From cfda05267f7bd02b5ae5ac6a37fbbdf3b9c41b57 Mon Sep 17 00:00:00 2001
From: Mike Rapoport <rppt@linux.vnet.ibm.com>
Date: Wed, 22 Feb 2017 15:43:37 -0800
Subject: [PATCH] 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.
Link: http://lkml.kernel.org/r/20161216144821.5183-33-aarcange@redhat.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/shmem.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 26c332c84e14b..ab6644194fee8 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -72,6 +72,7 @@ static struct vfsmount *shm_mnt;
#include <linux/syscalls.h>
#include <linux/fcntl.h>
#include <uapi/linux/memfd.h>
+#include <linux/userfaultfd_k.h>
#include <linux/rmap.h>
#include <linux/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)
@@ -1578,7 +1580,7 @@ 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 = SHMEM_I(inode);
@@ -1632,7 +1634,7 @@ repeat:
* bring it back from swap or allocate.
*/
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.. */
@@ -1642,7 +1644,8 @@ repeat:
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);
@@ -1711,6 +1714,11 @@ repeat:
swap_free(swap);
} else {
+ if (vma && userfaultfd_missing(vma)) {
+ *fault_type = handle_userfault(vmf, VM_UFFD_MISSING);
+ return 0;
+ }
+
/* shmem_symlink() */
if (mapping->a_ops != &shmem_aops)
goto alloc_nohuge;
@@ -1973,7 +1981,7 @@ 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;
@@ -4254,7 +4262,7 @@ 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
--
2.30.2