[PATCH v3] xfs_io: Allow -P and -L to be given to open for O_PATH and O_NOFOLLOW

[Jeff Layton <jlayton@kernel.org>]

From: David Howells <dhowells@redhat.com>

Allow "open -P" to specify O_PATH so that paths which would otherwise be
unopenable might be opened for stat()'ing.  Such things include files that
would incur an access error or device files for which no corresponding
driver is available.

Allow "-L" to be given in conjunction with O_PATH to specify O_NOFOLLOW
also.

We also have to avoid calling xfsctl() if O_PATH is given as ioctls are
forbidden on such fds.  This means we cannot retrieve the geometry
information on an XFS filesystem, so the record gets cleared instead.  For
the moment, only the xfsctl() calls in the 'open' command are
conditionalised.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 io/file.c         |  6 ++++--
 io/init.c         |  8 +++++++-
 io/io.h           |  2 ++
 io/open.c         | 29 +++++++++++++++++++++++++----
 man/man8/xfs_io.8 | 12 +++++++++++-
 5 files changed, 49 insertions(+), 8 deletions(-)

v3: print new options in print_fileio
    handle -P and -L in init()

diff --git a/io/file.c b/io/file.c
index 349b19cdc420..b7edf6ef841f 100644
--- a/io/file.c
+++ b/io/file.c
@@ -35,7 +35,7 @@ print_fileio(
 	int		index,
 	int		braces)
 {
-	printf(_("%c%03d%c %-14s (%s,%s,%s,%s%s%s%s%s)\n"),
+	printf(_("%c%03d%c %-14s (%s,%s,%s,%s%s%s%s%s%s%s)\n"),
 		braces? '[' : ' ', index, braces? ']' : ' ', file->name,
 		file->flags & IO_FOREIGN ? _("foreign") : _("xfs"),
 		file->flags & IO_OSYNC ? _("sync") : _("non-sync"),
@@ -44,7 +44,9 @@ print_fileio(
 		file->flags & IO_REALTIME ? _(",real-time") : "",
 		file->flags & IO_APPEND ? _(",append-only") : "",
 		file->flags & IO_NONBLOCK ? _(",non-block") : "",
-		file->flags & IO_TMPFILE ? _(",tmpfile") : "");
+		file->flags & IO_TMPFILE ? _(",tmpfile") : "",
+		file->flags & IO_PATH ? _(",path") : "",
+		file->flags & IO_NOFOLLOW ? _(",nofollow") : "");
 }
 
 int
diff --git a/io/init.c b/io/init.c
index 0336c9623beb..d54a2fb957cf 100644
--- a/io/init.c
+++ b/io/init.c
@@ -154,7 +154,7 @@ init(
 	gettimeofday(&stopwatch, NULL);
 
 	fs_table_initialise(0, NULL, 0, NULL);
-	while ((c = getopt(argc, argv, "ac:C:dFfim:p:nrRstTVx")) != EOF) {
+	while ((c = getopt(argc, argv, "ac:C:dFfiLm:p:PnrRstTVx")) != EOF) {
 		switch (c) {
 		case 'a':
 			flags |= IO_APPEND;
@@ -200,6 +200,12 @@ init(
 		case 't':
 			flags |= IO_TRUNC;
 			break;
+		case 'P':
+			flags |= IO_PATH;
+			break;
+		case 'L':
+			flags |= IO_NOFOLLOW;
+			break;
 		case 'R':
 			flags |= IO_REALTIME;
 			break;
diff --git a/io/io.h b/io/io.h
index a26763610877..f2569588b28f 100644
--- a/io/io.h
+++ b/io/io.h
@@ -40,6 +40,8 @@
 #define IO_FOREIGN	(1<<7)
 #define IO_NONBLOCK	(1<<8)
 #define IO_TMPFILE	(1<<9)
+#define IO_PATH		(1<<10)
+#define IO_NOFOLLOW	(1<<11)
 
 /*
  * Regular file I/O control
diff --git a/io/open.c b/io/open.c
index 2cce0455263a..7cda47cc85dd 100644
--- a/io/open.c
+++ b/io/open.c
@@ -74,6 +74,10 @@ openfile(
 		oflags |= O_NONBLOCK;
 	if (flags & IO_TMPFILE)
 		oflags |= O_TMPFILE;
+	if (flags & IO_PATH)
+		oflags |= O_PATH;
+	if (flags & IO_NOFOLLOW)
+		oflags |= O_NOFOLLOW;
 
 	fd = open(path, oflags, mode);
 	if (fd < 0) {
@@ -97,13 +101,16 @@ openfile(
 	if (!geom || !platform_test_xfs_fd(fd))
 		return fd;
 
