linux-kernel - Re: [PATCH v6 1/3] mm/gup: add make_dirty arg to put_user_pages_dirty

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Date:   Tue, 6 Aug 2019 13:43:42 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Ira Weiny <ira.weiny@...el.com>, <john.hubbard@...il.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Björn Töpel <bjorn.topel@...el.com>,
        Boaz Harrosh <boaz@...xistor.com>,
        Christoph Hellwig <hch@....de>,
        Daniel Vetter <daniel@...ll.ch>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        David Airlie <airlied@...ux.ie>,
        "David S . Miller" <davem@...emloft.net>,
        Ilya Dryomov <idryomov@...il.com>, Jan Kara <jack@...e.cz>,
        Jason Gunthorpe <jgg@...pe.ca>, Jens Axboe <axboe@...nel.dk>,
        Jérôme Glisse <jglisse@...hat.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Matthew Wilcox <willy@...radead.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        Ming Lei <ming.lei@...hat.com>, Sage Weil <sage@...hat.com>,
        Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        Yan Zheng <zyan@...hat.com>, <netdev@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-mm@...ck.org>,
        <linux-rdma@...r.kernel.org>, <bpf@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 1/3] mm/gup: add make_dirty arg to
 put_user_pages_dirty_lock()

On 8/6/19 10:40 AM, Ira Weiny wrote:
> On Sun, Aug 04, 2019 at 02:40:40PM -0700, john.hubbard@...il.com wrote:
>> From: John Hubbard <jhubbard@...dia.com>
>>
>> Provide a more capable variation of put_user_pages_dirty_lock(),
>> and delete put_user_pages_dirty(). This is based on the
>> following:
>>
>> 1. Lots of call sites become simpler if a bool is passed
>> into put_user_page*(), instead of making the call site
>> choose which put_user_page*() variant to call.
>>
>> 2. Christoph Hellwig's observation that set_page_dirty_lock()
>> is usually correct, and set_page_dirty() is usually a
>> bug, or at least questionable, within a put_user_page*()
>> calling chain.
>>
>> This leads to the following API choices:
>>
>>     * put_user_pages_dirty_lock(page, npages, make_dirty)
>>
>>     * There is no put_user_pages_dirty(). You have to
>>       hand code that, in the rare case that it's
>>       required.
>>
>> Reviewed-by: Christoph Hellwig <hch@....de>
>> Cc: Matthew Wilcox <willy@...radead.org>
>> Cc: Jan Kara <jack@...e.cz>
>> Cc: Ira Weiny <ira.weiny@...el.com>
>> Cc: Jason Gunthorpe <jgg@...pe.ca>
>> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> 
> I assume this is superseded by the patch in the large series?
> 

Actually, it's the other way around (there is a note that that effect
in the admittedly wall-of-text cover letter [1] in the 34-patch series.

However, I'm trying hard to ensure that it doesn't actually matter:

* Patch 1 in the latest of each patch series, is identical

* I'm reposting the two series together.

...and yes, it might have been better to merge the two patchsets, but
the smaller one is more reviewable. And as a result, Andrew has already
merged it into the akpm tree.


[1] https://lore.kernel.org/r/20190804224915.28669-1-jhubbard@nvidia.com

thanks,
-- 
John Hubbard
NVIDIA