFAT EXTEND BIOS parameter block (56 bytes) */ -struct bsx64 {
> - __le64 vol_offset;
> - __le64 vol_length;
> - __le32 fat_offset;
> - __le32 fat_length;
> - __le32 clu_offset;
> - __le32 clu_count;
> - __le32 root_cluster;
> - __le32 vol_serial;
> - __u8 fs_version[2];
> - __le16 vol_flags;
> - __u8 sect_size_bits;
> - __u8 sect_per_clus_bits;
> - __u8 num_fats;
> - __u8 phy_drv_no;
> - __u8 perc_in_use;
> - __u8 reserved2[7];
> -} __packed;
> -
> -/* EXFAT PBR[BPB+BSX] (120 bytes) */
> -struct pbr64 {
> - struct bpb64 bpb;
> - struct bsx64 bsx;
> -} __packed;
> -
> -/* Common PBR[Partition Boot Record] (512 bytes) */ -struct pbr {
> - union {
> - __u8 raw[64];
> - struct bpb64 f64;
> - } bpb;
> - union {
> - __u8 raw[56];
> - struct bsx64 f64;
> - } bsx;
> - __u8 boot_code[390];
> - __le16 signature;
> +/* EXFAT: Main and Backup Boot Sector (512 bytes) */ struct boot_sector
> +{
> + __u8 jmp_boot[BOOTSEC_JUMP_BOOT_LEN];
> + __u8 fs_name[BOOTSEC_FS_NAME_LEN];
> + __u8 must_be_zero[BOOTSEC_OLDBPB_LEN];
> + __le64 partition_offset;
> + __le64 vol_length;
> + __le32 fat_offset;
> + __le32 fat_length;
> + __le32 clu_offset;
> + __le32 clu_count;
> + __le32 root_cluster;
> + __le32 vol_serial;
> + __u8 fs_revision[2];
> + __le16 vol_flags;
> + __u8 sect_size_bits;
> + __u8 sect_per_clus_bits;
> + __u8 num_fats;
> + __u8 drv_sel;
> + __u8 percent_in_use;
> + __u8 reserved[7];
> + __u8 boot_code[390];
> + __le16 signature;
> } __packed;
>
> struct exfat_dentry {
> diff --git a/fs/exfat/super.c b/fs/exfat/super.c index
> c1f47f4071a8..e60d28e73ff0 100644
> --- a/fs/exfat/super.c
> +++ b/fs/exfat/super.c
> @@ -49,7 +49,7 @@ static void exfat_put_super(struct super_block *sb)
> sync_blockdev(sb->s_bdev);
> exfat_set_vol_flags(sb, VOL_CLEAN);
> exfat_free_bitmap(sbi);
> - brelse(sbi->pbr_bh);
> + brelse(sbi->boot_bh);
> mutex_unlock(&sbi->s_lock);
>
> call_rcu(&sbi->rcu, exfat_delayed_free); @@ -101,7 +101,7 @@ static
> int exfat_statfs(struct dentry *dentry, struct kstatfs *buf) int
> exfat_set_vol_flags(struct super_block *sb, unsigned short new_flag) {
> struct exfat_sb_info *sbi = EXFAT_SB(sb);
> - struct pbr64 *bpb = (struct pbr64 *)sbi->pbr_bh->b_data;
> + struct boot_sector *p_boot = (struct boot_sector
> +*)sbi->boot_bh->b_data;
> bool sync;
>
> /* flags are not changed */
> @@ -116,18 +116,18 @@ int exfat_set_vol_flags(struct super_block *sb,
> unsigned short new_flag)
> if (sb_rdonly(sb))
> return 0;
>
> - bpb->bsx.vol_flags = cpu_to_le16(new_flag);
> + p_boot->vol_flags = cpu_to_le16(new_flag);
>
> - if (new_flag == VOL_DIRTY && !buffer_dirty(sbi->pbr_bh))
> + if (new_flag == VOL_DIRTY && !buffer_dirty(sbi->boot_bh))
> sync = true;
> else
> sync = false;
>
> - set_buffer_uptodate(sbi->pbr_bh);
> - mark_buffer_dirty(sbi->pbr_bh);
> + set_buffer_uptodate(sbi->boot_bh);
> + mark_buffer_dirty(sbi->boot_bh);
>
> if (sync)
> - sync_dirty_buffer(sbi->pbr_bh);
