From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx165.postini.com [74.125.245.165]) by kanga.kvack.org (Postfix) with SMTP id 6718A6B0005 for ; Wed, 10 Apr 2013 17:44:14 -0400 (EDT) Date: Wed, 10 Apr 2013 14:44:12 -0700 From: Andrew Morton Subject: Re: [PATCH v3 2/3] resource: Add release_mem_region_adjustable() Message-Id: <20130410144412.395bf9f2fb8192920175e30a@linux-foundation.org> In-Reply-To: <1365614221-685-3-git-send-email-toshi.kani@hp.com> References: <1365614221-685-1-git-send-email-toshi.kani@hp.com> <1365614221-685-3-git-send-email-toshi.kani@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Toshi Kani Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, rientjes@google.com, linuxram@us.ibm.com, guz.fnst@cn.fujitsu.com, tmac@hp.com, isimatu.yasuaki@jp.fujitsu.com, wency@cn.fujitsu.com, tangchen@cn.fujitsu.com, jiang.liu@huawei.com On Wed, 10 Apr 2013 11:17:00 -0600 Toshi Kani wrote: > Added release_mem_region_adjustable(), which releases a requested > region from a currently busy memory resource. This interface > adjusts the matched memory resource accordingly even if the > requested region does not match exactly but still fits into. > > This new interface is intended for memory hot-delete. During > bootup, memory resources are inserted from the boot descriptor > table, such as EFI Memory Table and e820. Each memory resource > entry usually covers the whole contigous memory range. Memory > hot-delete request, on the other hand, may target to a particular > range of memory resource, and its size can be much smaller than > the whole contiguous memory. Since the existing release interfaces > like __release_region() require a requested region to be exactly > matched to a resource entry, they do not allow a partial resource > to be released. > > This new interface is restrictive (i.e. release under certain > conditions), which is consistent with other release interfaces, > __release_region() and __release_resource(). Additional release > conditions, such as an overlapping region to a resource entry, > can be supported after they are confirmed as valid cases. > > There is no change to the existing interfaces since their restriction > is valid for I/O resources. > > ... > > +int release_mem_region_adjustable(struct resource *parent, > + resource_size_t start, resource_size_t size) > +{ > + struct resource **p; > + struct resource *res, *new; > + resource_size_t end; > + int ret = -EINVAL; > + > + end = start + size - 1; > + if ((start < parent->start) || (end > parent->end)) > + return ret; > + > + p = &parent->child; > + write_lock(&resource_lock); > + > + while ((res = *p)) { > + if (res->start >= end) > + break; > + > + /* look for the next resource if it does not fit into */ > + if (res->start > start || res->end < end) { > + p = &res->sibling; > + continue; > + } > + > + if (!(res->flags & IORESOURCE_MEM)) > + break; > + > + if (!(res->flags & IORESOURCE_BUSY)) { > + p = &res->child; > + continue; > + } > + > + /* found the target resource; let's adjust accordingly */ > + if (res->start == start && res->end == end) { > + /* free the whole entry */ > + *p = res->sibling; > + kfree(res); > + ret = 0; > + } else if (res->start == start && res->end != end) { > + /* adjust the start */ > + ret = __adjust_resource(res, end + 1, > + res->end - end); > + } else if (res->start != start && res->end == end) { > + /* adjust the end */ > + ret = __adjust_resource(res, res->start, > + start - res->start); > + } else { > + /* split into two entries */ > + new = kzalloc(sizeof(struct resource), GFP_KERNEL); Nope, we can't perform a GFP_KERNEL allocation under write_lock(). Was this code path runtime tested? If no, please try to find a way to test it. If yes, please see Documentation/SubmitChecklist section 12 and use that in the future. I'll switch it to GFP_ATOMIC. Which is horridly lame but the allocation is small and alternatives are unobvious. > + if (!new) { > + ret = -ENOMEM; > + break; > + } > + new->name = res->name; > + new->start = end + 1; > + new->end = res->end; > + new->flags = res->flags; > + new->parent = res->parent; > + new->sibling = res->sibling; > + new->child = NULL; > + > + ret = __adjust_resource(res, res->start, > + start - res->start); > + if (ret) { > + kfree(new); > + break; > + } > + res->sibling = new; > + } > + > + break; > + } > + > + write_unlock(&resource_lock); > + return ret; > +} > +#endif /* CONFIG_MEMORY_HOTPLUG */ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org