[PATCH 33/46] hugetlb: userfaultfd: add support for high-granularity UFFDIO_CONTINUE
From: James Houghton
Date: Thu Jan 05 2023 - 05:23:06 EST
Changes here are similar to the changes made for hugetlb_no_page.
Pass vmf->real_address to userfaultfd_huge_must_wait because
vmf->address may be rounded down to the hugepage size, and a
high-granularity page table walk would look up the wrong PTE. Also
change the call to userfaultfd_must_wait in the same way for
consistency.
This commit introduces hugetlb_alloc_largest_pte which is used to find
the appropriate PTE size to map pages with UFFDIO_CONTINUE.
When MADV_SPLIT is provided, page fault events will report
PAGE_SIZE-aligned address instead of huge_page_size(h)-aligned
addresses, regardless of if UFFD_FEATURE_EXACT_ADDRESS is used.
Signed-off-by: James Houghton <jthoughton@xxxxxxxxxx>
---
fs/userfaultfd.c | 14 +++----
include/linux/hugetlb.h | 18 ++++++++-
mm/hugetlb.c | 85 +++++++++++++++++++++++++++++++++--------
mm/userfaultfd.c | 40 +++++++++++--------
4 files changed, 119 insertions(+), 38 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 15a5bf765d43..940ff63096a9 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -252,17 +252,17 @@ static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
unsigned long flags,
unsigned long reason)
{
- pte_t *ptep, pte;
+ pte_t pte;
bool ret = true;
+ struct hugetlb_pte hpte;
mmap_assert_locked(ctx->mm);
- ptep = hugetlb_walk(vma, address, vma_mmu_pagesize(vma));
- if (!ptep)
+ if (hugetlb_full_walk(&hpte, vma, address))
goto out;
ret = false;
- pte = huge_ptep_get(ptep);
+ pte = huge_ptep_get(hpte.ptep);
/*
* Lockless access: we're in a wait_event so it's ok if it
@@ -531,11 +531,11 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
spin_unlock_irq(&ctx->fault_pending_wqh.lock);
if (!is_vm_hugetlb_page(vma))
- must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags,
- reason);
+ must_wait = userfaultfd_must_wait(ctx, vmf->real_address,
+ vmf->flags, reason);
else
must_wait = userfaultfd_huge_must_wait(ctx, vma,
- vmf->address,
+ vmf->real_address,
vmf->flags, reason);
if (is_vm_hugetlb_page(vma))
hugetlb_vma_unlock_read(vma);
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 8a664a9dd0a8..c8524ac49b24 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -224,7 +224,8 @@ unsigned long hugetlb_total_pages(void);
vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, unsigned int flags);
#ifdef CONFIG_USERFAULTFD
-int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, pte_t *dst_pte,
+int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
+ struct hugetlb_pte *dst_hpte,
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
@@ -1292,16 +1293,31 @@ static inline enum hugetlb_level hpage_size_to_level(unsigned long sz)
#ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
bool hugetlb_hgm_enabled(struct vm_area_struct *vma);
+bool hugetlb_hgm_advised(struct vm_area_struct *vma);
bool hugetlb_hgm_eligible(struct vm_area_struct *vma);
+int hugetlb_alloc_largest_pte(struct hugetlb_pte *hpte, struct mm_struct *mm,
+ struct vm_area_struct *vma, unsigned long start,
+ unsigned long end);
#else
static inline bool hugetlb_hgm_enabled(struct vm_area_struct *vma)
{
return false;
}
+static inline bool hugetlb_hgm_advised(struct vm_area_struct *vma)
+{
+ return false;
+}
static inline bool hugetlb_hgm_eligible(struct vm_area_struct *vma)
{
return false;
}
+static inline
+int hugetlb_alloc_largest_pte(struct hugetlb_pte *hpte, struct mm_struct *mm,
+ struct vm_area_struct *vma, unsigned long start,
+ unsigned long end)
+{
+ return -EINVAL;
+}
#endif
static inline spinlock_t *huge_pte_lock(struct hstate *h,
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 1eef6968b1fa..5af6db52f34e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5936,6 +5936,13 @@ static inline vm_fault_t hugetlb_handle_userfault(struct vm_area_struct *vma,
unsigned long addr,
unsigned long reason)
{
+ /*
+ * Don't use the hpage-aligned address if the user has explicitly
+ * enabled HGM.
+ */
+ if (hugetlb_hgm_advised(vma) && reason == VM_UFFD_MINOR)
+ haddr = address & PAGE_MASK;
+
u32 hash;
struct vm_fault vmf = {
.vma = vma,
@@ -6420,7 +6427,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
* modifications for huge pages.
