Linux Virtualization - Jul 2019 - [PATCH 03/12] block: bio_release_pages: use flags arg instead of bool

From: John Hubbard <jhubbard at nvidia.com>

In commit d241a95f3514 ("block: optionally mark pages dirty in
bio_release_pages"), new "bool mark_dirty" argument was added to
bio_release_pages.

In upcoming work, another bool argument (to indicate that the pages came
from get_user_pages) is going to be added. That's one bool too many,
because it's not desirable have calls of the form:

    foo(true, false, true, etc);

In order to prepare for that, change the argument from a bool, to a
typesafe (enum-based) flags argument.

Cc: Christoph Hellwig <hch at infradead.org>
Cc: J?r?me Glisse <jglisse at redhat.com>
Cc: Minwoo Im <minwoo.im.dev at gmail.com>
Cc: Jens Axboe <axboe at kernel.dk>
Signed-off-by: John Hubbard <jhubbard at nvidia.com>
---
 block/bio.c         | 12 ++++++------
 fs/block_dev.c      |  4 ++--
 fs/direct-io.c      |  2 +-
 include/linux/bio.h | 13 ++++++++++++-
 4 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 299a0e7651ec..7675e2de509d 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -833,7 +833,7 @@ int bio_add_page(struct bio *bio, struct page *page,
 }
 EXPORT_SYMBOL(bio_add_page);
 
-void bio_release_pages(struct bio *bio, bool mark_dirty)
+void bio_release_pages(struct bio *bio, enum bio_rp_flags_t flags)
 {
 	struct bvec_iter_all iter_all;
 	struct bio_vec *bvec;
@@ -842,7 +842,7 @@ void bio_release_pages(struct bio *bio, bool mark_dirty)
 		return;
 
 	bio_for_each_segment_all(bvec, bio, iter_all) {
-		if (mark_dirty && !PageCompound(bvec->bv_page))
+		if ((flags & BIO_RP_MARK_DIRTY) &&
!PageCompound(bvec->bv_page))
 			set_page_dirty_lock(bvec->bv_page);
 		put_page(bvec->bv_page);
 	}
@@ -1421,7 +1421,7 @@ struct bio *bio_map_user_iov(struct request_queue *q,
 	return bio;
 
  out_unmap:
-	bio_release_pages(bio, false);
+	bio_release_pages(bio, BIO_RP_NORMAL);
 	bio_put(bio);
 	return ERR_PTR(ret);
 }
@@ -1437,7 +1437,7 @@ struct bio *bio_map_user_iov(struct request_queue *q,
  */
 void bio_unmap_user(struct bio *bio)
 {
-	bio_release_pages(bio, bio_data_dir(bio) == READ);
+	bio_release_pages(bio, bio_rp_dirty_flag(bio_data_dir(bio) == READ));
 	bio_put(bio);
 	bio_put(bio);
 }
@@ -1683,7 +1683,7 @@ static void bio_dirty_fn(struct work_struct *work)
 	while ((bio = next) != NULL) {
 		next = bio->bi_private;
 
-		bio_release_pages(bio, true);
+		bio_release_pages(bio, BIO_RP_MARK_DIRTY);
 		bio_put(bio);
 	}
 }
@@ -1699,7 +1699,7 @@ void bio_check_pages_dirty(struct bio *bio)
 			goto defer;
 	}
 
-	bio_release_pages(bio, false);
+	bio_release_pages(bio, BIO_RP_NORMAL);
 	bio_put(bio);
 	return;
 defer:
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 4707dfff991b..9fe6616f8788 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -259,7 +259,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct
iov_iter *iter,
 	}
 	__set_current_state(TASK_RUNNING);
 
-	bio_release_pages(&bio, should_dirty);
+	bio_release_pages(&bio, bio_rp_dirty_flag(should_dirty));
 	if (unlikely(bio.bi_status))
 		ret = blk_status_to_errno(bio.bi_status);
 
@@ -329,7 +329,7 @@ static void blkdev_bio_end_io(struct bio *bio)
 	if (should_dirty) {
 		bio_check_pages_dirty(bio);
 	} else {
-		bio_release_pages(bio, false);
+		bio_release_pages(bio, BIO_RP_NORMAL);
 		bio_put(bio);
 	}
 }
diff --git a/fs/direct-io.c b/fs/direct-io.c
index ae196784f487..423ef431ddda 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -551,7 +551,7 @@ static blk_status_t dio_bio_complete(struct dio *dio, struct
bio *bio)
 	if (dio->is_async && should_dirty) {
 		bio_check_pages_dirty(bio);	/* transfers ownership */
 	} else {
-		bio_release_pages(bio, should_dirty);
+		bio_release_pages(bio, bio_rp_dirty_flag(should_dirty));
 		bio_put(bio);
 	}
 	return err;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 3cdb84cdc488..2715e55679c1 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -440,7 +440,18 @@ bool __bio_try_merge_page(struct bio *bio, struct page
*page,
 void __bio_add_page(struct bio *bio, struct page *page,
 		unsigned int len, unsigned int off);
 int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter);
-void bio_release_pages(struct bio *bio, bool mark_dirty);
+
+enum bio_rp_flags_t {
+	BIO_RP_NORMAL		= 0,
+	BIO_RP_MARK_DIRTY	= 1,
+};
+
+static inline enum bio_rp_flags_t bio_rp_dirty_flag(bool mark_dirty)
+{
+	return mark_dirty ? BIO_RP_MARK_DIRTY : BIO_RP_NORMAL;
+}
+
+void bio_release_pages(struct bio *bio, enum bio_rp_flags_t flags);
 struct rq_map_data;
 extern struct bio *bio_map_user_iov(struct request_queue *,
 				    struct iov_iter *, gfp_t);
-- 
2.22.0

On Tue, Jul 23, 2019 at 10:30:53PM -0700, Christoph Hellwig
wrote:
> On Tue, Jul 23, 2019 at 09:25:09PM -0700, john.hubbard at gmail.com wrote:
> > From: John Hubbard <jhubbard at nvidia.com>
> > 
> > In commit d241a95f3514 ("block: optionally mark pages dirty in
> > bio_release_pages"), new "bool mark_dirty" argument was
added to
> > bio_release_pages.
> > 
> > In upcoming work, another bool argument (to indicate that the pages
came
> > from get_user_pages) is going to be added. That's one bool too
many,
> > because it's not desirable have calls of the form:
> 
> All pages releases by bio_release_pages should come from
> get_get_user_pages, so I don't really see the point here.
No they do not all comes from GUP for see various callers
of bio_check_pages_dirty() for instance iomap_dio_zero()

I have carefully tracked down all this and i did not do
anyconvertion just for the fun of it :)

Cheers,
J?r?me