On Wed, 17 Mar 2021, Brian Geffon wrote:
> This reverts commit cd544fd1dc9293c6702fab6effa63dac1cc67e99.
>
> As discussed in [1] this commit was a no-op because the mapping type was
> checked in vma_to_resize before move_vma is ever called. This meant that
> vm_ops->mremap() would never be called on such mappings. Furthermore,
> we've since expanded support of MREMAP_DONTUNMAP to non-anonymous
> mappings, and these special mappings are still protected by the existing
> check of !VM_DONTEXPAND and !VM_PFNMAP which will result in a -EFAULT.
One small fixup needed: -EFAULT was what the incorrect v2 gave, but
v3 issues -EINVAL like before, and I'm content with that difference.
>
> 1. https://lkml.org/lkml/2020/12/28/2340
>
> Signed-off-by: Brian Geffon
Acked-by: Hugh Dickins
Thanks Brian, I'm happy with this result.
> ---
> arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 2 +-
> fs/aio.c | 5 +
> include/linux/mm.h| 2 +-
> mm/mmap.c | 6 +-
> mm/mremap.c | 2 +-
> 5 files changed, 5 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> index e916646adc69..0daf2f1cf7a8 100644
> --- a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> +++ b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> @@ -1458,7 +1458,7 @@ static int pseudo_lock_dev_release(struct inode *inode,
> struct file *filp)
> return 0;
> }
>
> -static int pseudo_lock_dev_mremap(struct vm_area_struct *area, unsigned long
> flags)
> +static int pseudo_lock_dev_mremap(struct vm_area_struct *area)
> {
> /* Not supported */
> return -EINVAL;
> diff --git a/fs/aio.c b/fs/aio.c
> index 1f32da13d39e..76ce0cc3ee4e 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -323,16 +323,13 @@ static void aio_free_ring(struct kioctx *ctx)
> }
> }
>
> -static int aio_ring_mremap(struct vm_area_struct *vma, unsigned long flags)
> +static int aio_ring_mremap(struct vm_area_struct *vma)
> {
> struct file *file = vma->vm_file;
> struct mm_struct *mm = vma->vm_mm;
> struct kioctx_table *table;
> int i, res = -EINVAL;
>
> - if (flags & MREMAP_DONTUNMAP)
> - return -EINVAL;
> -
> spin_lock(>ioctx_lock);
> rcu_read_lock();
> table = rcu_dereference(mm->ioctx_table);
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 77e64e3eac80..8c3729eb3e38 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -570,7 +570,7 @@ struct vm_operations_struct {
> void (*close)(struct vm_area_struct * area);
> /* Called any time before splitting to check if it's allowed */
> int (*may_split)(struct vm_area_struct *area, unsigned long addr);
> - int (*mremap)(struct vm_area_struct *area, unsigned long flags);
> + int (*mremap)(struct vm_area_struct *area);
> /*
>* Called by mprotect() to make driver-specific permission
>* checks before mprotect() is finalised. The VMA must not
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 3f287599a7a3..9d7651e4e1fe 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -3403,14 +3403,10 @@ static const char *special_mapping_name(struct
> vm_area_struct *vma)
> return ((struct vm_special_mapping *)vma->vm_private_data)->name;
> }
>
> -static int special_mapping_mremap(struct vm_area_struct *new_vma,
> - unsigned long flags)
> +static int special_mapping_mremap(struct vm_area_struct *new_vma)
> {
> struct vm_special_mapping *sm = new_vma->vm_private_data;
>
> - if (flags & MREMAP_DONTUNMAP)
> - return -EINVAL;
> -
> if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))
> return -EFAULT;
>
> diff --git a/mm/mremap.c b/mm/mremap.c
> index db5b8b28c2dd..d22629ff8f3c 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -545,7 +545,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
> if (moved_len < old_len) {
> err = -ENOMEM;
> } else if (vma->vm_ops && vma->vm_ops->mremap) {
> - err = vma->vm_ops->mremap(new_vma, flags);
> + err = vma->vm_ops->mremap(new_vma);
> }
>
> if (unlikely(err)) {
> --
> 2.31.0.rc2.261.g7f71774620-goog
