Changes since v1: [1] * Kill support for mapping System RAM as a nop. No one uses this functionality and it is broken relative to percpu_ref management.
* Fix percpu_ref teardown. Given that devm_memremap_pages() has strict assumptions about when the percpu_ref is killed, give it responsibility to make the live-dead transition explicitly. (Logan)
* Split the patch that adds HMM support to devm_memremap_pages() from the patch that converts HMM to use devm_memremap_pages(). This caught an incomplete conversion in v1. (Logan)
* Collect Christoph's reviewed-by.
[1]: https://lkml.org/lkml/2018/5/21/1109
---
Hi Andrew, here's v2 to replace the 5 currently in mm. The first and last patch did not change.
For maintainability, as ZONE_DEVICE continues to attract new users, it is useful to keep all users consolidated on devm_memremap_pages() as the interface for create "device pages".
The devm_memremap_pages() implementation was recently reworked to make it more generic for arbitrary users, like the proposed peer-to-peer PCI-E enabling. HMM pre-dated this rework and opted to duplicate devm_memremap_pages() as hmm_devmem_pages_create().
Rework HMM to be a consumer of devm_memremap_pages() directly and fix up the licensing on the exports given the deep dependencies on the mm.
Patches based on v4.17-rc6 where there are no upstream consumers of the HMM functionality.
---
Dan Williams (7): mm, devm_memremap_pages: Mark devm_memremap_pages() EXPORT_SYMBOL_GPL mm, devm_memremap_pages: Kill mapping "System RAM" support mm, devm_memremap_pages: Fix shutdown handling mm, devm_memremap_pages: Add MEMORY_DEVICE_PRIVATE support mm, hmm: Use devm semantics for hmm_devmem_{add,remove} mm, hmm: Replace hmm_devmem_pages_create() with devm_memremap_pages() mm, hmm: Mark hmm_devmem_{add,add_resource} EXPORT_SYMBOL_GPL
Documentation/vm/hmm.txt | 1 drivers/dax/pmem.c | 10 - drivers/nvdimm/pmem.c | 18 +- include/linux/hmm.h | 4 include/linux/memremap.h | 7 + kernel/memremap.c | 85 +++++++--- mm/hmm.c | 307 +++++-------------------------------- tools/testing/nvdimm/test/iomap.c | 21 ++- 8 files changed, 130 insertions(+), 323 deletions(-)
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.
Cc: stable@vger.kernel.org Fixes: e8d513483300 ("memremap: change devm_memremap_pages interface...") Cc: Christoph Hellwig hch@lst.de Cc: "Jérôme Glisse" jglisse@redhat.com Reported-by: Logan Gunthorpe logang@deltatee.com Signed-off-by: Dan Williams dan.j.williams@intel.com --- drivers/dax/pmem.c | 10 ++-------- drivers/nvdimm/pmem.c | 18 ++++++++---------- include/linux/memremap.h | 7 +++++-- kernel/memremap.c | 36 +++++++++++++++++++----------------- tools/testing/nvdimm/test/iomap.c | 21 ++++++++++++++++++--- 5 files changed, 52 insertions(+), 40 deletions(-)
diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c index fd49b24fd6af..54cba20c8ba6 100644 --- a/drivers/dax/pmem.c +++ b/drivers/dax/pmem.c @@ -48,9 +48,8 @@ static void dax_pmem_percpu_exit(void *data) percpu_ref_exit(ref); }
-static void dax_pmem_percpu_kill(void *data) +static void dax_pmem_percpu_kill(struct percpu_ref *ref) { - struct percpu_ref *ref = data; struct dax_pmem *dax_pmem = to_dax_pmem(ref);
dev_dbg(dax_pmem->dev, "trace\n"); @@ -111,15 +110,10 @@ static int dax_pmem_probe(struct device *dev) return rc;
dax_pmem->pgmap.ref = &dax_pmem->ref; - addr = devm_memremap_pages(dev, &dax_pmem->pgmap); + addr = devm_memremap_pages(dev, &dax_pmem->pgmap, dax_pmem_percpu_kill); if (IS_ERR(addr)) return PTR_ERR(addr);
- rc = devm_add_action_or_reset(dev, dax_pmem_percpu_kill, - &dax_pmem->ref); - if (rc) - return rc; - /* adjust the dax_region resource to the start of data */ memcpy(&res, &dax_pmem->pgmap.res, sizeof(res)); res.start += le64_to_cpu(pfn_sb->dataoff); diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index 9d714926ecf5..49c9c1bab438 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -279,8 +279,11 @@ static void pmem_release_queue(void *q) blk_cleanup_queue(q); }
-static void pmem_freeze_queue(void *q) +static void pmem_freeze_queue(struct percpu_ref *ref) { + struct request_queue *q; + + q = container_of(ref, typeof(*q), q_usage_counter); blk_freeze_queue_start(q); }