> + sync_dirty_buffer(sbi->boot_bh);
> return 0;
> }
>
> @@ -366,13 +366,14 @@ static int exfat_read_root(struct inode *inode)
> return 0;
> }
>
> -static struct pbr *exfat_read_pbr_with_logical_sector(struct super_block
> *sb)
> +static struct boot_sector *exfat_read_boot_with_logical_sector(
> + struct super_block *sb)
> {
> struct exfat_sb_info *sbi = EXFAT_SB(sb);
> - struct pbr *p_pbr = (struct pbr *) (sbi->pbr_bh)->b_data;
> + struct boot_sector *p_boot = (struct boot_sector
> +*)sbi->boot_bh->b_data;
> unsigned short logical_sect = 0;
>
> - logical_sect = 1 << p_pbr->bsx.f64.sect_size_bits;
> + logical_sect = 1 << p_boot->sect_size_bits;
>
> if (!is_power_of_2(logical_sect) ||
> logical_sect < 512 || logical_sect > 4096) { @@ -387,49 +388,48
> @@ static struct pbr *exfat_read_pbr_with_logical_sector(struct
> super_block *sb)
> }
>
> if (logical_sect > sb->s_blocksize) {
> - brelse(sbi->pbr_bh);
> - sbi->pbr_bh = NULL;
> + brelse(sbi->boot_bh);
> + sbi->boot_bh = NULL;
>
> if (!sb_set_blocksize(sb, logical_sect)) {
> exfat_err(sb, "unable to set blocksize %u",
> logical_sect);
> return NULL;
> }
> - sbi->pbr_bh = sb_bread(sb, 0);
> - if (!sbi->pbr_bh) {
> + sbi->boot_bh = sb_bread(sb, 0);
> + if (!sbi->boot_bh) {
> exfat_err(sb, "unable to read boot sector (logical
> sector size = %lu)",
> sb->s_blocksize);
> return NULL;
> }
>
> - p_pbr = (struct pbr *)sbi->pbr_bh->b_data;
> + p_boot = (struct boot_sector *)sbi->boot_bh->b_data;
> }
> - return p_pbr;
> + return p_boot;
> }
>
> /* mount the file system volume */
> static int __exfat_fill_super(struct super_block *sb) {
> int ret;
> - struct pbr *p_pbr;
> - struct pbr64 *p_bpb;
> + struct boot_sector *p_boot;
> struct exfat_sb_info *sbi = EXFAT_SB(sb);
>
> /* set block size to read super block */
> sb_min_blocksize(sb, 512);
>
> /* read boot sector */
> - sbi->pbr_bh = sb_bread(sb, 0);
> - if (!sbi->pbr_bh) {
> + sbi->boot_bh = sb_bread(sb, 0);
> + if (!sbi->boot_bh) {
> exfat_err(sb, "unable to read boot sector");
> return -EIO;
> }
>
> /* PRB is read */
> - p_pbr = (struct pbr *)sbi->pbr_bh->b_data;
> + p_boot = (struct boot_sector *)sbi->boot_bh->b_data;
>
> - /* check the validity of PBR */
> - if (le16_to_cpu((p_pbr->signature)) != PBR_SIGNATURE) {
> + /* check the validity of BOOT */
> + if (le16_to_cpu((p_boot->signature)) != BOOT_SIGNATURE) {
> exfat_err(sb, "invalid boot record signature");
> ret = -EINVAL;
> goto free_bh;
> @@ -437,8 +437,8 @@ static int __exfat_fill_super(struct super_block *sb)
>
>
> /* check logical sector size */
> - p_pbr = exfat_read_pbr_with_logical_sector(sb);
> - if (!p_pbr) {
> + p_boot = exfat_read_boot_with_logical_sector(sb);
> + if (!p_boot) {
> ret = -EIO;
> goto free_bh;
> }
> @@ -447,43 +447,43 @@ static int __exfat_fill_super(struct super_block
*sb)
> * res_zero field must be filled with zero to prevent mounting
> * from FAT volume.
