Re: [PATCH v2] Do a proper locking for mmap and block size change

Linus Torvalds
2012-11-29T20:11:17Z

On Thu, Nov 29, 2012 at 11:55 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> The blkdev_get_blocks() this is just sad.
>
> The underlying data structure is actually byte-based (it's
> "i_size_read(bdev->bd_inode"), but we convert it to a block-based
> number.
>
> Oops.

Oh, it's even worse than that. The DIO code ends up passing in buffer
heads that have sizes bigger than the inode i_blksize, which can cause
problems at the end of the disk. So blkdev_get_blocks() knows about
it, and will then "fix" that and shrink them down. The games with
"max_block" are hilarious.

In a really sad way.

That whole blkdev_get_blocks() function is pure and utter shit.

Linus