init/do_mounts_rd.c: fix ramdisk identification for padded cramfs

When a cramfs ramdisk padded with 512 bytes is given to the kernel, the current identify_ramdisk_image function fails to identify it. Tested with a padded cramfs image on an ARM based board. Signed-off-by: Neil Armstrong <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Davidlohr Bueso <[email protected]> Cc: Al Viro <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
chewitt · Nov 2, 2011 · f919b92 · f919b92
1 parent 0620d91
commit f919b92
Showing 1 changed file with 14 additions and 0 deletions.
diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c
@@ -119,6 +119,20 @@ identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor)
 		goto done;
 	}
 
+	/*
+	 * Read 512 bytes further to check if cramfs is padded
+	 */
+	sys_lseek(fd, start_block * BLOCK_SIZE + 0x200, 0);
+	sys_read(fd, buf, size);
+
+	if (cramfsb->magic == CRAMFS_MAGIC) {
+		printk(KERN_NOTICE
+		       "RAMDISK: cramfs filesystem found at block %d\n",
+		       start_block);
+		nblocks = (cramfsb->size + BLOCK_SIZE - 1) >> BLOCK_SIZE_BITS;
+		goto done;
+	}
+
 	/*
 	 * Read block 1 to test for minix and ext2 superblock
 	 */