Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753920AbZIXRCz (ORCPT ); Thu, 24 Sep 2009 13:02:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753888AbZIXRCw (ORCPT ); Thu, 24 Sep 2009 13:02:52 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.141]:51026 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753886AbZIXRCw (ORCPT ); Thu, 24 Sep 2009 13:02:52 -0400 Date: Thu, 24 Sep 2009 10:01:31 -0700 From: Sukadev Bhattiprolu To: linux-kernel@vger.kernel.org Cc: Oren Laadan , serue@us.ibm.com, "Eric W. Biederman" , Alexey Dobriyan , Pavel Emelyanov , Andrew Morton , torvalds@linux-foundation.org, mikew@google.com, mingo@elte.hu, hpa@zytor.com, Nathan Lynch , arnd@arndb.de, peterz@infradead.org, Containers , sukadev@us.ibm.com Subject: [RFC][v7][PATCH 4/9]: Add target_pid parameter to alloc_pidmap() Message-ID: <20090924170131.GD16989@us.ibm.com> References: <20090924165548.GA16586@us.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090924165548.GA16586@us.ibm.com> X-Operating-System: Linux 2.0.32 on an i486 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2639 Lines: 91 Subject: [RFC][v7][PATCH 4/9]: Add target_pid parameter to alloc_pidmap() With support for setting a specific pid number for a process, alloc_pidmap() will need a 'target_pid' parameter. Changelog[v6]: - Separate target_pid > 0 case to minimize the number of checks needed. Changelog[v3]: - (Eric Biederman): Avoid set_pidmap() function. Added couple of checks for target_pid in alloc_pidmap() itself. Changelog[v2]: - (Serge Hallyn) Check for 'pid < 0' in set_pidmap().(Code actually checks for 'pid <= 0' for completeness). Signed-off-by: Sukadev Bhattiprolu Acked-by: Serge Hallyn --- kernel/pid.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) Index: linux-2.6/kernel/pid.c =================================================================== --- linux-2.6.orig/kernel/pid.c 2009-09-09 19:07:20.000000000 -0700 +++ linux-2.6/kernel/pid.c 2009-09-10 10:23:27.000000000 -0700 @@ -146,16 +146,22 @@ static int alloc_pidmap_page(struct pidm return 0; } -static int alloc_pidmap(struct pid_namespace *pid_ns) +static int alloc_pidmap(struct pid_namespace *pid_ns, int target_pid) { int i, offset, max_scan, pid, last = pid_ns->last_pid; int rc = -EAGAIN; int pid_max = pid_ns->pid_max; struct pidmap *map; - pid = last + 1; - if (pid >= pid_max) - pid = RESERVED_PIDS; + if (target_pid) { + pid = target_pid; + if (pid < 0 || pid >= pid_max) + return -EINVAL; + } else { + pid = last + 1; + if (pid >= pid_max) + pid = RESERVED_PIDS; + } offset = pid & BITS_PER_PAGE_MASK; map = &pid_ns->pidmap[pid/BITS_PER_PAGE]; max_scan = (pid_max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset; @@ -164,6 +170,15 @@ static int alloc_pidmap(struct pid_names if (rc) break; + if (target_pid) { + rc = -EBUSY; + if (!test_and_set_bit(offset, map->page)) { + atomic_dec(&map->nr_free); + rc = pid; + } + return rc; + } + if (likely(atomic_read(&map->nr_free))) { do { if (!test_and_set_bit(offset, map->page)) { @@ -196,6 +211,7 @@ static int alloc_pidmap(struct pid_names } pid = mk_pid(pid_ns, map, offset); } + return rc; } @@ -272,7 +288,7 @@ struct pid *alloc_pid(struct pid_namespa tmp = ns; for (i = ns->level; i >= 0; i--) { - nr = alloc_pidmap(tmp); + nr = alloc_pidmap(tmp, 0); if (nr < 0) goto out_free; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/