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From: Aleksa Sarai <cyphar@cyphar.com>
To: Al Viro <viro@zeniv.linux.org.uk>,
	Jeff Layton <jlayton@kernel.org>,
	"J. Bruce Fields" <bfields@fieldses.org>,
	Arnd Bergmann <arnd@arndb.de>,
	David Howells <dhowells@redhat.com>,
	Shuah Khan <shuah@kernel.org>,
	Shuah Khan <skhan@linuxfoundation.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>
Cc: Aleksa Sarai <cyphar@cyphar.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Andy Lutomirski <luto@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>,
	Tycho Andersen <tycho@tycho.ws>,
	David Drysdale <drysdale@google.com>,
	Chanho Min <chanho.min@lge.com>, Oleg Nesterov <oleg@redhat.com>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Christian Brauner <christian@brauner.io>,
	Aleksa Sarai <asarai@suse.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	containers@lists.linux-foundation.org,
	linux-alpha@vger.kernel.org, linux-api@vger.kernel.org,
	libc-alpha@sourceware.org, linux-arch@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-fsdevel@vger.kernel.org, linux-ia64@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
	linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
	linux-xtensa@linux-xtensa.org, sparclinux@vger.kernel.org
Subject: [PATCH v14 6/6] Documentation: path-lookup: mention LOOKUP_MAGICLINK_JUMPED
Date: Thu, 10 Oct 2019 16:41:40 +1100
Message-ID: <20191010054140.8483-7-cyphar@cyphar.com> (raw)
In-Reply-To: <20191010054140.8483-1-cyphar@cyphar.com>

Now that we have a special flag to signify magic-link jumps, mention it
within the path-lookup docs. And now that "magic link" is the correct
term for nd_jump_link()-style symlinks, clean up references to this type
of "symlink".

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
 Documentation/filesystems/path-lookup.rst | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/Documentation/filesystems/path-lookup.rst b/Documentation/filesystems/path-lookup.rst
index 434a07b0002b..2c32795389bd 100644
--- a/Documentation/filesystems/path-lookup.rst
+++ b/Documentation/filesystems/path-lookup.rst
@@ -405,6 +405,10 @@ is requested.  Keeping a reference in the ``nameidata`` ensures that
 only one root is in effect for the entire path walk, even if it races
 with a ``chroot()`` system call.
 
+It should be noted that in the case of ``LOOKUP_IN_ROOT`` or
+``LOOKUP_BENEATH``, the effective root becomes the directory file descriptor
+passed to ``openat2()`` (which exposes these ``LOOKUP_`` flags).
+
 The root is needed when either of two conditions holds: (1) either the
 pathname or a symbolic link starts with a "'/'", or (2) a "``..``"
 component is being handled, since "``..``" from the root must always stay
@@ -1149,7 +1153,7 @@ so ``NULL`` is returned to indicate that the symlink can be released and
 the stack frame discarded.
 
 The other case involves things in ``/proc`` that look like symlinks but
-aren't really::
+aren't really (and are therefore commonly referred to as "magic-links")::
 
      $ ls -l /proc/self/fd/1
      lrwx------ 1 neilb neilb 64 Jun 13 10:19 /proc/self/fd/1 -> /dev/pts/4
@@ -1310,12 +1314,14 @@ longer needed.
 ``LOOKUP_JUMPED`` means that the current dentry was chosen not because
 it had the right name but for some other reason.  This happens when
 following "``..``", following a symlink to ``/``, crossing a mount point
-or accessing a "``/proc/$PID/fd/$FD``" symlink.  In this case the
-filesystem has not been asked to revalidate the name (with
-``d_revalidate()``).  In such cases the inode may still need to be
-revalidated, so ``d_op->d_weak_revalidate()`` is called if
+or accessing a "``/proc/$PID/fd/$FD``" symlink (also known as a "magic
+link"). In this case the filesystem has not been asked to revalidate the
+name (with ``d_revalidate()``).  In such cases the inode may still need
+to be revalidated, so ``d_op->d_weak_revalidate()`` is called if
 ``LOOKUP_JUMPED`` is set when the look completes - which may be at the
-final component or, when creating, unlinking, or renaming, at the penultimate component.
+final component or, when creating, unlinking, or renaming, at the
+penultimate component. ``LOOKUP_MAGICLINK_JUMPED`` is set alongside
+``LOOKUP_JUMPED`` if a magic-link was traversed.
 
 Final-component flags
 ~~~~~~~~~~~~~~~~~~~~~
-- 
2.23.0


      parent reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-10  5:41 [PATCH v14 0/6] open: introduce openat2(2) syscall Aleksa Sarai
2019-10-10  5:41 ` [PATCH v14 1/6] namei: O_BENEATH-style resolution restriction flags Aleksa Sarai
2019-10-10  5:41 ` [PATCH v14 2/6] namei: LOOKUP_IN_ROOT: chroot-like path resolution Aleksa Sarai
2019-10-10 17:07   ` Linus Torvalds
2019-10-12  4:08     ` Aleksa Sarai
2019-10-12  4:15       ` Aleksa Sarai
2019-10-24  7:06         ` Aleksa Sarai
2019-10-10  5:41 ` [PATCH v14 3/6] namei: permit ".." resolution with LOOKUP_{IN_ROOT,BENEATH} Aleksa Sarai
2019-10-10  5:41 ` [PATCH v14 4/6] open: introduce openat2(2) syscall Aleksa Sarai
2019-10-10  5:41 ` [PATCH v14 5/6] selftests: add openat2(2) selftests Aleksa Sarai
2019-10-10  5:41 ` Aleksa Sarai [this message]

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