*/
int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
- pte_t *dst_pte,
+ struct hugetlb_pte *dst_hpte,
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
@@ -6431,13 +6438,14 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
bool is_continue = (mode == MCOPY_ATOMIC_CONTINUE);
struct hstate *h = hstate_vma(dst_vma);
struct address_space *mapping = dst_vma->vm_file->f_mapping;
- pgoff_t idx = vma_hugecache_offset(h, dst_vma, dst_addr);
+ unsigned long haddr = dst_addr & huge_page_mask(h);
+ pgoff_t idx = vma_hugecache_offset(h, dst_vma, haddr);
unsigned long size;
int vm_shared = dst_vma->vm_flags & VM_SHARED;
pte_t _dst_pte;
spinlock_t *ptl;
int ret = -ENOMEM;
- struct page *page;
+ struct page *page, *subpage;
int writable;
bool page_in_pagecache = false;
@@ -6452,12 +6460,12 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
* a non-missing case. Return -EEXIST.
*/
if (vm_shared &&
- hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) {
+ hugetlbfs_pagecache_present(h, dst_vma, haddr)) {
ret = -EEXIST;
goto out;
}
- page = alloc_huge_page(dst_vma, dst_addr, 0);
+ page = alloc_huge_page(dst_vma, haddr, 0);
if (IS_ERR(page)) {
ret = -ENOMEM;
goto out;
@@ -6473,13 +6481,13 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
/* Free the allocated page which may have
* consumed a reservation.
*/
- restore_reserve_on_error(h, dst_vma, dst_addr, page);
+ restore_reserve_on_error(h, dst_vma, haddr, page);
put_page(page);
/* Allocate a temporary page to hold the copied
* contents.
*/
- page = alloc_huge_page_vma(h, dst_vma, dst_addr);
+ page = alloc_huge_page_vma(h, dst_vma, haddr);
if (!page) {
ret = -ENOMEM;
goto out;
@@ -6493,14 +6501,14 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
}
} else {
if (vm_shared &&
- hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) {
+ hugetlbfs_pagecache_present(h, dst_vma, haddr)) {
put_page(*pagep);
ret = -EEXIST;
*pagep = NULL;
goto out;
}
- page = alloc_huge_page(dst_vma, dst_addr, 0);
+ page = alloc_huge_page(dst_vma, haddr, 0);
if (IS_ERR(page)) {
put_page(*pagep);
ret = -ENOMEM;
@@ -6548,7 +6556,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
page_in_pagecache = true;
}
- ptl = huge_pte_lock(h, dst_mm, dst_pte);
+ ptl = hugetlb_pte_lock(dst_hpte);
ret = -EIO;
if (PageHWPoison(page))
@@ -6560,7 +6568,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
* page backing it, then access the page.
*/
ret = -EEXIST;
- if (!huge_pte_none_mostly(huge_ptep_get(dst_pte)))
+ if (!huge_pte_none_mostly(huge_ptep_get(dst_hpte->ptep)))
goto out_release_unlock;
if (page_in_pagecache)
@@ -6577,7 +6585,10 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
else
writable = dst_vma->vm_flags & VM_WRITE;
- _dst_pte = make_huge_pte(dst_vma, page, writable);
+ subpage = hugetlb_find_subpage(h, page, dst_addr);
+
+ _dst_pte = make_huge_pte_with_shift(dst_vma, subpage, writable,
+ dst_hpte->shift);
/*
* Always mark UFFDIO_COPY page dirty; note that this may not be
* extremely important for hugetlbfs for now since swapping is not
@@ -6590,12 +6601,12 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
if (wp_copy)
_dst_pte = huge_pte_mkuffd_wp(_dst_pte);
- set_huge_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
+ set_huge_pte_at(dst_mm, dst_addr, dst_hpte->ptep, _dst_pte);
- hugetlb_count_add(pages_per_huge_page(h), dst_mm);
+ hugetlb_count_add(hugetlb_pte_size(dst_hpte) / PAGE_SIZE, dst_mm);
/* No need to invalidate - it was non-present before */
- update_mmu_cache(dst_vma, dst_addr, dst_pte);
+ update_mmu_cache(dst_vma, dst_addr, dst_hpte->ptep);
spin_unlock(ptl);
if (!is_continue)
@@ -7780,6 +7791,18 @@ bool hugetlb_hgm_enabled(struct vm_area_struct *vma)
{
return vma && (vma->vm_flags & VM_HUGETLB_HGM);
}
+bool hugetlb_hgm_advised(struct vm_area_struct *vma)
+{
+ /*
+ * Right now, the only way for HGM to be enabled is if a user
+ * explicitly enables it via MADV_SPLIT, but in the future, there
+ * may be cases where it gets enabled automatically.
+ *
+ * Provide hugetlb_hgm_advised() now for call sites where care that the
+ * user explicitly enabled HGM.
+ */
+ return hugetlb_hgm_enabled(vma);
+}
/* Should only be used by the for_each_hgm_shift macro. */
static unsigned int __shift_for_hstate(struct hstate *h)
{
@@ -7798,6 +7821,38 @@ static unsigned int __shift_for_hstate(struct hstate *h)
(tmp_h) <= &hstates[hugetlb_max_hstate]; \
(tmp_h)++)
+/*
+ * Find the HugeTLB PTE that maps as much of [start, end) as possible with a
+ * single page table entry. It is returned in @hpte.
