linux-kernel - [RFC][v4][PATCH 2/7]: Have alloc_pidmap() return actual error code

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Message-ID: <20090807061243.GB20672@us.ibm.com>
Date:	Thu, 6 Aug 2009 23:12:43 -0700
From:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	Oren Laadan <orenl@...columbia.edu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>, serue@...ibm.com,
	Alexey Dobriyan <adobriyan@...il.com>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Andrew Morton <akpm@...l.org>, torvalds@...ux-foundation.org,
	mikew@...gle.com, mingo@...e.hu, hpa@...or.com,
	Containers <containers@...ts.linux-foundation.org>,
	sukadev@...ibm.com
Subject: [RFC][v4][PATCH 2/7]: Have alloc_pidmap() return actual error code



Subject: [RFC][v4][PATCH 2/7]: Have alloc_pidmap() return actual error code

alloc_pidmap() can fail either because all pid numbers are in use or
because memory allocation failed.  With support for setting a specific
pid number, alloc_pidmap() would also fail if either the given pid
number is invalid or in use.

Rather than have callers assume -ENOMEM, have alloc_pidmap() return
the actual error.

Signed-off-by: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Acked-by: Serge Hallyn <serue@...ibm.com>
Reviewed-by: Oren Laadan <orenl@...columbia.edu>
---
 kernel/fork.c |    5 +++--
 kernel/pid.c  |    9 ++++++---
 2 files changed, 9 insertions(+), 5 deletions(-)

Index: linux-2.6/kernel/fork.c
===================================================================
--- linux-2.6.orig/kernel/fork.c	2009-08-05 17:00:22.000000000 -0700
+++ linux-2.6/kernel/fork.c	2009-08-05 17:02:45.000000000 -0700
@@ -1124,10 +1124,11 @@
 		goto bad_fork_cleanup_io;
 
 	if (pid != &init_struct_pid) {
-		retval = -ENOMEM;
 		pid = alloc_pid(p->nsproxy->pid_ns);
-		if (!pid)
+		if (IS_ERR(pid)) {
+			retval = PTR_ERR(pid);
 			goto bad_fork_cleanup_io;
+		}
 
 		if (clone_flags & CLONE_NEWPID) {
 			retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
Index: linux-2.6/kernel/pid.c
===================================================================
--- linux-2.6.orig/kernel/pid.c	2009-08-05 17:02:40.000000000 -0700
+++ linux-2.6/kernel/pid.c	2009-08-05 17:02:45.000000000 -0700
@@ -158,6 +158,7 @@
 	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;
+	rc = -EAGAIN;
 	for (i = 0; i <= max_scan; ++i) {
 		rc = alloc_pidmap_page(map);
 		if (rc)
@@ -188,12 +189,14 @@
 		} else {
 			map = &pid_ns->pidmap[0];
 			offset = RESERVED_PIDS;
-			if (unlikely(last == offset))
+			if (unlikely(last == offset)) {
+				rc = -EAGAIN;
 				break;
+			}
 		}
 		pid = mk_pid(pid_ns, map, offset);
 	}
-	return -1;
+	return rc;
 }
 
 int next_pidmap(struct pid_namespace *pid_ns, int last)
@@ -298,7 +301,7 @@
 		free_pidmap(pid->numbers + i);
 
 	kmem_cache_free(ns->pid_cachep, pid);
-	pid = NULL;
+	pid = ERR_PTR(nr);
 	goto out;
 }
 
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