Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933277AbbHZBd7 (ORCPT ); Tue, 25 Aug 2015 21:33:59 -0400 Received: from mga03.intel.com ([134.134.136.65]:39114 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932837AbbHZBd4 (ORCPT ); Tue, 25 Aug 2015 21:33:56 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.17,413,1437462000"; d="scan'208";a="775690543" Subject: [PATCH v2 9/9] devm_memremap_pages: protect against pmem device unbind From: Dan Williams To: linux-nvdimm@ml01.01.org Cc: boaz@plexistor.com, david@fromorbit.com, linux-kernel@vger.kernel.org, hch@lst.de, linux-mm@kvack.org, hpa@zytor.com, ross.zwisler@linux.intel.com, mingo@kernel.org Date: Tue, 25 Aug 2015 21:28:13 -0400 Message-ID: <20150826012813.8851.35482.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <20150826010220.8851.18077.stgit@dwillia2-desk3.amr.corp.intel.com> References: <20150826010220.8851.18077.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: StGit/0.17.1-8-g92dd MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6126 Lines: 219 Given that: 1/ device ->remove() can not be failed 2/ a pmem device may be unbound at any time 3/ we do not know what other parts of the kernel are actively using a 'struct page' from devm_memremap_pages() ...provide a facility for active usages of device memory to block pmem device unbind. With a percpu_ref it should be feasible to take a reference on a per-I/O or other high frequency basis. Cc: Christoph Hellwig Signed-off-by: Dan Williams --- include/linux/io.h | 37 ++++++++++++++++++++++ kernel/memremap.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 123 insertions(+), 3 deletions(-) diff --git a/include/linux/io.h b/include/linux/io.h index de64c1e53612..e20cc04f42b7 100644 --- a/include/linux/io.h +++ b/include/linux/io.h @@ -90,8 +90,31 @@ void devm_memunmap(struct device *dev, void *addr); void *__devm_memremap_pages(struct device *dev, struct resource *res); #ifdef CONFIG_ZONE_DEVICE +#include +#include +#include + +struct page_map { + struct resource res; + struct list_head list; + unsigned long flags; + struct percpu_ref percpu_ref; + struct device *dev; +}; + void *devm_memremap_pages(struct device *dev, struct resource *res); +struct page_map * __must_check get_page_map(resource_size_t addr); +static inline void ref_page_map(struct page_map *page_map) +{ + percpu_ref_get(&page_map->percpu_ref); +} + +static inline void put_page_map(struct page_map *page_map) +{ + percpu_ref_put(&page_map->percpu_ref); +} #else +struct page_map; static inline void *devm_memremap_pages(struct device *dev, struct resource *res) { /* @@ -102,6 +125,20 @@ static inline void *devm_memremap_pages(struct device *dev, struct resource *res WARN_ON_ONCE(1); return ERR_PTR(-ENXIO); } + +static inline __must_check struct page_map *get_page_map(resource_size_t addr) +{ + return NULL; +} + +static inline void ref_page_map(struct page_map *page_map) +{ + return false; +} + +static inline void put_page_map(struct page_map *page_map) +{ +} #endif /* diff --git a/kernel/memremap.c b/kernel/memremap.c index 72b0c66628b6..65a6c9396062 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -12,6 +12,8 @@ */ #include #include +#include +#include #include #include #include @@ -138,14 +140,66 @@ void devm_memunmap(struct device *dev, void *addr) EXPORT_SYMBOL(devm_memunmap); #ifdef CONFIG_ZONE_DEVICE -struct page_map { - struct resource res; +static DEFINE_MUTEX(page_map_lock); +static DECLARE_WAIT_QUEUE_HEAD(page_map_wait); +static LIST_HEAD(page_maps); + +enum { + PAGE_MAP_LIVE, + PAGE_MAP_CONFIRM, }; +static struct page_map *to_page_map(struct percpu_ref *ref) +{ + return container_of(ref, struct page_map, percpu_ref); +} + +static void page_map_release(struct percpu_ref *ref) +{ + struct page_map *page_map = to_page_map(ref); + + /* signal page_map is idle (no more refs) */ + clear_bit(PAGE_MAP_LIVE, &page_map->flags); + wake_up_all(&page_map_wait); +} + +static void page_map_confirm(struct percpu_ref *ref) +{ + struct page_map *page_map = to_page_map(ref); + + /* signal page_map is confirmed dead (slow path ref mode) */ + set_bit(PAGE_MAP_CONFIRM, &page_map->flags); + wake_up_all(&page_map_wait); +} + +static void page_map_destroy(struct page_map *page_map) +{ + long tmo; + + /* flush new lookups */ + mutex_lock(&page_map_lock); + list_del_rcu(&page_map->list); + mutex_unlock(&page_map_lock); + synchronize_rcu(); + + percpu_ref_kill_and_confirm(&page_map->percpu_ref, page_map_confirm); + do { + tmo = wait_event_interruptible_timeout(page_map_wait, + !test_bit(PAGE_MAP_LIVE, &page_map->flags) + && test_bit(PAGE_MAP_CONFIRM, &page_map->flags), 5*HZ); + if (tmo <= 0) + dev_dbg(page_map->dev, + "page map active, continuing to wait...\n"); + } while (tmo <= 0); +} + static void devm_memremap_pages_release(struct device *dev, void *res) { struct page_map *page_map = res; + if (test_bit(PAGE_MAP_LIVE, &page_map->flags)) + page_map_destroy(page_map); + /* pages are dead and unused, undo the arch mapping */ arch_remove_memory(page_map->res.start, resource_size(&page_map->res)); } @@ -155,7 +209,7 @@ void *devm_memremap_pages(struct device *dev, struct resource *res) int is_ram = region_intersects(res->start, resource_size(res), "System RAM"); struct page_map *page_map; - int error, nid; + int error, nid, rc; if (is_ram == REGION_MIXED) { WARN_ONCE(1, "%s attempted on mixed region %pr\n", @@ -172,6 +226,12 @@ void *devm_memremap_pages(struct device *dev, struct resource *res) return ERR_PTR(-ENOMEM); memcpy(&page_map->res, res, sizeof(*res)); + INIT_LIST_HEAD(&page_map->list); + page_map->dev = dev; + rc = percpu_ref_init(&page_map->percpu_ref, page_map_release, 0, + GFP_KERNEL); + if (rc) + return ERR_PTR(rc); nid = dev_to_node(dev); if (nid < 0) @@ -183,8 +243,31 @@ void *devm_memremap_pages(struct device *dev, struct resource *res) return ERR_PTR(error); } + set_bit(PAGE_MAP_LIVE, &page_map->flags); + mutex_lock(&page_map_lock); + list_add_rcu(&page_map->list, &page_maps); + mutex_unlock(&page_map_lock); + devres_add(dev, page_map); return __va(res->start); } EXPORT_SYMBOL(devm_memremap_pages); + +struct page_map * __must_check get_page_map(resource_size_t addr) +{ + struct page_map *page_map, *ret = NULL; + + rcu_read_lock(); + list_for_each_entry_rcu(page_map, &page_maps, list) { + if (addr >= page_map->res.start && addr <= page_map->res.end) { + if (percpu_ref_tryget(&page_map->percpu_ref)) + ret = page_map; + break; + } + } + rcu_read_unlock(); + + return ret; +} +EXPORT_SYMBOL_GPL(get_page_map); #endif /* CONFIG_ZONE_DEVICE */ -- 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/