Buffer cache confusion? Re: [reiserfs-list] bug? in using generic read/write functions to read/write block devices in 2.4.11-pre2

[Eric Whiting <ewhiting@amis.com>]

I see a similar odd failure with jfs in 2.4.11pre1. Is this related to
the 2.4.11preX buffer cache improvements?

eric


# uname -a
2.4.11-pre1 #1 SMP Tue Oct 2 12:28:07 MDT 2001 i686
# mkfs.jfs /dev/hdc3
mkfs.jfs development version: $Name: v1_0_6 $
Warning!  All data on device /dev/hdc3 will be lost!
Continue? (Y/N) Y
Format completed successfully.
10241436 kilobytes total disk space.
# mount -t jfs /dev/hdc3 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/hdc3,
        or too many mounted file systems


"Vladimir V. Saveliev" wrote:
> 
> Hi
> 
> It looks like something wrong happens with writing/reading to block
> device using generic read/write functions when one does:
> 
> mke2fs /dev/hda1 (blocksize is 4096)
> mount /dev/hda1
> umount /dev/hda1
> mke2fs /dev/hda1 - FAILS with
> Warning: could not write 8 blocks in inode table starting at 492004:
> Attempt to write block from filesystem resulted in short write
> 
> (note that /dev/hda1 should be big enough - 3gb is enogh for example)
> 
> Explanation of what happens (could be wrong and unclear):
> 
> blocksize of /dev/hda1 was 1024. So, /dev/hda1's inode->i_blkbits is set
> to 10.
> mount-ing used set_blocksize() to change blocksize to 4096 in
> blk_size[][].
> But inode of /dev/hda1 still has i_blkbits which makes
> block_prepare_write to create buffers of 1024 bytes and call
> blkdev_get_block for each of them.
> fs/block_dev.c:/max_block calculates number of blocks on the device
> using blk_size[][] and thinks that there are 4 times less blocks on the
> device.
> 
> Thanks,
> vs
> 
> PS: thanks to Elena <grev@namesys.botik.ru> for finding that