[PATCH v3 0/3] xfsprogs: Add support for preadv2() and RWF_DONTCACHE

[PATCH v3 0/3] xfsprogs: Add support for preadv2() and RWF_DONTCACHE

[Ritesh Harjani (IBM)]

This adds following support to xfs_io:
- Support for preadv2()
- Support for uncached buffered I/O (RWF_DONTCACHE) for preadv2() and pwritev2()

v2 -> v3:
==========
1. Minor update for -U option description.
2. Added reviewed-bys of Darrick.
[v2]: https://lore.kernel.org/linux-xfs/cover.1741170031.git.ritesh.list@gmail.com

v1 -> v2:
========
1. Based on pwritev2 autoconf support enable HAVE_PREADV2 support.
2. Check if preadv2/pwritev2 flags are passed w/o -V argument
3. Fixed space before tabs issue.
[v1]: https://lore.kernel.org/linux-xfs/cover.1741087191.git.ritesh.list@gmail.com/#t

Ritesh Harjani (IBM) (3):
  xfs_io: Add support for preadv2
  xfs_io: Add RWF_DONTCACHE support to pwritev2
  xfs_io: Add RWF_DONTCACHE support to preadv2

 include/linux.h   |  5 ++++
 io/Makefile       |  2 +-
 io/pread.c        | 62 ++++++++++++++++++++++++++++++++++-------------
 io/pwrite.c       | 14 +++++++++--
 man/man8/xfs_io.8 | 16 ++++++++++--
 5 files changed, 77 insertions(+), 22 deletions(-)

--
2.48.1

[PATCH v3 1/3] xfs_io: Add support for preadv2

[Ritesh Harjani (IBM)]

This patch adds support for preadv2() to xfs_io.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 io/Makefile |  2 +-
 io/pread.c  | 45 ++++++++++++++++++++++++++++++---------------
 2 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/io/Makefile b/io/Makefile
index 8f835ec7..14a3fe20 100644
--- a/io/Makefile
+++ b/io/Makefile
@@ -66,7 +66,7 @@ LLDLIBS += $(LIBEDITLINE) $(LIBTERMCAP)
 endif
 
 ifeq ($(HAVE_PWRITEV2),yes)
-LCFLAGS += -DHAVE_PWRITEV2
+LCFLAGS += -DHAVE_PWRITEV2 -DHAVE_PREADV2
 endif
 
 ifeq ($(HAVE_MAP_SYNC),yes)
diff --git a/io/pread.c b/io/pread.c
index 62c771fb..b314fbc7 100644
--- a/io/pread.c
+++ b/io/pread.c
@@ -162,7 +162,8 @@ static ssize_t
 do_preadv(
 	int		fd,
 	off_t		offset,
-	long long	count)
+	long long	count,
+	int			preadv2_flags)
 {
 	int		vecs = 0;
 	ssize_t		oldlen = 0;
@@ -181,8 +182,14 @@ do_preadv(
 	} else {
 		vecs = vectors;
 	}
+#ifdef HAVE_PREADV2
+	if (preadv2_flags)
+		bytes = preadv2(fd, iov, vectors, offset, preadv2_flags);
+	else
+		bytes = preadv(fd, iov, vectors, offset);
+#else
 	bytes = preadv(fd, iov, vectors, offset);
-
+#endif
 	/* restore trimmed iov */
 	if (oldlen)
 		iov[vecs - 1].iov_len = oldlen;
@@ -195,12 +202,13 @@ do_pread(
 	int		fd,
 	off_t		offset,
 	long long	count,
-	size_t		buffer_size)
+	size_t		buffer_size,
+	int			preadv2_flags)
 {
 	if (!vectors)
 		return pread(fd, io_buffer, min(count, buffer_size), offset);
 
-	return do_preadv(fd, offset, count);
+	return do_preadv(fd, offset, count, preadv2_flags);
 }
 
