From a95c90f1e2c253b280385ecf3d4ebfe476926b28 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Fri, 28 Dec 2018 00:34:57 -0800 Subject: mm, devm_memremap_pages: fix shutdown handling MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The last step before devm_memremap_pages() returns success is to allocate a release action, devm_memremap_pages_release(), to tear the entire setup down. However, the result from devm_add_action() is not checked. Checking the error from devm_add_action() is not enough. The api currently relies on the fact that the percpu_ref it is using is killed by the time the devm_memremap_pages_release() is run. Rather than continue this awkward situation, offload the responsibility of killing the percpu_ref to devm_memremap_pages_release() directly. This allows devm_memremap_pages() to do the right thing relative to init failures and shutdown. Without this change we could fail to register the teardown of devm_memremap_pages(). The likelihood of hitting this failure is tiny as small memory allocations almost always succeed. However, the impact of the failure is large given any future reconfiguration, or disable/enable, of an nvdimm namespace will fail forever as subsequent calls to devm_memremap_pages() will fail to setup the pgmap_radix since there will be stale entries for the physical address range. An argument could be made to require that the ->kill() operation be set in the @pgmap arg rather than passed in separately. However, it helps code readability, tracking the lifetime of a given instance, to be able to grep the kill routine directly at the devm_memremap_pages() call site. Link: http://lkml.kernel.org/r/154275558526.76910.7535251937849268605.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Dan Williams Fixes: e8d513483300 ("memremap: change devm_memremap_pages interface...") Reviewed-by: "Jérôme Glisse" Reported-by: Logan Gunthorpe Reviewed-by: Logan Gunthorpe Reviewed-by: Christoph Hellwig Cc: Balbir Singh Cc: Michal Hocko Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/memremap.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 0ac69ddf5fc4..55db66b3716f 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -111,6 +111,7 @@ typedef void (*dev_page_free_t)(struct page *page, void *data); * @altmap: pre-allocated/reserved memory for vmemmap allocations * @res: physical address range covered by @ref * @ref: reference count that pins the devm_memremap_pages() mapping + * @kill: callback to transition @ref to the dead state * @dev: host device of the mapping for debug * @data: private data pointer for page_free() * @type: memory type: see MEMORY_* in memory_hotplug.h @@ -122,6 +123,7 @@ struct dev_pagemap { bool altmap_valid; struct resource res; struct percpu_ref *ref; + void (*kill)(struct percpu_ref *ref); struct device *dev; void *data; enum memory_type type; -- cgit v1.2.3-59-g8ed1b