mremap.2: Add note about mremap() with locked areas

When mremap() is used to move or expand a mapping that is locked
with mlock() or equivalent it will attempt to populate the new
area.  However, like mmap(MAP_LOCKED), mremap() will not fail if
the area cannot be populated.  Also like mmap(MAP_LOCKED) this
might come as a surprise to users and should be noted.

Signed-off-by: Eric B Munson <emunson@akamai.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: linux-man@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man2/mremap.2 b/man2/mremap.2
index 071adb516a4d358edb4dc53a6f5dba38825ffefa..cf884e6e1ba6a730d390bf2c963c932c2fe68d5b 100644 (file)
--- a/man2/mremap.2
+++ b/man2/mremap.2
@@ -196,6 +196,17 @@ and the prototype for
 did not allow for the
 .I new_address
 argument.
+
+If
+.BR mremap ()
+is used to move or expand an area locked with
+.BR mlock (2)
+or equivalent, the
+.BR mremap ()
+call will make a best effort to populate the new area but will not fail
+with
+.B ENOMEM
+if the area cannot be populated.
 .SH SEE ALSO
 .BR brk (2),
 .BR getpagesize (2),