block/io_uring: implements interfaces for io_uring

Aborts when sqe fails to be set as sqes cannot be returned to the
ring. Adds slow path for short reads for older kernels

Signed-off-by: Aarushi Mehta <mehta.aaru20@gmail.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200120141858.587874-5-stefanha@redhat.com
Message-Id: <20200120141858.587874-5-stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

MAINTAINERS

@@ -2634,6 +2634,14 @@ F: block/file-posix.c
 F: block/file-win32.c
 F: block/win32-aio.c
 
+Linux io_uring
+M: Aarushi Mehta <mehta.aaru20@gmail.com>
+M: Julia Suvorova <jusual@redhat.com>
+M: Stefan Hajnoczi <stefanha@redhat.com>
+L: qemu-block@nongnu.org
+S: Maintained
+F: block/io_uring.c
+
 qcow2
 M: Kevin Wolf <kwolf@redhat.com>
 M: Max Reitz <mreitz@redhat.com>

block/Makefile.objs

@@ -18,6 +18,7 @@ block-obj-y += block-backend.o snapshot.o qapi.o
 block-obj-$(CONFIG_WIN32) += file-win32.o win32-aio.o
 block-obj-$(CONFIG_POSIX) += file-posix.o
 block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
+block-obj-$(CONFIG_LINUX_IO_URING) += io_uring.o
 block-obj-y += null.o mirror.o commit.o io.o create.o
 block-obj-y += throttle-groups.o
 block-obj-$(CONFIG_LINUX) += nvme.o
@@ -66,5 +67,7 @@ block-obj-$(if $(CONFIG_LZFSE),m,n) += dmg-lzfse.o
 dmg-lzfse.o-libs   := $(LZFSE_LIBS)
 qcow.o-libs        := -lz
 linux-aio.o-libs   := -laio
+io_uring.o-cflags  := $(LINUX_IO_URING_CFLAGS)
+io_uring.o-libs    := $(LINUX_IO_URING_LIBS)
 parallels.o-cflags := $(LIBXML2_CFLAGS)
 parallels.o-libs   := $(LIBXML2_LIBS)