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[Qemu-devel] [PATCH 07/21] userfaultfd: call handle_userfault() for user
From: |
Andrea Arcangeli |
Subject: |
[Qemu-devel] [PATCH 07/21] userfaultfd: call handle_userfault() for userfaultfd_missing() faults |
Date: |
Thu, 5 Mar 2015 18:17:50 +0100 |
This is where the page faults must be modified to call
handle_userfault() if userfaultfd_missing() is true (so if the
vma->vm_flags had VM_UFFD_MISSING set).
handle_userfault() then takes care of blocking the page fault and
delivering it to userland.
The fault flags must also be passed as parameter so the "read|write"
kind of fault can be passed to userland.
Signed-off-by: Andrea Arcangeli <address@hidden>
---
mm/huge_memory.c | 68 ++++++++++++++++++++++++++++++++++++++------------------
mm/memory.c | 16 +++++++++++++
2 files changed, 62 insertions(+), 22 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f0207cf..5374132 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -23,6 +23,7 @@
#include <linux/pagemap.h>
#include <linux/migrate.h>
#include <linux/hashtable.h>
+#include <linux/userfaultfd_k.h>
#include <asm/tlb.h>
#include <asm/pgalloc.h>
@@ -708,7 +709,7 @@ static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t
prot)
static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long haddr, pmd_t *pmd,
- struct page *page)
+ struct page *page, unsigned int flags)
{
struct mem_cgroup *memcg;
pgtable_t pgtable;
@@ -716,12 +717,16 @@ static int __do_huge_pmd_anonymous_page(struct mm_struct
*mm,
VM_BUG_ON_PAGE(!PageCompound(page), page);
- if (mem_cgroup_try_charge(page, mm, GFP_TRANSHUGE, &memcg))
- return VM_FAULT_OOM;
+ if (mem_cgroup_try_charge(page, mm, GFP_TRANSHUGE, &memcg)) {
+ put_page(page);
+ count_vm_event(THP_FAULT_FALLBACK);
+ return VM_FAULT_FALLBACK;
+ }
pgtable = pte_alloc_one(mm, haddr);
if (unlikely(!pgtable)) {
mem_cgroup_cancel_charge(page, memcg);
+ put_page(page);
return VM_FAULT_OOM;
}
@@ -741,6 +746,21 @@ static int __do_huge_pmd_anonymous_page(struct mm_struct
*mm,
pte_free(mm, pgtable);
} else {
pmd_t entry;
+
+ /* Deliver the page fault to userland */
+ if (userfaultfd_missing(vma)) {
+ int ret;
+
+ spin_unlock(ptl);
+ mem_cgroup_cancel_charge(page, memcg);
+ put_page(page);
+ pte_free(mm, pgtable);
+ ret = handle_userfault(vma, haddr, flags,
+ VM_UFFD_MISSING);
+ VM_BUG_ON(ret & VM_FAULT_FALLBACK);
+ return ret;
+ }
+
entry = mk_huge_pmd(page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
page_add_new_anon_rmap(page, vma, haddr);
@@ -751,6 +771,7 @@ static int __do_huge_pmd_anonymous_page(struct mm_struct
*mm,
add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
atomic_long_inc(&mm->nr_ptes);
spin_unlock(ptl);
+ count_vm_event(THP_FAULT_ALLOC);
}
return 0;
@@ -762,19 +783,16 @@ static inline gfp_t alloc_hugepage_gfpmask(int defrag,
gfp_t extra_gfp)
}
/* Caller must hold page table lock. */
-static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
+static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
struct page *zero_page)
{
pmd_t entry;
- if (!pmd_none(*pmd))
- return false;
entry = mk_pmd(zero_page, vma->vm_page_prot);
entry = pmd_mkhuge(entry);
pgtable_trans_huge_deposit(mm, pmd, pgtable);
set_pmd_at(mm, haddr, pmd, entry);
atomic_long_inc(&mm->nr_ptes);
- return true;
}
int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct
*vma,
@@ -797,6 +815,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct
vm_area_struct *vma,
pgtable_t pgtable;
struct page *zero_page;
bool set;
+ int ret;
pgtable = pte_alloc_one(mm, haddr);
if (unlikely(!pgtable))
return VM_FAULT_OOM;
@@ -807,14 +826,28 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm,
struct vm_area_struct *vma,
return VM_FAULT_FALLBACK;
}
ptl = pmd_lock(mm, pmd);
- set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
- zero_page);
- spin_unlock(ptl);
+ ret = 0;
+ set = false;
+ if (pmd_none(*pmd)) {
+ if (userfaultfd_missing(vma)) {
+ spin_unlock(ptl);
+ ret = handle_userfault(vma, haddr, flags,
+ VM_UFFD_MISSING);
+ VM_BUG_ON(ret & VM_FAULT_FALLBACK);
+ } else {
+ set_huge_zero_page(pgtable, mm, vma,
+ haddr, pmd,
+ zero_page);
+ spin_unlock(ptl);
+ set = true;
+ }
+ } else
+ spin_unlock(ptl);
if (!set) {
pte_free(mm, pgtable);
put_huge_zero_page();
}
- return 0;
+ return ret;
}
gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
@@ -822,14 +855,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm,
struct vm_area_struct *vma,
count_vm_event(THP_FAULT_FALLBACK);
return VM_FAULT_FALLBACK;
}
- if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page))) {
- put_page(page);
- count_vm_event(THP_FAULT_FALLBACK);
- return VM_FAULT_FALLBACK;
- }
-
- count_vm_event(THP_FAULT_ALLOC);
- return 0;
+ return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page, flags);
}
int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
@@ -864,16 +890,14 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct
mm_struct *src_mm,
*/
if (is_huge_zero_pmd(pmd)) {
struct page *zero_page;
- bool set;
/*
* get_huge_zero_page() will never allocate a new page here,
* since we already have a zero page to copy. It just takes a
* reference.
