xfs_io: add the lseek() SEEK_DATA/SEEK_HOLE support

Add the lseek() SEEK_DATA/SEEK_HOLE support into xfs_io. The result from the lseek() call is printed to the output:
xfs_io> lseek -h 609k
lseek for hole starting at offset 623616 result offset 630784

+#define _LARGEFILE64_SOURCE /* See feature_test_macros(7) */

io/lseek.c new file +4 -0

+static void
+lseek_help(void)
+{
+	printf(_(

+" -d -- search for data starting at the specified offset.\n"
+" -h -- search for a hole starting at the specified offset.\n"
+"\n"));

io/lseek.c new file +23 -0

+}
+
+static int
+lseek_f(
+	int		argc,
+	char		**argv)
+{
+	off64_t		offset, res_off;
+	size_t          fsblocksize, fssectsize;
+	int		flag;
+	int		c;
+
+	flag = 0;
+	init_cvtnum(&fsblocksize, &fssectsize);
+
+	while ((c = getopt(argc, argv, "dh")) != EOF) {
+		switch (c) {
+		case 'd':
+			flag = SEEK_DATA;
+			break;
+		case 'h':
+			flag = SEEK_HOLE;
+			break;

or by path
.RB ( \-i ).
+.TP
+.BI "lseek [ \-b " offset " | \-h " offset " ]

On Mon, Oct 22, 2012 at 04:38:00PM -0500, Mark Tinguely wrote:

Type Offset
HOLE 630784

xfs_io> lseek -r -d 0
Type Offset
DATA 0
DATA 65536
DATA 524288
xfs_io> lseek -r -h 0
Type Offset
HOLE 16384
HOLE 131072
HOLE 1049576

xfs_io> lseek -r -a 0
DATA 0
HOLE 16384
DATA 65536
HOLE 131072
DATA 524288
HOLE 1049576

Quoted 1 line

+#define _LARGEFILE64_SOURCE /* See feature_test_macros(7) */

That's defined by _GNU_SOURCE, which is set in the makefiles, so not necessary here.

Quoted 5 lines

io/lseek.c new file +4 -0

+static void
+lseek_help(void)
+{
+	printf(_(

io/lseek.c line 47

Quoted 10 lines

io/lseek.c new file +10 -0

+"\n"
+" returns the next hole or data offset at or after the specified offset\n"
+"\n"
+" Example:\n"
+" 'lseek -d 512'  - offset of data at or following offset 512\n"
+"\n"
+" Repositions and returns the offset of either the next data or hole.\n"
+" There is an implied hole at the end of file. If the specified offset is\n"
+" past end of file, or there is no data past the specied offset, the offset\n"
+" -1 is returned.\n"

I'd prefer that "EOF" rather than "-1" is printed in this case.

Given that we only support pread and pwrite operations, the repositioning of the file pointer is irrelevant so probably should not be mentioned. If it was relevant, then we'd also need to support the other seek modes to reposition the file pointer. So jsut mentioning that it returns the offset of the next ... is probably sufficient here.

Cheers,

Dave.

Add the lseek SEEK_DATA/SEEK_HOLE support into xfs_io. The result from the lseek() call will be printed to the output. For example:

xfs_io> lseek -h 609k
Type Offset
hole 630784

v1 -> v2 Add "-a" and "-r" options.
Simplify the output.
v2 -> v3 Refactor for configure.in -> configure.ac change.
SEEK_DATA with -1 offset behaves badly on older Linux. Display error message as "ERR <errno>".

io/lseek.c new file +9 -0

+static int
+lseek_f(
+	int		argc,
+	char		**argv)
+{
+	off64_t		offset, roff;
+	size_t          fsblocksize, fssectsize;
+	int		cseg;
+	int		flag;

Quoted 8 lines · Mark Tinguely

Add the lseek SEEK_DATA/SEEK_HOLE support into xfs_io. The result from the lseek() call will be printed to the output. For example:

xfs_io> lseek -h 609k
Type Offset
hole 630784

Quoted 5 lines

v1 -> v2 Add "-a" and "-r" options.
Simplify the output.
v2 -> v3 Refactor for configure.in -> configure.ac change.
SEEK_DATA with -1 offset behaves badly on older Linux. Display error message as "ERR<errno>".

