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- hugetlb_vmemmap cleanups from Muchun Song

Browse Source 
- hardware poisoning support for 1GB hugepages, from Naoya Horiguchi
 
 - highmem documentation fixups from Fabio De Francesco
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Merge tag 'mm-stable-2022-08-09' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull remaining MM updates from Andrew Morton:
 "Three patch series - two that perform cleanups and one feature:

   - hugetlb_vmemmap cleanups from Muchun Song

   - hardware poisoning support for 1GB hugepages, from Naoya Horiguchi

   - highmem documentation fixups from Fabio De Francesco"

* tag 'mm-stable-2022-08-09' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (23 commits)
  Documentation/mm: add details about kmap_local_page() and preemption
  highmem: delete a sentence from kmap_local_page() kdocs
  Documentation/mm: rrefer kmap_local_page() and avoid kmap()
  Documentation/mm: avoid invalid use of addresses from kmap_local_page()
  Documentation/mm: don't kmap*() pages which can't come from HIGHMEM
  highmem: specify that kmap_local_page() is callable from interrupts
  highmem: remove unneeded spaces in kmap_local_page() kdocs
  mm, hwpoison: enable memory error handling on 1GB hugepage
  mm, hwpoison: skip raw hwpoison page in freeing 1GB hugepage
  mm, hwpoison: make __page_handle_poison returns int
  mm, hwpoison: set PG_hwpoison for busy hugetlb pages
  mm, hwpoison: make unpoison aware of raw error info in hwpoisoned hugepage
  mm, hwpoison, hugetlb: support saving mechanism of raw error pages
  mm/hugetlb: make pud_huge() and follow_huge_pud() aware of non-present pud entry
  mm/hugetlb: check gigantic_page_runtime_supported() in return_unused_surplus_pages()
  mm: hugetlb_vmemmap: use PTRS_PER_PTE instead of PMD_SIZE / PAGE_SIZE
  mm: hugetlb_vmemmap: move code comments to vmemmap_dedup.rst
  mm: hugetlb_vmemmap: improve hugetlb_vmemmap code readability
  mm: hugetlb_vmemmap: replace early_param() with core_param()
  mm: hugetlb_vmemmap: move vmemmap code related to HugeTLB to hugetlb_vmemmap.c
  ...
This commit is contained in:
Linus Torvalds 2022-08-10 11:18:00 -07:00
commit b1701d5e29
21 changed files with 827 additions and 706 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
Documentation/admin-guide/kernel-parameters.txt
View File

@ -1735,12 +1735,13 @@
hugetlb_free_vmemmap=
[KNL] Reguires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
enabled.
Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
Allows heavy hugetlb users to free up some more
memory (7 * PAGE_SIZE for each 2MB hugetlb page).
Format: { [oO][Nn]/Y/y/1 | [oO][Ff]/N/n/0 (default) }
Format: { on | off (default) }
[oO][Nn]/Y/y/1: enable the feature
[oO][Ff]/N/n/0: disable the feature
on: enable HVO
off: disable HVO
Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
the default is on.

4
Documentation/admin-guide/mm/hugetlbpage.rst
View File

@ -164,8 +164,8 @@ default_hugepagesz
will all result in 256 2M huge pages being allocated. Valid default
huge page size is architecture dependent.
hugetlb_free_vmemmap
When CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is set, this enables optimizing
unused vmemmap pages associated with each HugeTLB page.
When CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is set, this enables HugeTLB
Vmemmap Optimization (HVO).
When multiple huge page sizes are supported, ``/proc/sys/vm/nr_hugepages``
indicates the current number of pre-allocated huge pages of the default size.

4
Documentation/admin-guide/mm/memory-hotplug.rst
View File

@ -653,8 +653,8 @@ block might fail:
- Concurrent activity that operates on the same physical memory area, such as
allocating gigantic pages, can result in temporary offlining failures.
- Out of memory when dissolving huge pages, especially when freeing unused
vmemmap pages associated with each hugetlb page is enabled.
- Out of memory when dissolving huge pages, especially when HugeTLB Vmemmap
Optimization (HVO) is enabled.
Offlining code may be able to migrate huge page contents, but may not be able
to dissolve the source huge page because it fails allocating (unmovable) pages

3
Documentation/admin-guide/sysctl/vm.rst
View File

@ -569,8 +569,7 @@ This knob is not available when the size of 'struct page' (a structure defined
in include/linux/mm_types.h) is not power of two (an unusual system config could
result in this).
Enable (set to 1) or disable (set to 0) the feature of optimizing vmemmap pages
associated with each HugeTLB page.
Enable (set to 1) or disable (set to 0) HugeTLB Vmemmap Optimization (HVO).
Once enabled, the vmemmap pages of subsequent allocation of HugeTLB pages from
buddy allocator will be optimized (7 pages per 2MB HugeTLB page and 4095 pages

31
Documentation/mm/highmem.rst
View File

@ -60,17 +60,40 @@ list shows them in order of preference of use.
This function should be preferred, where feasible, over all the others.
These mappings are thread-local and CPU-local, meaning that the mapping
can only be accessed from within this thread and the thread is bound the
CPU while the mapping is active. Even if the thread is preempted (since
preemption is never disabled by the function) the CPU can not be
unplugged from the system via CPU-hotplug until the mapping is disposed.
can only be accessed from within this thread and the thread is bound to the
CPU while the mapping is active. Although preemption is never disabled by
this function, the CPU can not be unplugged from the system via
CPU-hotplug until the mapping is disposed.
It's valid to take pagefaults in a local kmap region, unless the context
in which the local mapping is acquired does not allow it for other reasons.
As said, pagefaults and preemption are never disabled. There is no need to
disable preemption because, when context switches to a different task, the
maps of the outgoing task are saved and those of the incoming one are
restored.
kmap_local_page() always returns a valid virtual address and it is assumed
that kunmap_local() will never fail.
On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
virtual address of the direct mapping. Only real highmem pages are
temporarily mapped. Therefore, users may call a plain page_address()
for pages which are known to not come from ZONE_HIGHMEM. However, it is
always safe to use kmap_local_page() / kunmap_local().
While it is significantly faster than kmap(), for the higmem case it
comes with restrictions about the pointers validity. Contrary to kmap()
mappings, the local mappings are only valid in the context of the caller
and cannot be handed to other contexts. This implies that users must
be absolutely sure to keep the use of the return address local to the
thread which mapped it.
Most code can be designed to use thread local mappings. User should
therefore try to design their code to avoid the use of kmap() by mapping
pages in the same thread the address will be used and prefer
kmap_local_page().
Nesting kmap_local_page() and kmap_atomic() mappings is allowed to a certain
extent (up to KMAP_TYPE_NR) but their invocations have to be strictly ordered
because the map implementation is stack based. See kmap_local_page() kdocs

