On Tue 19-06-12 13:43:26, Jeff Moyer wrote:
> Torsten Hilbrich <torsten.hilbrich@xxxxxxxxxxx> writes:
>
> > The system where I reproduced the problem upstream is an amd64 based
> > ubuntu 12.04 installation. I used both v3.3.8 and v3.4 for reproducing.
> >
> > The partition layout is the following:
> >
> > ======================================================================
> >
> > Disk /dev/sda: 120.0 GB, 120034123776 bytes
> > 255 heads, 63 sectors/track, 14593 cylinders, total 234441648 sectors
> > Units = sectors of 1 * 512 = 512 bytes
> > Sector size (logical/physical): 512 bytes / 512 bytes
> > I/O size (minimum/optimal): 512 bytes / 512 bytes
> > Disk identifier: 0x1669c708
> >
> > Device Boot Start End Blocks Id System
> > /dev/sda1 * 63 86285114 43142526 83 Linux
> > /dev/sda2 216797175 234436544 8819685 82 Linux swap / Solaris
> > /dev/sda3 86285115 87088364 401625 83 Linux
> > /dev/sda4 87088426 216797174 64854374+ 5 Extended
> > /dev/sda5 87088428 91104614 2008093+ 83 Linux
> > /dev/sda6 91104678 216797174 62846248+ 8e Linux LVM
> >
> > Partition table entries are not in disk order
>
> OK, got it to reproduce, thanks for the info. The attached patch fixed
> the problem for me.
>
> Note, though, that the patch doesn't make sense to me. blkdev_max_block
> returns i_size_read(blkdev_inode) >> block_size. This should be the
> *size* of the block device, not the max block. The code in
> fs/block_device.c uses the return value in two different ways!
>
> static int
> blkdev_get_block(struct inode *inode, sector_t iblock,
> struct buffer_head *bh, int create)
> {
> if (iblock >= blkdev_max_block(I_BDEV(inode))) {
>
> Here, the return value from blkdev_max_block is interpreted as the size
> of the device, so actually max_block + 1.
>
> static int
> blkdev_get_blocks(struct inode *inode, sector_t iblock,
> struct buffer_head *bh, int create)
> {
> sector_t end_block = blkdev_max_block(I_BDEV(inode));
> unsigned long max_blocks = bh->b_size >> inode->i_blkbits;
>
> if ((iblock + max_blocks) > end_block) {
>
> Here, the return value is treated as the maximum addressable block
> number. Given the fact that I had to modify init_page_buffers to treat
> the return value from blkdev_max_block as the maximum addressable block,
> I clearly have something wrong with my logic. Nick, Jens, care to set
> my head straight?
I think it can have something to do with the fact that the partition size
is not a multiple of 4k (i.e. expected block size)?
BTW: blkdev_max_block() is a terrible name for something that intends to
return size in blocks...
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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