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

Mark Tinguely
2013-08-16T20:54:58Z

[-- Attachment #1: xfs_io-support-SEEK_DATA-SEEK_HOLE.patch --]
[-- Type: text/plain, Size: 9150 bytes --]

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

Signed-off-by: Mark Tinguely <tinguely@sgi.com>
---
Not trying to be difficult. Dave wanted the single hole/data/hole and data
seperated from the recursive loop, but doing it that way is basically unrolling
the loop into a if-then-else and is really terrible. If this is still not
acceptable, then we can throw this feature into /dev/null.

configure.ac | 1
include/builddefs.in | 1
io/Makefile | 5 +
io/init.c | 1
io/io.h | 6 +
io/seek.c | 187 ++++++++++++++++++++++++++++++++++++++++++++++++++
m4/package_libcdev.m4 | 15 ++++
man/man8/xfs_io.8 | 35 +++++++++
8 files changed, 251 insertions(+)

Index: b/configure.ac
===================================================================
--- a/configure.ac
+++ b/configure.ac
@@ -110,6 +110,7 @@ AC_HAVE_GETMNTINFO
AC_HAVE_FALLOCATE
AC_HAVE_FIEMAP
AC_HAVE_PREADV
+AC_HAVE_SEEK_DATA
AC_HAVE_SYNC_FILE_RANGE
AC_HAVE_BLKID_TOPO($enable_blkid)
AC_HAVE_READDIR
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_SEEK_DATA = @have_seek_data@
HAVE_SYNC_FILE_RANGE = @have_sync_file_range@
HAVE_READDIR = @have_readdir@

Index: b/io/Makefile
===================================================================
--- a/io/Makefile
+++ b/io/Makefile
@@ -85,6 +85,11 @@ CFILES += readdir.c
LCFLAGS += -DHAVE_READDIR
endif

