[lkml]   [2007]   [Feb]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [rfc][patch] mm: half-fix page tail zeroing on write problem
On Friday February 2, wrote:
> Hi,
> For no important reason, I've again looked at those zeroing patches that
> Neil did a while back. I've always thought that a simple
> `write(fd, NULL, size)` would cause the same sorts of problems.

Yeh, but who in their right mind would do that???
Oh, you did :-)

> Turns out it does. If you first write all 1s into a page, then do the
> `write(fd, NULL, size)` at the same position, you end up with all 0s in
> the page (test-case available on request). Incredible; surely this
> violates the spec?

Does it?
I guess filling with zeros isn't what one would expect, but you could
make a case for it being right.
write(fd, 0, size)
writes 'size' 0s. Cool. Ok, bad-cool.

> The buffered-write fixes I've got actually fix this properly, but they
> don't look like getting merged any time soon. We could do this simple
> patch which just reduces the chance of corruption from a certainty down
> to a small race.
> Any thoughts?

I cannot see why you make a change to fault_in_pages_writeable. Is it
just for symmetry?
For the rest, it certainly makes sense to return an early -EFAULT if
you cannot fault in the page.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2007-02-02 07:33    [W:0.037 / U:3.640 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site