From: Jeff Layton <jlayton@redhat.com>
Date: Mon, 10 Mar 2014 13:54:19 +0000 (-0400)
Subject: locks: make locks_mandatory_area check for file-private locks
X-Git-Tag: v3.15-rc1~98^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=29723adee11804b548903ddb1db666cf4a60f60e;p=pandora-kernel.git

locks: make locks_mandatory_area check for file-private locks

Allow locks_mandatory_area() to handle file-private locks correctly.
If there is a file-private lock set on an open file and we're doing I/O
via the same, then that should not cause anything to block.

Handle this by first doing a non-blocking FL_ACCESS check for a
file-private lock, and then fall back to checking for a classic POSIX
lock (and possibly blocking).

Note that this approach is subject to the same races that have always
plagued mandatory locking on Linux.

Reported-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
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