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[PATCH] xfs_io: add the lseek() SEEK_DATA/SEEK_HOLE support

To: xfs@xxxxxxxxxxx
Subject: [PATCH] xfs_io: add the lseek() SEEK_DATA/SEEK_HOLE support
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Mon, 22 Oct 2012 16:38:00 -0500
References: <20121022213759.033667921@xxxxxxx>
User-agent: quilt/0.51-1
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 <tinguely@xxxxxxx> 
---
 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
===================================================================
--- a/configure.in
+++ b/configure.in
@@ -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
===================================================================
--- a/include/builddefs.in
+++ b/include/builddefs.in
@@ -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
===================================================================
--- a/io/Makefile
+++ b/io/Makefile
@@ -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
===================================================================
--- a/io/init.c
+++ b/io/init.c
@@ -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
===================================================================
--- a/io/io.h
+++ b/io/io.h
@@ -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
===================================================================
--- /dev/null
+++ b/io/lseek.c
@@ -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
===================================================================
--- a/m4/package_libcdev.m4
+++ b/m4/package_libcdev.m4
@@ -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
===================================================================
--- a/man/man8/xfs_io.8
+++ b/man/man8/xfs_io.8
@@ -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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