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Commit cfda0526 authored by Mike Rapoport's avatar Mike Rapoport Committed by Linus Torvalds
Browse files

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: default avatarMike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: default avatarAndrea 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 26071ced

mm/shmem.c

+15 −7
Original line number Diff line number Diff line
@@ -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 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, 
	 * 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 @@ 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);
@@ -1711,6 +1714,11 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, 
		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