xfs_io: add the ability to do an O_PATH open

PATCH In review Jeff Layton 2 participants 9 messages May 16, 2018 – May 23, 2018

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Jeff Layton

author

2018-05-16 13:27 UTC #0 lore raw

PATCH 1/2 xfs_io: add the ability to do an O_PATH open

From: Jeff Layton <[email protected]>

Signed-off-by Jeff Layton <[email protected]>

---
 io/file.c         | 3 ++-
 io/init.c         | 5 ++++-
 io/io.h           | 1 +
 io/open.c         | 7 ++++++-
 io/stat.c         | 4 +++-
 man/man8/xfs_io.8 | 3 +++
 6 files changed, 19 insertions(+), 4 deletions(-)

io/file.c +2 -1

index 349b19cdc420..ff80652b183b 100644
@@ -44,7 +44,8 @@ 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") : "");
 }
 
 int

io/init.c +4 -1

index 0336c9623beb..d4e84e82a77e 100644
@@ -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:dFfim:Pp:nrRstTVx")) != EOF) {
 		switch (c) {
 		case 'a':
 			flags |= IO_APPEND;

@@ -200,6 +200,9 @@ init(
 		case 't':
 			flags |= IO_TRUNC;
 			break;
+		case 'P':
+			flags |= IO_PATH;
+			break;
 		case 'R':
 			flags |= IO_REALTIME;
 			break;

io/io.h +1 -0

index a26763610877..0acc332b5dbb 100644
@@ -40,6 +40,7 @@
 #define IO_FOREIGN	(1<<7)
 #define IO_NONBLOCK	(1<<8)
 #define IO_TMPFILE	(1<<9)
+#define IO_PATH		(1<<10)
 
 /*
  * Regular file I/O control

io/open.c +6 -1

index 2cce0455263a..ba73f1d0361f 100644
@@ -74,6 +74,8 @@ openfile(
 		oflags |= O_NONBLOCK;
 	if (flags & IO_TMPFILE)
 		oflags |= O_TMPFILE;
+	if (flags & IO_PATH)
+		oflags |= O_PATH;
 
 	fd = open(path, oflags, mode);
 	if (fd < 0) {

@@ -216,7 +218,7 @@ open_f(
 		return 0;
 	}
 
-	while ((c = getopt(argc, argv, "FRTacdfm:nrstx")) != EOF) {
+	while ((c = getopt(argc, argv, "FRTacdfm:nPrstx")) != EOF) {
 		switch (c) {
 		case 'F':
 			/* Ignored / deprecated now, handled automatically */

@@ -250,6 +252,9 @@ open_f(
 		case 't':
 			flags |= IO_TRUNC;
 			break;
+		case 'P':
+			flags |= IO_PATH;
+			break;
 		case 'R':
 		case 'x':	/* backwards compatibility */
 			flags |= IO_REALTIME;

io/stat.c +3 -1

index 41d421525791..2db2736359e0 100644
@@ -100,7 +100,9 @@ void print_file_info(void)
 		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") : "");
+
 }
 
 void print_xfs_info(int verbose)

man/man8/xfs_io.8 +3 -0

index c3ab532da03f..89e8e4be460e 100644
@@ -153,6 +153,9 @@ truncates on open (O_TRUNC).
 .B \-n
 opens in non-blocking mode if possible (O_NONBLOCK).
 .TP
+.B \-P
+opens the file for location only (O_PATH).
+.TP
 .B \-T
 create a temporary file not linked into the filesystem namespace
 (O_TMPFILE).  The pathname passed must refer to a directory which

Signature · 1 line

2.17.0

Jeff Layton

author

2018-05-16 13:27 UTC #1 lore raw

PATCH 2/2 xfs_io: syncfs can fail

From: Jeff Layton <[email protected]>

syncfs can return an error. Report one if it does.

Signed-off-by Jeff Layton <[email protected]>

---
 io/sync.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

io/sync.c +2 -2

index c77263804a35..868cea7c051e 100644
@@ -41,8 +41,8 @@ syncfs_f(
 	int			argc,
 	char			**argv)
 {
-	/* syncfs can't fail */
-	syncfs(file->fd);
+	if (syncfs(file->fd) < 0)
+		perror("syncfs");
 	return 0;
 }
 #endif

Signature · 1 line

2.17.0

Eric Sandeen

2018-05-16 14:26 UTC #2 lore raw

Re: [PATCH 2/2] xfs_io: syncfs can fail

Quoted 14 lines · Jeff Layton

From: Jeff Layton <[email protected]>
syncfs can return an error. Report one if it does.
Signed-off-by Jeff Layton <[email protected]>
---
  io/sync.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)
io/sync.c +0 -0
index c77263804a35..868cea7c051e 100644

io/sync.c syncfs_f( · line 45

Quoted 7 lines

io/sync.c +2 -2

@@ -41,8 +41,8 @@ syncfs_f(
  	int			argc,
  	char			**argv)
  {
-	/* syncfs can't fail */
-	syncfs(file->fd);
+	if (syncfs(file->fd) < 0)
+		perror("syncfs");

In light of dchinner's recent reminder on another of my patches, this should also set exitcode=1 here, so that the overall xfs_io exit code will be non-zero if syncfs fails.

