Commit 24d5493f authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: simplify bio_check_pages_dirty 



bio_check_pages_dirty currently inviolates the invariant that bv_page of
a bio_vec inside bi_vcnt shouldn't be zero, and that is going to become
really annoying with multpath biovecs.  Fortunately there isn't any
all that good reason for it - once we decide to defer freeing the bio
to a workqueue holding onto a few additional pages isn't really an
issue anymore.  So just check if there is a clean page that needs
dirtying in the first path, and do a second pass to free them if there
was none, while the cache is still hot.

Also use the chance to micro-optimize bio_dirty_fn a bit by not saving
irq state - we know we are called from a workqueue.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 76f17d8b

block/bio.c

+21 −35
Original line number Diff line number Diff line
@@ -1649,19 +1649,15 @@ static void bio_release_pages(struct bio *bio) 
	struct bio_vec *bvec;

	int i;



	bio_for_each_segment_all(bvec, bio, i) {

		struct page *page = bvec->bv_page;



		if (page)

			put_page(page);

	}

	bio_for_each_segment_all(bvec, bio, i)

		put_page(bvec->bv_page);

}



/*

 * bio_check_pages_dirty() will check that all the BIO's pages are still dirty.

 * If they are, then fine.  If, however, some pages are clean then they must

 * have been written out during the direct-IO read.  So we take another ref on

 * the BIO and the offending pages and re-dirty the pages in process context.

 * the BIO and re-dirty the pages in process context.

 *

 * It is expected that bio_check_pages_dirty() will wholly own the BIO from

 * here on.  It will run one put_page() against each page and will run one
@@ -1679,52 +1675,42 @@ static struct bio *bio_dirty_list; 
 */

static void bio_dirty_fn(struct work_struct *work)

{

	unsigned long flags;

	struct bio *bio;

	struct bio *bio, *next;



	spin_lock_irqsave(&bio_dirty_lock, flags);

	bio = bio_dirty_list;

	spin_lock_irq(&bio_dirty_lock);

	next = bio_dirty_list;

	bio_dirty_list = NULL;

	spin_unlock_irqrestore(&bio_dirty_lock, flags);

	spin_unlock_irq(&bio_dirty_lock);



	while (bio) {

		struct bio *next = bio->bi_private;

	while ((bio = next) != NULL) {

		next = bio->bi_private;



		bio_set_pages_dirty(bio);

		bio_release_pages(bio);

		bio_put(bio);

		bio = next;

	}

}



void bio_check_pages_dirty(struct bio *bio)

{

	struct bio_vec *bvec;

	int nr_clean_pages = 0;

	unsigned long flags;

	int i;



	bio_for_each_segment_all(bvec, bio, i) {

		struct page *page = bvec->bv_page;



		if (PageDirty(page) || PageCompound(page)) {

			put_page(page);

			bvec->bv_page = NULL;

		} else {

			nr_clean_pages++;

		if (!PageDirty(bvec->bv_page) && !PageCompound(bvec->bv_page))

			goto defer;

	}

	}



	if (nr_clean_pages) {

		unsigned long flags;



	bio_release_pages(bio);

	bio_put(bio);

	return;

defer:

	spin_lock_irqsave(&bio_dirty_lock, flags);

	bio->bi_private = bio_dirty_list;

	bio_dirty_list = bio;

	spin_unlock_irqrestore(&bio_dirty_lock, flags);

	schedule_work(&bio_dirty_work);

	} else {

		bio_put(bio);

	}

}

EXPORT_SYMBOL_GPL(bio_check_pages_dirty);

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