Re: 2.5.37 broke the floppy driver

[Jens Axboe]

On Mon, Sep 23 2002, Mikael Pettersson wrote:
> On Mon, 23 Sep 2002 11:10:41 +0200, Jens Axboe wrote:
> >On Sun, Sep 22 2002, Mikael Pettersson wrote:
> >> With 2.5.37, doing a write to floppy makes the kernel print
> >> "blk: request botched" and a few seconds later instantly reboot
> >> the machine (w/o any further messages). 2.5.36 works fine.
> >> 
> >> "dd bs=8k if=bzImage of=/dev/fd0" triggers this every time.
> >
> >Attached patch should fix the partial completion thing for floppy.
> >
> ># This is a BitKeeper generated patch for the following project:
> ># Project Name: Linux kernel tree
> ># This patch format is intended for GNU patch command version 2.5 or higher.
> ># This patch includes the following deltas:
> >#	           ChangeSet	1.601   -> 1.602  
> >#	drivers/block/ll_rw_blk.c	1.107   -> 1.108  
> 
> It's an improvement (the kernel doesn't reboot as soon as I
> read or write /dev/fd0), but there are still some strange
> things going on with floppy in 2.5.38 (this all worked in 2.5.36):
> 
> 1. dd if=/dev/fd0 bs=72k of=/tmp/a
>    (after reboot) only reads 2048 bytes; /dev/fd0 is actually 1.44M
> 2. dd if=/dev/fd0 bs=72k of=/tmp/a
>    (repeat the command) now it reads 10 records = 720K,
>    which is still only half of the true size
> 3. dd if=/dev/fd0H1440 bs=72k of=/tmp/a
>    oopses in blk_dev.c:do_open() line 676, see below:

Al? The first bug was a legitimate partial completion error in
ll_rw_blk, however there appears to be other breakage hitting floppy as
well.

> (2.5.38 tarball, plain UP config, gcc-2.95.3)
> 
> Unable to handle kernel paging request at virtual address 00001738
> c01370f0
> *pde = 00000000
> Oops: 0000
> CPU:    0
> EIP:    0060:[<c01370f0>]    Not tainted
> Using defaults from ksymoops -t elf32-i386 -a i386
> EFLAGS: 00010292
> eax: c02fe12c   ebx: c11a02a0   ecx: 00001810   edx: c7b09350
> esi: c11a0240   edi: c11a021c   ebp: 00000000   esp: c6c2df10
> ds: 0068   es: 0068   ss: 0068
> Stack: c7b09350 c6f09aa0 ffffffe9 c114b360 c11a0260 00000000 00000000 c0137276 
>        c11a0240 c7b09350 c6f09aa0 c7b09350 c6f09aa0 c7b09350 c0130869 c7b09350 
>        c6f09aa0 00000000 c118c000 00008000 bffff9a8 c01307a6 c6c96ca0 c114b360 
> Call Trace: [<c0137276>] [<c0130869>] [<c01307a6>] [<c0130b13>] [<c0106dbf>] 
> Code: 83 b9 28 ff ff ff 00 75 1f 8b 46 44 ff 48 50 8b 46 44 8d 48 
> 
> 
> >>EIP; c01370f0 <do_open+258/344>   <=====
> 
> >>eax; c02fe12c <blk_dev+22c/d340>
> >>ebx; c11a02a0 <END_OF_CODE+e87c20/????>
> >>ecx; 00001810 Before first symbol
> >>edx; c7b09350 <END_OF_CODE+77f0cd0/????>
> >>esi; c11a0240 <END_OF_CODE+e87bc0/????>
> >>edi; c11a021c <END_OF_CODE+e87b9c/????>
> >>esp; c6c2df10 <END_OF_CODE+6915890/????>
> 
> Trace; c0137276 <blkdev_open+22/28>
> Trace; c0130869 <dentry_open+b9/16c>
> Trace; c01307a6 <filp_open+52/5c>
> Trace; c0130b13 <sys_open+37/78>
> Trace; c0106dbf <syscall_call+7/b>
> 
> Code;  c01370f0 <do_open+258/344>
> 00000000 <_EIP>:
> Code;  c01370f0 <do_open+258/344>   <=====
>    0:   83 b9 28 ff ff ff 00      cmpl   $0x0,0xffffff28(%ecx)   <=====
> Code;  c01370f7 <do_open+25f/344>
>    7:   75 1f                     jne    28 <_EIP+0x28> c0137118 <do_open+280/344>
> Code;  c01370f9 <do_open+261/344>
>    9:   8b 46 44                  mov    0x44(%esi),%eax
> Code;  c01370fc <do_open+264/344>
>    c:   ff 48 50                  decl   0x50(%eax)
> Code;  c01370ff <do_open+267/344>
>    f:   8b 46 44                  mov    0x44(%esi),%eax
> Code;  c0137102 <do_open+26a/344>
>   12:   8d 48 00                  lea    0x0(%eax),%ecx
> 
> fs/block_dev.c:
> static int do_open(struct block_device *bdev, struct inode *inode, struct file *file)
> {
> 	...
> 	if (bdev->bd_contains == bdev) {
> 		...
> 	} else {
> 		down(&bdev->bd_contains->bd_sem);
> 		bdev->bd_contains->bd_part_count++;
> 		if (!bdev->bd_openers) {
> 			struct gendisk *g = get_gendisk(dev);
> 			struct hd_struct *p;
> BOGUS? ->		p = g->part + minor(dev) - g->first_minor - 1;
> 			inode->i_data.backing_dev_info =
> 			   bdev->bd_inode->i_data.backing_dev_info =
> 			   bdev->bd_contains->bd_inode->i_data.backing_dev_info;
> OOPS HERE ->		if (!p->nr_sects) {
> 				bdev->bd_contains->bd_part_count--;
> 				up(&bdev->bd_contains->bd_sem);
> 				ret = -ENXIO;
> 				goto out2;
> 			}
> 
> I correlated a gdb disassembly with do_open(), and it looks like
> 'p' got a bogus value (ecx, 0x1810) at the indicated line.
> 
> /Mikael
> 

-- 
Jens Axboe