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Message-ID: <de425aeb-4064-733a-52ed-e702c640c36f@redhat.com>
Date:   Wed, 31 May 2023 09:42:26 +0200
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To:     David Howells <dhowells@redhat.com>,
        Christoph Hellwig <hch@infradead.org>,
        Lorenzo Stoakes <lstoakes@gmail.com>
Cc:     Jens Axboe <axboe@kernel.dk>, Al Viro <viro@zeniv.linux.org.uk>,
        Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
        Jeff Layton <jlayton@kernel.org>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        Hillf Danton <hdanton@sina.com>,
        Christian Brauner <brauner@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>,
        John Hubbard <jhubbard@nvidia.com>
References: <20230526214142.958751-1-dhowells@redhat.com>
 <20230526214142.958751-3-dhowells@redhat.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
Subject: Re: [PATCH v4 2/3] mm: Provide a function to get an additional pin on
 a page
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On 26.05.23 23:41, David Howells wrote:
> Provide a function to get an additional pin on a page that we already have
> a pin on.  This will be used in fs/direct-io.c when dispatching multiple
> bios to a page we've extracted from a user-backed iter rather than redoing
> the extraction.
> 

I guess this function is only used for "replicating" an existing pin, 
and not changing the semantics of an existing pin: something that was 
pinned !FOLL_LONGTERM cannot suddenly become effectively pinned 
FOLL_LONGTERM.

Out of curiosity, could we end up passing in an anonymous page, or is 
this almost exclusively for pagecache+zero pages? (I rememebr John H. 
had a similar patch where he said it would not apply to anon pages)

> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Christoph Hellwig <hch@infradead.org>
> cc: David Hildenbrand <david@redhat.com>
> cc: Lorenzo Stoakes <lstoakes@gmail.com>
> cc: Andrew Morton <akpm@linux-foundation.org>
> cc: Jens Axboe <axboe@kernel.dk>
> cc: Al Viro <viro@zeniv.linux.org.uk>
> cc: Matthew Wilcox <willy@infradead.org>
> cc: Jan Kara <jack@suse.cz>
> cc: Jeff Layton <jlayton@kernel.org>
> cc: Jason Gunthorpe <jgg@nvidia.com>
> cc: Logan Gunthorpe <logang@deltatee.com>
> cc: Hillf Danton <hdanton@sina.com>
> cc: Christian Brauner <brauner@kernel.org>
> cc: Linus Torvalds <torvalds@linux-foundation.org>
> cc: linux-fsdevel@vger.kernel.org
> cc: linux-block@vger.kernel.org
> cc: linux-kernel@vger.kernel.org
> cc: linux-mm@kvack.org
> ---

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb