On Tue, 10 Aug 1999, Steve Dodd wrote:
> Date: Tue, 10 Aug 1999 09:03:58 +0100
> From: Steve Dodd <dirk@loth.demon.co.uk>
> To: Linus Torvalds <torvalds@transmeta.com>
> Cc: linux-kernel@vger.rutgers.edu
> Subject: filemap_nopage() tries to copy to page 0, eek.
>
> Hi,
>
> (Apologies in advance if you already know about this)
>
> I've just been chasing down the problem with writes to mmap()d areas hanging,
> and it turns out that filemap_nopage() will try to clobber page 0 if the
> page isn't found in the page cache and no_share is true:
>
> no_cached_page:
> .
> .
> .
> /*
> * Now it's ours and locked, we can do initial IO to it:
> */
> new_page = 0;
>
> page_not_uptodate:
> error = inode->i_op->readpage(file, page);
> if (!error) {
> wait_on_page(page);
> if (PageError(page))
> goto page_read_error;
> goto success;
> }
>
> success:
> old_page = page_address(page);
> if (!no_share) {
> ...
> }
>
> /*
> * No sharing ... copy to the new page.
> */
> if (!new_page)
> printk(KERN_CRIT "filemap_nopage(): erk, new_page == 0\n");
> copy_page(new_page, old_page);
>
> I don't claim to understand (yet) what the fix is; I'm also not on clear why
> the page fault handler just tries to re-enter itself, ultimately deadlocking
> on current->mm->mmap_sem -- does it show that I'm /way/ out of my depth
> here? ;-)
>
> --
> If breastfeeding a pig is sickening to you, what the hell are you
> doing on usenet? -- Aimee, on rec.music.tori-amos
>
> -
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- Chuck Lever
-- corporate: <chuckl@netscape.com> personal: <chucklever@netscape.net> or <cel@monkey.org>The Linux Scalability project: http://www.citi.umich.edu/projects/linux-scalability/
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