[Devel] Re: [v12][PATCH 2/9] Have alloc_pidmap() return actual error code

[Sukadev Bhattiprolu]

CC: LKML

Sukadev Bhattiprolu [sukadev at linux.vnet.ibm.com] wrote:
| 
| Subject: [v12][PATCH 2/9] 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 at linux.vnet.ibm.com>
| Acked-by: Serge Hallyn <serue at us.ibm.com>
| Reviewed-by: Oren Laadan <orenl at cs.columbia.edu>
| ---
|  kernel/fork.c |    5 +++--
|  kernel/pid.c  |   14 +++++++++-----
|  2 files changed, 12 insertions(+), 7 deletions(-)
| 
| diff --git a/kernel/fork.c b/kernel/fork.c
| index 4c20fff..93626b2 100644
| --- a/kernel/fork.c
| +++ b/kernel/fork.c
| @@ -1156,10 +1156,11 @@ static struct task_struct *copy_process(unsigned long clone_flags,
|  		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);
| diff --git a/kernel/pid.c b/kernel/pid.c
| index 7d4bb6e..c4d9914 100644
| --- a/kernel/pid.c
| +++ b/kernel/pid.c
| @@ -150,7 +150,7 @@ static int alloc_pidmap_page(struct pidmap *map)
|  static int alloc_pidmap(struct pid_namespace *pid_ns)
|  {
|  	int i, offset, max_scan, pid, last = pid_ns->last_pid;
| -	int rc;
| +	int rc = -EAGAIN;
|  	struct pidmap *map;
| 
|  	pid = last + 1;
| @@ -189,12 +189,14 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
|  		} 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)
| @@ -263,8 +265,10 @@ struct pid *alloc_pid(struct pid_namespace *ns)
|  	struct upid *upid;
| 
|  	pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
| -	if (!pid)
| +	if (!pid) {
| +		pid = ERR_PTR(-ENOMEM);
|  		goto out;
| +	}
| 
|  	tmp = ns;
|  	for (i = ns->level; i >= 0; i--) {
| @@ -299,7 +303,7 @@ out_free:
|  		free_pidmap(pid->numbers + i);
| 
|  	kmem_cache_free(ns->pid_cachep, pid);
| -	pid = NULL;
| +	pid = ERR_PTR(nr);
|  	goto out;
|  }
| 
| -- 
| 1.6.0.4
| 
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