72
Documentation/mm/vmemmap_dedup.rst
View File

@ -7,23 +7,25 @@ A vmemmap diet for HugeTLB and Device DAX
HugeTLB
=======
The struct page structures (page structs) are used to describe a physical
page frame. By default, there is a one-to-one mapping from a page frame to
it's corresponding page struct.
This section is to explain how HugeTLB Vmemmap Optimization (HVO) works.
The ``struct page`` structures are used to describe a physical page frame. By
default, there is a one-to-one mapping from a page frame to it's corresponding
``struct page``.
HugeTLB pages consist of multiple base page size pages and is supported by many
architectures. See Documentation/admin-guide/mm/hugetlbpage.rst for more
details. On the x86-64 architecture, HugeTLB pages of size 2MB and 1GB are
currently supported. Since the base page size on x86 is 4KB, a 2MB HugeTLB page
consists of 512 base pages and a 1GB HugeTLB page consists of 4096 base pages.
For each base page, there is a corresponding page struct.
For each base page, there is a corresponding ``struct page``.
Within the HugeTLB subsystem, only the first 4 page structs are used to
contain unique information about a HugeTLB page. __NR_USED_SUBPAGE provides
this upper limit. The only 'useful' information in the remaining page structs
Within the HugeTLB subsystem, only the first 4 ``struct page`` are used to
contain unique information about a HugeTLB page. ``__NR_USED_SUBPAGE`` provides
this upper limit. The only 'useful' information in the remaining ``struct page``
is the compound_head field, and this field is the same for all tail pages.
By removing redundant page structs for HugeTLB pages, memory can be returned
By removing redundant ``struct page`` for HugeTLB pages, memory can be returned
to the buddy allocator for other uses.
Different architectures support different HugeTLB pages. For example, the
@ -44,7 +46,7 @@ page.
| | 64KB | 2MB | 512MB | 16GB | |
+--------------+-----------+-----------+-----------+-----------+-----------+
When the system boot up, every HugeTLB page has more than one struct page
When the system boot up, every HugeTLB page has more than one ``struct page``
structs which size is (unit: pages)::
struct_size = HugeTLB_Size / PAGE_SIZE * sizeof(struct page) / PAGE_SIZE
@ -74,10 +76,10 @@ Where n is how many pte entries which one page can contains. So the value of
n is (PAGE_SIZE / sizeof(pte_t)).
This optimization only supports 64-bit system, so the value of sizeof(pte_t)
is 8. And this optimization also applicable only when the size of struct page
is a power of two. In most cases, the size of struct page is 64 bytes (e.g.
is 8. And this optimization also applicable only when the size of ``struct page``
is a power of two. In most cases, the size of ``struct page`` is 64 bytes (e.g.
x86-64 and arm64). So if we use pmd level mapping for a HugeTLB page, the
size of struct page structs of it is 8 page frames which size depends on the
size of ``struct page`` structs of it is 8 page frames which size depends on the
size of the base page.
For the HugeTLB page of the pud level mapping, then::
@ -86,7 +88,7 @@ For the HugeTLB page of the pud level mapping, then::
= PAGE_SIZE / 8 * 8 (pages)
= PAGE_SIZE (pages)
Where the struct_size(pmd) is the size of the struct page structs of a
Where the struct_size(pmd) is the size of the ``struct page`` structs of a
HugeTLB page of the pmd level mapping.
E.g.: A 2MB HugeTLB page on x86_64 consists in 8 page frames while 1GB
@ -94,7 +96,7 @@ HugeTLB page consists in 4096.
Next, we take the pmd level mapping of the HugeTLB page as an example to
show the internal implementation of this optimization. There are 8 pages
struct page structs associated with a HugeTLB page which is pmd mapped.
``struct page`` structs associated with a HugeTLB page which is pmd mapped.
Here is how things look before optimization::
@ -122,10 +124,10 @@ Here is how things look before optimization::
+-----------+
The value of page->compound_head is the same for all tail pages. The first
page of page structs (page 0) associated with the HugeTLB page contains the 4
page structs necessary to describe the HugeTLB. The only use of the remaining
pages of page structs (page 1 to page 7) is to point to page->compound_head.
Therefore, we can remap pages 1 to 7 to page 0. Only 1 page of page structs
page of ``struct page`` (page 0) associated with the HugeTLB page contains the 4
``struct page`` necessary to describe the HugeTLB. The only use of the remaining
pages of ``struct page`` (page 1 to page 7) is to point to page->compound_head.
Therefore, we can remap pages 1 to 7 to page 0. Only 1 page of ``struct page``
will be used for each HugeTLB page. This will allow us to free the remaining
7 pages to the buddy allocator.
@ -167,13 +169,37 @@ entries that can be cached in a single TLB entry.
The contiguous bit is used to increase the mapping size at the pmd and pte
(last) level. So this type of HugeTLB page can be optimized only when its
size of the struct page structs is greater than 1 page.
size of the ``struct page`` structs is greater than **1** page.
Notice: The head vmemmap page is not freed to the buddy allocator and all
tail vmemmap pages are mapped to the head vmemmap page frame. So we can see
more than one struct page struct with PG_head (e.g. 8 per 2 MB HugeTLB page)
associated with each HugeTLB page. The compound_head() can handle this
correctly (more details refer to the comment above compound_head()).
more than one ``struct page`` struct with ``PG_head`` (e.g. 8 per 2 MB HugeTLB
page) associated with each HugeTLB page. The ``compound_head()`` can handle
this correctly. There is only **one** head ``struct page``, the tail
``struct page`` with ``PG_head`` are fake head ``struct page``. We need an
approach to distinguish between those two different types of ``struct page`` so
that ``compound_head()`` can return the real head ``struct page`` when the
parameter is the tail ``struct page`` but with ``PG_head``. The following code
snippet describes how to distinguish between real and fake head ``struct page``.
.. code-block:: c
if (test_bit(PG_head, &page->flags)) {
unsigned long head = READ_ONCE(page[1].compound_head);
if (head & 1) {
if (head == (unsigned long)page + 1)
/* head struct page */
else
/* tail struct page */
} else {
/* head struct page */
}
}
We can safely access the field of the **page[1]** with ``PG_head`` because the
page is a compound page composed with at least two contiguous pages.
The implementation refers to ``page_fixed_fake_head()``.
Device DAX
==========
@ -187,7 +213,7 @@ PMD_SIZE (2M on x86_64) and PUD_SIZE (1G on x86_64).
The differences with HugeTLB are relatively minor.
It only use 3 page structs for storing all information as opposed
It only use 3 ``struct page`` for storing all information as opposed
to 4 on HugeTLB pages.
There's no remapping of vmemmap given that device-dax memory is not part of

13
arch/arm64/mm/flush.c
View File

@ -76,17 +76,10 @@ EXPORT_SYMBOL_GPL(__sync_icache_dcache);
void flush_dcache_page(struct page *page)
{
/*
* Only the head page's flags of HugeTLB can be cleared since the tail
* vmemmap pages associated with each HugeTLB page are mapped with
* read-only when CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is enabled (more
* details can refer to vmemmap_remap_pte()). Although
* __sync_icache_dcache() only set PG_dcache_clean flag on the head
* page struct, there is more than one page struct with PG_dcache_clean
* associated with the HugeTLB page since the head vmemmap page frame
* is reused (more details can refer to the comments above
* page_fixed_fake_head()).
* HugeTLB pages are always fully mapped and only head page will be
* set PG_dcache_clean (see comments in __sync_icache_dcache()).
*/
if (hugetlb_optimize_vmemmap_enabled() && PageHuge(page))
if (PageHuge(page))
page = compound_head(page);
if (test_bit(PG_dcache_clean, &page->flags))

8
arch/x86/mm/hugetlbpage.c
View File

@ -30,9 +30,15 @@ int pmd_huge(pmd_t pmd)
(pmd_val(pmd) & (_PAGE_PRESENT|_PAGE_PSE)) != _PAGE_PRESENT;
}
/*
* pud_huge() returns 1 if @pud is hugetlb related entry, that is normal
* hugetlb entry or non-present (migration or hwpoisoned) hugetlb entry.
* Otherwise, returns 0.
*/
int pud_huge(pud_t pud)
{
return !!(pud_val(pud) & _PAGE_PSE);
return !pud_none(pud) &&
(pud_val(pud) & (_PAGE_PRESENT|_PAGE_PSE)) != _PAGE_PRESENT;
}
#ifdef CONFIG_HUGETLB_PAGE

12
fs/Kconfig
View File

@ -247,8 +247,7 @@ config HUGETLB_PAGE
#
# Select this config option from the architecture Kconfig, if it is preferred
# to enable the feature of minimizing overhead of struct page associated with
# each HugeTLB page.
# to enable the feature of HugeTLB Vmemmap Optimization (HVO).
#
config ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
bool
@ -259,14 +258,13 @@ config HUGETLB_PAGE_OPTIMIZE_VMEMMAP
depends on SPARSEMEM_VMEMMAP
config HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON
bool "Default optimizing vmemmap pages of HugeTLB to on"
bool "HugeTLB Vmemmap Optimization (HVO) defaults to on"
default n
depends on HUGETLB_PAGE_OPTIMIZE_VMEMMAP
help
When using HUGETLB_PAGE_OPTIMIZE_VMEMMAP, the optimizing unused vmemmap
pages associated with each HugeTLB page is default off. Say Y here
to enable optimizing vmemmap pages of HugeTLB by default. It can then
be disabled on the command line via hugetlb_free_vmemmap=off.
The HugeTLB VmemmapvOptimization (HVO) defaults to off. Say Y here to
enable HVO by default. It can be disabled via hugetlb_free_vmemmap=off
(boot command line) or hugetlb_optimize_vmemmap (sysctl).
config MEMFD_CREATE
def_bool TMPFS || HUGETLBFS

7
include/linux/highmem.h
View File

@ -60,11 +60,11 @@ static inline void kmap_flush_unused(void);
/**
* kmap_local_page - Map a page for temporary usage
* @page: Pointer to the page to be mapped
* @page: Pointer to the page to be mapped
*
* Returns: The virtual address of the mapping
*
* Can be invoked from any context.
* Can be invoked from any context, including interrupts.
*
* Requires careful handling when nesting multiple mappings because the map
* management is stack based. The unmap has to be in the reverse order of
@ -86,8 +86,7 @@ static inline void kmap_flush_unused(void);
* temporarily mapped.
*
* While it is significantly faster than kmap() for the higmem case it
* comes with restrictions about the pointer validity. Only use when really
* necessary.
* comes with restrictions about the pointer validity.
*
* On HIGHMEM enabled systems mapping a highmem page has the side effect of
* disabling migration in order to keep the virtual address stable across

