io_uring: add notification slot registration

Let the userspace to register and unregister notification slots.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a0aa8161fe3ebb2a4cc6e5dbd0cffb96e6881cf5.1657643355.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 4c9b11e..dcfc7a0 100644 (file)
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -457,6 +457,10 @@ enum {
        /* register a range of fixed file slots for automatic slot allocation */
        IORING_REGISTER_FILE_ALLOC_RANGE        = 25,
 
+       /* zerocopy notification API */
+       IORING_REGISTER_NOTIFIERS               = 26,
+       IORING_UNREGISTER_NOTIFIERS             = 27,
+
        /* this goes last */
        IORING_REGISTER_LAST
 };
@@ -503,6 +507,19 @@ struct io_uring_rsrc_update2 {
        __u32 resv2;
 };
 
+struct io_uring_notification_slot {
+       __u64 tag;
+       __u64 resv[3];
+};
+
+struct io_uring_notification_register {
+       __u32 nr_slots;
+       __u32 resv;
+       __u64 resv2;
+       __u64 data;
+       __u64 resv3;
+};
+
 /* Skip updating fd indexes set to this value in the fd table */
 #define IORING_REGISTER_FILES_SKIP     (-2)
 

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 20e65d4..cae1137 100644 (file)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3870,6 +3870,15 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
                        break;
                ret = io_register_file_alloc_range(ctx, arg);
                break;
+       case IORING_REGISTER_NOTIFIERS:
+               ret = io_notif_register(ctx, arg, nr_args);
+               break;
+       case IORING_UNREGISTER_NOTIFIERS:
+               ret = -EINVAL;
+               if (arg || nr_args)
+                       break;
+               ret = io_notif_unregister(ctx);
+               break;
        default:
                ret = -EINVAL;
                break;

diff --git a/io_uring/notif.c b/io_uring/notif.c
index 0a2e98b..e6d98dc 100644 (file)
--- a/io_uring/notif.c
+++ b/io_uring/notif.c
@@ -162,5 +162,48 @@ __cold int io_notif_unregister(struct io_ring_ctx *ctx)
        kvfree(ctx->notif_slots);
        ctx->notif_slots = NULL;
        ctx->nr_notif_slots = 0;
+       io_notif_cache_purge(ctx);
+       return 0;
+}
+
+__cold int io_notif_register(struct io_ring_ctx *ctx,
+                            void __user *arg, unsigned int size)
+       __must_hold(&ctx->uring_lock)
+{
+       struct io_uring_notification_slot __user *slots;
+       struct io_uring_notification_slot slot;
+       struct io_uring_notification_register reg;
+       unsigned i;
+
+       if (ctx->nr_notif_slots)
+               return -EBUSY;
+       if (size != sizeof(reg))
+               return -EINVAL;
+       if (copy_from_user(&reg, arg, sizeof(reg)))
+               return -EFAULT;
+       if (!reg.nr_slots || reg.nr_slots > IORING_MAX_NOTIF_SLOTS)
+               return -EINVAL;
+       if (reg.resv || reg.resv2 || reg.resv3)
+               return -EINVAL;
+
+       slots = u64_to_user_ptr(reg.data);
+       ctx->notif_slots = kvcalloc(reg.nr_slots, sizeof(ctx->notif_slots[0]),
+                               GFP_KERNEL_ACCOUNT);
+       if (!ctx->notif_slots)
+               return -ENOMEM;
+
+       for (i = 0; i < reg.nr_slots; i++, ctx->nr_notif_slots++) {
+               struct io_notif_slot *notif_slot = &ctx->notif_slots[i];
+
+               if (copy_from_user(&slot, &slots[i], sizeof(slot))) {
+                       io_notif_unregister(ctx);
+                       return -EFAULT;
+               }
+               if (slot.resv[0] | slot.resv[1] | slot.resv[2]) {
+                       io_notif_unregister(ctx);
+                       return -EINVAL;
+               }
+               notif_slot->tag = slot.tag;
+       }
        return 0;
 }

diff --git a/io_uring/notif.h b/io_uring/notif.h
index 1dd48ef..00efe16 100644 (file)
--- a/io_uring/notif.h
+++ b/io_uring/notif.h
@@ -6,6 +6,7 @@
 #include <linux/nospec.h>
 
 #define IO_NOTIF_SPLICE_BATCH  32
+#define IORING_MAX_NOTIF_SLOTS (1U << 10)
 
 struct io_notif {
        struct ubuf_info        uarg;
@@ -48,6 +49,8 @@ struct io_notif_slot {
        u32                     seq;
 };
 
+int io_notif_register(struct io_ring_ctx *ctx,
+                     void __user *arg, unsigned int size);
 int io_notif_unregister(struct io_ring_ctx *ctx);
 void io_notif_cache_purge(struct io_ring_ctx *ctx);