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 <bgef...@google.com> Acked-by: Hugh Dickins <hu...@google.com> 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(&mm->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
