[PATCH 04/12] block: bio_release_pages: convert put_page() to put_user_page*()

john.hubbard
2019-07-24T04:27:12Z

From: Jérôme Glisse <jglisse@redhat.com>

For pages that were retained via get_user_pages*(), release those pages
via the new put_user_page*() routines, instead of via put_page() or
release_pages().

This is part a tree-wide conversion, as described in commit fc1d8e7cca2d
("mm: introduce put_user_page*(), placeholder versions").

Changes from Jérôme's original patch:
* reworked to be compatible with recent bio_release_pages() changes,
* refactored slightly to remove some code duplication,
* use an approach that changes fewer bio_check_pages_dirty()
callers.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Minwoo Im <minwoo.im.dev@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
---
block/bio.c | 60 ++++++++++++++++++++++++++++++++++++---------
include/linux/bio.h | 1 +
2 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 7675e2de509d..74f9eba2583b 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -844,7 +844,11 @@ void bio_release_pages(struct bio *bio, enum bio_rp_flags_t flags)
bio_for_each_segment_all(bvec, bio, iter_all) {
if ((flags & BIO_RP_MARK_DIRTY) && !PageCompound(bvec->bv_page))
set_page_dirty_lock(bvec->bv_page);
- put_page(bvec->bv_page);
+
+ if (flags & BIO_RP_FROM_GUP)
+ put_user_page(bvec->bv_page);
+ else
+ put_page(bvec->bv_page);
}
}

@@ -1667,28 +1671,50 @@ static void bio_dirty_fn(struct work_struct *work);
static DECLARE_WORK(bio_dirty_work, bio_dirty_fn);
static DEFINE_SPINLOCK(bio_dirty_lock);
static struct bio *bio_dirty_list;
+static struct bio *bio_gup_dirty_list;

-/*
- * This runs in process context
- */
-static void bio_dirty_fn(struct work_struct *work)
+static void __bio_dirty_fn(struct work_struct *work,
+ struct bio **dirty_list,
+ enum bio_rp_flags_t flags)
{
struct bio *bio, *next;

spin_lock_irq(&bio_dirty_lock);
- next = bio_dirty_list;
- bio_dirty_list = NULL;
+ next = *dirty_list;
+ *dirty_list = NULL;
spin_unlock_irq(&bio_dirty_lock);

while ((bio = next) != NULL) {
next = bio->bi_private;

- bio_release_pages(bio, BIO_RP_MARK_DIRTY);
+ bio_release_pages(bio, BIO_RP_MARK_DIRTY | flags);
bio_put(bio);
}
}

-void bio_check_pages_dirty(struct bio *bio)
+/*
+ * This runs in process context
+ */
+static void bio_dirty_fn(struct work_struct *work)
+{
+ __bio_dirty_fn(work, &bio_dirty_list, BIO_RP_NORMAL);
+ __bio_dirty_fn(work, &bio_gup_dirty_list, BIO_RP_FROM_GUP);
+}
+
+/**
+ * __bio_check_pages_dirty() - queue up pages on a workqueue to dirty them
+ * @bio: the bio struct containing the pages we should dirty
+ * @from_gup: did the pages in the bio came from GUP (get_user_pages*())
+ *
+ * This will go over all pages in the bio, and for each non dirty page, the
+ * bio is added to a list of bio's that need to get their pages dirtied.
+ *
+ * We also need to know if the pages in the bio are coming from GUP or not,
+ * as GUPed pages need to be released via put_user_page(), instead of
+ * put_page(). Please see Documentation/vm/get_user_pages.rst for details
+ * on that.
+ */
+void __bio_check_pages_dirty(struct bio *bio, bool from_gup)
{
struct bio_vec *bvec;
unsigned long flags;
@@ -1699,17 +1725,27 @@ void bio_check_pages_dirty(struct bio *bio)
goto defer;
}

- bio_release_pages(bio, BIO_RP_NORMAL);
+ bio_release_pages(bio, from_gup ? BIO_RP_FROM_GUP : BIO_RP_NORMAL);
bio_put(bio);
return;
defer:
spin_lock_irqsave(&bio_dirty_lock, flags);
- bio->bi_private = bio_dirty_list;
- bio_dirty_list = bio;
+ if (from_gup) {
+ bio->bi_private = bio_gup_dirty_list;
+ bio_gup_dirty_list = bio;
+ } else {
+ bio->bi_private = bio_dirty_list;
+ bio_dirty_list = bio;
+ }
spin_unlock_irqrestore(&bio_dirty_lock, flags);
schedule_work(&bio_dirty_work);
}

+void bio_check_pages_dirty(struct bio *bio)
+{
+ __bio_check_pages_dirty(bio, false);
+}
+
void update_io_ticks(struct hd_struct *part, unsigned long now)
{
unsigned long stamp;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 2715e55679c1..d68a40c2c9d4 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -444,6 +444,7 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter);
enum bio_rp_flags_t {
BIO_RP_NORMAL = 0,
BIO_RP_MARK_DIRTY = 1,
+ BIO_RP_FROM_GUP = 2,
};

static inline enum bio_rp_flags_t bio_rp_dirty_flag(bool mark_dirty)
--
2.22.0