Commit 0ab7620a authored by Erik van der Kouwe's avatar Erik van der Kouwe Committed by Al Viro
Browse files

fs/minix: bugfix, number of indirect block ptrs per block depends on block size 



The MINIX filesystem driver used a constant number of indirect block
pointers in an indirect block. This worked only for filesystems with 1kb
block, while the MINIX default block size is now 4kb. As a consequence,
large files were read incorrectly on such filesystems and writing a
large file would cause the filesystem to become corrupted. This patch
computes the number of indirect block pointers based on the block size,
making the driver work for each block size.

I would like to thank Feiran Zheng ('Fam') for pointing out the cause
of the corruption.

Signed-off-by: default avatarErik van der Kouwe <vdkouwe@cs.vu.nl>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 1b061d92

fs/minix/itree_v2.c

+15 −12
Original line number Diff line number Diff line
@@ -20,6 +20,9 @@ static inline block_t *i_data(struct inode *inode) 
	return (block_t *)minix_i(inode)->u.i2_data;

}



#define DIRCOUNT 7

#define INDIRCOUNT(sb) (1 << ((sb)->s_blocksize_bits - 2))



static int block_to_path(struct inode * inode, long block, int offsets[DEPTH])

{

	int n = 0;
@@ -34,21 +37,21 @@ static int block_to_path(struct inode * inode, long block, int offsets[DEPTH]) 
			printk("MINIX-fs: block_to_path: "

			       "block %ld too big on dev %s\n",

				block, bdevname(sb->s_bdev, b));

	} else if (block < 7) {

	} else if (block < DIRCOUNT) {

		offsets[n++] = block;

	} else if ((block -= 7) < 256) {

		offsets[n++] = 7;

	} else if ((block -= DIRCOUNT) < INDIRCOUNT(sb)) {

		offsets[n++] = DIRCOUNT;

		offsets[n++] = block;

	} else if ((block -= 256) < 256*256) {

		offsets[n++] = 8;

		offsets[n++] = block>>8;

		offsets[n++] = block & 255;

	} else if ((block -= INDIRCOUNT(sb)) < INDIRCOUNT(sb) * INDIRCOUNT(sb)) {

		offsets[n++] = DIRCOUNT + 1;

		offsets[n++] = block / INDIRCOUNT(sb);

		offsets[n++] = block % INDIRCOUNT(sb);

	} else {

		block -= 256*256;

		offsets[n++] = 9;

		offsets[n++] = block>>16;

		offsets[n++] = (block>>8) & 255;

		offsets[n++] = block & 255;

		block -= INDIRCOUNT(sb) * INDIRCOUNT(sb);

		offsets[n++] = DIRCOUNT + 2;

		offsets[n++] = (block / INDIRCOUNT(sb)) / INDIRCOUNT(sb);

		offsets[n++] = (block / INDIRCOUNT(sb)) % INDIRCOUNT(sb);

		offsets[n++] = block % INDIRCOUNT(sb);

	}

	return n;

}

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