+ifeq ($(HAVE_SEEK_DATA),yes)
+LCFLAGS += -DHAVE_SEEK_DATA
+CFILES += seek.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();
+ seek_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_SEEK_DATA
+extern void seek_init(void);
+#else
+#define seek_init() do { } while (0)
+#endif
+
#ifdef HAVE_FADVISE
extern void fadvise_init(void);
#else
Index: b/io/seek.c
===================================================================
--- /dev/null
+++ b/io/seek.c
@@ -0,0 +1,187 @@
+/*
+ * Copyright (c) 2013 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
+ */
+
+#include <libxfs.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 seek_cmd;
+
+static void
+seek_help(void)
+{
+ printf(_(
+"\n"
+" returns the next hole and/or data offset at or after the specified offset\n"
+"\n"
+" Example:\n"
+" 'seek -d 512' - offset of data at or following offset 512\n"
+" 'seek -a -r 0' - offsets of all data and hole in entire file\n"
+"\n"
+" Returns the offset of the next data and/or hole. There is an implied hole\n"
+" at the end of file. If the specified offset is past end of file, or there\n"
+" is no data past the specied offset, EOF is returned.\n"
+" -a -- return the next data and hole starting at the specified offset.\n"
+" -d -- return the next data starting at the specified offset.\n"
+" -h -- return the next hole starting at the specified offset.\n"
+" -r -- return all remaining type(s) starting at the specified offset.\n"
+"\n"));
+}
+
+#define SEEK_DFLAG (1 << 0)
+#define SEEK_HFLAG (1 << 1)
+#define SEEK_RFLAG (1 << 2)
+#define DATA 0
+#define HOLE 1
+
+struct seekinfo {
+ char *name;
+ int seektype;
+ int mask;
+} seekinfo[] = {
+ {"DATA", SEEK_DATA, SEEK_DFLAG},
+ {"HOLE", SEEK_HOLE, SEEK_HFLAG}
+};
+
+void
+seek_output(
+ char *type,
+ off64_t offset)
+{
+ if (offset == -1) {
+ if (errno == ENXIO)
+ printf("%s EOF\n", type);
+ else
+ printf("%s ERR %d\n", type, errno);
+ } else
+ printf("%s %ld\n", type, offset);
+}
+
+static int
+seek_f(
+ int argc,
+ char **argv)
+{
+ off64_t offset, result;
+ size_t fsblocksize, fssectsize;
+ int flag;
+ int current; /* specify data or hole */
+ int c;
+
+ flag = 0;
+ init_cvtnum(&fsblocksize, &fssectsize);
+
+ while ((c = getopt(argc, argv, "adhr")) != EOF) {
+ switch (c) {
+ case 'a':
+ flag |= (SEEK_HFLAG | SEEK_DFLAG);
+ break;
+ case 'd':
+ flag |= SEEK_DFLAG;
+ break;
+ case 'h':
+ flag |= SEEK_HFLAG;
+ break;
+ case 'r':
+ flag |= SEEK_RFLAG;
+ break;
+ default:
+ return command_usage(&seek_cmd);
+ }
+ }
+ /* must have hole or data specified and an offset */
+ if (!(flag & (SEEK_DFLAG | SEEK_HFLAG)) ||
+ optind != argc - 1)
+ return command_usage(&seek_cmd);
+
+ offset = cvtnum(fsblocksize, fssectsize, argv[optind]);
+
+ if (flag & SEEK_HFLAG) {
+ result = lseek64(file->fd, offset, SEEK_HOLE);
+ if ((result == offset) ||
+ !(flag & SEEK_DFLAG)) {
+ offset = result; /* in case it was EOF */
+ current = HOLE;
+ goto found_hole;
+ }
+ }
+
+ /* found data or -1 when "-a" option was requested */
+ current = DATA;
+ offset = lseek64(file->fd, offset, SEEK_DATA);
+
+found_hole:
+ printf("Type offset\n");
+
+ while (flag) {
+ /*
+ * handle the data / hole entries in assending order from
+ * the specified offset.
+ *
+ * flag determines if there are more items to be displayed.
+ * SEEK_RFLAG is an infinite loop that is terminated with
+ * a offset at EOF.
+ *
+ * current determines next type to process/display where
+ * 0 is data and 1 is data.
+ */
+
+ if (flag & seekinfo[current].mask) {
+ seek_output(seekinfo[current].name, offset);
+ if (offset == -1)
+ break; /* stop on error or EOF */
+ }
+
+ /*
+ * When displaying only a single data and/or hole item, mask
+ * off the item as it is displayed. The loop will end when all
+ * requested items have been displayed.
+ */
+ if (!(flag & SEEK_RFLAG))
+ flag &= ~seekinfo[current].mask;
+
+ current ^= 1; /* alternate between data and hole */
+ if (offset != -1)
+ offset = lseek64(file->fd, offset,
+ seekinfo[current].seektype);
+ }
+ return 0;
+}
+
+void
+seek_init(void)
+{
+ seek_cmd.name = "seek";
+ seek_cmd.altname = "seek";
+ seek_cmd.cfunc = seek_f;
+ seek_cmd.argmin = 2;
+ seek_cmd.argmax = 5;
+ seek_cmd.flags = CMD_NOMAP_OK | CMD_FOREIGN_OK;
+ seek_cmd.args = _("-a | -d | -h [-r] off");
+ seek_cmd.oneline = _("locate the next data and/or hole");
+ seek_cmd.help = seek_help;
+
+ add_command(&seek_cmd);
+}
Index: b/m4/package_libcdev.m4
===================================================================
--- a/m4/package_libcdev.m4
+++ b/m4/package_libcdev.m4
@@ -154,6 +154,21 @@ AC_DEFUN([AC_HAVE_PREADV],
])

#
+# Check if we have a working fadvise system call
+#
+AC_DEFUN([AC_HAVE_SEEK_DATA],
+ [ AC_MSG_CHECKING([for seek_data ])
+ AC_TRY_COMPILE([
+#include <linux/fs.h>
+ ], [
+ lseek(0, 0, SEEK_DATA);
+ ], have_seek_data=yes
+ AC_MSG_RESULT(yes),
+ AC_MSG_RESULT(no))
+ AC_SUBST(have_seek_data)
+ ])
+
+#
# Check if we have a sync_file_range libc call (Linux)
#
AC_DEFUN([AC_HAVE_SYNC_FILE_RANGE],
Index: b/man/man8/xfs_io.8
===================================================================
--- a/man/man8/xfs_io.8
+++ b/man/man8/xfs_io.8
@@ -418,6 +418,41 @@ to read (in bytes)
.RE
.PD
.TP
+.TP
+.BI "seek \-a | \-d | \-h [ \-r ] offset"
+On platforms that support the
+.BR lseek (2)
+.B SEEK_DATA
+and
+.B SEEK_HOLE
+options, display the offsets of the specified segments.
+.RS 1.0i
+.PD 0
+.TP 0.4i
+.B \-a
+Display both
+.B data
+and
+.B hole
+segments starting at the specified
+.B offset.
+.TP
+.B \-d
+Display the
+.B data
+segment starting at the specified
+.B offset.
+.TP
+.B \-h
+Display the
+.B hole
+segment starting at the specified
+.B offset.
+.TP
+.B \-r
+Recursively display all the specified segments starting at the specified
+.B offset.
+.TP

.SH MEMORY MAPPED I/O COMMANDS
.TP