On Fri, Nov 04, 2016 at 04:59:32PM +0800, Hillf Danton wrote:
> > @@ -1542,7 +1544,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
> > */
> > static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
> > struct page **pagep, enum sgp_type sgp, gfp_t gfp,
> > - struct mm_struct *fault_mm, int *fault_type)
> > + struct vm_area_struct *vma, struct vm_fault *vmf, int *fault_type)
> > {
> > struct address_space *mapping = inode->i_mapping;
> > struct shmem_inode_info *info;
> > @@ -1597,7 +1599,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
> > */
> > info = SHMEM_I(inode);
> > sbinfo = SHMEM_SB(inode->i_sb);
> > - charge_mm = fault_mm ? : current->mm;
> > + charge_mm = vma ? vma->vm_mm : current->mm;
> >
> > if (swap.val) {
> > /* Look it up and read it in.. */
> > @@ -1607,7 +1609,8 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
> > if (fault_type) {
> > *fault_type |= VM_FAULT_MAJOR;
> > count_vm_event(PGMAJFAULT);
> > - mem_cgroup_count_vm_event(fault_mm, PGMAJFAULT);
> > + mem_cgroup_count_vm_event(vma->vm_mm,
> > + PGMAJFAULT);
> Seems vma is not valid in some cases.
>
> > }
> > /* Here we actually start the io */
> > page = shmem_swapin(swap, gfp, info, index);
>
Below is the updated patch that uses charge_mm instead of vma which might
be not valid.
>From 98cd0ed3bb2692f83eeb4668aae136cec073dbc4 Mon Sep 17 00:00:00 2001
From: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Date: Thu, 4 Aug 2016 11:14:16 +0300
Subject: [PATCH v2] userfaultfd: shmem: add userfaultfd hook for shared memory
faults
When processing a page fault in shared memory area for not present page,
check the VMA determine if faults are to be handled by userfaultfd. If so,
delegate the page fault to handle_userfault.
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 34 +++++++++++++++++++++++++++-------
1 file changed, 27 insertions(+), 7 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index acf80c2..4f37244 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -72,6 +72,7 @@
#include <linux/syscalls.h>
#include <linux/fcntl.h>
#include <uapi/linux/memfd.h>
+#include <linux/userfaultfd_k.h>
#include <linux/rmap.h>
#include <asm/uaccess.h>
@@ -118,13 +119,14 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index);
static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
struct page **pagep, enum sgp_type sgp,
- gfp_t gfp, struct mm_struct *fault_mm, int *fault_type);
+ gfp_t gfp, struct vm_area_struct *vma,
+ struct vm_fault *vmf, int *fault_type);
int shmem_getpage(struct inode *inode, pgoff_t index,
struct page **pagep, enum sgp_type sgp)
{
return shmem_getpage_gfp(inode, index, pagep, sgp,
- mapping_gfp_mask(inode->i_mapping), NULL, NULL);
+ mapping_gfp_mask(inode->i_mapping), NULL, NULL, NULL);
}
static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
@@ -1542,7 +1544,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
*/
static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
struct page **pagep, enum sgp_type sgp, gfp_t gfp,
- struct mm_struct *fault_mm, int *fault_type)
+ struct vm_area_struct *vma, struct vm_fault *vmf, int *fault_type)
{
struct address_space *mapping = inode->i_mapping;
struct shmem_inode_info *info;
@@ -1597,7 +1599,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
*/
info = SHMEM_I(inode);
sbinfo = SHMEM_SB(inode->i_sb);
- charge_mm = fault_mm ? : current->mm;
+ charge_mm = vma ? vma->vm_mm : current->mm;
if (swap.val) {
/* Look it up and read it in.. */
@@ -1607,7 +1609,8 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
if (fault_type) {
*fault_type |= VM_FAULT_MAJOR;
count_vm_event(PGMAJFAULT);
- mem_cgroup_count_vm_event(fault_mm, PGMAJFAULT);
+ mem_cgroup_count_vm_event(charge_mm,
+ PGMAJFAULT);
}
/* Here we actually start the io */
page = shmem_swapin(swap, gfp, info, index);
@@ -1676,6 +1679,23 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
swap_free(swap);
} else {
+ if (vma && userfaultfd_missing(vma)) {
+ struct fault_env fe = {
+ .vma = vma,
+ .address = (unsigned long)vmf->virtual_address,
+ .flags = vmf->flags,
+ /*
+ * Hard to debug if it ends up being
+ * used by a callee that assumes
+ * something about the other
+ * uninitialized fields... same as in
+ * memory.c
+ */
+ };
+ *fault_type = handle_userfault(&fe, VM_UFFD_MISSING);
+ return 0;
+ }
+
/* shmem_symlink() */
if (mapping->a_ops != &shmem_aops)
goto alloc_nohuge;
@@ -1927,7 +1947,7 @@ static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
sgp = SGP_NOHUGE;
error = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
- gfp, vma->vm_mm, &ret);
+ gfp, vma, vmf, &ret);
if (error)
return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
return ret;
@@ -4212,7 +4232,7 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
BUG_ON(mapping->a_ops != &shmem_aops);
error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
- gfp, NULL, NULL);
+ gfp, NULL, NULL, NULL);
if (error)
page = ERR_PTR(error);
else
--
1.9.1
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