From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f47.google.com (mail-lf0-f47.google.com [209.85.215.47]) by kanga.kvack.org (Postfix) with ESMTP id 8220A82FD8 for ; Sun, 27 Dec 2015 03:46:57 -0500 (EST) Received: by mail-lf0-f47.google.com with SMTP id p203so188418933lfa.0 for ; Sun, 27 Dec 2015 00:46:57 -0800 (PST) Received: from mail-lb0-x233.google.com (mail-lb0-x233.google.com. [2a00:1450:4010:c04::233]) by mx.google.com with ESMTPS id k64si11023657lfg.244.2015.12.27.00.46.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 27 Dec 2015 00:46:56 -0800 (PST) Received: by mail-lb0-x233.google.com with SMTP id sv6so74022553lbb.0 for ; Sun, 27 Dec 2015 00:46:55 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20151221054521.34542.62283.stgit@dwillia2-desk3.jf.intel.com> References: <20151221054406.34542.64393.stgit@dwillia2-desk3.jf.intel.com> <20151221054521.34542.62283.stgit@dwillia2-desk3.jf.intel.com> Date: Sun, 27 Dec 2015 16:46:55 +0800 Message-ID: Subject: Re: [-mm PATCH v4 14/18] mm, dax, pmem: introduce {get|put}_dev_pagemap() for dax-gup From: Bob Liu Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: Andrew Morton , Dave Hansen , linux-nvdimm@lists.01.org, Linux-MM , Alexander Viro , Matthew Wilcox , Ross Zwisler , Logan Gunthorpe On Mon, Dec 21, 2015 at 1:45 PM, Dan Williams wrote: > get_dev_page() enables paths like get_user_pages() to pin a dynamically > mapped pfn-range (devm_memremap_pages()) while the resulting struct page > objects are in use. Unlike get_page() it may fail if the device is, or > is in the process of being, disabled. While the initial lookup of the > range may be an expensive list walk, the result is cached to speed up > subsequent lookups which are likely to be in the same mapped range. > > devm_memremap_pages() now requires a reference counter to be specified > at init time. For pmem this means moving request_queue allocation into > pmem_alloc() so the existing queue usage counter can track "device > pages". > > ZONE_DEVICE pages always have an elevated count and will never be on an > lru reclaim list. That space in 'struct page' can be redirected for > other uses, but for safety introduce a poison value that will always > trip __list_add() to assert. This allows half of the struct list_head > storage to be reclaimed with some assurance to back up the assumption > that the page count never goes to zero and a list_add() is never > attempted. > > Cc: Dave Hansen > Cc: Andrew Morton > Cc: Matthew Wilcox > Cc: Ross Zwisler > Cc: Alexander Viro > Tested-by: Logan Gunthorpe > Signed-off-by: Dan Williams > --- > drivers/nvdimm/pmem.c | 6 +++-- > include/linux/list.h | 12 ++++++++++ > include/linux/memremap.h | 49 +++++++++++++++++++++++++++++++++++++++++-- > include/linux/mm_types.h | 5 ++++ > kernel/memremap.c | 53 +++++++++++++++++++++++++++++++++++++++++++--- > lib/list_debug.c | 9 ++++++++ > 6 files changed, 126 insertions(+), 8 deletions(-) > > diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c > index 2c6096ab2ce6..37ebf42c0415 100644 > --- a/drivers/nvdimm/pmem.c > +++ b/drivers/nvdimm/pmem.c > @@ -150,7 +150,7 @@ static struct pmem_device *pmem_alloc(struct device *dev, > pmem->pfn_flags = PFN_DEV; > if (pmem_should_map_pages(dev)) { > pmem->virt_addr = (void __pmem *) devm_memremap_pages(dev, res, > - NULL); > + &q->q_usage_counter, NULL); > pmem->pfn_flags |= PFN_MAP; > } else > pmem->virt_addr = (void __pmem *) devm_memremap(dev, > @@ -324,6 +324,7 @@ static int nvdimm_namespace_attach_pfn(struct nd_namespace_common *ndns) > struct vmem_altmap *altmap; > struct nd_pfn_sb *pfn_sb; > struct pmem_device *pmem; > + struct request_queue *q; > phys_addr_t offset; > int rc; > struct vmem_altmap __altmap = { > @@ -375,9 +376,10 @@ static int nvdimm_namespace_attach_pfn(struct nd_namespace_common *ndns) > > /* establish pfn range for lookup, and switch to direct map */ > pmem = dev_get_drvdata(dev); > + q = pmem->pmem_queue; > devm_memunmap(dev, (void __force *) pmem->virt_addr); > pmem->virt_addr = (void __pmem *) devm_memremap_pages(dev, &nsio->res, > - altmap); > + &q->q_usage_counter, altmap); > pmem->pfn_flags |= PFN_MAP; > if (IS_ERR(pmem->virt_addr)) { > rc = PTR_ERR(pmem->virt_addr); > diff --git a/include/linux/list.h b/include/linux/list.h > index 993395a2e55c..d870ba3315f8 100644 > --- a/include/linux/list.h > +++ b/include/linux/list.h > @@ -113,6 +113,18 @@ extern void __list_del_entry(struct list_head *entry); > extern void list_del(struct list_head *entry); > #endif > > +#ifdef CONFIG_DEBUG_LIST > +/* > + * See devm_memremap_pages() which wants DEBUG_LIST=y to assert if one > + * of the pages it allocates is ever passed to list_add() > + */ > +extern void list_force_poison(struct list_head *entry); > +#else > +static inline void list_force_poison(struct list_head *entry) > +{ > +} > +#endif > + > /** > * list_replace - replace old entry by new one > * @old : the element to be replaced > diff --git a/include/linux/memremap.h b/include/linux/memremap.h > index aa3e82a80d7b..bcaa634139a9 100644 > --- a/include/linux/memremap.h > +++ b/include/linux/memremap.h > @@ -1,6 +1,8 @@ > #ifndef _LINUX_MEMREMAP_H_ > #define _LINUX_MEMREMAP_H_ > #include > +#include > +#include > > struct resource; > struct device; > @@ -36,21 +38,25 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start) > /** > * struct dev_pagemap - metadata for ZONE_DEVICE mappings > * @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 > * @dev: host device of the mapping for debug > */ > struct dev_pagemap { > struct vmem_altmap *altmap; > const struct resource *res; > + struct percpu_ref *ref; > struct device *dev; > }; > > #ifdef CONFIG_ZONE_DEVICE > void *devm_memremap_pages(struct device *dev, struct resource *res, > - struct vmem_altmap *altmap); > + struct percpu_ref *ref, struct vmem_altmap *altmap); > struct dev_pagemap *find_dev_pagemap(resource_size_t phys); > #else > static inline void *devm_memremap_pages(struct device *dev, > - struct resource *res, struct vmem_altmap *altmap) > + struct resource *res, struct percpu_ref *ref, > + struct vmem_altmap *altmap) > { > /* > * Fail attempts to call devm_memremap_pages() without > @@ -66,4 +72,43 @@ static inline struct dev_pagemap *find_dev_pagemap(resource_size_t phys) > return NULL; > } > #endif > + > +/** > + * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn > + * @pfn: page frame number to lookup page_map > + * @pgmap: optional known pgmap that already has a reference > + * > + * @pgmap allows the overhead of a lookup to be bypassed when @pfn lands in the > + * same mapping. > + */ > +static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn, > + struct dev_pagemap *pgmap) > +{ > + const struct resource *res = pgmap ? pgmap->res : NULL; > + resource_size_t phys = PFN_PHYS(pfn); > + > + /* > + * In the cached case we're already holding a live reference so > + * we can simply do a blind increment > + */ > + if (res && phys >= res->start && phys <= res->end) { > + percpu_ref_get(pgmap->ref); > + return pgmap; > + } > + > + /* fall back to slow path lookup */ > + rcu_read_lock(); > + pgmap = find_dev_pagemap(phys); Is it possible just use pfn_to_page() and then return page->pgmap? Then we can get rid of the pgmap_radix tree totally. Regards, Bob > + if (pgmap && !percpu_ref_tryget_live(pgmap->ref)) > + pgmap = NULL; > + rcu_read_unlock(); > + > + return pgmap; > +} > + > +static inline void put_dev_pagemap(struct dev_pagemap *pgmap) > +{ > + if (pgmap) > + percpu_ref_put(pgmap->ref); > +} > #endif /* _LINUX_MEMREMAP_H_ */ > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 22beb225e88f..c67ea476991e 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -116,6 +116,11 @@ struct page { > * Can be used as a generic list > * by the page owner. > */ > + struct dev_pagemap *pgmap; /* ZONE_DEVICE pages are never on an > + * lru or handled by a slab > + * allocator, this points to the > + * hosting device page map. > + */ > struct { /* slub per cpu partial pages */ > struct page *next; /* Next partial slab */ > #ifdef CONFIG_64BIT -- 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