linux-kernel - Re: [PATCH] aio: propogate post-EIOCBQUEUED errors to completion event

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Message-ID: <20070220160615.GT31205@kvack.org>
Date:	Tue, 20 Feb 2007 11:06:15 -0500
From:	Benjamin LaHaise <bcrl@...ck.org>
To:	Trond Myklebust <trond.myklebust@....uio.no>
Cc:	Chris Mason <chris.mason@...cle.com>,
	"Ananiev, Leonid I" <leonid.i.ananiev@...el.com>,
	Zach Brown <zach.brown@...cle.com>, linux-aio@...ck.org,
	linux-kernel@...r.kernel.org,
	Suparna bhattacharya <suparna@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] aio: propogate post-EIOCBQUEUED errors to completion event

On Tue, Feb 20, 2007 at 11:01:50AM -0500, Trond Myklebust wrote:
> 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?

Yes we do -- both writes will succeed.  More importantly, if one modifies 
the first 512 bytes of a page and the other modifies the last 512 bytes of 
the page, both writes will show up in the completed result.  This is not the 
case with the -EIO bailout.

> 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".

Except that we're not handling cases like the one mentioned above, which 
is quite broken.

		-ben
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