42f4614821
The fstatat(2) and statx() calls can pass the flag AT_NO_AUTOMOUNT which is meant to clear the LOOKUP_AUTOMOUNT flag and prevent triggering of an automount by the call. But this flag is unconditionally cleared for all stat family system calls except statx(). stat family system calls have always triggered mount requests for the negative dentry case in follow_automount() which is intended but prevents the fstatat(2) and statx() AT_NO_AUTOMOUNT case from being handled. In order to handle the AT_NO_AUTOMOUNT for both system calls the negative dentry case in follow_automount() needs to be changed to return ENOENT when the LOOKUP_AUTOMOUNT flag is clear (and the other required flags are clear). AFAICT this change doesn't have any noticable side effects and may, in some use cases (although I didn't see it in testing) prevent unnecessary callbacks to the automount daemon. It's also possible that a stat family call has been made with a path that is in the process of being mounted by some other process. But stat family calls should return the automount state of the path as it is "now" so it shouldn't wait for mount completion. This is the same semantic as the positive dentry case already handled. Link: http://lkml.kernel.org/r/150216641255.11652.4204561328197919771.stgit@pluto.themaw.net Fixes: deccf497d804a4c5fca ("Make stat/lstat/fstatat pass AT_NO_AUTOMOUNT to vfs_statx()") Signed-off-by: Ian Kent <raven@themaw.net> Cc: David Howells <dhowells@redhat.com> Cc: Colin Walters <walters@redhat.com> Cc: Ondrej Holy <oholy@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.