From: Andrew Morton <akpm@digeo.com>
To: Steve Lord <lord@sgi.com>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: 2.5 O)DIRECT problem
Date: Fri, 04 Oct 2002 13:29:40 -0700 [thread overview]
Message-ID: <3D9DFA34.581D9D98@digeo.com> (raw)
In-Reply-To: 1033762674.2457.73.camel@jen.americas.sgi.com
Steve Lord wrote:
>
> Hi Andrew,
>
> I ran into a problem with 2.5's O_DIRECT read path,
>
> generic_file_direct_IO usually ends up in generic_direct_IO
> this does bounds checking on the I/O and then flushes any
> cached data.
>
> Once we return to generic_file_direct_IO we unconditionally
> call invalidate_inode_pages2 if there are any cached pages.
>
> If we make a non-aligned O_DIRECT read call, the end result is we
> call invalidate_inode_pages2, but we do not do the filemap_fdatawrite,
> filemap_fdatawait calls. End result is we throw the buffered data away.
Well you could always switch to Linus' current BK tree, in
which invalidate_inode_pages2() is a no-op (whoops).
> Either the flush needs to happen before the bounds checks, or the
> invalidate should only be done on a successful write. It looks
> pretty hard to detect the latter case with the current structure,
> we can get EINVAL from the bounds check and possibly from an
> aligned, but invalid memory address being passed in.
Yes I agree; let's just do the sync before any checks.
I think it should be moved into generic_file_direct_IO(),
because that's the place where the invalidation happens, yes?
next prev parent reply other threads:[~2002-10-04 20:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-04 20:17 2.5 O)DIRECT problem Steve Lord
2002-10-04 20:29 ` Andrew Morton [this message]
2002-10-04 20:38 ` Steve Lord
2002-10-04 20:51 ` Andrew Morton
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