Re: ramdisk size bug in 2.4.17-pre2

[Tachino Nobuhiro]

Hello,

I think following one-line patch fixes the bug.

diff -Nur linux-2.4.17-pre7.org/fs/block_dev.c linux-2.4.17-pre7/fs/block_dev.c
--- linux-2.4.17-pre7.org/fs/block_dev.c	Mon Dec 10 17:34:52 2001
+++ linux-2.4.17-pre7/fs/block_dev.c	Mon Dec 10 17:48:21 2001
@@ -329,6 +329,7 @@
 			inode->i_bdev = new_bdev;
 			inode->i_data.a_ops = &def_blk_aops;
 			inode->i_data.gfp_mask = GFP_USER;
+			inode->i_mode = S_IFBLK;
 			spin_lock(&bdev_lock);
 			bdev = bdfind(dev, head);
 			if (!bdev) {

generic_file_write() checks whether i_mapping->host is a block device and
if it is a block device, i_size is used as a size of block device.
but it does not work because bdget() does not set inode->i_mode to S_IFBLK.

At Fri, 7 Dec 2001 16:07:02 +0100,
Erik Mouw wrote:
> 
> Hi,
> 
> It looks like the ramdisk driver in 2.4.17-pre2 doesn't honor the
> rd_size parameter:
> 
>   root@arthur:/tmp #uname -a
>   Linux arthur 2.4.17-pre2 #1 Sat Dec 1 00:47:24 CET 2001 i686 unknown
>   root@arthur:/tmp #cat /proc/sys/kernel/tainted 
>   0
>   root@arthur:/tmp #modinfo rd
>   filename:    /lib/modules/2.4.17-pre2/kernel/drivers/block/rd.o
>   description: <none>
>   author:      <none>
>   license:     "GPL"
>   parm:        rd_size int, description "Size of each RAM disk in kbytes."
>   parm:        rd_blocksize int, description "Blocksize of each RAM disk in bytes."
>   root@arthur:/tmp #modprobe rd rd_size=8192
>   RAMDISK driver initialized: 16 RAM disks of 8192K size 1024 blocksize
> 
> So I would expect that each ramdisk is 8192kB. But:
> 
>   root@arthur:/tmp #dd if=/dev/zero of=/dev/ram1 bs=1k count=16384
>   16384+0 records in
>   16384+0 records out
> 
> IOW: writing 16MB to a 8MB ramdisk happily succeeds.
> 
> The last time I tried this was with 2.4.10-ac10, which didn't have this
> bug.
> 
> 
> Erik
> [who will investigate further but is currently -ENOTIME]
> 
> -- 
> J.A.K. (Erik) Mouw, Information and Communication Theory Group, Faculty
> of Information Technology and Systems, Delft University of Technology,
> PO BOX 5031, 2600 GA Delft, The Netherlands  Phone: [phone]
> Fax: [phone]  Email: [e-mail]
> WWW: http://www-ict.its.tudelft.nl/~erik/
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