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

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Date:   Mon, 23 Jan 2023 06:49:21 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        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

On Mon, Jan 23, 2023 at 11:28:40AM +0000, David Howells wrote:
> 	void __bio_release_pages(struct bio *bio, bool mark_dirty)
> 	{
> 		unsigned int gup_flags = bio_to_gup_flags(bio);
> 		struct bvec_iter_all iter_all;
> 		struct bio_vec *bvec;
> 
> 		bio_for_each_segment_all(bvec, bio, iter_all) {
> 			if (mark_dirty && !PageCompound(bvec->bv_page))
> 				set_page_dirty_lock(bvec->bv_page);
> 	>>>>		page_put_unpin(bvec->bv_page, gup_flags);
> 		}
> 	}
> 
> that ought to be a call to bio_release_page(), but the optimiser doesn't want
> to inline it:-/

Why?  __bio_release_pages is the fast path, no need to force using
bio_relese_page which is otherwise only used for error cleanup.