24
include/linux/hugetlb.h
View File

@ -42,6 +42,9 @@ enum {
SUBPAGE_INDEX_CGROUP, /* reuse page->private */
SUBPAGE_INDEX_CGROUP_RSVD, /* reuse page->private */
__MAX_CGROUP_SUBPAGE_INDEX = SUBPAGE_INDEX_CGROUP_RSVD,
#endif
#ifdef CONFIG_MEMORY_FAILURE
SUBPAGE_INDEX_HWPOISON,
#endif
__NR_USED_SUBPAGE,
};
@ -551,7 +554,7 @@ generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
* Synchronization: Initially set after new page allocation with no
* locking. When examined and modified during migration processing
* (isolate, migrate, putback) the hugetlb_lock is held.
* HPG_temporary - - Set on a page that is temporarily allocated from the buddy
* HPG_temporary - Set on a page that is temporarily allocated from the buddy
* allocator. Typically used for migration target pages when no pages
* are available in the pool. The hugetlb free page path will
* immediately free pages with this flag set to the buddy allocator.
@ -561,6 +564,8 @@ generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
* HPG_freed - Set when page is on the free lists.
* Synchronization: hugetlb_lock held for examination and modification.
* HPG_vmemmap_optimized - Set when the vmemmap pages of the page are freed.
* HPG_raw_hwp_unreliable - Set when the hugetlb page has a hwpoison sub-page
* that is not tracked by raw_hwp_page list.
*/
enum hugetlb_page_flags {
HPG_restore_reserve = 0,
@ -568,6 +573,7 @@ enum hugetlb_page_flags {
HPG_temporary,
HPG_freed,
HPG_vmemmap_optimized,
HPG_raw_hwp_unreliable,
__NR_HPAGEFLAGS,
};
@ -614,6 +620,7 @@ HPAGEFLAG(Migratable, migratable)
HPAGEFLAG(Temporary, temporary)
HPAGEFLAG(Freed, freed)
HPAGEFLAG(VmemmapOptimized, vmemmap_optimized)
HPAGEFLAG(RawHwpUnreliable, raw_hwp_unreliable)
#ifdef CONFIG_HUGETLB_PAGE
@ -638,9 +645,6 @@ struct hstate {
unsigned int nr_huge_pages_node[MAX_NUMNODES];
unsigned int free_huge_pages_node[MAX_NUMNODES];
unsigned int surplus_huge_pages_node[MAX_NUMNODES];
#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
unsigned int optimize_vmemmap_pages;
#endif
#ifdef CONFIG_CGROUP_HUGETLB
/* cgroup control files */
struct cftype cgroup_files_dfl[8];
@ -716,7 +720,7 @@ static inline struct hstate *hstate_vma(struct vm_area_struct *vma)
return hstate_file(vma->vm_file);
}
static inline unsigned long huge_page_size(struct hstate *h)
static inline unsigned long huge_page_size(const struct hstate *h)
{
return (unsigned long)PAGE_SIZE << h->order;
}
@ -745,7 +749,7 @@ static inline bool hstate_is_gigantic(struct hstate *h)
return huge_page_order(h) >= MAX_ORDER;
}
static inline unsigned int pages_per_huge_page(struct hstate *h)
static inline unsigned int pages_per_huge_page(const struct hstate *h)
{
return 1 << h->order;
}
@ -799,6 +803,14 @@ extern int dissolve_free_huge_page(struct page *page);
extern int dissolve_free_huge_pages(unsigned long start_pfn,
unsigned long end_pfn);
#ifdef CONFIG_MEMORY_FAILURE
extern void hugetlb_clear_page_hwpoison(struct page *hpage);
#else
static inline void hugetlb_clear_page_hwpoison(struct page *hpage)
{
}
#endif
#ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
#ifndef arch_hugetlb_migration_supported
static inline bool arch_hugetlb_migration_supported(struct hstate *h)

9
include/linux/mm.h
View File

@ -3142,13 +3142,6 @@ static inline void print_vma_addr(char *prefix, unsigned long rip)
}
#endif
#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
int vmemmap_remap_free(unsigned long start, unsigned long end,
unsigned long reuse);
int vmemmap_remap_alloc(unsigned long start, unsigned long end,
unsigned long reuse, gfp_t gfp_mask);
#endif
void *sparse_buffer_alloc(unsigned long size);
struct page * __populate_section_memmap(unsigned long pfn,
unsigned long nr_pages, int nid, struct vmem_altmap *altmap,
@ -3183,6 +3176,7 @@ enum mf_flags {
MF_SOFT_OFFLINE = 1 << 3,
MF_UNPOISON = 1 << 4,
MF_SW_SIMULATED = 1 << 5,
MF_NO_RETRY = 1 << 6,
};
int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
unsigned long count, int mf_flags);
@ -3235,7 +3229,6 @@ enum mf_action_page_type {
MF_MSG_DIFFERENT_COMPOUND,
MF_MSG_HUGE,
MF_MSG_FREE_HUGE,
MF_MSG_NON_PMD_HUGE,
MF_MSG_UNMAP_FAILED,
MF_MSG_DIRTY_SWAPCACHE,
MF_MSG_CLEAN_SWAPCACHE,

32
include/linux/page-flags.h
View File

@ -205,34 +205,15 @@ enum pageflags {
#ifndef __GENERATING_BOUNDS_H
#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
DECLARE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON,
hugetlb_optimize_vmemmap_key);
static __always_inline bool hugetlb_optimize_vmemmap_enabled(void)
{
return static_branch_maybe(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON,
&hugetlb_optimize_vmemmap_key);
}
DECLARE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key);
/*
* If the feature of optimizing vmemmap pages associated with each HugeTLB
* page is enabled, the head vmemmap page frame is reused and all of the tail
* vmemmap addresses map to the head vmemmap page frame (furture details can
* refer to the figure at the head of the mm/hugetlb_vmemmap.c). In other
* words, there are more than one page struct with PG_head associated with each
* HugeTLB page. We __know__ that there is only one head page struct, the tail
* page structs with PG_head are fake head page structs. We need an approach
* to distinguish between those two different types of page structs so that
* compound_head() can return the real head page struct when the parameter is
* the tail page struct but with PG_head.
*
* The page_fixed_fake_head() returns the real head page struct if the @page is
* fake page head, otherwise, returns @page which can either be a true page
* head or tail.
* Return the real head page struct iff the @page is a fake head page, otherwise
* return the @page itself. See Documentation/mm/vmemmap_dedup.rst.
*/
static __always_inline const struct page *page_fixed_fake_head(const struct page *page)
{
if (!hugetlb_optimize_vmemmap_enabled())
if (!static_branch_unlikely(&hugetlb_optimize_vmemmap_key))
return page;
/*
@ -260,11 +241,6 @@ static inline const struct page *page_fixed_fake_head(const struct page *page)
{
return page;
}
static inline bool hugetlb_optimize_vmemmap_enabled(void)
{
return false;
}
#endif
static __always_inline int page_is_fake_head(struct page *page)

9
include/linux/swapops.h
View File

@ -490,6 +490,11 @@ static inline void num_poisoned_pages_dec(void)
atomic_long_dec(&num_poisoned_pages);
}
static inline void num_poisoned_pages_sub(long i)
{
atomic_long_sub(i, &num_poisoned_pages);
}
#else
static inline swp_entry_t make_hwpoison_entry(struct page *page)
@ -505,6 +510,10 @@ static inline int is_hwpoison_entry(swp_entry_t swp)
static inline void num_poisoned_pages_inc(void)
{
}
static inline void num_poisoned_pages_sub(long i)
{
}
#endif
static inline int non_swap_entry(swp_entry_t entry)

4
include/linux/sysctl.h
View File

@ -268,6 +268,10 @@ static inline struct ctl_table_header *register_sysctl_table(struct ctl_table *
return NULL;
}
static inline void register_sysctl_init(const char *path, struct ctl_table *table)
{
}
static inline struct ctl_table_header *register_sysctl_mount_point(const char *path)
{
return NULL;

1
include/ras/ras_event.h
View File

@ -360,7 +360,6 @@ TRACE_EVENT(aer_event,
EM ( MF_MSG_DIFFERENT_COMPOUND, "different compound page after locking" ) \
EM ( MF_MSG_HUGE, "huge page" ) \
EM ( MF_MSG_FREE_HUGE, "free huge page" ) \
EM ( MF_MSG_NON_PMD_HUGE, "non-pmd-sized huge page" ) \
EM ( MF_MSG_UNMAP_FAILED, "unmapping failed page" ) \
EM ( MF_MSG_DIRTY_SWAPCACHE, "dirty swapcache page" ) \
EM ( MF_MSG_CLEAN_SWAPCACHE, "clean swapcache page" ) \

