linux-kernel - Re: [PATCH v7 6/8] block: Make bio structs pin pages rather than ref'ing if appropriate

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Message-ID: <Y8vjlH+w1sNBPJjU@infradead.org>
Date:   Sat, 21 Jan 2023 05:07:32 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v7 6/8] block: Make bio structs pin pages rather than
 ref'ing if appropriate

This really does three things:
 
 1) add the BIO_PAGE_PINNED infrastructure
 2) convert bio_iov_iter_get_pages to use iov_iter_extract_pages
 3) convert bio_map_user_iov to use iov_iter_extract_pages

so it should be three pages, with the first one also containing
what is in your previous patch.

> @@ -1183,7 +1185,7 @@ void __bio_release_pages(struct bio *bio, bool mark_dirty)
>  	bio_for_each_segment_all(bvec, bio, iter_all) {
>  		if (mark_dirty && !PageCompound(bvec->bv_page))
>  			set_page_dirty_lock(bvec->bv_page);
> -		put_page(bvec->bv_page);
> +		bio_release_page(bio, bvec->bv_page);

This can be micro-optimized a bit by only doing the flags conversion
once.