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Commit 6100e34b authored by Dan Williams's avatar Dan Williams Committed by Dave Jiang
Browse files

mm, memory_failure: Teach memory_failure() about dev_pagemap pages 



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.

Cc: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarDave Jiang <dave.jiang@intel.com>
parent c2a7d2a1

include/linux/mm.h

+1 −0
Original line number Diff line number Diff line
@@ -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,

};

mm/memory-failure.c

+123 −2
Original line number Diff line number Diff line
@@ -55,6 +55,7 @@ 
#include <linux/hugetlb.h>

#include <linux/memory_hotplug.h>

#include <linux/mm_inline.h>

#include <linux/memremap.h>

#include <linux/kfifo.h>

#include <linux/ratelimit.h>

#include "internal.h"
@@ -263,6 +264,40 @@ void shake_page(struct page *p, int access) 
}

EXPORT_SYMBOL_GPL(shake_page);



static unsigned long dev_pagemap_mapping_shift(struct page *page,

		struct vm_area_struct *vma)

{

	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))

		return 0;

	p4d = p4d_offset(pgd, address);

	if (!p4d_present(*p4d))

		return 0;

	pud = pud_offset(p4d, address);

	if (!pud_present(*pud))

		return 0;

	if (pud_devmap(*pud))

		return PUD_SHIFT;

	pmd = pmd_offset(pud, address);

	if (!pmd_present(*pmd))

		return 0;

	if (pmd_devmap(*pmd))

		return PMD_SHIFT;

	pte = pte_offset_map(pmd, address);

	if (!pte_present(*pte))

		return 0;

	if (pte_devmap(*pte))

		return PAGE_SHIFT;

	return 0;

}



/*

 * 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 otherwise.
@@ -292,6 +327,9 @@ static void add_to_kill(struct task_struct *tsk, struct page *p, 
	}

	tk->addr = page_address_in_vma(p, vma);

	tk->addr_valid = 1;

	if (is_zone_device_page(p))

		tk->size_shift = dev_pagemap_mapping_shift(p, vma);

	else

		tk->size_shift = compound_order(compound_head(p)) + PAGE_SHIFT;



	/*
@@ -300,7 +338,7 @@ static void add_to_kill(struct task_struct *tsk, struct 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 == -EFAULT) {

	if (tk->addr == -EFAULT || tk->size_shift == 0) {

		pr_info("Memory failure: Unable to find user space address %lx in %s\n",

			page_to_pfn(p), tsk->comm);

		tk->addr_valid = 0;
@@ -514,6 +552,7 @@ static const char * const action_page_types[] = { 
	[MF_MSG_TRUNCATED_LRU]		= "already truncated LRU page",

	[MF_MSG_BUDDY]			= "free buddy page",

	[MF_MSG_BUDDY_2ND]		= "free buddy page (2nd try)",

	[MF_MSG_DAX]			= "dax page",

	[MF_MSG_UNKNOWN]		= "unknown page",

};
@@ -1111,6 +1150,83 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags) 
	return res;

}



static int memory_failure_dev_pagemap(unsigned long pfn, int flags,

		struct dev_pagemap *pgmap)

{

	struct page *page = pfn_to_page(pfn);

	const bool unmap_success = true;

	unsigned long size = 0;

	struct to_kill *tk;

	LIST_HEAD(tokill);

	int rc = -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 = 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);



	/*

	 * Unlike System-RAM there is no possibility to swap in a

	 * different physical page at a given virtual address, so all

	 * userspace consumption of ZONE_DEVICE memory necessitates

	 * SIGBUS (i.e. MF_MUST_KILL)

	 */

	flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;

	collect_procs(page, &tokill, flags & MF_ACTION_REQUIRED);



	list_for_each_entry(tk, &tokill, nd)

		if (tk->size_shift)

			size = max(size, 1UL << tk->size_shift);

	if (size) {

		/*

		 * Unmap the largest mapping to avoid breaking up

		 * device-dax mappings which are constant size. The

		 * actual size of the mapping being torn down is

		 * communicated in siginfo, see kill_proc()

		 */

		start = (page->index << PAGE_SHIFT) & ~(size - 1);

		unmap_mapping_range(page->mapping, start, start + size, 0);

	}

	kill_procs(&tokill, flags & MF_MUST_KILL, !unmap_success, pfn, flags);

	rc = 0;

unlock:

	dax_unlock_mapping_entry(page);

out:

	/* drop pgmap ref acquired in caller */

	put_dev_pagemap(pgmap);

	action_result(pfn, MF_MSG_DAX, rc ? MF_FAILED : MF_RECOVERED);

	return rc;

}



/**

 * memory_failure - Handle memory failure of a page.

 * @pfn: Page Number of the corrupted page
@@ -1133,6 +1249,7 @@ int memory_failure(unsigned long pfn, int flags) 
	struct page *p;

	struct page *hpage;

	struct page *orig_head;

	struct dev_pagemap *pgmap;

	int res;

	unsigned long page_flags;
@@ -1145,6 +1262,10 @@ int memory_failure(unsigned long pfn, int flags) 
		return -ENXIO;

	}



	pgmap = get_dev_pagemap(pfn, NULL);

	if (pgmap)

		return memory_failure_dev_pagemap(pfn, flags, pgmap);



	p = pfn_to_page(pfn);

	if (PageHuge(p))

		return memory_failure_hugetlb(pfn, flags);