73
mm/hugetlb.c
View File

@ -1535,7 +1535,14 @@ static void __update_and_free_page(struct hstate *h, struct page *page)
if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
return;
if (hugetlb_vmemmap_alloc(h, page)) {
/*
* If we don't know which subpages are hwpoisoned, we can't free
* the hugepage, so it's leaked intentionally.
*/
if (HPageRawHwpUnreliable(page))
return;
if (hugetlb_vmemmap_restore(h, page)) {
spin_lock_irq(&hugetlb_lock);
/*
* If we cannot allocate vmemmap pages, just refuse to free the
@ -1547,6 +1554,13 @@ static void __update_and_free_page(struct hstate *h, struct page *page)
return;
}
/*
* Move PageHWPoison flag from head page to the raw error pages,
* which makes any healthy subpages reusable.
*/
if (unlikely(PageHWPoison(page)))
hugetlb_clear_page_hwpoison(page);
for (i = 0; i < pages_per_huge_page(h);
i++, subpage = mem_map_next(subpage, page, i)) {
subpage->flags &= ~(1 << PG_locked | 1 << PG_error |
@ -1612,7 +1626,7 @@ static DECLARE_WORK(free_hpage_work, free_hpage_workfn);
static inline void flush_free_hpage_work(struct hstate *h)
{
if (hugetlb_optimize_vmemmap_pages(h))
if (hugetlb_vmemmap_optimizable(h))
flush_work(&free_hpage_work);
}
@ -1734,7 +1748,7 @@ static void __prep_account_new_huge_page(struct hstate *h, int nid)
static void __prep_new_huge_page(struct hstate *h, struct page *page)
{
hugetlb_vmemmap_free(h, page);
hugetlb_vmemmap_optimize(h, page);
INIT_LIST_HEAD(&page->lru);
set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
hugetlb_set_page_subpool(page, NULL);
@ -2107,17 +2121,8 @@ int dissolve_free_huge_page(struct page *page)
* Attempt to allocate vmemmmap here so that we can take
* appropriate action on failure.
*/
rc = hugetlb_vmemmap_alloc(h, head);
rc = hugetlb_vmemmap_restore(h, head);
if (!rc) {
/*
* Move PageHWPoison flag from head page to the raw
* error page, which makes any subpages rather than
* the error page reusable.
*/
if (PageHWPoison(head) && page != head) {
SetPageHWPoison(page);
ClearPageHWPoison(head);
}
update_and_free_page(h, head, false);
} else {
spin_lock_irq(&hugetlb_lock);
@ -2432,8 +2437,7 @@ static void return_unused_surplus_pages(struct hstate *h,
/* Uncommit the reservation */
h->resv_huge_pages -= unused_resv_pages;
/* Cannot return gigantic pages currently */
if (hstate_is_gigantic(h))
if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
goto out;
/*
@ -3182,8 +3186,10 @@ static void __init report_hugepages(void)
char buf[32];
string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
pr_info("HugeTLB registered %s page size, pre-allocated %ld pages\n",
pr_info("HugeTLB: registered %s page size, pre-allocated %ld pages\n",
buf, h->free_huge_pages);
pr_info("HugeTLB: %d KiB vmemmap can be freed for a %s page\n",
hugetlb_vmemmap_optimizable_size(h) / SZ_1K, buf);
}
}
@ -3421,7 +3427,7 @@ static int demote_free_huge_page(struct hstate *h, struct page *page)
remove_hugetlb_page_for_demote(h, page, false);
spin_unlock_irq(&hugetlb_lock);
rc = hugetlb_vmemmap_alloc(h, page);
rc = hugetlb_vmemmap_restore(h, page);
if (rc) {
/* Allocation of vmemmmap failed, we can not demote page */
spin_lock_irq(&hugetlb_lock);
@ -4111,7 +4117,6 @@ void __init hugetlb_add_hstate(unsigned int order)
h->next_nid_to_free = first_memory_node;
snprintf(h->name, HSTATE_NAME_LEN, "hugepages-%lukB",
huge_page_size(h)/1024);
hugetlb_vmemmap_init(h);
parsed_hstate = h;
}
@ -6985,10 +6990,38 @@ struct page * __weak
follow_huge_pud(struct mm_struct *mm, unsigned long address,
pud_t *pud, int flags)
{
if (flags & (FOLL_GET | FOLL_PIN))
struct page *page = NULL;
spinlock_t *ptl;
pte_t pte;
if (WARN_ON_ONCE(flags & FOLL_PIN))
return NULL;
return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
retry:
ptl = huge_pte_lock(hstate_sizelog(PUD_SHIFT), mm, (pte_t *)pud);
if (!pud_huge(*pud))
goto out;
pte = huge_ptep_get((pte_t *)pud);
if (pte_present(pte)) {
page = pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
if (WARN_ON_ONCE(!try_grab_page(page, flags))) {
page = NULL;
goto out;
}
} else {
if (is_hugetlb_entry_migration(pte)) {
spin_unlock(ptl);
__migration_entry_wait(mm, (pte_t *)pud, ptl);
goto retry;
}
/*
* hwpoisoned entry is treated as no_page_table in
* follow_page_mask().
*/
}
out:
spin_unlock(ptl);
return page;
}
struct page * __weak

