From: Dan Williams <dan.j.williams@intel.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-nvdimm <linux-nvdimm@lists.01.org>,
"Christoph Hellwig" <hch@lst.de>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Matthew Wilcox" <mawilcox@microsoft.com>,
"Naoya Horiguchi" <n-horiguchi@ah.jp.nec.com>,
"Ross Zwisler" <ross.zwisler@linux.intel.com>,
"Linux MM" <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v4 11/12] mm, memory_failure: Teach memory_failure() about dev_pagemap pages
Date: Mon, 11 Jun 2018 09:45:40 -0700 [thread overview]
Message-ID: <CAPcyv4iwEOKKO92AcV=0R_-cuH9FzRO98=NVNX-sa4Fe2A3K2Q@mail.gmail.com> (raw)
In-Reply-To: <20180611155013.tt4sykwh2dp2vq2e@quack2.suse.cz>
On Mon, Jun 11, 2018 at 8:50 AM, Jan Kara <jack@suse.cz> wrote:
> On Fri 08-06-18 16:51:19, 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 further 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.
>
> ...
>
>> +static unsigned long dax_mapping_size(struct page *page)
>> +{
>> + struct address_space *mapping = page->mapping;
>> + pgoff_t pgoff = page_to_pgoff(page);
>> + struct vm_area_struct *vma;
>> + unsigned long size = 0;
>> +
>> + i_mmap_lock_read(mapping);
>> + vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
>> + unsigned long address = vma_address(page, vma);
>> + pgd_t *pgd;
>> + p4d_t *p4d;
>> + pud_t *pud;
>> + pmd_t *pmd;
>> + pte_t *pte;
>> +
>> + pgd = pgd_offset(vma->vm_mm, address);
>> + if (!pgd_present(*pgd))
>> + continue;
>> + p4d = p4d_offset(pgd, address);
>> + if (!p4d_present(*p4d))
>> + continue;
>> + pud = pud_offset(p4d, address);
>> + if (!pud_present(*pud))
>> + continue;
>> + if (pud_devmap(*pud)) {
>> + size = PUD_SIZE;
>> + break;
>> + }
>> + pmd = pmd_offset(pud, address);
>> + if (!pmd_present(*pmd))
>> + continue;
>> + if (pmd_devmap(*pmd)) {
>> + size = PMD_SIZE;
>> + break;
>> + }
>> + pte = pte_offset_map(pmd, address);
>> + if (!pte_present(*pte))
>> + continue;
>> + if (pte_devmap(*pte)) {
>> + size = PAGE_SIZE;
>> + break;
>> + }
>> + }
>> + i_mmap_unlock_read(mapping);
>> +
>> + return size;
>> +}
>
> Correct me if I'm wrong but cannot the same pfn be mapped by different VMAs
> with different granularity? I recall that if we have a fully allocated PMD
> entry in the radix tree we can hand out 4k entries from inside of it just
> fine...
Oh, I thought we broke up the 2M entry when that happened.
> So whether dax_mapping_size() returns 4k or 2MB would be random?
> Why don't we use the entry size in the radix tree when we have done all the
> work and looked it up there to lock it anyway?
Device-dax has no use case to populate the radix.
I think this means that we need to track the mapping size in the
memory_failure() path per vma that has the pfn mapped. I'd prefer that
over teaching device-dax to populate the radix, or teaching fs-dax to
break up huge pages when another vma wants 4K.
next prev parent reply other threads:[~2018-06-11 16:45 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-08 23:50 [PATCH v4 00/12] mm: Teach memory_failure() about ZONE_DEVICE pages Dan Williams
2018-06-08 23:50 ` [PATCH v4 01/12] device-dax: Convert to vmf_insert_mixed and vm_fault_t Dan Williams
2018-06-08 23:50 ` [PATCH v4 02/12] device-dax: Cleanup vm_fault de-reference chains Dan Williams
2018-06-11 17:12 ` Laurent Dufour
2018-06-11 17:14 ` Dan Williams
2018-06-08 23:50 ` [PATCH v4 03/12] device-dax: Enable page_mapping() Dan Williams
2018-06-08 23:50 ` [PATCH v4 04/12] device-dax: Set page->index Dan Williams
2018-06-08 23:50 ` [PATCH v4 05/12] filesystem-dax: " Dan Williams
2018-06-08 23:50 ` [PATCH v4 06/12] mm, madvise_inject_error: Let memory_failure() optionally take a page reference Dan Williams
2018-06-08 23:50 ` [PATCH v4 07/12] x86/mm/pat: Prepare {reserve, free}_memtype() for "decoy" addresses Dan Williams
2018-06-08 23:51 ` [PATCH v4 08/12] x86/memory_failure: Introduce {set, clear}_mce_nospec() Dan Williams
2018-06-08 23:51 ` [PATCH v4 09/12] mm, memory_failure: Pass page size to kill_proc() Dan Williams
2018-06-08 23:51 ` [PATCH v4 10/12] filesystem-dax: Introduce dax_lock_page() Dan Williams
2018-06-11 15:41 ` Jan Kara
2018-06-11 16:48 ` Dan Williams
2018-06-12 18:07 ` Ross Zwisler
2018-07-04 15:20 ` Dan Williams
2018-07-04 15:17 ` Dan Williams
2018-06-12 18:15 ` Ross Zwisler
2018-07-04 15:11 ` Dan Williams
2018-06-08 23:51 ` [PATCH v4 11/12] mm, memory_failure: Teach memory_failure() about dev_pagemap pages Dan Williams
2018-06-11 15:50 ` Jan Kara
2018-06-11 16:45 ` Dan Williams [this message]
2018-06-12 20:14 ` Ross Zwisler
2018-06-12 23:38 ` Dan Williams
2018-06-08 23:51 ` [PATCH v4 12/12] libnvdimm, pmem: Restore page attributes when clearing errors Dan Williams
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