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-rw-r--r--include/uapi/linux/hyperv.h11
1 files changed, 11 insertions, 0 deletions
diff --git a/include/uapi/linux/hyperv.h b/include/uapi/linux/hyperv.h
index daf82a230c0e..aaa502a7bff4 100644
--- a/include/uapi/linux/hyperv.h
+++ b/include/uapi/linux/hyperv.h
@@ -90,6 +90,17 @@ struct hv_vss_check_dm_info {
__u32 flags;
} __attribute__((packed));
+/*
+ * struct hv_vss_msg encodes the fields that the Linux VSS
+ * driver accesses. However, FREEZE messages from Hyper-V contain
+ * additional LUN information that Linux doesn't use and are not
+ * represented in struct hv_vss_msg. A received FREEZE message may
+ * be as large as 6,260 bytes, so the driver must allocate at least
+ * that much space, not sizeof(struct hv_vss_msg). Other messages
+ * such as AUTO_RECOVER may be as large as 12,500 bytes. However,
+ * because the Linux VSS driver responds that it doesn't support
+ * auto-recovery, it should not receive such messages.
+ */
struct hv_vss_msg {
union {
struct hv_vss_hdr vss_hdr;