595
mm/hugetlb_vmemmap.c
View File

@ -1,8 +1,8 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Optimize vmemmap pages associated with HugeTLB
* HugeTLB Vmemmap Optimization (HVO)
*
* Copyright (c) 2020, Bytedance. All rights reserved.
* Copyright (c) 2020, ByteDance. All rights reserved.
*
* Author: Muchun Song <songmuchun@bytedance.com>
*
@ -10,84 +10,443 @@
*/
#define pr_fmt(fmt) "HugeTLB: " fmt
#include <linux/memory.h>
#include <linux/pgtable.h>
#include <linux/bootmem_info.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include "hugetlb_vmemmap.h"
/*
* There are a lot of struct page structures associated with each HugeTLB page.
* For tail pages, the value of compound_head is the same. So we can reuse first
* page of head page structures. We map the virtual addresses of all the pages
* of tail page structures to the head page struct, and then free these page
* frames. Therefore, we need to reserve one pages as vmemmap areas.
/**
* struct vmemmap_remap_walk - walk vmemmap page table
*
* @remap_pte: called for each lowest-level entry (PTE).
* @nr_walked: the number of walked pte.
* @reuse_page: the page which is reused for the tail vmemmap pages.
* @reuse_addr: the virtual address of the @reuse_page page.
* @vmemmap_pages: the list head of the vmemmap pages that can be freed
* or is mapped from.
*/
#define RESERVE_VMEMMAP_NR 1U
#define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT)
enum vmemmap_optimize_mode {
VMEMMAP_OPTIMIZE_OFF,
VMEMMAP_OPTIMIZE_ON,
struct vmemmap_remap_walk {
void (*remap_pte)(pte_t *pte, unsigned long addr,
struct vmemmap_remap_walk *walk);
unsigned long nr_walked;
struct page *reuse_page;
unsigned long reuse_addr;
struct list_head *vmemmap_pages;
};
DEFINE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON,
hugetlb_optimize_vmemmap_key);
EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key);
static enum vmemmap_optimize_mode vmemmap_optimize_mode =
IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON);
static void vmemmap_optimize_mode_switch(enum vmemmap_optimize_mode to)
static int __split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
{
if (vmemmap_optimize_mode == to)
return;
pmd_t __pmd;
int i;
unsigned long addr = start;
struct page *page = pmd_page(*pmd);
pte_t *pgtable = pte_alloc_one_kernel(&init_mm);
if (to == VMEMMAP_OPTIMIZE_OFF)
static_branch_dec(&hugetlb_optimize_vmemmap_key);
else
static_branch_inc(&hugetlb_optimize_vmemmap_key);
WRITE_ONCE(vmemmap_optimize_mode, to);
}
if (!pgtable)
return -ENOMEM;
static int __init hugetlb_vmemmap_early_param(char *buf)
{
bool enable;
enum vmemmap_optimize_mode mode;
pmd_populate_kernel(&init_mm, &__pmd, pgtable);
if (kstrtobool(buf, &enable))
return -EINVAL;
for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
pte_t entry, *pte;
pgprot_t pgprot = PAGE_KERNEL;
mode = enable ? VMEMMAP_OPTIMIZE_ON : VMEMMAP_OPTIMIZE_OFF;
vmemmap_optimize_mode_switch(mode);
entry = mk_pte(page + i, pgprot);
pte = pte_offset_kernel(&__pmd, addr);
set_pte_at(&init_mm, addr, pte, entry);
}
spin_lock(&init_mm.page_table_lock);
if (likely(pmd_leaf(*pmd))) {
/*
* Higher order allocations from buddy allocator must be able to
* be treated as indepdenent small pages (as they can be freed
* individually).
*/
if (!PageReserved(page))
split_page(page, get_order(PMD_SIZE));
/* Make pte visible before pmd. See comment in pmd_install(). */
smp_wmb();
pmd_populate_kernel(&init_mm, pmd, pgtable);
flush_tlb_kernel_range(start, start + PMD_SIZE);
} else {
pte_free_kernel(&init_mm, pgtable);
}
spin_unlock(&init_mm.page_table_lock);
return 0;
}
static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
{
int leaf;
spin_lock(&init_mm.page_table_lock);
leaf = pmd_leaf(*pmd);
spin_unlock(&init_mm.page_table_lock);
if (!leaf)
return 0;
return __split_vmemmap_huge_pmd(pmd, start);
}
static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
pte_t *pte = pte_offset_kernel(pmd, addr);
/*
* The reuse_page is found 'first' in table walk before we start
* remapping (which is calling @walk->remap_pte).
*/
if (!walk->reuse_page) {
walk->reuse_page = pte_page(*pte);
/*
* Because the reuse address is part of the range that we are
* walking, skip the reuse address range.
*/
addr += PAGE_SIZE;
pte++;
walk->nr_walked++;
}
for (; addr != end; addr += PAGE_SIZE, pte++) {
walk->remap_pte(pte, addr, walk);
walk->nr_walked++;
}
}
static int vmemmap_pmd_range(pud_t *pud, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
pmd_t *pmd;
unsigned long next;
pmd = pmd_offset(pud, addr);
do {
int ret;
ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK);
if (ret)
return ret;
next = pmd_addr_end(addr, end);
vmemmap_pte_range(pmd, addr, next, walk);
} while (pmd++, addr = next, addr != end);
return 0;
}
static int vmemmap_pud_range(p4d_t *p4d, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
pud_t *pud;
unsigned long next;
pud = pud_offset(p4d, addr);
do {
int ret;
next = pud_addr_end(addr, end);
ret = vmemmap_pmd_range(pud, addr, next, walk);
if (ret)
return ret;
} while (pud++, addr = next, addr != end);
return 0;
}
static int vmemmap_p4d_range(pgd_t *pgd, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
p4d_t *p4d;
unsigned long next;
p4d = p4d_offset(pgd, addr);
do {
int ret;
next = p4d_addr_end(addr, end);
ret = vmemmap_pud_range(p4d, addr, next, walk);
if (ret)
return ret;
} while (p4d++, addr = next, addr != end);
return 0;
}
static int vmemmap_remap_range(unsigned long start, unsigned long end,
struct vmemmap_remap_walk *walk)
{
unsigned long addr = start;
unsigned long next;
pgd_t *pgd;
VM_BUG_ON(!PAGE_ALIGNED(start));
VM_BUG_ON(!PAGE_ALIGNED(end));
pgd = pgd_offset_k(addr);
do {
int ret;
next = pgd_addr_end(addr, end);
ret = vmemmap_p4d_range(pgd, addr, next, walk);
if (ret)
return ret;
} while (pgd++, addr = next, addr != end);
/*
* We only change the mapping of the vmemmap virtual address range
* [@start + PAGE_SIZE, end), so we only need to flush the TLB which
* belongs to the range.
*/
flush_tlb_kernel_range(start + PAGE_SIZE, end);
return 0;
}
early_param("hugetlb_free_vmemmap", hugetlb_vmemmap_early_param);
/*
* Previously discarded vmemmap pages will be allocated and remapping
* after this function returns zero.
* Free a vmemmap page. A vmemmap page can be allocated from the memblock
* allocator or buddy allocator. If the PG_reserved flag is set, it means
* that it allocated from the memblock allocator, just free it via the
* free_bootmem_page(). Otherwise, use __free_page().
*/
int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head)
static inline void free_vmemmap_page(struct page *page)
{
if (PageReserved(page))
free_bootmem_page(page);
else
__free_page(page);
}
/* Free a list of the vmemmap pages */
static void free_vmemmap_page_list(struct list_head *list)
{
struct page *page, *next;
list_for_each_entry_safe(page, next, list, lru) {
list_del(&page->lru);
free_vmemmap_page(page);
}
}
static void vmemmap_remap_pte(pte_t *pte, unsigned long addr,
struct vmemmap_remap_walk *walk)
{
/*
* Remap the tail pages as read-only to catch illegal write operation
* to the tail pages.
*/
pgprot_t pgprot = PAGE_KERNEL_RO;
pte_t entry = mk_pte(walk->reuse_page, pgprot);
struct page *page = pte_page(*pte);
list_add_tail(&page->lru, walk->vmemmap_pages);
set_pte_at(&init_mm, addr, pte, entry);
}
/*
* How many struct page structs need to be reset. When we reuse the head
* struct page, the special metadata (e.g. page->flags or page->mapping)
* cannot copy to the tail struct page structs. The invalid value will be
* checked in the free_tail_pages_check(). In order to avoid the message
* of "corrupted mapping in tail page". We need to reset at least 3 (one
* head struct page struct and two tail struct page structs) struct page
* structs.
*/
#define NR_RESET_STRUCT_PAGE 3
static inline void reset_struct_pages(struct page *start)
{
int i;
struct page *from = start + NR_RESET_STRUCT_PAGE;
for (i = 0; i < NR_RESET_STRUCT_PAGE; i++)
memcpy(start + i, from, sizeof(*from));
}
static void vmemmap_restore_pte(pte_t *pte, unsigned long addr,
struct vmemmap_remap_walk *walk)
{
pgprot_t pgprot = PAGE_KERNEL;
struct page *page;
void *to;
BUG_ON(pte_page(*pte) != walk->reuse_page);
page = list_first_entry(walk->vmemmap_pages, struct page, lru);
list_del(&page->lru);
to = page_to_virt(page);
copy_page(to, (void *)walk->reuse_addr);
reset_struct_pages(to);
set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot));
}
/**
* vmemmap_remap_free - remap the vmemmap virtual address range [@start, @end)
* to the page which @reuse is mapped to, then free vmemmap
* which the range are mapped to.
* @start: start address of the vmemmap virtual address range that we want
* to remap.
* @end: end address of the vmemmap virtual address range that we want to
* remap.
* @reuse: reuse address.
*
* Return: %0 on success, negative error code otherwise.
*/
static int vmemmap_remap_free(unsigned long start, unsigned long end,
unsigned long reuse)
{
int ret;
unsigned long vmemmap_addr = (unsigned long)head;
unsigned long vmemmap_end, vmemmap_reuse, vmemmap_pages;
LIST_HEAD(vmemmap_pages);
struct vmemmap_remap_walk walk = {
.remap_pte = vmemmap_remap_pte,
.reuse_addr = reuse,
.vmemmap_pages = &vmemmap_pages,
};
/*
* In order to make remapping routine most efficient for the huge pages,
* the routine of vmemmap page table walking has the following rules
* (see more details from the vmemmap_pte_range()):
*
* - The range [@start, @end) and the range [@reuse, @reuse + PAGE_SIZE)
* should be continuous.
* - The @reuse address is part of the range [@reuse, @end) that we are
* walking which is passed to vmemmap_remap_range().
* - The @reuse address is the first in the complete range.
*
* So we need to make sure that @start and @reuse meet the above rules.
*/
BUG_ON(start - reuse != PAGE_SIZE);
mmap_read_lock(&init_mm);
ret = vmemmap_remap_range(reuse, end, &walk);
if (ret && walk.nr_walked) {
end = reuse + walk.nr_walked * PAGE_SIZE;
/*
* vmemmap_pages contains pages from the previous
* vmemmap_remap_range call which failed. These
* are pages which were removed from the vmemmap.
* They will be restored in the following call.
*/
walk = (struct vmemmap_remap_walk) {
.remap_pte = vmemmap_restore_pte,
.reuse_addr = reuse,
.vmemmap_pages = &vmemmap_pages,
};
vmemmap_remap_range(reuse, end, &walk);
}
mmap_read_unlock(&init_mm);
free_vmemmap_page_list(&vmemmap_pages);
return ret;
}
static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
gfp_t gfp_mask, struct list_head *list)
{
unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
int nid = page_to_nid((struct page *)start);
struct page *page, *next;
while (nr_pages--) {
page = alloc_pages_node(nid, gfp_mask, 0);
if (!page)
goto out;
list_add_tail(&page->lru, list);
}
return 0;
out:
list_for_each_entry_safe(page, next, list, lru)
__free_pages(page, 0);
return -ENOMEM;
}
/**
* vmemmap_remap_alloc - remap the vmemmap virtual address range [@start, end)
* to the page which is from the @vmemmap_pages
* respectively.
* @start: start address of the vmemmap virtual address range that we want
* to remap.
* @end: end address of the vmemmap virtual address range that we want to
* remap.
* @reuse: reuse address.
* @gfp_mask: GFP flag for allocating vmemmap pages.
*
* Return: %0 on success, negative error code otherwise.
*/
static int vmemmap_remap_alloc(unsigned long start, unsigned long end,
unsigned long reuse, gfp_t gfp_mask)
{
LIST_HEAD(vmemmap_pages);
struct vmemmap_remap_walk walk = {
.remap_pte = vmemmap_restore_pte,
.reuse_addr = reuse,
.vmemmap_pages = &vmemmap_pages,
};
/* See the comment in the vmemmap_remap_free(). */
BUG_ON(start - reuse != PAGE_SIZE);
if (alloc_vmemmap_page_list(start, end, gfp_mask, &vmemmap_pages))
return -ENOMEM;
mmap_read_lock(&init_mm);
vmemmap_remap_range(reuse, end, &walk);
mmap_read_unlock(&init_mm);
return 0;
}
DEFINE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key);
EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key);
static bool vmemmap_optimize_enabled = IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON);
core_param(hugetlb_free_vmemmap, vmemmap_optimize_enabled, bool, 0);
/**
* hugetlb_vmemmap_restore - restore previously optimized (by
* hugetlb_vmemmap_optimize()) vmemmap pages which
* will be reallocated and remapped.
* @h: struct hstate.
* @head: the head page whose vmemmap pages will be restored.
*
* Return: %0 if @head's vmemmap pages have been reallocated and remapped,
* negative error code otherwise.
*/
int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
{
int ret;
unsigned long vmemmap_start = (unsigned long)head, vmemmap_end;
unsigned long vmemmap_reuse;
if (!HPageVmemmapOptimized(head))
return 0;
vmemmap_addr += RESERVE_VMEMMAP_SIZE;
vmemmap_pages = hugetlb_optimize_vmemmap_pages(h);
vmemmap_end = vmemmap_addr + (vmemmap_pages << PAGE_SHIFT);
vmemmap_reuse = vmemmap_addr - PAGE_SIZE;
vmemmap_end = vmemmap_start + hugetlb_vmemmap_size(h);
vmemmap_reuse = vmemmap_start;
vmemmap_start += HUGETLB_VMEMMAP_RESERVE_SIZE;
/*
* The pages which the vmemmap virtual address range [@vmemmap_addr,
* The pages which the vmemmap virtual address range [@vmemmap_start,
* @vmemmap_end) are mapped to are freed to the buddy allocator, and
* the range is mapped to the page which @vmemmap_reuse is mapped to.
* When a HugeTLB page is freed to the buddy allocator, previously
* discarded vmemmap pages must be allocated and remapping.
*/
ret = vmemmap_remap_alloc(vmemmap_addr, vmemmap_end, vmemmap_reuse,
ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, vmemmap_reuse,
GFP_KERNEL | __GFP_NORETRY | __GFP_THISNODE);
if (!ret) {
ClearHPageVmemmapOptimized(head);
@ -97,11 +456,14 @@ int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head)
return ret;
}
static unsigned int vmemmap_optimizable_pages(struct hstate *h,
struct page *head)
/* Return true iff a HugeTLB whose vmemmap should and can be optimized. */
static bool vmemmap_should_optimize(const struct hstate *h, const struct page *head)
{
if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
return 0;
if (!READ_ONCE(vmemmap_optimize_enabled))
return false;
if (!hugetlb_vmemmap_optimizable(h))
return false;
if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) {
pmd_t *pmdp, pmd;
@ -144,118 +506,73 @@ static unsigned int vmemmap_optimizable_pages(struct hstate *h,
* +-------------------------------------------+
*/
if (PageVmemmapSelfHosted(vmemmap_page))
return 0;
return false;
}
return hugetlb_optimize_vmemmap_pages(h);
return true;
}
void hugetlb_vmemmap_free(struct hstate *h, struct page *head)
/**
* hugetlb_vmemmap_optimize - optimize @head page's vmemmap pages.
* @h: struct hstate.
* @head: the head page whose vmemmap pages will be optimized.
*
* This function only tries to optimize @head's vmemmap pages and does not
* guarantee that the optimization will succeed after it returns. The caller
* can use HPageVmemmapOptimized(@head) to detect if @head's vmemmap pages
* have been optimized.
*/
void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
{
unsigned long vmemmap_addr = (unsigned long)head;
unsigned long vmemmap_end, vmemmap_reuse, vmemmap_pages;
unsigned long vmemmap_start = (unsigned long)head, vmemmap_end;
unsigned long vmemmap_reuse;
vmemmap_pages = vmemmap_optimizable_pages(h, head);
if (!vmemmap_pages)
if (!vmemmap_should_optimize(h, head))
return;
static_branch_inc(&hugetlb_optimize_vmemmap_key);
vmemmap_addr += RESERVE_VMEMMAP_SIZE;
vmemmap_end = vmemmap_addr + (vmemmap_pages << PAGE_SHIFT);
vmemmap_reuse = vmemmap_addr - PAGE_SIZE;
vmemmap_end = vmemmap_start + hugetlb_vmemmap_size(h);
vmemmap_reuse = vmemmap_start;
vmemmap_start += HUGETLB_VMEMMAP_RESERVE_SIZE;
/*
* Remap the vmemmap virtual address range [@vmemmap_addr, @vmemmap_end)
* Remap the vmemmap virtual address range [@vmemmap_start, @vmemmap_end)
* to the page which @vmemmap_reuse is mapped to, then free the pages
* which the range [@vmemmap_addr, @vmemmap_end] is mapped to.
* which the range [@vmemmap_start, @vmemmap_end] is mapped to.
*/
if (vmemmap_remap_free(vmemmap_addr, vmemmap_end, vmemmap_reuse))
if (vmemmap_remap_free(vmemmap_start, vmemmap_end, vmemmap_reuse))
static_branch_dec(&hugetlb_optimize_vmemmap_key);
else
SetHPageVmemmapOptimized(head);
}
void __init hugetlb_vmemmap_init(struct hstate *h)
{
unsigned int nr_pages = pages_per_huge_page(h);
unsigned int vmemmap_pages;
/*
* There are only (RESERVE_VMEMMAP_SIZE / sizeof(struct page)) struct
* page structs that can be used when CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP,
* so add a BUILD_BUG_ON to catch invalid usage of the tail struct page.
*/
BUILD_BUG_ON(__NR_USED_SUBPAGE >=
RESERVE_VMEMMAP_SIZE / sizeof(struct page));
if (!is_power_of_2(sizeof(struct page))) {
pr_warn_once("cannot optimize vmemmap pages because \"struct page\" crosses page boundaries\n");
static_branch_disable(&hugetlb_optimize_vmemmap_key);
return;
}
vmemmap_pages = (nr_pages * sizeof(struct page)) >> PAGE_SHIFT;
/*
* The head page is not to be freed to buddy allocator, the other tail
* pages will map to the head page, so they can be freed.
*
* Could RESERVE_VMEMMAP_NR be greater than @vmemmap_pages? It is true
* on some architectures (e.g. aarch64). See Documentation/arm64/
* hugetlbpage.rst for more details.
*/
if (likely(vmemmap_pages > RESERVE_VMEMMAP_NR))
h->optimize_vmemmap_pages = vmemmap_pages - RESERVE_VMEMMAP_NR;
pr_info("can optimize %d vmemmap pages for %s\n",
h->optimize_vmemmap_pages, h->name);
}
#ifdef CONFIG_PROC_SYSCTL
static int hugetlb_optimize_vmemmap_handler(struct ctl_table *table, int write,
void *buffer, size_t *length,
loff_t *ppos)
{
int ret;
enum vmemmap_optimize_mode mode;
static DEFINE_MUTEX(sysctl_mutex);
if (write && !capable(CAP_SYS_ADMIN))
return -EPERM;
mutex_lock(&sysctl_mutex);
mode = vmemmap_optimize_mode;
table->data = &mode;
ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
if (write && !ret)
vmemmap_optimize_mode_switch(mode);
mutex_unlock(&sysctl_mutex);
return ret;
}
static struct ctl_table hugetlb_vmemmap_sysctls[] = {
{
.procname = "hugetlb_optimize_vmemmap",
.maxlen = sizeof(enum vmemmap_optimize_mode),
.data = &vmemmap_optimize_enabled,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = hugetlb_optimize_vmemmap_handler,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
.proc_handler = proc_dobool,
},
{ }
};
static __init int hugetlb_vmemmap_sysctls_init(void)
static int __init hugetlb_vmemmap_init(void)
{
/*
* If "struct page" crosses page boundaries, the vmemmap pages cannot
* be optimized.
*/
if (is_power_of_2(sizeof(struct page)))
register_sysctl_init("vm", hugetlb_vmemmap_sysctls);
/* HUGETLB_VMEMMAP_RESERVE_SIZE should cover all used struct pages */
BUILD_BUG_ON(__NR_USED_SUBPAGE * sizeof(struct page) > HUGETLB_VMEMMAP_RESERVE_SIZE);
if (IS_ENABLED(CONFIG_PROC_SYSCTL)) {
const struct hstate *h;
for_each_hstate(h) {
if (hugetlb_vmemmap_optimizable(h)) {
register_sysctl_init("vm", hugetlb_vmemmap_sysctls);
break;
}
}
}
return 0;
}
late_initcall(hugetlb_vmemmap_sysctls_init);
#endif /* CONFIG_PROC_SYSCTL */
late_initcall(hugetlb_vmemmap_init);