*/
zero_page = get_huge_zero_page();
- set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
+ set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
zero_page);
- BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
ret = 0;
goto out_unlock;
}
diff --git a/mm/memory.c b/mm/memory.c
index 8068893..0ae719c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -61,6 +61,7 @@
#include <linux/string.h>
#include <linux/dma-debug.h>
#include <linux/debugfs.h>
+#include <linux/userfaultfd_k.h>
#include <asm/io.h>
#include <asm/pgalloc.h>
@@ -2585,6 +2586,12 @@ static int do_anonymous_page(struct mm_struct *mm,
struct vm_area_struct *vma,
page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
if (!pte_none(*page_table))
goto unlock;
+ /* Deliver the page fault to userland, check inside PT lock */
+ if (userfaultfd_missing(vma)) {
+ pte_unmap_unlock(page_table, ptl);
+ return handle_userfault(vma, address, flags,
+ VM_UFFD_MISSING);
+ }
goto setpte;
}
@@ -2612,6 +2619,15 @@ static int do_anonymous_page(struct mm_struct *mm,
struct vm_area_struct *vma,
if (!pte_none(*page_table))
goto release;
+ /* Deliver the page fault to userland, check inside PT lock */
+ if (userfaultfd_missing(vma)) {
+ pte_unmap_unlock(page_table, ptl);
+ mem_cgroup_cancel_charge(page, memcg);
+ page_cache_release(page);
+ return handle_userfault(vma, address, flags,
+ VM_UFFD_MISSING);
+ }
+
inc_mm_counter_fast(mm, MM_ANONPAGES);
page_add_new_anon_rmap(page, vma, address);
mem_cgroup_commit_charge(page, memcg, false);
- [Qemu-devel] [PATCH 06/21] userfaultfd: add VM_UFFD_MISSING and VM_UFFD_WP, (continued)
- [Qemu-devel] [PATCH 06/21] userfaultfd: add VM_UFFD_MISSING and VM_UFFD_WP, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 16/21] userfaultfd: remap_pages: rmap preparation, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 17/21] userfaultfd: remap_pages: swp_entry_swapcount() preparation, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 12/21] userfaultfd: activate syscall, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 11/21] userfaultfd: buildsystem activation, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 08/21] userfaultfd: teach vma_merge to merge across vma->vm_userfaultfd_ctx, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 01/21] userfaultfd: waitqueue: add nr wake parameter to __wake_up_locked_key, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 13/21] userfaultfd: UFFDIO_COPY|UFFDIO_ZEROPAGE uAPI, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 15/21] userfaultfd: UFFDIO_COPY and UFFDIO_ZEROPAGE, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 20/21] userfaultfd: UFFDIO_REMAP, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 07/21] userfaultfd: call handle_userfault() for userfaultfd_missing() faults,
Andrea Arcangeli <=
- [Qemu-devel] [PATCH 10/21] userfaultfd: add new syscall to provide memory externalization, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 21/21] userfaultfd: add userfaultfd_wp mm helpers, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 19/21] userfaultfd: remap_pages: UFFDIO_REMAP preparation, Andrea Arcangeli, 2015/03/05
- Re: [Qemu-devel] [PATCH 19/21] userfaultfd: remap_pages: UFFDIO_REMAP preparation, Pavel Emelyanov, 2015/03/05
- [Qemu-devel] [PATCH 04/21] userfaultfd: linux/userfaultfd_k.h, Andrea Arcangeli, 2015/03/05