Attachment 909385 Details for Bug 1017478 – flock.2 NFS flock for MPO

[patch] flock.2 NFS flock for MPO

0001-flock.2-NFS-flock.patch (text/plain), 2.15 KB, created by Jan Chaloupka on 2014-06-17 05:58:34 UTC

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Creator: Jan Chaloupka

Created: 2014-06-17 05:58:34 UTC

Size: 2.15 KB

patch

obsolete

>From 48b8e89f4a555cb90282abc3cdff8a8a101362b2 Mon Sep 17 00:00:00 2001
>From: jchaloup <jchaloup@redhat.com>
>Date: Tue, 17 Jun 2014 07:56:23 +0200
>Subject: [PATCH] flock.2 NFS flock
>
>---
> man2/flock.2 | 48 ++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 40 insertions(+), 8 deletions(-)
>
>diff --git a/man2/flock.2 b/man2/flock.2
>index 86d47f3..1ecf48a 100644
>--- a/man2/flock.2
>+++ b/man2/flock.2
>@@ -143,19 +143,12 @@ possibly implemented in terms of
> .BR fcntl (2),
> appears on most Unix systems.
> .SH NOTES
>-.BR flock ()
>-does not lock files over NFS.
>-Use
>-.BR fcntl (2)
>-instead: that does work over NFS, given a sufficiently recent version of
>-Linux and a server which supports locking.
>-.PP
> Since kernel 2.0,
> .BR flock ()
> is implemented as a system call in its own right rather
> than being emulated in the GNU C library as a call to
> .BR fcntl (2).
>-This yields true BSD semantics:
>+This yields classical BSD semantics:
> there is no interaction between the types of lock
> placed by
> .BR flock ()
>@@ -164,6 +157,45 @@ and
> and
> .BR flock ()
> does not detect deadlock.
>+(Note, however, that on some modern BSDs,
>+.\" E.g., according to the flock(2) man page, FreeBSD since at least 5.3
>+.BR flock ()
>+and
>+.BR fcntl (2)
>+locks
>+.I do
>+interact with one another.)
>+.PP
>+In Linux kernels up to 2.6.11,
>+.BR flock ()
>+does not lock files over NFS
>+(i.e., the scope of locks was limited to the local system).
>+Instead, one could use
>+.BR fcntl (2)
>+byte-range locking, which does work over NFS,
>+given a sufficiently recent version of
>+Linux and a server which supports locking.
>+Since Linux 2.6.12, NFS clients support
>+.BR flock ()
>+locks by emulating them as byte-range locks on the entire file.
>+This means that
>+.BR fcntl (2)
>+and
>+.BR flock ()
>+locks
>+.I do
>+interact with one another over NFS.
>+Since Linux 2.6.37,
>+.\" commit 5eebde23223aeb0ad2d9e3be6590ff8bbfab0fc2
>+the kernel supports a compatibility mode that allows
>+.BR flock ()
>+locks (and also
>+.BR fcntl (2)
>+byte region locks) to be treated as local;
>+see the discussion of the
>+.I "local_lock"
>+option in
>+.BR nfs (5).
> .PP
> .BR flock ()
> places advisory locks only; given suitable permissions on a file,
>-- 
>1.9.3
>

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Attachments on bug 1017478: 909193 | 909385