Messages in this thread | | | Date | Mon, 3 Mar 2008 21:17:28 +0900 | Subject | Re: [PATCH] block: fix residual byte count handling | From | FUJITA Tomonori <> |
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On Mon, 03 Mar 2008 18:21:13 +0900 Tejun Heo <htejun@gmail.com> wrote:
> FUJITA Tomonori wrote: > >>> I can't see what changing the meaning of rq->data_len (and > >>> investigating all the block drivers) gives us. > >> No matter which way you go, you change the meaning of rq->data_len and > >> you MUST inspect rq->data_len usage whichever way you go. > > > > The patch doens't change that rq->data_len means the true data > > length. But yeah, it breaks rq->data_len == sum(sg). So it might break > > some drivers. > > Yeah, that's what I was saying. You end up breaking one of the two > assumptions. As sglist is getting modified for any driver if it has DMA > alignment set, whether rq->data_len is adjusted together or not, sglist > and data_len usages have to be audited.
My patch (well, James' original approach) doesn't affect drivers that don't use drain buffer. rq->data_len still means the true data length and rq->data_len is equal to sum(sg) for them. So right now we need to audit only libata.
But your patch changes the meaning of rq->data_len. It affects all the drivers. So it breaks non libata stuff, like the SMP handler. We need to audit all the drivers.
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