On Mon, 12 Apr 2021, Axel Rasmussen wrote:
Previously, we did a dance where we had one calling path in userfaultfd.c (mfill_atomic_pte), but then we split it into two in shmem_fs.h (shmem_{mcopy_atomic,mfill_zeropage}_pte), and then rejoined into a single shared function in shmem.c (shmem_mfill_atomic_pte).
This is all a bit overly complex. Just call the single combined shmem function directly, allowing us to clean up various branches, boilerplate, etc.
While we're touching this function, two other small cleanup changes:
- offset is equivalent to pgoff, so we can get rid of offset entirely.
- Split two VM_BUG_ON cases into two statements. This means the line number reported when the BUG is hit specifies exactly which condition was true.
Reviewed-by: Peter Xu peterx@redhat.com Signed-off-by: Axel Rasmussen axelrasmussen@google.com
Acked-by: Hugh Dickins hughd@google.com though you've dropped one minor fix I did like, see below...
include/linux/shmem_fs.h | 15 +++++------- mm/shmem.c | 52 +++++++++++++--------------------------- mm/userfaultfd.c | 10 +++----- 3 files changed, 25 insertions(+), 52 deletions(-)
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index d82b6f396588..919e36671fe6 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -122,21 +122,18 @@ static inline bool shmem_file(struct file *file) extern bool shmem_charge(struct inode *inode, long pages); extern void shmem_uncharge(struct inode *inode, long pages); +#ifdef CONFIG_USERFAULTFD #ifdef CONFIG_SHMEM extern 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,
bool zeropage, 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 +#else /* !CONFIG_SHMEM */ #define shmem_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, dst_addr, \
In a previous version, you quietly corrected that "dst_pte" to "dst_pmd": of course it makes no difference to the code generated, but it was a good correction, helping to prevent confusion.
src_addr, pagep) ({ BUG(); 0; })-#define shmem_mfill_zeropage_pte(dst_mm, dst_pmd, dst_vma, \
dst_addr) ({ BUG(); 0; })-#endif
src_addr, zeropage, pagep) ({ BUG(); 0; })+#endif /* CONFIG_SHMEM */ +#endif /* CONFIG_USERFAULTFD */ #endif diff --git a/mm/shmem.c b/mm/shmem.c index 26c76b13ad23..b72c55aa07fc 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2354,13 +2354,14 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode return inode; } -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)+#ifdef CONFIG_USERFAULTFD +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,bool zeropage,struct page **pagep){ struct inode *inode = file_inode(dst_vma->vm_file); struct shmem_inode_info *info = SHMEM_I(inode); @@ -2372,7 +2373,7 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, struct page *page; pte_t _dst_pte, *dst_pte; int ret;
- pgoff_t offset, max_off;
- pgoff_t max_off;
ret = -ENOMEM; if (!shmem_inode_acct_block(inode, 1)) @@ -2383,7 +2384,7 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, if (!page) goto out_unacct_blocks;
if (!zeropage) { /* mcopy_atomic */
if (!zeropage) { /* COPY */ page_kaddr = kmap_atomic(page); ret = copy_from_user(page_kaddr, (const void __user *)src_addr,@@ -2397,7 +2398,7 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, /* don't free the page */ return -ENOENT; }
} else { /* mfill_zeropage_atomic */
} else { /* ZEROPAGE */ clear_highpage(page);@@ -2405,15 +2406,15 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, *pagep = NULL; }
- VM_BUG_ON(PageLocked(page) || PageSwapBacked(page));
- VM_BUG_ON(PageLocked(page));
- VM_BUG_ON(PageSwapBacked(page)); __SetPageLocked(page); __SetPageSwapBacked(page); __SetPageUptodate(page);
ret = -EFAULT;
- offset = linear_page_index(dst_vma, dst_addr); max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
- if (unlikely(offset >= max_off))
- if (unlikely(pgoff >= max_off)) goto out_release;
ret = shmem_add_to_page_cache(page, mapping, pgoff, NULL, @@ -2439,7 +2440,7 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, ret = -EFAULT; max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
- if (unlikely(offset >= max_off))
- if (unlikely(pgoff >= max_off)) goto out_release_unlock;
ret = -EEXIST; @@ -2476,28 +2477,7 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, shmem_inode_unacct_blocks(inode, 1); 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);-} +#endif /* CONFIG_USERFAULTFD */ #ifdef CONFIG_TMPFS static const struct inode_operations shmem_symlink_inode_operations; diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e14b3820c6a8..23fa2583bbd1 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -440,13 +440,9 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm, dst_vma, dst_addr); } else { VM_WARN_ON_ONCE(wp_copy);
if (!zeropage)err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd,dst_vma, dst_addr,src_addr, page);elseerr = shmem_mfill_zeropage_pte(dst_mm, dst_pmd,dst_vma, dst_addr);
err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,dst_addr, src_addr, zeropage,page);return err; -- 2.31.1.295.g9ea45b61b8-goog