(I could just add that on merge if you prefer... assuming I remember)

Thanks,
-Eric

Quoted 4 lines

io/sync.c +0 -0

  	return 0;
  }
  #endif

Jeff Layton

author

2018-05-16 17:17 UTC #3 lore raw

PATCH v2 1/1 xfs_io: syncfs can fail

In reply to Jeff Layton

From: Jeff Layton <[email protected]>

syncfs can return an error. Report one if it does. Also, ensure that xfs_io will exit with a non-zero status in that case.

Signed-off-by Jeff Layton <[email protected]>

---
 io/sync.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

v2: also set exitcode when reporting error

io/sync.c +4 -2

index c77263804a35..20ab50a7fcd4 100644
@@ -41,8 +41,10 @@ syncfs_f(
 	int			argc,
 	char			**argv)
 {
-	/* syncfs can't fail */
-	syncfs(file->fd);
+	if (syncfs(file->fd) < 0) {
+		perror("syncfs");
+		exitcode = 1;
+	}
 	return 0;
 }
 #endif

Signature · 1 line

2.17.0

Eric Sandeen

Reviewed-by on v2 1/1

2018-05-23 21:37 UTC #4 lore raw

Re: [PATCH v2] xfs_io: syncfs can fail

Quoted 6 lines · Jeff Layton

From: Jeff Layton <[email protected]>
syncfs can return an error. Report one if it does. Also, ensure that xfs_io will exit with a non-zero status in that case.
Signed-off-by Jeff Layton <[email protected]>

Reviewed-by Eric Sandeen <[email protected]>

Quoted 24 lines

---
  io/sync.c | 6 ++++--
  1 file changed, 4 insertions(+), 2 deletions(-)

v2: also set exitcode when reporting error

io/sync.c +4 -2

index c77263804a35..20ab50a7fcd4 100644
@@ -41,8 +41,10 @@ syncfs_f(
  	int			argc,
  	char			**argv)
  {
-	/* syncfs can't fail */
-	syncfs(file->fd);
+	if (syncfs(file->fd) < 0) {
+		perror("syncfs");
+		exitcode = 1;
+	}
  	return 0;
  }
  #endif

Eric Sandeen

2018-05-16 14:32 UTC #5 lore raw

In reply to Jeff Layton

Quoted 3 lines · Jeff Layton

From: Jeff Layton <[email protected]>
Signed-off-by Jeff Layton <[email protected]>

Thanks. dhowells also sent something similar long ago,

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

But you have some things here he missed (and he has some things you missed, like command help output)

Could you maybe compare this to his patch, and resend a superset with both SOBs if that seems appropriate?

Thanks,
-Eric

Quoted 120 lines

---
  io/file.c         | 3 ++-
  io/init.c         | 5 ++++-
  io/io.h           | 1 +
  io/open.c         | 7 ++++++-
  io/stat.c         | 4 +++-
  man/man8/xfs_io.8 | 3 +++
  6 files changed, 19 insertions(+), 4 deletions(-)

io/file.c +2 -1

index 349b19cdc420..ff80652b183b 100644
@@ -44,7 +44,8 @@ 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") : "");
  }
 
  int

io/init.c +4 -1

index 0336c9623beb..d4e84e82a77e 100644
@@ -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:dFfim:Pp:nrRstTVx")) != EOF) {
  		switch (c) {
  		case 'a':
  			flags |= IO_APPEND;

@@ -200,6 +200,9 @@ init(
  		case 't':
  			flags |= IO_TRUNC;
  			break;
+		case 'P':
+			flags |= IO_PATH;
+			break;
  		case 'R':
  			flags |= IO_REALTIME;
  			break;

io/io.h +1 -0

index a26763610877..0acc332b5dbb 100644
@@ -40,6 +40,7 @@
  #define IO_FOREIGN	(1<<7)
  #define IO_NONBLOCK	(1<<8)
  #define IO_TMPFILE	(1<<9)
+#define IO_PATH		(1<<10)
 
