nvme: simplify the compat ioctl handling

Don't bother defining a separate compat_ioctl handler, and just handle
the NVME_IOCTL_SUBMIT_IO32 case inline.  Also only defined it for those
ABIs (currently just i386 vs x86_64) that are affected.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>

drivers/nvme/host/core.c

@@ -1783,6 +1783,24 @@ static int nvme_handle_ctrl_ioctl(struct nvme_ns *ns, unsigned int cmd,
 	return ret;
 }
 
+#ifdef COMPAT_FOR_U64_ALIGNMENT
+struct nvme_user_io32 {
+	__u8	opcode;
+	__u8	flags;
+	__u16	control;
+	__u16	nblocks;
+	__u16	rsvd;
+	__u64	metadata;
+	__u64	addr;
+	__u64	slba;
+	__u32	dsmgmt;
+	__u32	reftag;
+	__u16	apptag;
+	__u16	appmask;
+} __attribute__((__packed__));
+#define NVME_IOCTL_SUBMIT_IO32	_IOW('N', 0x42, struct nvme_user_io32)
+#endif /* COMPAT_FOR_U64_ALIGNMENT */
+
 static int nvme_ns_ioctl(struct nvme_ns *ns, unsigned int cmd,
 		void __user *argp)
 {
@@ -1792,6 +1810,14 @@ static int nvme_ns_ioctl(struct nvme_ns *ns, unsigned int cmd,
 		return ns->head->ns_id;
 	case NVME_IOCTL_IO_CMD:
 		return nvme_user_cmd(ns->ctrl, ns, argp);
+	/*
+	 * struct nvme_user_io can have different padding on some 32-bit ABIs.
+	 * Just accept the compat version as all fields that are used are the
+	 * same size and at the same offset.
+	 */
+#ifdef COMPAT_FOR_U64_ALIGNMENT
+	case NVME_IOCTL_SUBMIT_IO32:
+#endif
 	case NVME_IOCTL_SUBMIT_IO:
 		return nvme_submit_io(ns, argp);
 	case NVME_IOCTL_IO64_CMD:
@@ -1828,47 +1854,6 @@ static int nvme_ioctl(struct block_device *bdev, fmode_t mode,
 	return ret;
 }
 
-#ifdef CONFIG_COMPAT
-struct nvme_user_io32 {
-	__u8	opcode;
-	__u8	flags;
-	__u16	control;
-	__u16	nblocks;
-	__u16	rsvd;
-	__u64	metadata;
-	__u64	addr;
-	__u64	slba;
-	__u32	dsmgmt;
-	__u32	reftag;
-	__u16	apptag;
-	__u16	appmask;
-} __attribute__((__packed__));
-
-#define NVME_IOCTL_SUBMIT_IO32	_IOW('N', 0x42, struct nvme_user_io32)
-
-static int nvme_compat_ioctl(struct block_device *bdev, fmode_t mode,
-		unsigned int cmd, unsigned long arg)
-{
-	/*
-	 * Corresponds to the difference of NVME_IOCTL_SUBMIT_IO
-	 * between 32 bit programs and 64 bit kernel.
-	 * The cause is that the results of sizeof(struct nvme_user_io),
-	 * which is used to define NVME_IOCTL_SUBMIT_IO,
-	 * are not same between 32 bit compiler and 64 bit compiler.
-	 * NVME_IOCTL_SUBMIT_IO32 is for 64 bit kernel handling
-	 * NVME_IOCTL_SUBMIT_IO issued from 32 bit programs.
-	 * Other IOCTL numbers are same between 32 bit and 64 bit.
-	 * So there is nothing to do regarding to other IOCTL numbers.
-	 */
-	if (cmd == NVME_IOCTL_SUBMIT_IO32)
-		return nvme_ioctl(bdev, mode, NVME_IOCTL_SUBMIT_IO, arg);
-
-	return nvme_ioctl(bdev, mode, cmd, arg);
-}
-#else
-#define nvme_compat_ioctl	NULL
-#endif /* CONFIG_COMPAT */
-
 static int nvme_open(struct block_device *bdev, fmode_t mode)
 {
 	struct nvme_ns *ns = bdev->bd_disk->private_data;
@@ -2356,7 +2341,6 @@ EXPORT_SYMBOL_GPL(nvme_sec_submit);
 static const struct block_device_operations nvme_bdev_ops = {
 	.owner		= THIS_MODULE,
 	.ioctl		= nvme_ioctl,
-	.compat_ioctl	= nvme_compat_ioctl,
 	.open		= nvme_open,
 	.release	= nvme_release,
 	.getgeo		= nvme_getgeo,
@@ -2385,7 +2369,6 @@ const struct block_device_operations nvme_ns_head_ops = {
 	.open		= nvme_ns_head_open,
 	.release	= nvme_ns_head_release,
 	.ioctl		= nvme_ioctl,
-	.compat_ioctl	= nvme_compat_ioctl,
 	.getgeo		= nvme_getgeo,
 	.report_zones	= nvme_report_zones,
 	.pr_ops		= &nvme_pr_ops,