[PATCH v3 3/8] mm: userfaultfd: extract file size check out into a helper

Axel Rasmussen
2023-07-06T22:51:15Z

This code is already duplicated twice, and UFFDIO_POISON will do the
same check a third time. So, it's worth extracting into a helper to save
repetitive lines of code.

Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
---
mm/userfaultfd.c | 38 ++++++++++++++++++++------------------
1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index a2bf37ee276d..4244ca7ee903 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -45,6 +45,22 @@ struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm,
return dst_vma;
}

+/* Check if dst_addr is outside of file's size. Must be called with ptl held. */
+static bool mfill_file_over_size(struct vm_area_struct *dst_vma,
+ unsigned long dst_addr)
+{
+ struct inode *inode;
+ pgoff_t offset, max_off;
+
+ if (!dst_vma->vm_file)
+ return false;
+
+ inode = dst_vma->vm_file->f_inode;
+ offset = linear_page_index(dst_vma, dst_addr);
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ return offset >= max_off;
+}
+
/*
* Install PTEs, to map dst_addr (within dst_vma) to page.
*
@@ -64,8 +80,6 @@ int mfill_atomic_install_pte(pmd_t *dst_pmd,
bool page_in_cache = page_mapping(page);
spinlock_t *ptl;
struct folio *folio;
- struct inode *inode;
- pgoff_t offset, max_off;

_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
_dst_pte = pte_mkdirty(_dst_pte);
@@ -81,14 +95,9 @@ int mfill_atomic_install_pte(pmd_t *dst_pmd,
if (!dst_pte)
goto out;

- if (vma_is_shmem(dst_vma)) {
- /* serialize against truncate with the page table lock */
- inode = dst_vma->vm_file->f_inode;
- offset = linear_page_index(dst_vma, dst_addr);
- max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ if (mfill_file_over_size(dst_vma, dst_addr)) {
ret = -EFAULT;
- if (unlikely(offset >= max_off))
- goto out_unlock;
+ goto out_unlock;
}

ret = -EEXIST;
@@ -211,8 +220,6 @@ static int mfill_atomic_pte_zeropage(pmd_t *dst_pmd,
pte_t _dst_pte, *dst_pte;
spinlock_t *ptl;
int ret;
- pgoff_t offset, max_off;
- struct inode *inode;

_dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
dst_vma->vm_page_prot));
@@ -220,14 +227,9 @@ static int mfill_atomic_pte_zeropage(pmd_t *dst_pmd,
dst_pte = pte_offset_map_lock(dst_vma->vm_mm, dst_pmd, dst_addr, &ptl);
if (!dst_pte)
goto out;
- if (dst_vma->vm_file) {
- /* the shmem MAP_PRIVATE case requires checking the i_size */
- inode = dst_vma->vm_file->f_inode;
- offset = linear_page_index(dst_vma, dst_addr);
- max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ if (mfill_file_over_size(dst_vma, dst_addr)) {
ret = -EFAULT;
- if (unlikely(offset >= max_off))
- goto out_unlock;
+ goto out_unlock;
}
ret = -EEXIST;
if (!pte_none(ptep_get(dst_pte)))
--
2.41.0.255.g8b1d071c50-goog