 static int
@@ -210,7 +218,8 @@ read_random(
 	long long	count,
 	long long	*total,
 	unsigned int	seed,
-	int		eof)
+	int		eof,
+	int		preadv2_flags)
 {
 	off_t		end, off, range;
 	ssize_t		bytes;
@@ -234,7 +243,7 @@ read_random(
 				io_buffersize;
 		else
 			off = offset;
-		bytes = do_pread(fd, off, io_buffersize, io_buffersize);
+		bytes = do_pread(fd, off, io_buffersize, io_buffersize, preadv2_flags);
 		if (bytes == 0)
 			break;
 		if (bytes < 0) {
@@ -256,7 +265,8 @@ read_backward(
 	off_t		*offset,
 	long long	*count,
 	long long	*total,
-	int		eof)
+	int		eof,
+	int		preadv2_flags)
 {
 	off_t		end, off = *offset;
 	ssize_t		bytes = 0, bytes_requested;
@@ -276,7 +286,7 @@ read_backward(
 	/* Do initial unaligned read if needed */
 	if ((bytes_requested = (off % io_buffersize))) {
 		off -= bytes_requested;
-		bytes = do_pread(fd, off, bytes_requested, io_buffersize);
+		bytes = do_pread(fd, off, bytes_requested, io_buffersize, preadv2_flags);
 		if (bytes == 0)
 			return ops;
 		if (bytes < 0) {
@@ -294,7 +304,7 @@ read_backward(
 	while (cnt > end) {
 		bytes_requested = min(cnt, io_buffersize);
 		off -= bytes_requested;
-		bytes = do_pread(fd, off, cnt, io_buffersize);
+		bytes = do_pread(fd, off, cnt, io_buffersize, preadv2_flags);
 		if (bytes == 0)
 			break;
 		if (bytes < 0) {
@@ -318,14 +328,15 @@ read_forward(
 	long long	*total,
 	int		verbose,
 	int		onlyone,
-	int		eof)
+	int		eof,
+	int		preadv2_flags)
 {
 	ssize_t		bytes;
 	int		ops = 0;
 
 	*total = 0;
 	while (count > 0 || eof) {
-		bytes = do_pread(fd, offset, count, io_buffersize);
+		bytes = do_pread(fd, offset, count, io_buffersize, preadv2_flags);
 		if (bytes == 0)
 			break;
 		if (bytes < 0) {
@@ -353,7 +364,7 @@ read_buffer(
 	int		verbose,
 	int		onlyone)
 {
-	return read_forward(fd, offset, count, total, verbose, onlyone, 0);
+	return read_forward(fd, offset, count, total, verbose, onlyone, 0, 0);
 }
 
 static int
@@ -371,6 +382,7 @@ pread_f(
 	int		Cflag, qflag, uflag, vflag;
 	int		eof = 0, direction = IO_FORWARD;
 	int		c;
+	int		preadv2_flags = 0;
 
 	Cflag = qflag = uflag = vflag = 0;
 	init_cvtnum(&fsblocksize, &fssectsize);
@@ -463,15 +475,18 @@ pread_f(
 	case IO_RANDOM:
 		if (!zeed)	/* srandom seed */
 			zeed = time(NULL);
-		c = read_random(file->fd, offset, count, &total, zeed, eof);
+		c = read_random(file->fd, offset, count, &total, zeed, eof,
+						preadv2_flags);
 		break;
 	case IO_FORWARD:
-		c = read_forward(file->fd, offset, count, &total, vflag, 0, eof);
+		c = read_forward(file->fd, offset, count, &total, vflag, 0, eof,
+						 preadv2_flags);
 		if (eof)
 			count = total;
 		break;
 	case IO_BACKWARD:
-		c = read_backward(file->fd, &offset, &count, &total, eof);
+		c = read_backward(file->fd, &offset, &count, &total, eof,
+						  preadv2_flags);
 		break;
 	default:
 		ASSERT(0);
-- 
2.48.1

[PATCH v3 2/3] xfs_io: Add RWF_DONTCACHE support to pwritev2

[Ritesh Harjani (IBM)]

Add per-io RWF_DONTCACHE support flag to pwritev2().
This enables xfs_io to perform uncached buffered-io writes.

e.g. xfs_io -fc "pwrite -U -V 1 0 16K" /mnt/f1

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 include/linux.h   |  5 +++++
 io/pwrite.c       | 14 ++++++++++++--
 man/man8/xfs_io.8 |  8 +++++++-
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/include/linux.h b/include/linux.h
index b3516d54..6e83e073 100644
--- a/include/linux.h
+++ b/include/linux.h
@@ -237,6 +237,11 @@ struct fsxattr {
 #define RWF_ATOMIC	((__kernel_rwf_t)0x00000040)
 #endif
 
