[RFC 5/7] io_uring/rsrc: add buffer release callbacks

[Pavel Begunkov <asml.silence@gmail.com>]

With other buffer types we may want to have a different way of releasing
them. For example, we may want to put pages in some kind of cache or
bulk put them. Add a release callback.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 include/linux/io_uring.h |  2 ++
 io_uring/rsrc.c          | 14 ++++++++++----
 io_uring/rsrc.h          |  5 +++++
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index fddb5d52b776..e0e7df5beefc 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -26,6 +26,8 @@ struct iou_buf_desc {
 	unsigned		nr_bvecs;
 	unsigned		max_bvecs;
 	struct bio_vec		*bvec;
+	void			(*release)(struct iou_buf_desc *);
+	void			*private;
 };
 
 struct io_uring_cmd {
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 0edcebb6b5cb..3799470fd45e 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -111,6 +111,8 @@ static struct io_mapped_ubuf *io_alloc_reg_buf(struct io_ring_ctx *ctx,
 	}
 	imu->desc.bvec = imu->bvec;
 	imu->desc.max_bvecs = nr_bvecs;
+	imu->desc.private = NULL;
+	imu->desc.release = NULL;
 	return imu;
 }
 
@@ -169,10 +171,14 @@ static void io_buffer_unmap(struct io_ring_ctx *ctx, struct io_mapped_ubuf **slo
 	unsigned int i;
 
 	if (imu != ctx->dummy_ubuf) {
-		for (i = 0; i < imu->desc.nr_bvecs; i++)
-			unpin_user_page(imu->bvec[i].bv_page);
-		if (imu->acct_pages)
-			io_unaccount_mem(ctx, imu->acct_pages);
+		if (imu->desc.release) {
+			io_reg_buf_release(imu);
+		} else {
+			for (i = 0; i < imu->desc.nr_bvecs; i++)
+				unpin_user_page(imu->bvec[i].bv_page);
+			if (imu->acct_pages)
+				io_unaccount_mem(ctx, imu->acct_pages);
+		}
 		io_put_reg_buf(ctx, imu);
 	}
 	*slot = NULL;
diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 9ac10b3d25ac..29ce9a8a2277 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -169,4 +169,9 @@ static inline void __io_unaccount_mem(struct user_struct *user,
 	atomic_long_sub(nr_pages, &user->locked_vm);
 }
 
+static inline void io_reg_buf_release(struct io_mapped_ubuf *imu)
+{
+	imu->desc.release(&imu->desc);
+}
+
 #endif
-- 
2.40.0