linux-kernel - Re: [PATCH v5 8/9] iov_iter, block: Make bio structs pin pages rather than ref'ing if appropriate

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Message-ID: <147887.1673535529@warthog.procyon.org.uk>
Date:   Thu, 12 Jan 2023 14:58:49 +0000
From:   David Howells <dhowells@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     dhowells@...hat.com, Al Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        Christoph Hellwig <hch@....de>,
        Matthew Wilcox <willy@...radead.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        linux-block@...r.kernel.org, Jeff Layton <jlayton@...nel.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 8/9] iov_iter, block: Make bio structs pin pages rather than ref'ing if appropriate

Christoph Hellwig <hch@...radead.org> wrote:

> But given that all calls for the same iter type return the same
> cleanup_mode by defintion I'm not even sure we need any of this
> debug checking, and might as well just do:
> 
> 	if (cleanup_mode & FOLL_GET)
>  		bio_set_flag(bio, BIO_PAGE_REFFED);
>  	else if (cleanup_mode & FOLL_PIN)
>  		bio_set_flag(bio, BIO_PAGE_PINNED);

That's kind of what I'm doing - though I've left out the else just in case the
VM decides to indicate back both FOLL_GET and FOLL_PIN.  I'm not sure why it
would but...

David