[PATCH v4 2/4] xfs_io: Add support for pwritev2()

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

Changes since v2:
	Line wrap to 80 chars
---
 configure.ac          |  1 +
 include/builddefs.in  |  1 +
 io/Makefile           |  4 ++++
 io/pwrite.c           | 43 ++++++++++++++++++++++++++++++-------------
 m4/package_libcdev.m4 | 16 ++++++++++++++++
 5 files changed, 52 insertions(+), 13 deletions(-)

diff --git a/configure.ac b/configure.ac
index 4161c3b4..2320e3e3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -132,6 +132,7 @@ AC_HAVE_GETMNTENT
 AC_HAVE_GETMNTINFO
 AC_HAVE_FALLOCATE
 AC_HAVE_FIEMAP
+AC_HAVE_PWRITEV2
 AC_HAVE_PREADV
 AC_HAVE_COPY_FILE_RANGE
 AC_HAVE_SYNC_FILE_RANGE
diff --git a/include/builddefs.in b/include/builddefs.in
index ec630bd9..cd58ea8e 100644
--- a/include/builddefs.in
+++ b/include/builddefs.in
@@ -103,6 +103,7 @@ HAVE_GETMNTINFO = @have_getmntinfo@
 HAVE_FALLOCATE = @have_fallocate@
 HAVE_FIEMAP = @have_fiemap@
 HAVE_PREADV = @have_preadv@
+HAVE_PWRITEV2 = @have_pwritev2@
 HAVE_COPY_FILE_RANGE = @have_copy_file_range@
 HAVE_SYNC_FILE_RANGE = @have_sync_file_range@
 HAVE_SYNCFS = @have_syncfs@
diff --git a/io/Makefile b/io/Makefile
index 47b0a669..050d6bd0 100644
--- a/io/Makefile
+++ b/io/Makefile
@@ -90,6 +90,10 @@ ifeq ($(HAVE_PREADV),yes)
 LCFLAGS += -DHAVE_PREADV -DHAVE_PWRITEV
 endif
 
+ifeq ($(HAVE_PWRITEV2),yes)
+LCFLAGS += -DHAVE_PWRITEV2
+endif
+
 ifeq ($(HAVE_READDIR),yes)
 CFILES += readdir.c
 LCFLAGS += -DHAVE_READDIR
diff --git a/io/pwrite.c b/io/pwrite.c
index 5f149a68..2cdf0954 100644
--- a/io/pwrite.c
+++ b/io/pwrite.c
@@ -62,7 +62,8 @@ do_pwritev(
 	int		fd,
 	off64_t		offset,
 	ssize_t		count,
-	ssize_t		buffer_size)
+	ssize_t		buffer_size,
+	int 		pwritev2_flags)
 {
 	int vecs = 0;
 	ssize_t oldlen = 0;
@@ -81,7 +82,14 @@ do_pwritev(
 	} else {
 		vecs = vectors;
 	}
+#ifdef HAVE_PWRITEV2
+	if (pwritev2_flags)
+		bytes = pwritev2(fd, iov, vectors, offset, pwritev2_flags);
+	else
+		bytes = pwritev(fd, iov, vectors, offset);
+#else
 	bytes = pwritev(fd, iov, vectors, offset);
+#endif
 
 	/* restore trimmed iov */
 	if (oldlen)
@@ -98,12 +106,13 @@ do_pwrite(
 	int		fd,
 	off64_t		offset,
 	ssize_t		count,
-	ssize_t		buffer_size)
+	ssize_t		buffer_size,
+	int		pwritev2_flags)
 {
 	if (!vectors)
 		return pwrite(fd, buffer, min(count, buffer_size), offset);
 
