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userfaultfd: shmem: add shmem_mfill_zeropage_pte for userfaultfd support 

shmem_mfill_zeropage_pte is the low level routine that implements the
userfaultfd UFFDIO_ZEROPAGE command.  Since for shmem mappings zero
pages are always allocated and accounted, the new method is a slight
extension of the existing shmem_mcopy_atomic_pte.

Link: http://lkml.kernel.org/r/1497939652-16528-4-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mike Rapoport 2017-09-06 16:23:02 -07:00 committed by Linus Torvalds
parent 0f07969456
commit 8d10396342
2 changed files with 50 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/shmem_fs.h
View File

@ -137,9 +137,15 @@ extern int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
unsigned long dst_addr,
unsigned long src_addr,
struct page **pagep);
extern int shmem_mfill_zeropage_pte(struct mm_struct *dst_mm,
pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
unsigned long dst_addr);
#else
#define shmem_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, dst_addr, \
src_addr, pagep) ({ BUG(); 0; })
#define shmem_mfill_zeropage_pte(dst_mm, dst_pmd, dst_vma, \
dst_addr) ({ BUG(); 0; })
#endif
#endif

60
mm/shmem.c
View File

@ -2207,12 +2207,13 @@ bool shmem_mapping(struct address_space *mapping)
return mapping->a_ops == &shmem_aops;
}
int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm,
pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
struct page **pagep)
static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
bool zeropage,
struct page **pagep)
{
struct inode *inode = file_inode(dst_vma->vm_file);
struct shmem_inode_info *info = SHMEM_I(inode);
@ -2235,17 +2236,22 @@ int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm,
if (!page)
goto out_unacct_blocks;
page_kaddr = kmap_atomic(page);
ret = copy_from_user(page_kaddr, (const void __user *)src_addr,
PAGE_SIZE);
kunmap_atomic(page_kaddr);
if (!zeropage) { /* mcopy_atomic */
page_kaddr = kmap_atomic(page);
ret = copy_from_user(page_kaddr,
(const void __user *)src_addr,
PAGE_SIZE);
kunmap_atomic(page_kaddr);
/* fallback to copy_from_user outside mmap_sem */
if (unlikely(ret)) {
*pagep = page;
shmem_inode_unacct_blocks(inode, 1);
/* don't free the page */
return -EFAULT;
/* fallback to copy_from_user outside mmap_sem */
if (unlikely(ret)) {
*pagep = page;
shmem_inode_unacct_blocks(inode, 1);
/* don't free the page */
return -EFAULT;
}
} else { /* mfill_zeropage_atomic */
clear_highpage(page);
}
} else {
page = *pagep;
@ -2311,6 +2317,28 @@ out_unacct_blocks:
goto out;
}
int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm,
pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
struct page **pagep)
{
return shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
dst_addr, src_addr, false, pagep);
}
int shmem_mfill_zeropage_pte(struct mm_struct *dst_mm,
pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
unsigned long dst_addr)
{
struct page *page = NULL;
return shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
dst_addr, 0, true, &page);
}
#ifdef CONFIG_TMPFS
static const struct inode_operations shmem_symlink_inode_operations;
static const struct inode_operations shmem_short_symlink_operations;