> */
> - if (memchr_inv(p_pbr->bpb.f64.res_zero, 0,
> - sizeof(p_pbr->bpb.f64.res_zero))) {
> + if (memchr_inv(p_boot->must_be_zero, 0,
> + sizeof(p_boot->must_be_zero))) {
> ret = -EINVAL;
> goto free_bh;
> }
>
> - p_bpb = (struct pbr64 *)p_pbr;
> - if (!p_bpb->bsx.num_fats) {
> + p_boot = (struct boot_sector *)p_boot;
> + if (!p_boot->num_fats) {
> exfat_err(sb, "bogus number of FAT structure");
> ret = -EINVAL;
> goto free_bh;
> }
>
> - sbi->sect_per_clus = 1 << p_bpb->bsx.sect_per_clus_bits;
> - sbi->sect_per_clus_bits = p_bpb->bsx.sect_per_clus_bits;
> + sbi->sect_per_clus = 1 << p_boot->sect_per_clus_bits;
> + sbi->sect_per_clus_bits = p_boot->sect_per_clus_bits;
> sbi->cluster_size_bits = sbi->sect_per_clus_bits + sb-
> >s_blocksize_bits;
> sbi->cluster_size = 1 << sbi->cluster_size_bits;
> - sbi->num_FAT_sectors = le32_to_cpu(p_bpb->bsx.fat_length);
> - sbi->FAT1_start_sector = le32_to_cpu(p_bpb->bsx.fat_offset);
> - sbi->FAT2_start_sector = p_bpb->bsx.num_fats == 1 ?
> + sbi->num_FAT_sectors = le32_to_cpu(p_boot->fat_length);
> + sbi->FAT1_start_sector = le32_to_cpu(p_boot->fat_offset);
> + sbi->FAT2_start_sector = p_boot->num_fats == 1 ?
> sbi->FAT1_start_sector :
> sbi->FAT1_start_sector + sbi->num_FAT_sectors;
> - sbi->data_start_sector = le32_to_cpu(p_bpb->bsx.clu_offset);
> - sbi->num_sectors = le64_to_cpu(p_bpb->bsx.vol_length);
> + sbi->data_start_sector = le32_to_cpu(p_boot->clu_offset);
> + sbi->num_sectors = le64_to_cpu(p_boot->vol_length);
> /* because the cluster index starts with 2 */
> - sbi->num_clusters = le32_to_cpu(p_bpb->bsx.clu_count) +
> + sbi->num_clusters = le32_to_cpu(p_boot->clu_count) +
> EXFAT_RESERVED_CLUSTERS;
>
> - sbi->root_dir = le32_to_cpu(p_bpb->bsx.root_cluster);
> + sbi->root_dir = le32_to_cpu(p_boot->root_cluster);
> sbi->dentries_per_clu = 1 <<
> (sbi->cluster_size_bits - DENTRY_SIZE_BITS);
>
> - sbi->vol_flag = le16_to_cpu(p_bpb->bsx.vol_flags);
> + sbi->vol_flag = le16_to_cpu(p_boot->vol_flags);
> sbi->clu_srch_ptr = EXFAT_FIRST_CLUSTER;
> sbi->used_clusters = EXFAT_CLUSTERS_UNTRACKED;
>
> - if (le16_to_cpu(p_bpb->bsx.vol_flags) & VOL_DIRTY) {
> + if (le16_to_cpu(p_boot->vol_flags) & VOL_DIRTY) {
> sbi->vol_flag |= VOL_DIRTY;
> exfat_warn(sb, "Volume was not properly unmounted. Some data
> may be corrupt. Please run fsck.");
> }
> @@ -517,7 +517,7 @@ static int __exfat_fill_super(struct super_block *sb)
> free_upcase_table:
> exfat_free_upcase_table(sbi);
> free_bh:
> - brelse(sbi->pbr_bh);
> + brelse(sbi->boot_bh);
> return ret;
> }
>
> @@ -608,7 +608,7 @@ static int exfat_fill_super(struct super_block *sb,
> struct fs_context *fc)
> free_table:
> exfat_free_upcase_table(sbi);
> exfat_free_bitmap(sbi);
> - brelse(sbi->pbr_bh);
> + brelse(sbi->boot_bh);
>
> check_nls_io:
> unload_nls(sbi->nls_io);
> --
> 2.25.1

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