....

Review

Quoted 2 lines

(quoted diff) +2 -0

+
+#include<linux/fs.h>

I missed this first time around - why is this include necessary?

Quoted 14 lines · Dave Chinner

Quoted 13 lines · Mark Tinguely

Add the lseek SEEK_DATA/SEEK_HOLE support into xfs_io. The result from the lseek() call will be printed to the output. For example:

xfs_io> lseek -h 609k
Type Offset
hole 630784

v1 -> v2 Add "-a" and "-r" options.
Simplify the output.
v2 -> v3 Refactor for configure.in -> configure.ac change.
SEEK_DATA with -1 offset behaves badly on older Linux. Display error message as "ERR<errno>".

Quoted 5 lines

....

Review

Quoted 2 lines

(quoted diff) +2 -0

+
+#include<linux/fs.h>

I missed this first time around - why is this include necessary?

Take it out and you will find that it contains the defines for SEEK_DATA/SEEK_HOLE.

Add the lseek() SEEK_DATA/SEEK_HOLE support into xfs_io. The result from the lseek() call is printed to the output:
xfs_io> lseek -h 609k
lseek for hole starting at offset 623616 result offset 630784

Configure this feature only on Linux distributions that support SEEK_DATA/SEEK_HOLE.

Signed-off-by Mark Tinguely <[email protected]>

---
 configure.in          |    1 
 include/builddefs.in  |    1 
 io/Makefile           |    5 ++
 io/init.c             |    1 
 io/io.h               |    6 ++
 io/lseek.c            |  101 ++++++++++++++++++++++++++++++++++++++++++++++++++
 m4/package_libcdev.m4 |   15 +++++++
 man/man8/xfs_io.8     |    7 +++
 8 files changed, 137 insertions(+)

Index: b/configure.in
===================================================================

configure.in +1 -0

@@ -109,6 +109,7 @@ AC_HAVE_GETMNTINFO
 AC_HAVE_FALLOCATE
 AC_HAVE_FIEMAP
 AC_HAVE_PREADV
+AC_HAVE_LSEEK_DATA
 AC_HAVE_SYNC_FILE_RANGE
 AC_HAVE_BLKID_TOPO($enable_blkid)
 

Index: b/include/builddefs.in
===================================================================

include/builddefs.in +1 -0

@@ -102,6 +102,7 @@ HAVE_GETMNTINFO = @have_getmntinfo@
 HAVE_FALLOCATE = @have_fallocate@
 HAVE_FIEMAP = @have_fiemap@
 HAVE_PREADV = @have_preadv@
+HAVE_LSEEK_DATA = @have_lseek_data@
 HAVE_SYNC_FILE_RANGE = @have_sync_file_range@
 
 GCCFLAGS = -funsigned-char -fno-strict-aliasing -Wall 

Index: b/io/Makefile
===================================================================

io/Makefile +5 -0

@@ -80,6 +80,11 @@ ifeq ($(HAVE_PREADV),yes)
 LCFLAGS += -DHAVE_PREADV -DHAVE_PWRITEV
 endif
 
+ifeq ($(HAVE_LSEEK_DATA),yes)
+LCFLAGS += -DHAVE_LSEEK_DATA
+CFILES += lseek.c
+endif
+
 default: depend $(LTCOMMAND)
 
 include $(BUILDRULES)

Index: b/io/init.c
===================================================================

io/init.c +1 -0

@@ -64,6 +64,7 @@ init_commands(void)
 	help_init();
 	imap_init();
 	inject_init();
+	lseek_init();
 	madvise_init();
 	mincore_init();
 	mmap_init();

Index: b/io/io.h
===================================================================

io/io.h +6 -0

@@ -108,6 +108,12 @@ extern void		quit_init(void);
 extern void		shutdown_init(void);
 extern void		truncate_init(void);
 
+#ifdef HAVE_LSEEK_DATA
+extern void		lseek_init(void);
+#else
+#define lseek_init()	do { } while (0)
+#endif
+
 #ifdef HAVE_FADVISE
 extern void		fadvise_init(void);
 #else

