Re: [PATCH v4 2/3] mm: Provide a function to get an additional pin on a page

[David Hildenbrand]

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@xxxxxxxxxx>
> cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> cc: David Hildenbrand <david@xxxxxxxxxx>
> cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
> cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> cc: Jens Axboe <axboe@xxxxxxxxx>
> cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> cc: Jan Kara <jack@xxxxxxx>
> cc: Jeff Layton <jlayton@xxxxxxxxxx>
> cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
> cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> cc: Hillf Danton <hdanton@xxxxxxxx>
> cc: Christian Brauner <brauner@xxxxxxxxxx>
> cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> cc: linux-fsdevel@xxxxxxxxxxxxxxx
> cc: linux-block@xxxxxxxxxxxxxxx
> cc: linux-kernel@xxxxxxxxxxxxxxx
> cc: linux-mm@xxxxxxxxx
> ---

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Thanks,

David / dhildenb