47
mm/hugetlb_vmemmap.h
View File

@ -1,8 +1,8 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Optimize vmemmap pages associated with HugeTLB
* HugeTLB Vmemmap Optimization (HVO)
*
* Copyright (c) 2020, Bytedance. All rights reserved.
* Copyright (c) 2020, ByteDance. All rights reserved.
*
* Author: Muchun Song <songmuchun@bytedance.com>
*/
@ -11,35 +11,50 @@
#include <linux/hugetlb.h>
#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head);
void hugetlb_vmemmap_free(struct hstate *h, struct page *head);
void hugetlb_vmemmap_init(struct hstate *h);
int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head);
void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head);
/*
* How many vmemmap pages associated with a HugeTLB page that can be
* optimized and freed to the buddy allocator.
* Reserve one vmemmap page, all vmemmap addresses are mapped to it. See
* Documentation/vm/vmemmap_dedup.rst.
*/
static inline unsigned int hugetlb_optimize_vmemmap_pages(struct hstate *h)
#define HUGETLB_VMEMMAP_RESERVE_SIZE PAGE_SIZE
static inline unsigned int hugetlb_vmemmap_size(const struct hstate *h)
{
return h->optimize_vmemmap_pages;
return pages_per_huge_page(h) * sizeof(struct page);
}
/*
* Return how many vmemmap size associated with a HugeTLB page that can be
* optimized and can be freed to the buddy allocator.
*/
static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
{
int size = hugetlb_vmemmap_size(h) - HUGETLB_VMEMMAP_RESERVE_SIZE;
if (!is_power_of_2(sizeof(struct page)))
return 0;
return size > 0 ? size : 0;
}
#else
static inline int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head)
static inline int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
{
return 0;
}
static inline void hugetlb_vmemmap_free(struct hstate *h, struct page *head)
static inline void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
{
}
static inline void hugetlb_vmemmap_init(struct hstate *h)
{
}
static inline unsigned int hugetlb_optimize_vmemmap_pages(struct hstate *h)
static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
{
return 0;
}
#endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */
static inline bool hugetlb_vmemmap_optimizable(const struct hstate *h)
{
return hugetlb_vmemmap_optimizable_size(h) != 0;
}
#endif /* _LINUX_HUGETLB_VMEMMAP_H */