+/* buffered IO that drops the cache after reading or writing data */
+#ifndef RWF_DONTCACHE
+#define RWF_DONTCACHE	((__kernel_rwf_t)0x00000080)
+#endif
+
 /*
  * Reminder: anything added to this file will be compiled into downstream
  * userspace projects!
diff --git a/io/pwrite.c b/io/pwrite.c
index fab59be4..7df71e23 100644
--- a/io/pwrite.c
+++ b/io/pwrite.c
@@ -45,6 +45,7 @@ pwrite_help(void)
 " -N   -- Perform the pwritev2() with RWF_NOWAIT\n"
 " -D   -- Perform the pwritev2() with RWF_DSYNC\n"
 " -A   -- Perform the pwritev2() with RWF_ATOMIC\n"
+" -U   -- Perform the pwritev2() with RWF_DONTCACHE\n"
 #endif
 "\n"));
 }
@@ -285,7 +286,7 @@ pwrite_f(
 	init_cvtnum(&fsblocksize, &fssectsize);
 	bsize = fsblocksize;
 
-	while ((c = getopt(argc, argv, "Ab:BCdDf:Fi:NqRs:OS:uV:wWZ:")) != EOF) {
+	while ((c = getopt(argc, argv, "Ab:BCdDf:Fi:NqRs:OS:uUV:wWZ:")) != EOF) {
 		switch (c) {
 		case 'b':
 			tmp = cvtnum(fsblocksize, fssectsize, optarg);
@@ -328,6 +329,9 @@ pwrite_f(
 		case 'A':
 			pwritev2_flags |= RWF_ATOMIC;
 			break;
+		case 'U':
+			pwritev2_flags |= RWF_DONTCACHE;
+			break;
 #endif
 		case 's':
 			skip = cvtnum(fsblocksize, fssectsize, optarg);
@@ -392,6 +396,12 @@ pwrite_f(
 		exitcode = 1;
 		return command_usage(&pwrite_cmd);
 	}
+	if (pwritev2_flags != 0 && vectors == 0) {
+		printf(_("pwritev2 flags require vectored I/O (-V)\n"));
+		exitcode = 1;
+		return command_usage(&pwrite_cmd);
+	}
+
 	offset = cvtnum(fsblocksize, fssectsize, argv[optind]);
 	if (offset < 0) {
 		printf(_("non-numeric offset argument -- %s\n"), argv[optind]);
@@ -480,7 +490,7 @@ pwrite_init(void)
 	pwrite_cmd.argmax = -1;
 	pwrite_cmd.flags = CMD_NOMAP_OK | CMD_FOREIGN_OK;
 	pwrite_cmd.args =
-_("[-i infile [-qAdDwNOW] [-s skip]] [-b bs] [-S seed] [-FBR [-Z N]] [-V N] off len");
+_("[-i infile [-qAdDwNOUW] [-s skip]] [-b bs] [-S seed] [-FBR [-Z N]] [-V N] off len");
 	pwrite_cmd.oneline =
 		_("writes a number of bytes at a specified offset");
 	pwrite_cmd.help = pwrite_help;
diff --git a/man/man8/xfs_io.8 b/man/man8/xfs_io.8
index 59d5ddc5..47af5232 100644
--- a/man/man8/xfs_io.8
+++ b/man/man8/xfs_io.8
@@ -244,7 +244,7 @@ See the
 .B pread
 command.
 .TP
-.BI "pwrite [ \-i " file " ] [ \-qAdDwNOW ] [ \-s " skip " ] [ \-b " size " ] [ \-S " seed " ] [ \-FBR [ \-Z " zeed " ] ] [ \-V " vectors " ] " "offset length"
+.BI "pwrite [ \-i " file " ] [ \-qAdDwNOUW ] [ \-s " skip " ] [ \-b " size " ] [ \-S " seed " ] [ \-FBR [ \-Z " zeed " ] ] [ \-V " vectors " ] " "offset length"
 Writes a range of bytes in a specified blocksize from the given
 .IR offset .
 The bytes written can be either a set pattern or read in from another
@@ -287,6 +287,12 @@ Perform the
 call with
 .IR RWF_ATOMIC .
 .TP
+.B \-U
+Perform the
+.BR pwritev2 (2)
+call with
+.IR RWF_DONTCACHE .
+.TP
 .B \-O
 perform pwrite once and return the (maybe partial) bytes written.
 .TP
-- 
2.48.1

[PATCH v3 3/3] xfs_io: Add RWF_DONTCACHE support to preadv2

[Ritesh Harjani (IBM)]

Add per-io RWF_DONTCACHE support flag to preadv2().
This enables xfs_io to perform uncached buffered-io reads.

