On 3/29/17 4:52 PM, David Howells wrote:
> 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.
Hey David -
Trolling through old patches and finding lots of stuff that fell through
the cracks. :( This seems ok, but what is the usecase for it? Was this
designed for some particular testcase?
Thanks,
-Eric
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> ---
> io/io.h | 2 ++
> io/open.c | 22 ++++++++++++++++++++--
> man/man8/xfs_io.8 | 12 +++++++++++-
> 3 files changed, 33 insertions(+), 3 deletions(-)
>
> diff --git a/io/io.h b/io/io.h
> index 952bdb8..4399419 100644
> --- a/io/io.h
> +++ b/io/io.h
> @@ -38,6 +38,8 @@
> #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 2ed55cf..f7f508a 100644
> --- a/io/open.c
> +++ b/io/open.c
> @@ -72,6 +72,10 @@ 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) {
> @@ -179,6 +183,8 @@ 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"
> @@ -203,7 +209,7 @@ 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 */
> @@ -244,6 +250,12 @@ 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);
> }
> @@ -257,6 +269,12 @@ 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);
> if (fd < 0)
> return 0;
> @@ -772,7 +790,7 @@ 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 022f0ea..e77be40 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
> --
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