179
mm/memory-failure.c
View File

@ -74,7 +74,13 @@ atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
static bool hw_memory_failure __read_mostly = false;
static bool __page_handle_poison(struct page *page)
/*
* Return values:
* 1: the page is dissolved (if needed) and taken off from buddy,
* 0: the page is dissolved (if needed) and not taken off from buddy,
* < 0: failed to dissolve.
*/
static int __page_handle_poison(struct page *page)
{
int ret;
@ -84,7 +90,7 @@ static bool __page_handle_poison(struct page *page)
ret = take_page_off_buddy(page);
zone_pcp_enable(page_zone(page));
return ret > 0;
return ret;
}
static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release)
@ -94,7 +100,7 @@ static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, boo
* Doing this check for free pages is also fine since dissolve_free_huge_page
* returns 0 for non-hugetlb pages as well.
*/
if (!__page_handle_poison(page))
if (__page_handle_poison(page) <= 0)
/*
* We could fail to take off the target page from buddy
* for example due to racy page allocation, but that's
@ -762,7 +768,6 @@ static const char * const action_page_types[] = {
[MF_MSG_DIFFERENT_COMPOUND] = "different compound page after locking",
[MF_MSG_HUGE] = "huge page",
[MF_MSG_FREE_HUGE] = "free huge page",
[MF_MSG_NON_PMD_HUGE] = "non-pmd-sized huge page",
[MF_MSG_UNMAP_FAILED] = "unmapping failed page",
[MF_MSG_DIRTY_SWAPCACHE] = "dirty swapcache page",
[MF_MSG_CLEAN_SWAPCACHE] = "clean swapcache page",
@ -1078,7 +1083,6 @@ static int me_huge_page(struct page_state *ps, struct page *p)
res = truncate_error_page(hpage, page_to_pfn(p), mapping);
unlock_page(hpage);
} else {
res = MF_FAILED;
unlock_page(hpage);
/*
* migration entry prevents later access on error hugepage,
@ -1086,9 +1090,11 @@ static int me_huge_page(struct page_state *ps, struct page *p)
* subpages.
*/
put_page(hpage);
if (__page_handle_poison(p)) {
if (__page_handle_poison(p) >= 0) {
page_ref_inc(p);
res = MF_RECOVERED;
} else {
res = MF_FAILED;
}
}
@ -1662,6 +1668,113 @@ int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
EXPORT_SYMBOL_GPL(mf_dax_kill_procs);
#endif /* CONFIG_FS_DAX */
#ifdef CONFIG_HUGETLB_PAGE
/*
* Struct raw_hwp_page represents information about "raw error page",
* constructing singly linked list originated from ->private field of
* SUBPAGE_INDEX_HWPOISON-th tail page.
*/
struct raw_hwp_page {
struct llist_node node;
struct page *page;
};
static inline struct llist_head *raw_hwp_list_head(struct page *hpage)
{
return (struct llist_head *)&page_private(hpage + SUBPAGE_INDEX_HWPOISON);
}
static unsigned long __free_raw_hwp_pages(struct page *hpage, bool move_flag)
{
struct llist_head *head;
struct llist_node *t, *tnode;
unsigned long count = 0;
head = raw_hwp_list_head(hpage);
llist_for_each_safe(tnode, t, head->first) {
struct raw_hwp_page *p = container_of(tnode, struct raw_hwp_page, node);
if (move_flag)
SetPageHWPoison(p->page);
kfree(p);
count++;
}
llist_del_all(head);
return count;
}
static int hugetlb_set_page_hwpoison(struct page *hpage, struct page *page)
{
struct llist_head *head;
struct raw_hwp_page *raw_hwp;
struct llist_node *t, *tnode;
int ret = TestSetPageHWPoison(hpage) ? -EHWPOISON : 0;
/*
* Once the hwpoison hugepage has lost reliable raw error info,
* there is little meaning to keep additional error info precisely,
* so skip to add additional raw error info.
*/
if (HPageRawHwpUnreliable(hpage))
return -EHWPOISON;
head = raw_hwp_list_head(hpage);
llist_for_each_safe(tnode, t, head->first) {
struct raw_hwp_page *p = container_of(tnode, struct raw_hwp_page, node);
if (p->page == page)
return -EHWPOISON;
}
raw_hwp = kmalloc(sizeof(struct raw_hwp_page), GFP_ATOMIC);
if (raw_hwp) {
raw_hwp->page = page;
llist_add(&raw_hwp->node, head);
/* the first error event will be counted in action_result(). */
if (ret)
num_poisoned_pages_inc();
} else {
/*
* Failed to save raw error info. We no longer trace all
* hwpoisoned subpages, and we need refuse to free/dissolve
* this hwpoisoned hugepage.
*/
SetHPageRawHwpUnreliable(hpage);
/*
* Once HPageRawHwpUnreliable is set, raw_hwp_page is not
* used any more, so free it.
*/
__free_raw_hwp_pages(hpage, false);
}
return ret;
}
static unsigned long free_raw_hwp_pages(struct page *hpage, bool move_flag)
{
/*
* HPageVmemmapOptimized hugepages can't be freed because struct
* pages for tail pages are required but they don't exist.
*/
if (move_flag && HPageVmemmapOptimized(hpage))
return 0;
/*
* HPageRawHwpUnreliable hugepages shouldn't be unpoisoned by
* definition.
*/
if (HPageRawHwpUnreliable(hpage))
return 0;
return __free_raw_hwp_pages(hpage, move_flag);
}
void hugetlb_clear_page_hwpoison(struct page *hpage)
{
if (HPageRawHwpUnreliable(hpage))
return;
ClearPageHWPoison(hpage);
free_raw_hwp_pages(hpage, true);
}
/*
* Called from hugetlb code with hugetlb_lock held.
*
@ -1693,10 +1806,11 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
count_increased = true;
} else {
ret = -EBUSY;
goto out;
if (!(flags & MF_NO_RETRY))
goto out;
}
if (TestSetPageHWPoison(head)) {
if (hugetlb_set_page_hwpoison(head, page)) {
ret = -EHWPOISON;
goto out;
}
@ -1708,7 +1822,6 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
return ret;
}
#ifdef CONFIG_HUGETLB_PAGE
/*
* Taking refcount of hugetlb pages needs extra care about race conditions
* with basic operations like hugepage allocation/free/demotion.
@ -1721,7 +1834,6 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
struct page *p = pfn_to_page(pfn);
struct page *head;
unsigned long page_flags;
bool retry = true;
*hugetlb = 1;
retry:
@ -1737,8 +1849,8 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
}
return res;
} else if (res == -EBUSY) {
if (retry) {
retry = false;
if (!(flags & MF_NO_RETRY)) {
flags |= MF_NO_RETRY;
goto retry;
}
action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED);
@ -1749,7 +1861,7 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
lock_page(head);
if (hwpoison_filter(p)) {
ClearPageHWPoison(head);
hugetlb_clear_page_hwpoison(head);
res = -EOPNOTSUPP;
goto out;
}
@ -1760,10 +1872,11 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
*/
if (res == 0) {
unlock_page(head);
res = MF_FAILED;
if (__page_handle_poison(p)) {
if (__page_handle_poison(p) >= 0) {
page_ref_inc(p);
res = MF_RECOVERED;
} else {
res = MF_FAILED;
}
action_result(pfn, MF_MSG_FREE_HUGE, res);
return res == MF_RECOVERED ? 0 : -EBUSY;
@ -1771,21 +1884,6 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
page_flags = head->flags;
/*
* TODO: hwpoison for pud-sized hugetlb doesn't work right now, so
* simply disable it. In order to make it work properly, we need
* make sure that:
* - conversion of a pud that maps an error hugetlb into hwpoison
* entry properly works, and
* - other mm code walking over page table is aware of pud-aligned
* hwpoison entries.
*/
if (huge_page_size(page_hstate(head)) > PMD_SIZE) {
action_result(pfn, MF_MSG_NON_PMD_HUGE, MF_IGNORED);
res = -EBUSY;
goto out;
}
if (!hwpoison_user_mappings(p, pfn, flags, head)) {
action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
res = -EBUSY;
@ -1804,6 +1902,10 @@ static inline int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *
return 0;
}
static inline unsigned long free_raw_hwp_pages(struct page *hpage, bool flag)
{
return 0;
}
#endif /* CONFIG_HUGETLB_PAGE */
static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
@ -2209,6 +2311,7 @@ int unpoison_memory(unsigned long pfn)
struct page *p;
int ret = -EBUSY;
int freeit = 0;
unsigned long count = 1;
static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
DEFAULT_RATELIMIT_BURST);
@ -2256,6 +2359,13 @@ int unpoison_memory(unsigned long pfn)
ret = get_hwpoison_page(p, MF_UNPOISON);
if (!ret) {
if (PageHuge(p)) {
count = free_raw_hwp_pages(page, false);
if (count == 0) {
ret = -EBUSY;
goto unlock_mutex;
}
}
ret = TestClearPageHWPoison(page) ? 0 : -EBUSY;
} else if (ret < 0) {
if (ret == -EHWPOISON) {
@ -2264,6 +2374,13 @@ int unpoison_memory(unsigned long pfn)
unpoison_pr_info("Unpoison: failed to grab page %#lx\n",
pfn, &unpoison_rs);
} else {
if (PageHuge(p)) {
count = free_raw_hwp_pages(page, false);
if (count == 0) {
ret = -EBUSY;
goto unlock_mutex;
}
}
freeit = !!TestClearPageHWPoison(p);
put_page(page);
@ -2276,7 +2393,7 @@ int unpoison_memory(unsigned long pfn)
unlock_mutex:
mutex_unlock(&mf_mutex);
if (!ret || freeit) {
num_poisoned_pages_dec();
num_poisoned_pages_sub(count);
unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
page_to_pfn(p), &unpoison_rs);
}