-	return do_pwritev(fd, offset, count, buffer_size);
+	return do_pwritev(fd, offset, count, buffer_size, pwritev2_flags);
 }
 
 static int
@@ -111,7 +120,8 @@ write_random(
 	off64_t		offset,
 	long long	count,
 	unsigned int	seed,
-	long long	*total)
+	long long	*total,
+	int 		pwritev2_flags)
 {
 	off64_t		off, range;
 	ssize_t		bytes;
@@ -133,7 +143,8 @@ write_random(
 				buffersize;
 		else
 			off = offset;
-		bytes = do_pwrite(file->fd, off, buffersize, buffersize);
+		bytes = do_pwrite(file->fd, off, buffersize, buffersize,
+				pwritev2_flags);
 		if (bytes == 0)
 			break;
 		if (bytes < 0) {
@@ -153,7 +164,8 @@ static int
 write_backward(
 	off64_t		offset,
 	long long	*count,
-	long long	*total)
+	long long	*total,
+	int		pwritev2_flags)
 {
 	off64_t		end, off = offset;
 	ssize_t		bytes = 0, bytes_requested;
@@ -171,7 +183,8 @@ write_backward(
 	if ((bytes_requested = (off % buffersize))) {
 		bytes_requested = min(cnt, bytes_requested);
 		off -= bytes_requested;
-		bytes = do_pwrite(file->fd, off, bytes_requested, buffersize);
+		bytes = do_pwrite(file->fd, off, bytes_requested, buffersize,
+				pwritev2_flags);
 		if (bytes == 0)
 			return ops;
 		if (bytes < 0) {
@@ -189,7 +202,8 @@ write_backward(
 	while (cnt > end) {
 		bytes_requested = min(cnt, buffersize);
 		off -= bytes_requested;
-		bytes = do_pwrite(file->fd, off, cnt, buffersize);
+		bytes = do_pwrite(file->fd, off, cnt, buffersize,
+				pwritev2_flags);
 		if (bytes == 0)
 			break;
 		if (bytes < 0) {
@@ -212,7 +226,8 @@ write_buffer(
 	size_t		bs,
 	int		fd,
 	off64_t		skip,
-	long long	*total)
+	long long	*total,
+	int		pwritev2_flags)
 {
 	ssize_t		bytes;
 	long long	bar = min(bs, count);
@@ -224,7 +239,7 @@ write_buffer(
 			if (read_buffer(fd, skip + *total, bs, &bar, 0, 1) < 0)
 				break;
 		}
-		bytes = do_pwrite(file->fd, offset, count, bar);
+		bytes = do_pwrite(file->fd, offset, count, bar, pwritev2_flags);
 		if (bytes == 0)
 			break;
 		if (bytes < 0) {
@@ -258,6 +273,7 @@ pwrite_f(
 	int		Cflag, qflag, uflag, dflag, wflag, Wflag;
 	int		direction = IO_FORWARD;
 	int		c, fd = -1;
+	int		pwritev2_flags = 0;
 
 	Cflag = qflag = uflag = dflag = wflag = Wflag = 0;
 	init_cvtnum(&fsblocksize, &fssectsize);
@@ -368,13 +384,14 @@ pwrite_f(
 	case IO_RANDOM:
 		if (!zeed)	/* srandom seed */
 			zeed = time(NULL);
-		c = write_random(offset, count, zeed, &total);
+		c = write_random(offset, count, zeed, &total, pwritev2_flags);
 		break;
 	case IO_FORWARD:
-		c = write_buffer(offset, count, bsize, fd, skip, &total);
+		c = write_buffer(offset, count, bsize, fd, skip, &total,
+				pwritev2_flags);
 		break;
 	case IO_BACKWARD:
-		c = write_backward(offset, &count, &total);
+		c = write_backward(offset, &count, &total, pwritev2_flags);
 		break;
 	default:
 		total = 0;
diff --git a/m4/package_libcdev.m4 b/m4/package_libcdev.m4
index fa5b6397..48da0783 100644
--- a/m4/package_libcdev.m4
+++ b/m4/package_libcdev.m4
@@ -146,6 +146,22 @@ AC_DEFUN([AC_HAVE_PREADV],
     AC_SUBST(have_preadv)
   ])
 
+#
+# Check if we have a pwritev2 libc call (Linux)
+#
+AC_DEFUN([AC_HAVE_PWRITEV2],
+  [ AC_MSG_CHECKING([for pwritev2])
+    AC_TRY_LINK([
+#define _BSD_SOURCE
+#include <sys/uio.h>
+    ], [
+         pwritev2(0, 0, 0, 0, 0);
+    ], have_pwritev2=yes
+       AC_MSG_RESULT(yes),
+       AC_MSG_RESULT(no))
+    AC_SUBST(have_pwritev2)
+  ])
+
 #
 # Check if we have a copy_file_range system call (Linux)
 #
-- 
2.14.2