[PATCH] xfs_io: v7 add the lseek() SEEK_DATA/SEEK_HOLE support

Mark Tinguely
2013-08-22T21:31:42Z

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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> seek -h 609k
HOLE 630784

Signed-off-by: Mark Tinguely <tinguely@sgi.com>
---
version 7 or 8 - Eric what number is this?

I think I added all the old Dave and new Eric changes.

Unconditionally compile the feature into xfs_io.

(Too) many comments added. This routine basically is a seek and print loop.

Removed the ending EOF, except where that was the only entry.
No output looked bad.
This print the only entry exception changed the loop/if statements.

Changed error message to perror.

Ran the fine-tune kernel test on the following XFS kernel version:
Linux 3.0 no support.
Linux 3.1 vfs default support.
Linux 3.5 XFS first support.
Linux 3.7 XFS fine-tuned support.

Each version has different output - as expected. Eric you want the output?

io/Makefile | 3
io/init.c | 1
io/io.h | 1
io/seek.c | 197 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
man/man8/xfs_io.8 | 35 +++++++++
5 files changed, 236 insertions(+), 1 deletion(-)

Index: b/io/Makefile
===================================================================
--- a/io/Makefile
+++ b/io/Makefile
@@ -10,7 +10,8 @@ LSRCFILES = xfs_bmap.sh xfs_freeze.sh xf
HFILES = init.h io.h
CFILES = init.c \
attr.c bmap.c file.c freeze.c fsync.c getrusage.c imap.c mmap.c \
- open.c parent.c pread.c prealloc.c pwrite.c shutdown.c truncate.c
+ open.c parent.c pread.c prealloc.c pwrite.c seek.c shutdown.c \
+ truncate.c

LLDLIBS = $(LIBXCMD) $(LIBHANDLE)
LTDEPENDENCIES = $(LIBXCMD) $(LIBHANDLE)
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
@@ -105,6 +105,7 @@ extern void pread_init(void);
extern void prealloc_init(void);
extern void pwrite_init(void);
extern void quit_init(void);
+extern void seek_init(void);
extern void shutdown_init(void);
extern void truncate_init(void);

Index: b/io/seek.c
===================================================================
--- /dev/null
+++ b/io/seek.c
@@ -0,0 +1,197 @@
+/*
+ * 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 <xfs/xfs.h>
+#include <xfs/command.h>
+#include <xfs/input.h>
+#include <sys/types.h>
+#include <unistd.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 requested 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 specified 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"));
+}
+
+#ifndef HAVE_SEEK_DATA
+#define SEEK_DATA 3 /* seek to the next data */
+#define SEEK_HOLE 4 /* seek to the next hole */
+#endif
+
+/* values for flag variable */
+#define SEEK_DFLAG (1 << 0)
+#define SEEK_HFLAG (1 << 1)
+#define SEEK_RFLAG (1 << 2)
+
+/* indexes into the seekinfo array */
+#define DATA 0
+#define HOLE 1
+
+struct seekinfo {
+ char *name; /* display item name */
+ int seektype; /* data or hole */
+ int mask; /* compared for print and looping */
+} seekinfo[] = {
+ {"DATA", SEEK_DATA, SEEK_DFLAG},
+ {"HOLE", SEEK_HOLE, SEEK_HFLAG}
+};
+
+/* print item type and offset. catch special cases of eof and error */
+void
+seek_output(
+ char *type,
+ off64_t offset)
+{
+ if (offset == -1) {
+ if (errno == ENXIO)
+ printf("%s EOF\n", type);
+ else
+ perror("ERR");
+ } else
+ printf("%s %lld\n", type, (long long)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);
+ }
+ }
+ if (!(flag & (SEEK_DFLAG | SEEK_HFLAG)) || optind != argc - 1)
+ return command_usage(&seek_cmd);
+
+ offset = cvtnum(fsblocksize, fssectsize, argv[optind]);
+ if (offset < 0)
+ return command_usage(&seek_cmd);
+
+ /*
+ * check to see if the offset is a data or hole entry and
+ * decide if we want to display that type of entry.
+ */
+ if (flag & SEEK_HFLAG) {
+ result = lseek64(file->fd, offset, SEEK_HOLE);
+ if ((result == offset) || !(flag & SEEK_DFLAG)) {
+ /*
+ * this offset is a hole or are only displaying holes.
+ * if this offset is for data and we are displaying
+ * data, then we will fall through below to
+ * initialize the data search.
+ */
+ offset = result;
+ current = HOLE;
+ goto found_hole;
+ }
+ }
+
+ /* The offset is not a hole, or we are looking just for data */
+ current = DATA;
+ offset = lseek64(file->fd, offset, SEEK_DATA);
+
+found_hole:
+ /*
+ * At this point we know which type and the offset of the starting
+ * item. "current" alternates between data / hole entries in
+ * assending order - this alternation is needed even if only one
+ * type is to be displayed.
+ *
+ * An error or EOF will terminate the display, otherwise "flag"
+ * determines if there are more items to be displayed.
+ */
+ for (c = 0; flag; c++) {
+ if (offset == -1) {
+ /* print error or eof if the only entry */
+ if (errno != ENXIO || c == 0 )
+ seek_output(seekinfo[current].name, offset);
+ return 0; /* stop on error or EOF */
+ }
+
+ seek_output(seekinfo[current].name, offset);
+
+ /*
+ * 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 */
+ offset = lseek64(file->fd, offset, seekinfo[current].seektype);
+ }
+ return 0;
+}
+
+void
+seek_init(void)
+{
+ seek_cmd.name = "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/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