399
mm/sparse-vmemmap.c
View File

@ -27,408 +27,9 @@
#include <linux/spinlock.h>
#include <linux/vmalloc.h>
#include <linux/sched.h>
#include <linux/pgtable.h>
#include <linux/bootmem_info.h>
#include <asm/dma.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
/**
* struct vmemmap_remap_walk - walk vmemmap page table
*
* @remap_pte: called for each lowest-level entry (PTE).
* @nr_walked: the number of walked pte.
* @reuse_page: the page which is reused for the tail vmemmap pages.
* @reuse_addr: the virtual address of the @reuse_page page.
* @vmemmap_pages: the list head of the vmemmap pages that can be freed
* or is mapped from.
*/
struct vmemmap_remap_walk {
void (*remap_pte)(pte_t *pte, unsigned long addr,
struct vmemmap_remap_walk *walk);
unsigned long nr_walked;
struct page *reuse_page;
unsigned long reuse_addr;
struct list_head *vmemmap_pages;
};
static int __split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
{
pmd_t __pmd;
int i;
unsigned long addr = start;
struct page *page = pmd_page(*pmd);
pte_t *pgtable = pte_alloc_one_kernel(&init_mm);
if (!pgtable)
return -ENOMEM;
pmd_populate_kernel(&init_mm, &__pmd, pgtable);
for (i = 0; i < PMD_SIZE / PAGE_SIZE; i++, addr += PAGE_SIZE) {
pte_t entry, *pte;
pgprot_t pgprot = PAGE_KERNEL;
entry = mk_pte(page + i, pgprot);
pte = pte_offset_kernel(&__pmd, addr);
set_pte_at(&init_mm, addr, pte, entry);
}
spin_lock(&init_mm.page_table_lock);
if (likely(pmd_leaf(*pmd))) {
/*
* Higher order allocations from buddy allocator must be able to
* be treated as indepdenent small pages (as they can be freed
* individually).
*/
if (!PageReserved(page))
split_page(page, get_order(PMD_SIZE));
/* Make pte visible before pmd. See comment in pmd_install(). */
smp_wmb();
pmd_populate_kernel(&init_mm, pmd, pgtable);
flush_tlb_kernel_range(start, start + PMD_SIZE);
} else {
pte_free_kernel(&init_mm, pgtable);
}
spin_unlock(&init_mm.page_table_lock);
return 0;
}
static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
{
int leaf;
spin_lock(&init_mm.page_table_lock);
leaf = pmd_leaf(*pmd);
spin_unlock(&init_mm.page_table_lock);
if (!leaf)
return 0;
return __split_vmemmap_huge_pmd(pmd, start);
}
static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
pte_t *pte = pte_offset_kernel(pmd, addr);
/*
* The reuse_page is found 'first' in table walk before we start
* remapping (which is calling @walk->remap_pte).
*/
if (!walk->reuse_page) {
walk->reuse_page = pte_page(*pte);
/*
* Because the reuse address is part of the range that we are
* walking, skip the reuse address range.
*/
addr += PAGE_SIZE;
pte++;
walk->nr_walked++;
}
for (; addr != end; addr += PAGE_SIZE, pte++) {
walk->remap_pte(pte, addr, walk);
walk->nr_walked++;
}
}
static int vmemmap_pmd_range(pud_t *pud, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
pmd_t *pmd;
unsigned long next;
pmd = pmd_offset(pud, addr);
do {
int ret;
ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK);
if (ret)
return ret;
next = pmd_addr_end(addr, end);
vmemmap_pte_range(pmd, addr, next, walk);
} while (pmd++, addr = next, addr != end);
return 0;
}
static int vmemmap_pud_range(p4d_t *p4d, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
pud_t *pud;
unsigned long next;
pud = pud_offset(p4d, addr);
do {
int ret;
next = pud_addr_end(addr, end);
ret = vmemmap_pmd_range(pud, addr, next, walk);
if (ret)
return ret;
} while (pud++, addr = next, addr != end);
return 0;
}
static int vmemmap_p4d_range(pgd_t *pgd, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)
{
p4d_t *p4d;
unsigned long next;
p4d = p4d_offset(pgd, addr);
do {
int ret;
next = p4d_addr_end(addr, end);
ret = vmemmap_pud_range(p4d, addr, next, walk);
if (ret)
return ret;
} while (p4d++, addr = next, addr != end);
return 0;
}
static int vmemmap_remap_range(unsigned long start, unsigned long end,
struct vmemmap_remap_walk *walk)
{
unsigned long addr = start;
unsigned long next;
pgd_t *pgd;
VM_BUG_ON(!PAGE_ALIGNED(start));
VM_BUG_ON(!PAGE_ALIGNED(end));
pgd = pgd_offset_k(addr);
do {
int ret;
next = pgd_addr_end(addr, end);
ret = vmemmap_p4d_range(pgd, addr, next, walk);
if (ret)
return ret;
} while (pgd++, addr = next, addr != end);
/*
* We only change the mapping of the vmemmap virtual address range
* [@start + PAGE_SIZE, end), so we only need to flush the TLB which
* belongs to the range.
*/
flush_tlb_kernel_range(start + PAGE_SIZE, end);
return 0;
}
/*
* Free a vmemmap page. A vmemmap page can be allocated from the memblock
* allocator or buddy allocator. If the PG_reserved flag is set, it means
* that it allocated from the memblock allocator, just free it via the
* free_bootmem_page(). Otherwise, use __free_page().
*/
static inline void free_vmemmap_page(struct page *page)
{
if (PageReserved(page))
free_bootmem_page(page);
else
__free_page(page);
}
/* Free a list of the vmemmap pages */
static void free_vmemmap_page_list(struct list_head *list)
{
struct page *page, *next;
list_for_each_entry_safe(page, next, list, lru) {
list_del(&page->lru);
free_vmemmap_page(page);
}
}
static void vmemmap_remap_pte(pte_t *pte, unsigned long addr,
struct vmemmap_remap_walk *walk)
{
/*
* Remap the tail pages as read-only to catch illegal write operation
* to the tail pages.
*/
pgprot_t pgprot = PAGE_KERNEL_RO;
pte_t entry = mk_pte(walk->reuse_page, pgprot);
struct page *page = pte_page(*pte);
list_add_tail(&page->lru, walk->vmemmap_pages);
set_pte_at(&init_mm, addr, pte, entry);
}
/*
* How many struct page structs need to be reset. When we reuse the head
* struct page, the special metadata (e.g. page->flags or page->mapping)
* cannot copy to the tail struct page structs. The invalid value will be
* checked in the free_tail_pages_check(). In order to avoid the message
* of "corrupted mapping in tail page". We need to reset at least 3 (one
* head struct page struct and two tail struct page structs) struct page
* structs.
*/
#define NR_RESET_STRUCT_PAGE 3
static inline void reset_struct_pages(struct page *start)
{
int i;
struct page *from = start + NR_RESET_STRUCT_PAGE;
for (i = 0; i < NR_RESET_STRUCT_PAGE; i++)
memcpy(start + i, from, sizeof(*from));
}
static void vmemmap_restore_pte(pte_t *pte, unsigned long addr,
struct vmemmap_remap_walk *walk)
{
pgprot_t pgprot = PAGE_KERNEL;
struct page *page;
void *to;
BUG_ON(pte_page(*pte) != walk->reuse_page);
page = list_first_entry(walk->vmemmap_pages, struct page, lru);
list_del(&page->lru);
to = page_to_virt(page);
copy_page(to, (void *)walk->reuse_addr);
reset_struct_pages(to);
set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot));
}
/**
* vmemmap_remap_free - remap the vmemmap virtual address range [@start, @end)
* to the page which @reuse is mapped to, then free vmemmap
* which the range are mapped to.
* @start: start address of the vmemmap virtual address range that we want
* to remap.
* @end: end address of the vmemmap virtual address range that we want to
* remap.
* @reuse: reuse address.
*
* Return: %0 on success, negative error code otherwise.
*/
int vmemmap_remap_free(unsigned long start, unsigned long end,
unsigned long reuse)
{
int ret;
LIST_HEAD(vmemmap_pages);
struct vmemmap_remap_walk walk = {
.remap_pte = vmemmap_remap_pte,
.reuse_addr = reuse,
.vmemmap_pages = &vmemmap_pages,
};
/*
* In order to make remapping routine most efficient for the huge pages,
* the routine of vmemmap page table walking has the following rules
* (see more details from the vmemmap_pte_range()):
*
* - The range [@start, @end) and the range [@reuse, @reuse + PAGE_SIZE)
* should be continuous.
* - The @reuse address is part of the range [@reuse, @end) that we are
* walking which is passed to vmemmap_remap_range().
* - The @reuse address is the first in the complete range.
*
* So we need to make sure that @start and @reuse meet the above rules.
*/
BUG_ON(start - reuse != PAGE_SIZE);
mmap_read_lock(&init_mm);
ret = vmemmap_remap_range(reuse, end, &walk);
if (ret && walk.nr_walked) {
end = reuse + walk.nr_walked * PAGE_SIZE;
/*
* vmemmap_pages contains pages from the previous
* vmemmap_remap_range call which failed. These
* are pages which were removed from the vmemmap.
* They will be restored in the following call.
*/
walk = (struct vmemmap_remap_walk) {
.remap_pte = vmemmap_restore_pte,
.reuse_addr = reuse,
.vmemmap_pages = &vmemmap_pages,
};
vmemmap_remap_range(reuse, end, &walk);
}
mmap_read_unlock(&init_mm);
free_vmemmap_page_list(&vmemmap_pages);
return ret;
}
static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
gfp_t gfp_mask, struct list_head *list)
{
unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
int nid = page_to_nid((struct page *)start);
struct page *page, *next;
while (nr_pages--) {
page = alloc_pages_node(nid, gfp_mask, 0);
if (!page)
goto out;
list_add_tail(&page->lru, list);
}
return 0;
out:
list_for_each_entry_safe(page, next, list, lru)
__free_pages(page, 0);
return -ENOMEM;
}
/**
* vmemmap_remap_alloc - remap the vmemmap virtual address range [@start, end)
* to the page which is from the @vmemmap_pages
* respectively.
* @start: start address of the vmemmap virtual address range that we want
* to remap.
* @end: end address of the vmemmap virtual address range that we want to
* remap.
* @reuse: reuse address.
* @gfp_mask: GFP flag for allocating vmemmap pages.
*
* Return: %0 on success, negative error code otherwise.
*/
int vmemmap_remap_alloc(unsigned long start, unsigned long end,
unsigned long reuse, gfp_t gfp_mask)
{
LIST_HEAD(vmemmap_pages);
struct vmemmap_remap_walk walk = {
.remap_pte = vmemmap_restore_pte,
.reuse_addr = reuse,
.vmemmap_pages = &vmemmap_pages,
};
/* See the comment in the vmemmap_remap_free(). */
BUG_ON(start - reuse != PAGE_SIZE);
if (alloc_vmemmap_page_list(start, end, gfp_mask, &vmemmap_pages))
return -ENOMEM;
mmap_read_lock(&init_mm);
vmemmap_remap_range(reuse, end, &walk);
mmap_read_unlock(&init_mm);
return 0;
}
#endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */
/*
* Allocate a block of memory to be used to back the virtual memory map