From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 31 Jan 2001 16:35:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 31 Jan 2001 16:35:38 -0500 Received: from [194.213.32.137] ([194.213.32.137]:4356 "EHLO bug.ucw.cz") by vger.kernel.org with ESMTP id ; Wed, 31 Jan 2001 16:35:25 -0500 Message-ID: <20010131223441.D231@bug.ucw.cz> Date: Wed, 31 Jan 2001 22:34:41 +0100 From: Pavel Machek To: kernel list Subject: CRC loop device: when you do not trust your disk subsystem Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.93i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! Here it is. With crc loop device, you can no longer get silent data corruption due to disk subsystem... Pavel --- clean/drivers/block/loop.c Mon Jan 8 22:49:50 2001 +++ linux/drivers/block/loop.c Mon Jan 8 22:44:09 2001 @@ -61,6 +61,7 @@ #include #include +#include #include @@ -118,6 +119,101 @@ return 0; } +#define ID printk(KERN_ERR "crc: info about (%s, %d, %d) ", kdevname(lo->lo_device), real_block, blksize); + + +static int transfer_crc(struct loop_device *lo, int cmd, char *raw_buf, + char *loop_buf, int size, int real_block) +{ + struct buffer_head *bh; + int blksize = 1024, nsect; /* Size of block on auxilary media */ + int cksum; + u32 *data; + nsect = blksize / 4; + + if (!lo->second_device) { + ID; printk( "reading from not-yet-setup crc device can result in armagedon. Dont try again.\n" ); + return -1; + } + bh = getblk(lo->second_device, 1+real_block/nsect, blksize); + if (!bh) { + ID; printk( "getblk returned NULL.\n" ); + return -1; + } + if (!buffer_uptodate(bh)) { + ll_rw_block(READ, 1, &bh); + wait_on_buffer(bh); + if (!buffer_uptodate(bh)) { + ID; printk( "could not read block with CRC\n" ); + goto error; + } + } + + data = (u32 *) bh->b_data; + if (cmd == READ) + cksum = csum_partial_copy_nocheck(raw_buf, loop_buf, size, 0); + else + cksum = csum_partial_copy_nocheck(loop_buf, raw_buf, size, 0); + + if (cmd == READ) { + if (le32_to_cpu(data[real_block%nsect]) != cksum) { + if (lo->lo_encrypt_key_size == 0) { /* Normal mode */ + ID; printk( "wrong checksum reading, is %x, should be %x\n", cksum, 0x1234 ); + goto error; + } else { + ID; printk( "wrong checksum repairing, setting to %x\n", cksum ); + goto repair; + } + } + } else { + repair: + data[real_block%nsect] = cpu_to_le32(cksum); + mark_buffer_uptodate(bh, 1); + mark_buffer_dirty(bh); + } + + brelse(bh); + return 0; +error: + brelse(bh); + return -1; + +} + +static int ioctl_crc(struct loop_device *lo, int cmd, unsigned long arg) +{ + struct file *file; + struct inode *inode; + int error; + + printk( "Entering ioctl_crc\n" ); + if (cmd != LOOP_CRC_SET_FD) + return -EINVAL; + + error = -EBADF; + file = fget(arg); + if (!file) + return -EINVAL; + + error = -EINVAL; + inode = file->f_dentry->d_inode; + if (!inode) { + printk(KERN_ERR "ioctl_crc: NULL inode?!?\n"); + goto out; + } + + if (S_ISBLK(inode->i_mode)) { + error = blkdev_open(inode, file); + lo->second_device = inode->i_rdev; + printk( "loop_crc: Registered device %x\n", lo->second_device ); + return error; + } else { + out: + fput(file); + return -EINVAL; + } +} + static int none_status(struct loop_device *lo, struct loop_info *info) { return 0; @@ -142,10 +238,19 @@ init: xor_status }; +struct loop_func_table crc_funcs = { + number: LO_CRYPT_CRC, + transfer: transfer_crc, + init: none_status, + ioctl: ioctl_crc +}; + /* xfer_funcs[0] is special - its release function is never called */ struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = { &none_funcs, - &xor_funcs + &xor_funcs, + NULL, NULL, NULL, NULL, NULL, + &crc_funcs, }; #define MAX_DISK_SIZE 1024*1024*1024 @@ -551,6 +656,7 @@ lo->transfer = NULL; lo->ioctl = NULL; lo->lo_device = 0; + lo->second_device = 0; lo->lo_encrypt_type = 0; lo->lo_offset = 0; lo->lo_encrypt_key_size = 0; --- clean/include/linux/loop.h Mon Nov 23 06:29:54 1998 +++ linux/include/linux/loop.h Sat Apr 15 13:22:57 2000 @@ -22,6 +22,7 @@ struct dentry *lo_dentry; int lo_refcnt; kdev_t lo_device; + kdev_t second_device; int lo_offset; int lo_encrypt_type; int lo_encrypt_key_size; @@ -94,6 +95,7 @@ #define LO_CRYPT_BLOW 4 #define LO_CRYPT_CAST128 5 #define LO_CRYPT_IDEA 6 +#define LO_CRYPT_CRC 7 #define LO_CRYPT_DUMMY 9 #define LO_CRYPT_SKIPJACK 10 #define MAX_LO_CRYPT 20 @@ -126,5 +128,6 @@ #define LOOP_CLR_FD 0x4C01 #define LOOP_SET_STATUS 0x4C02 #define LOOP_GET_STATUS 0x4C03 +#define LOOP_CRC_SET_FD 0x4C04 #endif -- I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care." Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org ----- End forwarded message ----- -- I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care." Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/