2007-02-06 23:39:15

by Andrew Morton

[permalink] [raw]
Subject: Re: [PATCH 0/1][RFC] mm: prepare_write positive return value

On Tue, 06 Feb 2007 11:33:46 +0300
Dmitriy Monakhov <[email protected]> wrote:

> Almost all read/write operation handles data with chunks(segments or pages)
> and result has integral behaviour for folowing scenario:
> for_each_chunk() {
> res = op(....);
> if(IS_ERROR(res))
> return progress ? progress : res;
> progress += res;
> }
> prepare_write may has integral behaviour in case of blksize < pgsize,
> for example we successfully allocated/read some blocks, but not all of them,
> and than some error happend. Currently we eliminate this progress by doing
> vmtrunate() after prepare_has failed.
> It is good to have ability to signal about this progress. Interprete positive
> prepare_write() ret code as bytes num that fs ready to handle at this moment.
> I've ask SAW, he think it is sane. This size always less than PAGE_CACHE_SIZE
> so it less than AOP_TRUNCATED_PAGE too.
> BTH: This approach was used in OpenVZ 2.6.9 kernel in order to make FS with
> delayed allocation more correct, and its works well.
> I think not everybody will happy about this, but let's discuss all advantages
> and disadvantages of this change.

That seems to be a logical change. We'd need to review all the callers and
callees to make sure that they handle this change correctly.

Your changes deviate quite a lot from standard kernel coding style. Please fix

Please cc [email protected] on the next version of these patches. I'm
seriously running out of bandwidth over here and ext4 has other maintainers.