[lkml]   [2007]   [Feb]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] aio: propogate post-EIOCBQUEUED errors to completion event
On Tue, Feb 20, 2007 at 11:01:50AM -0500, Trond Myklebust wrote:
> On Mon, 2007-02-19 at 19:21 -0500, Benjamin LaHaise wrote:
> > On Mon, Feb 19, 2007 at 04:50:48PM -0500, Chris Mason wrote:
> > > aio is not responsible for this particular synchronization. Those fixes
> > > (if we make them) should come from other places. The patch is important
> > > to get aio error handling right.
> > >
> > > I would argue that one common cause of the EIO is userland
> > > error (mmap concurrent with O_DIRECT), and EIO is the correct answer.
> >
> > I disagree. That means that using the pagecache to synchronize things like
> > the proposed online defragmentation will occasionally make O_DIRECT users
> > fail. O_DIRECT doesn't prevent the sysadmin from copying files or other
> > page cache uses, which implies that generating an error in these cases is
> > horrifically broken. If only root could do it, I wouldn't complain, but
> > this would seem to imply that user vs root holes still exist.
> We don't try to resolve "conflicting" writes between ordinary mmap() and
> write(), so why should we be doing it for mmap and O_DIRECT?
> mmap() is designed to violate the ordinary mutex locks for write(), so
> if a conflict arises, whether it be with O_DIRECT or ordinary writes
> then it is a case of "last writer wins".

There are some strange O_DIRECT corner cases in here such that the 'last
writer' may actually be a 'last reader' and winning can mean have a copy
of the page in page cache older than the copy on disk.

One option is to have invalidate_inode_pages2_range continue if it can't
toss a page but still return something that O_DIRECT ignores (living
with the race), but it looks like I can make a launder_page op that does
the right thing. I'll give it a shot.


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: 2007-02-20 17:13    [W:0.224 / U:0.232 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site