From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sukadev Bhattiprolu Subject: Re: [RFC][v8][PATCH 0/10] Implement clone3() system call Date: Tue, 20 Oct 2009 23:20:21 -0700 Message-ID: <20091021062021.GA2667@us.ibm.com> References: <4AD8C7E4.9000903@free.fr> <20091016194451.GA28706@us.ibm.com> <4ADCCD68.9030003@free.fr> <4ADCDE7F.4090501@librato.com> <20091020005125.GG27627@count0.beaverton.ibm.com> <20091020040315.GA26632@us.ibm.com> <20091020183329.GB22646@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Eric W. Biederman" Cc: Matt Helsley , Oren Laadan , Daniel Lezcano , randy.dunlap-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, arnd-r2nGTMty4D4@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Containers , Nathan Lynch , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Louis.Rilling-aw0BnHfMbSpBDgjK7y7TUQ@public.gmane.org, kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org, hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org, mingo-X9Un+BFzKDI@public.gmane.org, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, Alexey Dobriyan , roland-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Pavel Emelyanov List-Id: linux-api@vger.kernel.org Eric W. Biederman [ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org] wrote: | > I will post a version of the patch outside this patchset with min | > and max parameters and we can see if it can be optimized/beautified. | | Thanks, | Eric Here is the patch. alloc_pid() calls alloc_pidmap() as follows: - nr = alloc_pidmap(tmp); + min = max = 0; + if (target_pids) { + min = target_pids[i]; + max = min + 1; + } + nr = alloc_pidmap(tmp, min, max); It does look like this patch executes a bit more code even in the common case but let me know if you think this is better. --- From: Sukadev Bhattiprolu Date: Tue, 20 Oct 2009 17:01:18 -0700 Subject: [PATCH] Add min and max parameters to alloc_pidmap() With support for setting a specific pid number for a process, alloc_pidmap() will need a 'min' and a 'max' parameter. --- kernel/pid.c | 47 ++++++++++++++++++++++++++++++++++------------- 1 files changed, 34 insertions(+), 13 deletions(-) diff --git a/kernel/pid.c b/kernel/pid.c index c4d9914..56e13c1 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -147,18 +147,30 @@ static int alloc_pidmap_page(struct pidmap *map) return 0; } -static int alloc_pidmap(struct pid_namespace *pid_ns) +static int alloc_pidmap(struct pid_namespace *pid_ns, int min, int max) { int i, offset, max_scan, pid, last = pid_ns->last_pid; int rc = -EAGAIN; struct pidmap *map; - pid = last + 1; - if (pid >= pid_max) - pid = RESERVED_PIDS; + if (min < 0 || max < 0 || max > pid_max) + return -EINVAL; + + if (!max) + max = pid_max; + + pid = min; + if (pid && pid >= max) + return -EINVAL; + else if (!pid) { + 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; + max_scan = (max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset; for (i = 0; i <= max_scan; ++i) { rc = alloc_pidmap_page(map); if (rc) @@ -168,7 +180,12 @@ static int alloc_pidmap(struct pid_namespace *pid_ns) do { if (!test_and_set_bit(offset, map->page)) { atomic_dec(&map->nr_free); - pid_ns->last_pid = pid; + /* + * 'last_pid' only makes sense when + * choosing from entire range + */ + if (!min) + pid_ns->last_pid = pid; return pid; } offset = find_next_offset(map, offset); @@ -179,22 +196,26 @@ static int alloc_pidmap(struct pid_namespace *pid_ns) * bitmap block and the final block was the same * as the starting point, pid is before last_pid. */ - } while (offset < BITS_PER_PAGE && pid < pid_max && + } while (offset < BITS_PER_PAGE && pid < max && (i != max_scan || pid < last || !((last+1) & BITS_PER_PAGE_MASK))); } - if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) { + if (map < &pid_ns->pidmap[(max-1)/BITS_PER_PAGE]) { ++map; offset = 0; } else { map = &pid_ns->pidmap[0]; offset = RESERVED_PIDS; - if (unlikely(last == offset)) { - rc = -EAGAIN; - break; - } } pid = mk_pid(pid_ns, map, offset); + /* + * If we are back to where we started, well, no pids are + * currently available in selected range. + */ + if (pid < min || unlikely(last == offset)) { + rc = -EAGAIN; + break; + } } return rc; } @@ -272,7 +293,7 @@ struct pid *alloc_pid(struct pid_namespace *ns) tmp = ns; for (i = ns->level; i >= 0; i--) { - nr = alloc_pidmap(tmp); + nr = alloc_pidmap(tmp, 0, 0); if (nr < 0) goto out_free; -- 1.6.0.4