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    SubjectRe: [PATCH 0/1][RFC] mm: prepare_write positive return value
    On Tue, 06 Feb 2007 11:33:46 +0300
    Dmitriy Monakhov <dmonakhov@sw.ru> 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
    that.

    Please cc linux-ext4@vger.kernel.org on the next version of these patches. I'm
    seriously running out of bandwidth over here and ext4 has other maintainers.

    Thanks.
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