@@ -353,7 +356,8 @@ static int pmem_attach_disk(struct device *dev, pmem->pfn_flags = PFN_DEV; pmem->pgmap.ref = &q->q_usage_counter; if (is_nd_pfn(dev)) { - addr = devm_memremap_pages(dev, &pmem->pgmap); + addr = devm_memremap_pages(dev, &pmem->pgmap, + pmem_freeze_queue); pfn_sb = nd_pfn->pfn_sb; pmem->data_offset = le64_to_cpu(pfn_sb->dataoff); pmem->pfn_pad = resource_size(res) - @@ -364,20 +368,14 @@ static int pmem_attach_disk(struct device *dev, } else if (pmem_should_map_pages(dev)) { memcpy(&pmem->pgmap.res, &nsio->res, sizeof(pmem->pgmap.res)); pmem->pgmap.altmap_valid = false; - addr = devm_memremap_pages(dev, &pmem->pgmap); + addr = devm_memremap_pages(dev, &pmem->pgmap, + pmem_freeze_queue); pmem->pfn_flags |= PFN_MAP; memcpy(&bb_res, &pmem->pgmap.res, sizeof(bb_res)); } else addr = devm_memremap(dev, pmem->phys_addr, pmem->size, ARCH_MEMREMAP_PMEM);
- /* - * At release time the queue must be frozen before - * devm_memremap_pages is unwound - */ - if (devm_add_action_or_reset(dev, pmem_freeze_queue, q)) - return -ENOMEM; - if (IS_ERR(addr)) return PTR_ERR(addr); pmem->virt_addr = addr; diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 7b4899c06f49..b5e894133cf6 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -106,6 +106,7 @@ 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 @@ -117,13 +118,15 @@ 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; };
#ifdef CONFIG_ZONE_DEVICE -void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap); +void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap, + void (*kill)(struct percpu_ref *)); struct dev_pagemap *get_dev_pagemap(unsigned long pfn, struct dev_pagemap *pgmap);
@@ -133,7 +136,7 @@ void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns); static inline bool is_zone_device_page(const struct page *page); #else static inline void *devm_memremap_pages(struct device *dev, - struct dev_pagemap *pgmap) + struct dev_pagemap *pgmap, void (*kill)(struct percpu_ref *)) { /* * Fail attempts to call devm_memremap_pages() without diff --git a/kernel/memremap.c b/kernel/memremap.c index dd11607671eb..dfec0801f652 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -293,14 +293,10 @@ static void devm_memremap_pages_release(void *data) resource_size_t align_start, align_size; unsigned long pfn;
+ pgmap->kill(pgmap->ref); for_each_device_pfn(pfn, pgmap) put_page(pfn_to_page(pfn));
- if (percpu_ref_tryget_live(pgmap->ref)) { - dev_WARN(dev, "%s: page mapping is still live!\n", __func__); - percpu_ref_put(pgmap->ref); - } - /* pages are dead and unused, undo the arch mapping */ align_start = res->start & ~(SECTION_SIZE - 1); align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE) @@ -320,7 +316,8 @@ static void devm_memremap_pages_release(void *data) /** * devm_memremap_pages - remap and provide memmap backing for the given resource * @dev: hosting device for @res - * @pgmap: pointer to a struct dev_pgmap + * @pgmap: pointer to a struct dev_pagemap + * @kill: routine to kill @pgmap->ref * * Notes: * 1/ At a minimum the res, ref and type members of @pgmap must be initialized @@ -329,17 +326,15 @@ static void devm_memremap_pages_release(void *data) * 2/ The altmap field may optionally be initialized, in which case altmap_valid * must be set to true * - * 3/ pgmap.ref must be 'live' on entry and 'dead' before devm_memunmap_pages() - * time (or devm release event). The expected order of events is that ref has - * been through percpu_ref_kill() before devm_memremap_pages_release(). The - * wait for the completion of all references being dropped and - * percpu_ref_exit() must occur after devm_memremap_pages_release(). + * 3/ pgmap->ref must be 'live' on entry and will be killed at + * devm_memremap_pages_release() time, or if this routine fails. * * 4/ res is expected to be a host memory range that could feasibly be * treated as a "System RAM" range, i.e. not a device mmio range, but * this is not enforced. */ -void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) +void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap, + void (*kill)(struct percpu_ref *)) { resource_size_t align_start, align_size, align_end; struct vmem_altmap *altmap = pgmap->altmap_valid ? @@ -349,6 +344,9 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) pgprot_t pgprot = PAGE_KERNEL; int error, nid, is_ram;
+ if (!pgmap->ref || !kill) + return ERR_PTR(-EINVAL); + align_start = res->start & ~(SECTION_SIZE - 1); align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE) - align_start; @@ -358,12 +356,10 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) if (is_ram != REGION_DISJOINT) { WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__, is_ram == REGION_MIXED ? "mixed" : "ram", res); - return ERR_PTR(-ENXIO); + error = -ENXIO; + goto err_init; }