	e.g. xfs_io -c "pread -U -V 1 0 16K" /mnt/f1

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 io/pread.c        | 17 +++++++++++++++--
 man/man8/xfs_io.8 |  8 +++++++-
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/io/pread.c b/io/pread.c
index b314fbc7..606bfe36 100644
--- a/io/pread.c
+++ b/io/pread.c
@@ -38,6 +38,9 @@ pread_help(void)
 " -Z N -- zeed the random number generator (used when reading randomly)\n"
 "         (heh, zorry, the -s/-S arguments were already in use in pwrite)\n"
 " -V N -- use vectored IO with N iovecs of blocksize each (preadv)\n"
+#ifdef HAVE_PREADV2
+" -U   -- Perform the preadv2() with RWF_DONTCACHE\n"
+#endif
 "\n"
 " When in \"random\" mode, the number of read operations will equal the\n"
 " number required to do a complete forward/backward scan of the range.\n"
@@ -388,7 +391,7 @@ pread_f(
 	init_cvtnum(&fsblocksize, &fssectsize);
 	bsize = fsblocksize;

-	while ((c = getopt(argc, argv, "b:BCFRquvV:Z:")) != EOF) {
+	while ((c = getopt(argc, argv, "b:BCFRquUvV:Z:")) != EOF) {
 		switch (c) {
 		case 'b':
 			tmp = cvtnum(fsblocksize, fssectsize, optarg);
@@ -417,6 +420,11 @@ pread_f(
 		case 'u':
 			uflag = 1;
 			break;
+#ifdef HAVE_PREADV2
+		case 'U':
+			preadv2_flags |= RWF_DONTCACHE;
+			break;
+#endif
 		case 'v':
 			vflag = 1;
 			break;
@@ -446,6 +454,11 @@ pread_f(
 		exitcode = 1;
 		return command_usage(&pread_cmd);
 	}
+	if (preadv2_flags != 0 && vectors == 0) {
+		printf(_("preadv2 flags require vectored I/O (-V)\n"));
+		exitcode = 1;
+		return command_usage(&pread_cmd);
+	}

 	offset = cvtnum(fsblocksize, fssectsize, argv[optind]);
 	if (offset < 0 && (direction & (IO_RANDOM|IO_BACKWARD))) {
@@ -514,7 +527,7 @@ pread_init(void)
 	pread_cmd.argmin = 2;
 	pread_cmd.argmax = -1;
 	pread_cmd.flags = CMD_NOMAP_OK | CMD_FOREIGN_OK;
-	pread_cmd.args = _("[-b bs] [-qv] [-i N] [-FBR [-Z N]] off len");
+	pread_cmd.args = _("[-b bs] [-qUv] [-i N] [-FBR [-Z N]] off len");
 	pread_cmd.oneline = _("reads a number of bytes at a specified offset");
 	pread_cmd.help = pread_help;

diff --git a/man/man8/xfs_io.8 b/man/man8/xfs_io.8
index 47af5232..df508054 100644
--- a/man/man8/xfs_io.8
+++ b/man/man8/xfs_io.8
@@ -200,7 +200,7 @@ option will set the file permissions to read-write (0644). This allows xfs_io to
 set up mismatches between the file permissions and the open file descriptor
 read/write mode to exercise permission checks inside various syscalls.
 .TP
-.BI "pread [ \-b " bsize " ] [ \-qv ] [ \-FBR [ \-Z " seed " ] ] [ \-V " vectors " ] " "offset length"
+.BI "pread [ \-b " bsize " ] [ \-qUv ] [ \-FBR [ \-Z " seed " ] ] [ \-V " vectors " ] " "offset length"
 Reads a range of bytes in a specified blocksize from the given
 .IR offset .
 .RS 1.0i
@@ -214,6 +214,12 @@ requests will be split. The default blocksize is 4096 bytes.
 .B \-q
 quiet mode, do not write anything to standard output.
 .TP
+.B \-U
+Perform the
+.BR preadv2 (2)
+call with
+.IR RWF_DONTCACHE .
+.TP
 .B \-v
 dump the contents of the buffer after reading,
 by default only the count of bytes actually read is dumped.
--
2.48.1

Re: [PATCH v3 0/3] xfsprogs: Add support for preadv2() and RWF_DONTCACHE

[Jens Axboe]

On 3/15/25 2:20 AM, Ritesh Harjani (IBM) wrote:
> This adds following support to xfs_io:
> - Support for preadv2()
> - Support for uncached buffered I/O (RWF_DONTCACHE) for preadv2() and pwritev2()

Looks good to me:

Reviewed-by: Jens Axboe <axboe@kernel.dk>

-- 
Jens Axboe