-	if (xfsctl(path, fd, XFS_IOC_FSGEOMETRY, geom) < 0) {
+	if (flags & IO_PATH) {
+		/* Can't call ioctl() on O_PATH fds */
+		memset(geom, 0, sizeof(*geom));
+	} else if (xfsctl(path, fd, XFS_IOC_FSGEOMETRY, geom) < 0) {
 		perror("XFS_IOC_FSGEOMETRY");
 		close(fd);
 		return -1;
 	}
 
-	if (!(flags & IO_READONLY) && (flags & IO_REALTIME)) {
+	if (!(flags & (IO_READONLY | IO_PATH)) && (flags & IO_REALTIME)) {
 		struct fsxattr	attr;
 
 		if (xfsctl(path, fd, FS_IOC_FSGETXATTR, &attr) < 0) {
@@ -191,6 +198,8 @@ open_help(void)
 " -t -- open with O_TRUNC (truncate the file to zero length if it exists)\n"
 " -R -- mark the file as a realtime XFS file immediately after opening it\n"
 " -T -- open with O_TMPFILE (create a file not visible in the namespace)\n"
+" -P -- open with O_PATH (create an fd that is merely a location reference)\n"
+" -L -- open with O_NOFOLLOW (don't follow symlink)\n"
 " Note1: usually read/write direct IO requests must be blocksize aligned;\n"
 "        some kernels, however, allow sectorsize alignment for direct IO.\n"
 " Note2: the bmap for non-regular files can be obtained provided the file\n"
@@ -216,7 +225,7 @@ open_f(
 		return 0;
 	}
 
-	while ((c = getopt(argc, argv, "FRTacdfm:nrstx")) != EOF) {
+	while ((c = getopt(argc, argv, "FLPRTacdfm:nrstx")) != EOF) {
 		switch (c) {
 		case 'F':
 			/* Ignored / deprecated now, handled automatically */
@@ -257,6 +266,12 @@ open_f(
 		case 'T':
 			flags |= IO_TMPFILE;
 			break;
+		case 'P':
+			flags |= IO_PATH;
+			break;
+		case 'L':
+			flags |= IO_NOFOLLOW;
+			break;
 		default:
 			return command_usage(&open_cmd);
 		}
@@ -270,6 +285,12 @@ open_f(
 		return -1;
 	}
 
+	if ((flags & (IO_PATH|IO_NOFOLLOW)) &&
+	    (flags & ~(IO_PATH|IO_NOFOLLOW))) {
+		fprintf(stderr, _("-P and -L are incompatible with the other options\n"));
+		return -1;
+	}
+
 	fd = openfile(argv[optind], &geometry, flags, mode, &fsp);
 	if (fd < 0)
 		return 0;
@@ -785,7 +806,7 @@ open_init(void)
 	open_cmd.argmax = -1;
 	open_cmd.flags = CMD_NOMAP_OK | CMD_NOFILE_OK |
 			 CMD_FOREIGN_OK | CMD_FLAG_ONESHOT;
-	open_cmd.args = _("[-acdrstxT] [-m mode] [path]");
+	open_cmd.args = _("[-acdrstxRTPL] [-m mode] [path]");
 	open_cmd.oneline = _("open the file specified by path");
 	open_cmd.help = open_help;
 
diff --git a/man/man8/xfs_io.8 b/man/man8/xfs_io.8
index c3ab532da03f..a49d067100fe 100644
--- a/man/man8/xfs_io.8
+++ b/man/man8/xfs_io.8
@@ -122,7 +122,7 @@ command for more details on any command.
 Display a list of all open files and (optionally) switch to an alternate
 current open file.
 .TP
-.BI "open [[ \-acdfrstRT ] " path " ]"
+.BI "open [[ \-acdfrstRTPL ] " path " ]"
 Closes the current file, and opens the file specified by
 .I path
 instead. Without any arguments, displays statistics about the current
@@ -164,6 +164,16 @@ option.
 .B \-R
 marks the file as a realtime XFS file after
 opening it, if it is not already marked as such.
+.TP
+.B \-P
+opens the path as a referent only (O_PATH).  This is incompatible with other
+flags specifying other O_xxx flags apart from
+.BR \-L .
+.TP
+.B \-L
+doesn't follow symlinks (O_NOFOLLOW).  This is incompatible with other
+flags specifying other O_xxx flags apart from
+.BR \-P .
 .PD
 .RE
 .TP
-- 
2.17.0