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

From: Alexander Viro (
Date: Wed Oct 03 2001 - 02:05:17 EST

On Wed, 3 Oct 2001, Neil Brown wrote:

> On Wednesday October 3, 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.

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