bug? in using generic read/write functions to read/write block devices in 2.4.11-pre2

["Vladimir V. Saveliev" <vs@namesys.com>]

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