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From: NeilBrown <neilb@suse.com>
To: "Michael Kerrisk \(man-pages\)" <mtk.manpages@gmail.com>
Cc: linux-man@vger.kernel.org,
	Lennart Poettering <lennart@poettering.net>,
	linux-fsdevel@vger.kernel.org
Subject: [PATCH man-pages] open.2: improve O_PATH documentation.
Date: Thu, 10 Aug 2017 13:25:21 +1000	[thread overview]
Message-ID: <873790rtni.fsf@notabene.neil.brown.name> (raw)

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- fstatfs is now permitted.
- ioctl isn't, and is worth listing explicitly
- O_PATH allows an automount point to be opened with
  triggering the mount.

All tested

Signed-off-by: NeilBrown <neilb@suse.com>
---
 man2/open.2 | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/man2/open.2 b/man2/open.2
index e3b00939790c..38d532397b02 100644
--- a/man2/open.2
+++ b/man2/open.2
@@ -585,6 +585,7 @@ The file itself is not opened, and other file operations (e.g.,
 .BR fchmod (2),
 .BR fchown (2),
 .BR fgetxattr (2),
+.BR ioctl (2),
 .BR mmap (2))
 fail with the error
 .BR EBADF .
@@ -599,8 +600,11 @@ be performed on the resulting file descriptor:
 (since Linux 3.5);
 .\" commit 332a2e1244bd08b9e3ecd378028513396a004a24
 .BR fstat (2)
-(since Linux 3.6).
+(since Linux 3.6);
 .\" fstat(): commit 55815f70147dcfa3ead5738fd56d3574e2e3c1c2
+.BR fstatfs (2)
+(since Linux 3.12).
+.\" fstatfs(): commit 9d05746e7b16d8565dddbe3200faa1e669d23bbf
 .IP *
 Duplicating the file descriptor
 .RB ( dup (2),
@@ -666,6 +670,16 @@ argument in calls to
 and
 .BR readlinkat (2)
 with an empty pathname to have the calls operate on the symbolic link.
+
+If
+.I pathname
+refers to an automount point that has not yet been triggered, so no
+other filesystem is mounted on it, then the call returns a file
+descriptor referring to the automount directory without triggering a mount.
+.BR fstatfs (2)
+can then be used to determine if it is, in fact, an untriggered
+automount point
+.RB ( ".f_type == AUTOFS_SUPER_MAGIC" ).
 .TP
 .B O_SYNC
 Write operations on the file will complete according to the requirements of
-- 
2.14.0.rc0.dirty


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WARNING: multiple messages have this Message-ID (diff)
From: NeilBrown <neilb-IBi9RG/b67k@public.gmane.org>
To: "Michael Kerrisk (man-pages)"
	<mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Lennart Poettering
	<lennart-mdGvqq1h2p+GdvJs77BJ7Q@public.gmane.org>,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: [PATCH man-pages] open.2: improve O_PATH documentation.
Date: Thu, 10 Aug 2017 13:25:21 +1000	[thread overview]
Message-ID: <873790rtni.fsf@notabene.neil.brown.name> (raw)

[-- Attachment #1: Type: text/plain, Size: 1734 bytes --]


- fstatfs is now permitted.
- ioctl isn't, and is worth listing explicitly
- O_PATH allows an automount point to be opened with
  triggering the mount.

All tested

Signed-off-by: NeilBrown <neilb-IBi9RG/b67k@public.gmane.org>
---
 man2/open.2 | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/man2/open.2 b/man2/open.2
index e3b00939790c..38d532397b02 100644
--- a/man2/open.2
+++ b/man2/open.2
@@ -585,6 +585,7 @@ The file itself is not opened, and other file operations (e.g.,
 .BR fchmod (2),
 .BR fchown (2),
 .BR fgetxattr (2),
+.BR ioctl (2),
 .BR mmap (2))
 fail with the error
 .BR EBADF .
@@ -599,8 +600,11 @@ be performed on the resulting file descriptor:
 (since Linux 3.5);
 .\" commit 332a2e1244bd08b9e3ecd378028513396a004a24
 .BR fstat (2)
-(since Linux 3.6).
+(since Linux 3.6);
 .\" fstat(): commit 55815f70147dcfa3ead5738fd56d3574e2e3c1c2
+.BR fstatfs (2)
+(since Linux 3.12).
+.\" fstatfs(): commit 9d05746e7b16d8565dddbe3200faa1e669d23bbf
 .IP *
 Duplicating the file descriptor
 .RB ( dup (2),
@@ -666,6 +670,16 @@ argument in calls to
 and
 .BR readlinkat (2)
 with an empty pathname to have the calls operate on the symbolic link.
+
+If
+.I pathname
+refers to an automount point that has not yet been triggered, so no
+other filesystem is mounted on it, then the call returns a file
+descriptor referring to the automount directory without triggering a mount.
+.BR fstatfs (2)
+can then be used to determine if it is, in fact, an untriggered
+automount point
+.RB ( ".f_type == AUTOFS_SUPER_MAGIC" ).
 .TP
 .B O_SYNC
 Write operations on the file will complete according to the requirements of
-- 
2.14.0.rc0.dirty


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             reply	other threads:[~2017-08-10  3:25 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-10  3:25 NeilBrown [this message]
2017-08-10  3:25 ` [PATCH man-pages] open.2: improve O_PATH documentation NeilBrown
2017-08-10 10:21 ` Lennart Poettering
2017-08-10 14:02   ` Krzysztof Błaszkowski
2017-08-10 14:02     ` Krzysztof Błaszkowski
2017-08-10 23:04     ` NeilBrown
2017-08-10 23:04       ` NeilBrown
2017-08-12 20:13       ` Michael Kerrisk (man-pages)
2017-08-10 15:50   ` Matthew Wilcox
2017-08-10 15:50     ` Matthew Wilcox
2017-08-12 20:11 ` Michael Kerrisk (man-pages)
2017-08-12 20:11   ` Michael Kerrisk (man-pages)

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