diff mbox series

[03/12] block: bio_release_pages: use flags arg instead of bool

Message ID 20190724042518.14363-4-jhubbard@nvidia.com (mailing list archive)
State New, archived
Headers show
Series block/bio, fs: convert put_page() to put_user_page*() | expand

Commit Message

john.hubbard@gmail.com July 24, 2019, 4:25 a.m. UTC 
From: John Hubbard <jhubbard@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@infradead.org>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Minwoo Im <minwoo.im.dev@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: John Hubbard <jhubbard@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(-)

Comments

'Christoph Hellwig' July 24, 2019, 5:30 a.m. UTC | #1 
On Tue, Jul 23, 2019 at 09:25:09PM -0700, john.hubbard@gmail.com wrote:
> From: John Hubbard <jhubbard@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.
Jerome Glisse July 29, 2019, 8:57 p.m. UTC | #2 
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@gmail.com wrote:
> > From: John Hubbard <jhubbard@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,
Jérôme
Christoph Hellwig July 30, 2019, 10:25 a.m. UTC | #3 
On Mon, Jul 29, 2019 at 04:57:21PM -0400, Jerome Glisse wrote:
> > 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 :)

Well, the point is _should_ not necessarily do.  iomap_dio_zero adds the
ZERO_PAGE, which we by definition don't need to refcount.  So we can
mark this bio BIO_NO_PAGE_REF safely after removing the get_page there.

Note that the equivalent in the old direct I/O code, dio_refill_pages,
will be a little more complicated as it can match user pages and the
ZERO_PAGE in a single bio, so a per-bio flag won't handle it easily.
Maybe we just need to use a separate bio there as well.

In general with series like this we should not encode the status quo an
pile new hacks upon the old one, but thing where we should be and fix
up the old warts while having to wade through all that code.
Jerome Glisse July 30, 2019, 3:57 p.m. UTC | #4 
On Tue, Jul 30, 2019 at 12:25:57PM +0200, Christoph Hellwig wrote:
> On Mon, Jul 29, 2019 at 04:57:21PM -0400, Jerome Glisse wrote:
> > > 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 :)
> 
> Well, the point is _should_ not necessarily do.  iomap_dio_zero adds the
> ZERO_PAGE, which we by definition don't need to refcount.  So we can
> mark this bio BIO_NO_PAGE_REF safely after removing the get_page there.
> 
> Note that the equivalent in the old direct I/O code, dio_refill_pages,
> will be a little more complicated as it can match user pages and the
> ZERO_PAGE in a single bio, so a per-bio flag won't handle it easily.
> Maybe we just need to use a separate bio there as well.
> 
> In general with series like this we should not encode the status quo an
> pile new hacks upon the old one, but thing where we should be and fix
> up the old warts while having to wade through all that code.

Other user can also add page that are not coming from GUP but need to
have a reference see __blkdev_direct_IO() saddly bio get fill from many
different places and not always with GUP. So we can not say that all
pages here are coming from bio. I had a different version of the patchset
i think that was adding a new release dirty function for GUP versus non
GUP bio. I posted it a while ago, i will try to dig it up once i am
back.

Cheers,
Jérôme
Christoph Hellwig Aug. 1, 2019, 8:20 a.m. UTC | #5 
On Tue, Jul 30, 2019 at 11:57:02AM -0400, Jerome Glisse wrote:
> Other user can also add page that are not coming from GUP but need to
> have a reference see __blkdev_direct_IO()

Except for the zero page case I mentioned in my last mail explicitly,
and the KVEC/PIPE type iov vecs from the original mail what other
pages do you see to get added?
diff mbox series

Patch

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);