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mm, dax, pmem: introduce {get|put}_dev_pagemap() for dax-gup

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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.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dan Williams 2016-01-15 16:56:49 -08:00 • committed by Linus Torvalds
parent 468ded03c0
commit 5c2c2587b1
6 changed files with 125 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

9
lib/list_debug.c
View file

@ -12,6 +12,13 @@
#include <linux/kernel.h>
#include <linux/rculist.h>
static struct list_head force_poison;
void list_force_poison(struct list_head *entry)
{
entry->next = &force_poison;
entry->prev = &force_poison;
}
/*
* Insert a new entry between two known consecutive entries.
*
@ -23,6 +30,8 @@ void __list_add(struct list_head *new,
struct list_head *prev,
struct list_head *next)
{
WARN(new->next == &force_poison || new->prev == &force_poison,
"list_add attempted on force-poisoned entry\n");
WARN(next->prev != prev,
"list_add corruption. next->prev should be "
"prev (%p), but was %p. (next=%p).\n",