drbd: introduce WRITE_SAME support
We will support WRITE_SAME, if
* all peers support WRITE_SAME (both in kernel and DRBD version),
* all peer devices support WRITE_SAME
* logical_block_size is identical on all peers.
We may at some point introduce a fallback on the receiving side
for devices/kernels that do not support WRITE_SAME,
by open-coding a submit loop. But not yet.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/block/drbd/drbd_protocol.h b/drivers/block/drbd/drbd_protocol.h
index 95ca458..4d29680 100644
--- a/drivers/block/drbd/drbd_protocol.h
+++ b/drivers/block/drbd/drbd_protocol.h
@@ -64,6 +64,11 @@
P_RS_THIN_REQ = 0x32, /* Request a block for resync or reply P_RS_DEALLOCATED */
P_RS_DEALLOCATED = 0x33, /* Contains only zeros on sync source node */
+ /* REQ_WRITE_SAME.
+ * On a receiving side without REQ_WRITE_SAME,
+ * we may fall back to an opencoded loop instead. */
+ P_WSAME = 0x34,
+
P_MAY_IGNORE = 0x100, /* Flag to test if (cmd > P_MAY_IGNORE) ... */
P_MAX_OPT_CMD = 0x101,
@@ -110,8 +115,11 @@
u32 pad;
} __packed;
-/* these defines must not be changed without changing the protocol version */
-#define DP_HARDBARRIER 1 /* depricated */
+/* These defines must not be changed without changing the protocol version.
+ * New defines may only be introduced together with protocol version bump or
+ * new protocol feature flags.
+ */
+#define DP_HARDBARRIER 1 /* no longer used */
#define DP_RW_SYNC 2 /* equals REQ_SYNC */
#define DP_MAY_SET_IN_SYNC 4
#define DP_UNPLUG 8 /* not used anymore */
@@ -120,6 +128,7 @@
#define DP_DISCARD 64 /* equals REQ_DISCARD */
#define DP_SEND_RECEIVE_ACK 128 /* This is a proto B write request */
#define DP_SEND_WRITE_ACK 256 /* This is a proto C write request */
+#define DP_WSAME 512 /* equiv. REQ_WRITE_SAME */
struct p_data {
u64 sector; /* 64 bits sector number */
@@ -133,6 +142,11 @@
u32 size; /* == bio->bi_size */
} __packed;
+struct p_wsame {
+ struct p_data p_data;
+ u32 size; /* == bio->bi_size */
+} __packed;
+
/*
* commands which share a struct:
* p_block_ack:
@@ -164,8 +178,23 @@
* ReportParams
*/
-#define FF_TRIM 1
-#define FF_THIN_RESYNC 2
+/* supports TRIM/DISCARD on the "wire" protocol */
+#define DRBD_FF_TRIM 1
+
+/* Detect all-zeros during resync, and rather TRIM/UNMAP/DISCARD those blocks
+ * instead of fully allocate a supposedly thin volume on initial resync */
+#define DRBD_FF_THIN_RESYNC 2
+
+/* supports REQ_WRITE_SAME on the "wire" protocol.
+ * Note: this flag is overloaded,
+ * its presence also
+ * - indicates support for 128 MiB "batch bios",
+ * max discard size of 128 MiB
+ * instead of 4M before that.
+ * - indicates that we exchange additional settings in p_sizes
+ * drbd_send_sizes()/receive_sizes()
+ */
+#define DRBD_FF_WSAME 4
struct p_connection_features {
u32 protocol_min;
@@ -240,6 +269,40 @@
u64 uuid;
} __packed;
+/* optional queue_limits if (agreed_features & DRBD_FF_WSAME)
+ * see also struct queue_limits, as of late 2015 */
+struct o_qlim {
+ /* we don't need it yet, but we may as well communicate it now */
+ u32 physical_block_size;
+
+ /* so the original in struct queue_limits is unsigned short,
+ * but I'd have to put in padding anyways. */
+ u32 logical_block_size;
+
+ /* One incoming bio becomes one DRBD request,
+ * which may be translated to several bio on the receiving side.
+ * We don't need to communicate chunk/boundary/segment ... limits.
+ */
+
+ /* various IO hints may be useful with "diskless client" setups */
+ u32 alignment_offset;
+ u32 io_min;
+ u32 io_opt;
+
+ /* We may need to communicate integrity stuff at some point,
+ * but let's not get ahead of ourselves. */
+
+ /* Backend discard capabilities.
+ * Receiving side uses "blkdev_issue_discard()", no need to communicate
+ * more specifics. If the backend cannot do discards, the DRBD peer
+ * may fall back to blkdev_issue_zeroout().
+ */
+ u8 discard_enabled;
+ u8 discard_zeroes_data;
+ u8 write_same_capable;
+ u8 _pad;
+} __packed;
+
struct p_sizes {
u64 d_size; /* size of disk */
u64 u_size; /* user requested size */
@@ -247,6 +310,9 @@
u32 max_bio_size; /* Maximal size of a BIO */
u16 queue_order_type; /* not yet implemented in DRBD*/
u16 dds_flags; /* use enum dds_flags here. */
+
+ /* optional queue_limits if (agreed_features & DRBD_FF_WSAME) */
+ struct o_qlim qlim[0];
} __packed;
struct p_state {