[PATCH 04/17] logwrites: use BLKZEROOUT if it's available

["Darrick J. Wong" <djwong@xxxxxxxxxx>]

From: Darrick J. Wong <djwong@xxxxxxxxxx>

Use the BLKZEROOUT ioctl instead of writing zeroed buffers if the kernel
supports it.

Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
---
 src/log-writes/log-writes.c |   10 ++++++++++
 src/log-writes/log-writes.h |    1 +
 2 files changed, 11 insertions(+)


diff --git a/src/log-writes/log-writes.c b/src/log-writes/log-writes.c
index aa53473974d9e8..8f94ae5629e085 100644
--- a/src/log-writes/log-writes.c
+++ b/src/log-writes/log-writes.c
@@ -42,6 +42,7 @@ static int discard_range(struct log *log, u64 start, u64 len)
 
 static int zero_range(struct log *log, u64 start, u64 len)
 {
+	u64 range[2] = { start, len };
 	u64 bufsize = len;
 	ssize_t ret;
 	char *buf = NULL;
@@ -54,6 +55,15 @@ static int zero_range(struct log *log, u64 start, u64 len)
 		return 0;
 	}
 
+	if (!(log->flags & LOG_ZEROOUT_NOT_SUPP)) {
+		if (ioctl(log->replayfd, BLKZEROOUT, &range) < 0) {
+			if (log_writes_verbose)
+				printf(
+ "replay device doesn't support zeroout, switching to writing zeros\n");
+			log->flags |= LOG_ZEROOUT_NOT_SUPP;
+		}
+	}
+
 	while (!buf) {
 		buf = malloc(bufsize);
 		if (!buf)
diff --git a/src/log-writes/log-writes.h b/src/log-writes/log-writes.h
index b9f571ac3b2384..f659931634e64a 100644
--- a/src/log-writes/log-writes.h
+++ b/src/log-writes/log-writes.h
@@ -63,6 +63,7 @@ struct log_write_entry {
 
 #define LOG_IGNORE_DISCARD (1 << 0)
 #define LOG_DISCARD_NOT_SUPP (1 << 1)
+#define LOG_ZEROOUT_NOT_SUPP (1 << 2)
 
 struct log {
 	int logfd;