Re: 2.4.11-pre2 fs/buffer.c: invalidate: busy buffer

Alexander Viro
2001-10-03T07:05:07Z

On Wed, 3 Oct 2001, Neil Brown wrote:

> On Wednesday October 3, adilger@turbolabs.com wrote:

> > 3) Rewrite to do I/O directly via pagecache?
>
> 4) Rewrite to do I/O directly via generic_make_request just like it
> does for all other I/O to underlying devices.
> It is on my (mental) todo list, but doesn't have a high priority.
> At the same time, it would be good to get write_disk_sb to notice
> if the write failed.....

Folks, there's a problem aside of set_blocksize(). You are doing memset
and memcpy on unlocked buffer returned by getblk(). That's a race -
if that buffer is currently being read into, we will get a random crap.
And write it to disk afterwards.

General rule: don't modify buffer you've got from getblk() unless you've
locked it and mark it uptodate before you unlock. We had the same
bug in ext2, BTW.