  /*
   * Regular file I/O control

io/open.c +6 -1

index 2cce0455263a..ba73f1d0361f 100644
@@ -74,6 +74,8 @@ openfile(
  		oflags |= O_NONBLOCK;
  	if (flags & IO_TMPFILE)
  		oflags |= O_TMPFILE;
+	if (flags & IO_PATH)
+		oflags |= O_PATH;
 
  	fd = open(path, oflags, mode);
  	if (fd < 0) {

@@ -216,7 +218,7 @@ open_f(
  		return 0;
  	}
 
-	while ((c = getopt(argc, argv, "FRTacdfm:nrstx")) != EOF) {
+	while ((c = getopt(argc, argv, "FRTacdfm:nPrstx")) != EOF) {
  		switch (c) {
  		case 'F':
  			/* Ignored / deprecated now, handled automatically */

@@ -250,6 +252,9 @@ open_f(
  		case 't':
  			flags |= IO_TRUNC;
  			break;
+		case 'P':
+			flags |= IO_PATH;
+			break;
  		case 'R':
  		case 'x':	/* backwards compatibility */
  			flags |= IO_REALTIME;

io/stat.c +3 -1

index 41d421525791..2db2736359e0 100644
@@ -100,7 +100,9 @@ void print_file_info(void)
  		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") : "");
+
  }
 
  void print_xfs_info(int verbose)

man/man8/xfs_io.8 +3 -0

index c3ab532da03f..89e8e4be460e 100644
@@ -153,6 +153,9 @@ truncates on open (O_TRUNC).
  .B \-n
  opens in non-blocking mode if possible (O_NONBLOCK).
  .TP
+.B \-P
+opens the file for location only (O_PATH).
+.TP
  .B \-T
  create a temporary file not linked into the filesystem namespace
  (O_TMPFILE).  The pathname passed must refer to a directory which

Jeff Layton

author

2018-05-16 17:14 UTC #6 lore raw

PATCH v3 1/1 xfs_io: Allow -P and -L to be given to open for O_PATH and O_NOFOLLOW

In reply to Jeff Layton

From: David Howells <[email protected]>

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 <[email protected]>

Signed-off-by Jeff Layton <[email protected]>

---
 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()

io/file.c +4 -2

index 349b19cdc420..b7edf6ef841f 100644
@@ -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

io/init.c +7 -1

index 0336c9623beb..d54a2fb957cf 100644
@@ -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;

io/io.h +2 -0

index a26763610877..f2569588b28f 100644
@@ -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

io/open.c +25 -4

index 2cce0455263a..7cda47cc85dd 100644
@@ -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;

man/man8/xfs_io.8 +11 -1

index c3ab532da03f..a49d067100fe 100644
@@ -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

Signature · 1 line

2.17.0

Eric Sandeen

Reviewed-by on v3 1/1

2018-05-23 21:51 UTC #7 lore raw

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

Quoted 10 lines · Jeff Layton

From: David Howells <[email protected]>
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.

Quoted 8 lines

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 <[email protected]>
Signed-off-by Jeff Layton <[email protected]>

Reviewed-by Eric Sandeen <[email protected]>

Quoted 192 lines

---
  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()

io/file.c +4 -2

index 349b19cdc420..b7edf6ef841f 100644
@@ -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

io/init.c +7 -1

index 0336c9623beb..d54a2fb957cf 100644
@@ -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;

io/io.h +2 -0

index a26763610877..f2569588b28f 100644
@@ -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

io/open.c +25 -4

index 2cce0455263a..7cda47cc85dd 100644
@@ -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;

man/man8/xfs_io.8 +11 -1

index c3ab532da03f..a49d067100fe 100644
@@ -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

Eric Sandeen

2018-05-23 22:03 UTC #8 lore raw

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

Quoted 17 lines · Eric Sandeen

Quoted 16 lines · Jeff Layton
From: David Howells <[email protected]>
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.

Quoted 4 lines

Quoted 2 lines
Signed-off-by David Howells <[email protected]>
Signed-off-by Jeff Layton <[email protected]>
Reviewed-by Eric Sandeen <[email protected]>

hm actually I'll need to locally define O_PATH so it builds on older systems:

+#ifndef O_PATH
+#if defined __alpha__
+#define O_PATH 040000000
+#elif defined(__hppa__)
+#define O_PATH 020000000
+#elif defined(__sparc__)
+#define O_PATH 0x1000000
+#else
+#define O_PATH 010000000
+#endif
+#endif /* O_PATH */

... like we do for O_TMPFILE. I can do that on the way in.

-Eric