lkml.org 
[lkml]   [2006]   [May]   [31]   [last100]   RSS Feed
Views: [more markup]   [less markup]   [headers]   [forward]  
 
 
Messages in this thread
/
DateWed, 31 May 2006 16:09:06 +0100 (BST)
FromHugh Dickins <>
SubjectRe: [rfc][patch] remove racy sync_page?
On Wed, 31 May 2006, Nick Piggin wrote:
> Jens Axboe wrote:
> > 
> > Maybe I'm being dense, but I don't see a problem there. You _should_
> > call the new mapping sync page if it has been migrated.
> 
> But can some other thread calling lock_page first find the old mapping,
> and then run its ->sync_page which finds the new mapping? While it may
> not matter for anyone in-tree, it does break the API so it would be
> better to either fix it or rip it out than be silently buggy.

Splicing a page from one mapping to another is rather worrying/exciting,
but it does look safely done to me.  remove_mapping checks page_count
while page lock and old mapping->tree_lock are held, and gives up if
anyone else has an interest in the page.  And we already know it's
unsafe to lock_page without holding a reference to the page, don't we?

Hugh
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-05-31 17:11    [from the cache]
©2003-2008