linux-kernel - Re: [PATCH v5] fs: FAT: Add support for DOS 1.x formatted volumes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87vbucvpus.fsf@devron.myhome.or.jp>
Date:	Mon, 14 Apr 2014 07:14:51 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Conrad Meyer <cse.cem@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] fs: FAT: Add support for DOS 1.x formatted volumes

Conrad Meyer <cse.cem@...il.com> writes:

> +	sbi->sec_per_clus = fdefaults->sec_per_clus;
> +	sbi->cluster_size = sb->s_blocksize * sbi->sec_per_clus;
> +	sbi->cluster_bits = ffs(sbi->cluster_size) - 1;
> +	sbi->fats = 2;
> +	sbi->fat_start = 1;
> +	sbi->fat_length = fdefaults->fat_length;
> +
> +	sbi->dir_per_block = sb->s_blocksize / sizeof(struct msdos_dir_entry);
> +	sbi->dir_per_block_bits = ffs(sbi->dir_per_block) - 1;
> +	sbi->dir_start = sbi->fat_start + sbi->fats * sbi->fat_length;
> +	sbi->dir_entries = fdefaults->dir_entries;
> +
> +	rootdir_sectors = sbi->dir_entries
> +		* sizeof(struct msdos_dir_entry) / sb->s_blocksize;
> +	sbi->data_start = sbi->dir_start + rootdir_sectors;
> +	total_sectors = fdefaults->nr_sectors;
> +	total_clusters = (total_sectors - sbi->data_start) / sbi->sec_per_clus;
> +	sbi->fat_bits = (total_clusters > MAX_FAT12) ? 16 : 12;
> +
> +	/* some OSes set FAT_STATE_DIRTY and clean it on unmount. */
> +	sbi->dirty = b->fat16.state & FAT_STATE_DIRTY;
> +
> +	/* check that FAT table does not overflow */
> +	fat_clusters = calc_fat_clusters(sb);
> +	total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT);

Ah, you meant this duplicated one.

Let's use structure like fat_boot_sector (but more cpu friendly) on
stack or something, instead of modify bh (BPB). Modifying bh in bdev is
visible via /dev/foo, this is why I want to avoid to modify.

With this, we can share almost all codes on both of read_bpb() and
static_bpb(), and avoids to modify bdev buffer? And those 2 helpers only
has small chunk of code, and provide the required parameters?

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/