+ */
+int hugetlb_alloc_largest_pte(struct hugetlb_pte *hpte, struct mm_struct *mm,
+ struct vm_area_struct *vma, unsigned long start,
+ unsigned long end)
+{
+ struct hstate *h = hstate_vma(vma), *tmp_h;
+ unsigned int shift;
+ unsigned long sz;
+ int ret;
+
+ for_each_hgm_shift(h, tmp_h, shift) {
+ sz = 1UL << shift;
+
+ if (!IS_ALIGNED(start, sz) || start + sz > end)
+ continue;
+ goto found;
+ }
+ return -EINVAL;
+found:
+ ret = hugetlb_full_walk_alloc(hpte, vma, start, sz);
+ if (ret)
+ return ret;
+
+ if (hpte->shift > shift)
+ return -EEXIST;
+
+ return 0;
+}
+
#endif /* CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING */
/*
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 65ad172add27..2b233d31be24 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -320,14 +320,16 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
{
int vm_shared = dst_vma->vm_flags & VM_SHARED;
ssize_t err;
- pte_t *dst_pte;
unsigned long src_addr, dst_addr;
long copied;
struct page *page;
- unsigned long vma_hpagesize;
+ unsigned long vma_hpagesize, target_pagesize;
pgoff_t idx;
u32 hash;
struct address_space *mapping;
+ bool use_hgm = hugetlb_hgm_advised(dst_vma) &&
+ mode == MCOPY_ATOMIC_CONTINUE;
+ struct hstate *h = hstate_vma(dst_vma);
/*
* There is no default zero huge page for all huge page sizes as
@@ -345,12 +347,13 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
copied = 0;
page = NULL;
vma_hpagesize = vma_kernel_pagesize(dst_vma);
+ target_pagesize = use_hgm ? PAGE_SIZE : vma_hpagesize;
/*
- * Validate alignment based on huge page size
+ * Validate alignment based on the targeted page size.
*/
err = -EINVAL;
- if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
+ if (dst_start & (target_pagesize - 1) || len & (target_pagesize - 1))
goto out_unlock;
retry:
@@ -381,13 +384,14 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
}
while (src_addr < src_start + len) {
+ struct hugetlb_pte hpte;
BUG_ON(dst_addr >= dst_start + len);
/*
* Serialize via vma_lock and hugetlb_fault_mutex.
- * vma_lock ensures the dst_pte remains valid even
- * in the case of shared pmds. fault mutex prevents
- * races with other faulting threads.
+ * vma_lock ensures the hpte.ptep remains valid even
+ * in the case of shared pmds and page table collapsing.
+ * fault mutex prevents races with other faulting threads.
*/
idx = linear_page_index(dst_vma, dst_addr);
mapping = dst_vma->vm_file->f_mapping;
@@ -395,23 +399,28 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
mutex_lock(&hugetlb_fault_mutex_table[hash]);
hugetlb_vma_lock_read(dst_vma);
- err = -ENOMEM;
- dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize);
- if (!dst_pte) {
+ if (use_hgm)
+ err = hugetlb_alloc_largest_pte(&hpte, dst_mm, dst_vma,
+ dst_addr,
+ dst_start + len);
+ else
+ err = hugetlb_full_walk_alloc(&hpte, dst_vma, dst_addr,
+ vma_hpagesize);
+ if (err) {
hugetlb_vma_unlock_read(dst_vma);
mutex_unlock(&hugetlb_fault_mutex_table[hash]);
goto out_unlock;
}
if (mode != MCOPY_ATOMIC_CONTINUE &&
- !huge_pte_none_mostly(huge_ptep_get(dst_pte))) {
+ !huge_pte_none_mostly(huge_ptep_get(hpte.ptep))) {
err = -EEXIST;
hugetlb_vma_unlock_read(dst_vma);
mutex_unlock(&hugetlb_fault_mutex_table[hash]);
goto out_unlock;
}
- err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma,
+ err = hugetlb_mcopy_atomic_pte(dst_mm, &hpte, dst_vma,
dst_addr, src_addr, mode, &page,
wp_copy);
@@ -423,6 +432,7 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
if (unlikely(err == -ENOENT)) {
mmap_read_unlock(dst_mm);
BUG_ON(!page);
+ WARN_ON_ONCE(hpte.shift != huge_page_shift(h));
err = copy_huge_page_from_user(page,
(const void __user *)src_addr,
@@ -440,9 +450,9 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
BUG_ON(page);
if (!err) {
- dst_addr += vma_hpagesize;
- src_addr += vma_hpagesize;
- copied += vma_hpagesize;
+ dst_addr += hugetlb_pte_size(&hpte);
+ src_addr += hugetlb_pte_size(&hpte);
+ copied += hugetlb_pte_size(&hpte);
if (fatal_signal_pending(current))
err = -EINTR;
--
2.39.0.314.g84b9a713c41-goog