- if (!pgmap->ref) - return ERR_PTR(-EINVAL); - pgmap->dev = dev;
mutex_lock(&pgmap_lock); @@ -415,7 +411,11 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) percpu_ref_get(pgmap->ref); }
- devm_add_action(dev, devm_memremap_pages_release, pgmap); + pgmap->kill = kill; + error = devm_add_action_or_reset(dev, devm_memremap_pages_release, + pgmap); + if (error) + return ERR_PTR(error);
return __va(res->start);
@@ -424,6 +424,8 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) err_pfn_remap: err_radix: pgmap_radix_release(res, pgoff); + err_init: + kill(pgmap->ref); return ERR_PTR(error); } EXPORT_SYMBOL_GPL(devm_memremap_pages); diff --git a/tools/testing/nvdimm/test/iomap.c b/tools/testing/nvdimm/test/iomap.c index ff9d3a5825e1..ad544e6476a9 100644 --- a/tools/testing/nvdimm/test/iomap.c +++ b/tools/testing/nvdimm/test/iomap.c @@ -104,14 +104,29 @@ void *__wrap_devm_memremap(struct device *dev, resource_size_t offset, } EXPORT_SYMBOL(__wrap_devm_memremap);
-void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap) +static void nfit_test_kill(void *_pgmap) +{ + struct dev_pagemap *pgmap = _pgmap; + + pgmap->kill(pgmap->ref); +} + +void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap, + void (*kill)(struct percpu_ref *)) { resource_size_t offset = pgmap->res.start; struct nfit_test_resource *nfit_res = get_nfit_res(offset);
- if (nfit_res) + if (nfit_res) { + int rc; + + pgmap->kill = kill; + rc = devm_add_action_or_reset(dev, nfit_test_kill, pgmap); + if (rc) + return ERR_PTR(rc); return nfit_res->buf + offset - nfit_res->res.start; - return devm_memremap_pages(dev, pgmap); + } + return devm_memremap_pages(dev, pgmap, kill); } EXPORT_SYMBOL(__wrap_devm_memremap_pages);
On 22/05/18 11:10 PM, Dan Williams wrote:
diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 7b4899c06f49..b5e894133cf6 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -106,6 +106,7 @@ 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
@@ -117,13 +118,15 @@ 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;
}; #ifdef CONFIG_ZONE_DEVICE -void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap); +void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap,
void (*kill)(struct percpu_ref *));
It seems redundant to me to have the kill pointer both passed in as an argument and passed in as part of pgmap... Why not just expect the user to set it in the *pgmap that's passed in just like we expect ref to be set ahead of time?
Another thought (that may be too forward looking) is to pass the dev_pagemap struct to the kill function instead of the reference. That way, if some future user wants to do something extra on kill they can use container_of() to get extra context to work with.
Thanks,
Logan
On Wed, May 23, 2018 at 8:47 AM, Logan Gunthorpe logang@deltatee.com wrote:
On 22/05/18 11:10 PM, Dan Williams wrote:
diff --git a/include/linux/memremap.h b/include/linux/memremap.h index 7b4899c06f49..b5e894133cf6 100644 --- a/include/linux/memremap.h +++ b/include/linux/memremap.h @@ -106,6 +106,7 @@ 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
@@ -117,13 +118,15 @@ 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;};
#ifdef CONFIG_ZONE_DEVICE -void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap); +void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap,
void (*kill)(struct percpu_ref *));It seems redundant to me to have the kill pointer both passed in as an argument and passed in as part of pgmap... Why not just expect the user to set it in the *pgmap that's passed in just like we expect ref to be set ahead of time?
I did this for grep-ability. Now you can grep for all devm_memremap_pages and see the associated teardown actions, everything else in pgmap is data. I'm not opposed to just requiring it to be passed in with the pgmap, but I thought removing a step for someone trying to grep through the code flow was worth it. Yes, not the strongest argument, so if folks feel it adds too much clutter we can switch it.
Another thought (that may be too forward looking) is to pass the dev_pagemap struct to the kill function instead of the reference. That way, if some future user wants to do something extra on kill they can use container_of() to get extra context to work with.
We can cross that bridge if it comes to it, but as it stands being able to get the container of the reference count seems to be enough for all users.
linux-stable-mirror@lists.linaro.org
-
Dan Williams -
Logan Gunthorpe