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.
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
---
include/linux/shmem_fs.h | 6 +++++
mm/shmem.c | 62 +++++++++++++++++++++++++++++++++++-------------
2 files changed, 51 insertions(+), 17 deletions(-)
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index a7d6bd2..b6c3540 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -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
diff --git a/mm/shmem.c b/mm/shmem.c
index a92e3d7..e775a49 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2197,12 +2197,13 @@ 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);
@@ -2225,17 +2226,22 @@ 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);
-
- /* 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;
+ 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;
+ }
+ } else { /* mfill_zeropage_atomic */
+ clear_highpage(page);
}
} else {
page = *pagep;
@@ -2301,6 +2307,28 @@ int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm,
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;
--
2.7.4
--
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