From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: MIME-Version: 1.0 In-Reply-To: <20180713085241.GA26980@hori1.linux.bs1.fc.nec.co.jp> References: <153074042316.27838.17319837331947007626.stgit@dwillia2-desk3.amr.corp.intel.com> <153074046610.27838.329669845580014251.stgit@dwillia2-desk3.amr.corp.intel.com> <20180713085241.GA26980@hori1.linux.bs1.fc.nec.co.jp> From: Dan Williams Date: Fri, 13 Jul 2018 17:28:05 -0700 Message-ID: Subject: Re: [PATCH v5 08/11] mm, memory_failure: Teach memory_failure() about dev_pagemap pages To: Naoya Horiguchi Cc: "linux-nvdimm@lists.01.org" , Jan Kara , Christoph Hellwig , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Matthew Wilcox , Ross Zwisler , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: On Fri, Jul 13, 2018 at 1:52 AM, Naoya Horiguchi wrote: > On Wed, Jul 04, 2018 at 02:41:06PM -0700, Dan Williams wrote: >> mce: Uncorrected hardware memory error in user-access at af34214200 >> {1}[Hardware Error]: It has been corrected by h/w and requires no fu= rther action >> mce: [Hardware Error]: Machine check events logged >> {1}[Hardware Error]: event severity: corrected >> Memory failure: 0xaf34214: reserved kernel page still referenced by = 1 users >> [..] >> Memory failure: 0xaf34214: recovery action for reserved kernel page:= Failed >> mce: Memory error not recovered >> >> In contrast to typical memory, dev_pagemap pages may be dax mapped. With >> dax there is no possibility to map in another page dynamically since dax >> establishes 1:1 physical address to file offset associations. Also >> dev_pagemap pages associated with NVDIMM / persistent memory devices can >> internal remap/repair addresses with poison. While memory_failure() >> assumes that it can discard typical poisoned pages and keep them >> unmapped indefinitely, dev_pagemap pages may be returned to service >> after the error is cleared. >> >> Teach memory_failure() to detect and handle MEMORY_DEVICE_HOST >> dev_pagemap pages that have poison consumed by userspace. Mark the >> memory as UC instead of unmapping it completely to allow ongoing access >> via the device driver (nd_pmem). Later, nd_pmem will grow support for >> marking the page back to WB when the error is cleared. > > By the way, what happens if madvise(MADV_SOFT_OFFLINE) is called on > a dev_pagemap page? I'm not sure that cmci can be triggered on the > nvdimm device, but this injection interface is open for such a case. > Maybe simply ignoring the event is an expected behavior? Yeah, I should explicitly block attempts to MADV_SOFT_OFFLINE a dev_pagemap page because they are never onlined. They'll never appear on an lru and never be available via the page allocator. > > A few comments/quetions below ... > >> >> Cc: Jan Kara >> Cc: Christoph Hellwig >> Cc: J=C3=A9r=C3=B4me Glisse >> Cc: Matthew Wilcox >> Cc: Naoya Horiguchi >> Cc: Ross Zwisler >> Signed-off-by: Dan Williams >> --- >> include/linux/mm.h | 1 >> mm/memory-failure.c | 124 ++++++++++++++++++++++++++++++++++++++++++++= ++++++- >> 2 files changed, 123 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index a0fbb9ffe380..374e5e9284f7 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -2725,6 +2725,7 @@ enum mf_action_page_type { >> MF_MSG_TRUNCATED_LRU, >> MF_MSG_BUDDY, >> MF_MSG_BUDDY_2ND, >> + MF_MSG_DAX, >> MF_MSG_UNKNOWN, >> }; >> >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >> index 4d70753af59c..161aa1b70212 100644 >> --- a/mm/memory-failure.c >> +++ b/mm/memory-failure.c >> @@ -55,6 +55,7 @@ >> #include >> #include >> #include >> +#include >> #include >> #include >> #include "internal.h" >> @@ -263,6 +264,39 @@ void shake_page(struct page *p, int access) >> } >> EXPORT_SYMBOL_GPL(shake_page); >> >> +static unsigned long mapping_size(struct page *page, struct vm_area_str= uct *vma) >> +{ >> + unsigned long address =3D vma_address(page, vma); >> + pgd_t *pgd; >> + p4d_t *p4d; >> + pud_t *pud; >> + pmd_t *pmd; >> + pte_t *pte; >> + >> + pgd =3D pgd_offset(vma->vm_mm, address); >> + if (!pgd_present(*pgd)) >> + return 0; >> + p4d =3D p4d_offset(pgd, address); >> + if (!p4d_present(*p4d)) >> + return 0; >> + pud =3D pud_offset(p4d, address); >> + if (!pud_present(*pud)) >> + return 0; >> + if (pud_devmap(*pud)) >> + return PUD_SIZE; >> + pmd =3D pmd_offset(pud, address); >> + if (!pmd_present(*pmd)) >> + return 0; >> + if (pmd_devmap(*pmd)) >> + return PMD_SIZE; >> + pte =3D pte_offset_map(pmd, address); >> + if (!pte_present(*pte)) >> + return 0; >> + if (pte_devmap(*pte)) >> + return PAGE_SIZE; >> + return 0; >> +} >> + > > The function name looks generic, but this function seems to focus on > devmap thing, so could you include the word 'devmap' in the name? Ok. > >> /* >> * Failure handling: if we can't find or can't kill a process there's >> * not much we can do. We just print a message and ignore otherwi= se. >> @@ -292,7 +326,10 @@ static void add_to_kill(struct task_struct *tsk, st= ruct page *p, >> } >> tk->addr =3D page_address_in_vma(p, vma); >> tk->addr_valid =3D 1; >> - tk->size_shift =3D compound_order(compound_head(p)) + PAGE_SHIFT; >> + if (is_zone_device_page(p)) >> + tk->size_shift =3D ilog2(mapping_size(p, vma)); >> + else >> + tk->size_shift =3D compound_order(compound_head(p)) + PAGE= _SHIFT; >> >> /* >> * In theory we don't have to kill when the page was >> @@ -300,7 +337,7 @@ static void add_to_kill(struct task_struct *tsk, str= uct page *p, >> * likely very rare kill anyways just out of paranoia, but use >> * a SIGKILL because the error is not contained anymore. >> */ >> - if (tk->addr =3D=3D -EFAULT) { >> + if (tk->addr =3D=3D -EFAULT || tk->size_shift =3D=3D 0) { >> pr_info("Memory failure: Unable to find user space address= %lx in %s\n", >> page_to_pfn(p), tsk->comm); >> tk->addr_valid =3D 0; >> @@ -514,6 +551,7 @@ static const char * const action_page_types[] =3D { >> [MF_MSG_TRUNCATED_LRU] =3D "already truncated LRU page", >> [MF_MSG_BUDDY] =3D "free buddy page", >> [MF_MSG_BUDDY_2ND] =3D "free buddy page (2nd try)", >> + [MF_MSG_DAX] =3D "dax page", >> [MF_MSG_UNKNOWN] =3D "unknown page", >> }; >> >> @@ -1111,6 +1149,83 @@ static int memory_failure_hugetlb(unsigned long p= fn, int flags) >> return res; >> } >> >> +static int memory_failure_dev_pagemap(unsigned long pfn, int flags, >> + struct dev_pagemap *pgmap) >> +{ >> + struct page *page =3D pfn_to_page(pfn); >> + const bool unmap_success =3D true; >> + unsigned long size =3D 0; >> + struct to_kill *tk; >> + LIST_HEAD(tokill); >> + int rc =3D -EBUSY; >> + loff_t start; >> + >> + /* >> + * Prevent the inode from being freed while we are interrogating >> + * the address_space, typically this would be handled by >> + * lock_page(), but dax pages do not use the page lock. This >> + * also prevents changes to the mapping of this pfn until >> + * poison signaling is complete. >> + */ >> + if (!dax_lock_mapping_entry(page)) >> + goto out; >> + >> + if (hwpoison_filter(page)) { >> + rc =3D 0; >> + goto unlock; >> + } >> + >> + switch (pgmap->type) { >> + case MEMORY_DEVICE_PRIVATE: >> + case MEMORY_DEVICE_PUBLIC: >> + /* >> + * TODO: Handle HMM pages which may need coordination >> + * with device-side memory. >> + */ >> + goto unlock; >> + default: >> + break; >> + } >> + >> + /* >> + * Use this flag as an indication that the dax page has been >> + * remapped UC to prevent speculative consumption of poison. >> + */ >> + SetPageHWPoison(page); > > The number of hwpoison pages is maintained by num_poisoned_pages, > so you can call num_poisoned_pages_inc()? I don't think we want these pages accounted in num_poisoned_pages(). We have the badblocks infrastructure in libnvdimm to track how many errors and where they are located, and since they can be repaired via driver actions I think we should track them separately. > Related to this, I'm interested in whether/how unpoison_page() works > on a hwpoisoned dev_pagemap page. unpoison_page() is only triggered via freeing pages to the page allocator, and that never happens for dev_pagemap / ZONE_DEVICE pages.