From 9d6023a856a1c4f84415dff59b0d5459cc8768db Mon Sep 17 00:00:00 2001

From: Eric Sandeen <sandeen@redhat.com>

Date: Thu, 27 Feb 2020 15:05:48 -0500

Subject: [PATCH] libxfs: use FALLOC_FL_ZERO_RANGE in libxfs_device_zero

I had a request from someone who cared about mkfs speed over

a slower network block device to look into using faster zeroing

methods, particularly for the log, during mkfs.

Using FALLOC_FL_ZERO_RANGE is faster in this case than writing

a bunch of zeros across a wire.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Reviewed-by: Christoph Hellwig <hch@lst.de>

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

---

 include/builddefs.in |  3 +++

 include/linux.h      | 22 ++++++++++++++++++++++

 libxfs/rdwr.c        | 15 +++++++++++----

 3 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/include/builddefs.in b/include/builddefs.in

index 4700b52..1dd27f7 100644

--- a/include/builddefs.in

+++ b/include/builddefs.in

@@ -144,6 +144,9 @@ endif

 ifeq ($(HAVE_GETFSMAP),yes)

 PCFLAGS+= -DHAVE_GETFSMAP

 endif

+ifeq ($(HAVE_FALLOCATE),yes)

+PCFLAGS += -DHAVE_FALLOCATE

+endif

 LIBICU_LIBS = @libicu_LIBS@

 LIBICU_CFLAGS = @libicu_CFLAGS@

diff --git a/include/linux.h b/include/linux.h

index 8f3c32b..57726bb 100644

--- a/include/linux.h

+++ b/include/linux.h

@@ -20,6 +20,10 @@

 #include <stdio.h>

 #include <asm/types.h>

 #include <mntent.h>

+#include <fcntl.h>

+#if defined(HAVE_FALLOCATE)

+#include <linux/falloc.h>

+#endif

 #ifdef OVERRIDE_SYSTEM_FSXATTR

 # define fsxattr sys_fsxattr

 #endif

@@ -164,6 +168,24 @@ static inline void platform_mntent_close(struct mntent_cursor * cursor)

 	endmntent(cursor->mtabp);

 }

+#if defined(FALLOC_FL_ZERO_RANGE)

+static inline int

+platform_zero_range(

+	int		fd,

+	xfs_off_t	start,

+	size_t		len)

+{

+	int ret;

+

+	ret = fallocate(fd, FALLOC_FL_ZERO_RANGE, start, len);

+	if (!ret)

+		return 0;

+	return -errno;

+}

+#else

+#define platform_zero_range(fd, s, l)	(-EOPNOTSUPP)

+#endif

+

 /*

  * Check whether we have to define FS_IOC_FS[GS]ETXATTR ourselves. These

  * are a copy of the definitions moved to linux/uapi/fs.h in the 4.5 kernel,

diff --git a/libxfs/rdwr.c b/libxfs/rdwr.c

index 0d9d720..e2d9d79 100644

--- a/libxfs/rdwr.c

+++ b/libxfs/rdwr.c

@@ -61,8 +61,18 @@ libxfs_device_zero(struct xfs_buftarg *btp, xfs_daddr_t start, uint len)

 {

 	xfs_off_t	start_offset, end_offset, offset;

 	ssize_t		zsize, bytes;

+	size_t		len_bytes;

 	char		*z;

-	int		fd;

+	int		error, fd;

+

+	fd = libxfs_device_to_fd(btp->dev);

+	start_offset = LIBXFS_BBTOOFF64(start);

+

+	/* try to use special zeroing methods, fall back to writes if needed */

+	len_bytes = LIBXFS_BBTOOFF64(len);

+	error = platform_zero_range(fd, start_offset, len_bytes);

+	if (!error)

+		return 0;

 	zsize = min(BDSTRAT_SIZE, BBTOB(len));

 	if ((z = memalign(libxfs_device_alignment(), zsize)) == NULL) {

@@ -73,9 +83,6 @@ libxfs_device_zero(struct xfs_buftarg *btp, xfs_daddr_t start, uint len)

 	}

 	memset(z, 0, zsize);

-	fd = libxfs_device_to_fd(btp->dev);

-	start_offset = LIBXFS_BBTOOFF64(start);

-

 	if ((lseek(fd, start_offset, SEEK_SET)) < 0) {

 		fprintf(stderr, _("%s: %s seek to offset %llu failed: %s\n"),

 			progname, __FUNCTION__,

-- 

2.9.5