Index: b/io/lseek.c
===================================================================

io/lseek.c new file +101 -0

@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2012 SGI
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#define _LARGEFILE64_SOURCE     /* See feature_test_macros(7) */
+#include <sys/types.h>
+#include <unistd.h>
+#include <linux/fs.h>
+
+#include <sys/uio.h>
+#include <xfs/xfs.h>
+#include <xfs/command.h>
+#include <xfs/input.h>
+#include <ctype.h>
+#include "init.h"
+#include "io.h"
+
+static cmdinfo_t lseek_cmd;
+
+static void
+lseek_help(void)
+{
+	printf(_(
+"\n"
+" returns the next hole or data offset at or after the specified offset\n"
+"\n"
+" Example:\n"
+" 'lseek -d 512'  - offset of data at or following offset 512\n"
+"\n"
+" Repositions and returns the offset of either the next data or hole.\n"
+" There is an implied hole at the end of file. If the specified offset is\n"
+" past end of file, or there is no data past the specied offset, the offset\n"
+" -1 is returned.\n"
+" -d   -- search for data starting at the specified offset.\n"
+" -h   -- search for a hole starting at the specified offset.\n"
+"\n"));
+}
+
+static int
+lseek_f(
+	int		argc,
+	char		**argv)
+{
+	off64_t		offset, res_off;
+	size_t          fsblocksize, fssectsize;
+	int		flag;
+	int		c;
+
+	flag = 0;
+	init_cvtnum(&fsblocksize, &fssectsize);
+
+	while ((c = getopt(argc, argv, "dh")) != EOF) {
+		switch (c) {
+		case 'd':
+			flag = SEEK_DATA;
+			break;
+		case 'h':
+			flag = SEEK_HOLE;
+			break;
+		default:
+			return command_usage(&lseek_cmd);
+		}
+	}
+	if (!flag  || optind > 2)
+		return command_usage(&lseek_cmd);
+	offset = cvtnum(fsblocksize, fssectsize, argv[optind]);
+	res_off = lseek64(file->fd, offset, flag);
+	printf("lseek for %s starting at offset %lld result offset %lld\n",
+		(flag == SEEK_DATA) ? "data" : "hole",	offset, res_off);
+	return 0;
+}
+
+void
+lseek_init(void)
+{
+	lseek_cmd.name = "lseek";
+	lseek_cmd.altname = "seek";
+	lseek_cmd.cfunc = lseek_f;
+	lseek_cmd.argmin = 2;
+	lseek_cmd.argmax = 2;
+	lseek_cmd.flags = CMD_NOMAP_OK | CMD_FOREIGN_OK;
+	lseek_cmd.args = _("[-d | -h] off");
+	lseek_cmd.oneline = _("locate and postition to next data or hole");
+	lseek_cmd.help = lseek_help;
+
+	add_command(&lseek_cmd);
+}

Index: b/m4/package_libcdev.m4
===================================================================

m4/package_libcdev.m4 +15 -0

@@ -153,6 +153,21 @@ AC_DEFUN([AC_HAVE_PREADV],
     AC_SUBST(have_preadv)
   ])
 
+# 
+# Check if we have a working fadvise system call
+# 
+AC_DEFUN([AC_HAVE_LSEEK_DATA],
+  [ AC_MSG_CHECKING([for lseek SEEK_DATA])
+    AC_TRY_COMPILE([
+#include <linux/fs.h>
+    ], [
+	lseek(0, 0, SEEK_DATA);
+    ],	have_lseek_data=yes
+	AC_MSG_RESULT(yes),
+	AC_MSG_RESULT(no))
+    AC_SUBST(have_lseek_data)
+  ])
+
 #
 # Check if we have a sync_file_range libc call (Linux)
 #

Index: b/man/man8/xfs_io.8
===================================================================

man/man8/xfs_io.8 +7 -0

@@ -377,6 +377,13 @@ must be specified as another open file
 .RB ( \-f )
 or by path
 .RB ( \-i ).
+.TP
+.BI "lseek [ \-b " offset " | \-h " offset " ]
+Repositions and prints the file pointer to the next offset containing data
+.RB ( \-d )
+or next offset containing a hole 
+.RB ( \-h )
+.TP
 
 .SH MEMORY MAPPED I/O COMMANDS
 .TP

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