On 07/13/2017 12:11 PM, Vlastimil Babka wrote: > [+CC linux-api] > > On 07/13/2017 05:58 PM, Mike Kravetz wrote: >> mremap will create a 'duplicate' mapping if old_size == 0 is >> specified. Such duplicate mappings make no sense for private >> mappings. If duplication is attempted for a private mapping, >> mremap creates a separate private mapping unrelated to the >> original mapping and makes no modifications to the original. >> This is contrary to the purpose of mremap which should return >> a mapping which is in some way related to the original. >> >> Therefore, return EINVAL in the case where if an attempt is >> made to duplicate a private mapping. >> >> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > > Acked-by: Vlastimil Babka <vbabka@xxxxxxx> After considering Michal's concerns with follow on patch, it appears this patch provides the most desired behavior. Any other concerns or issues with this patch? If this moves forward, I will create man page updates to describe the mremap(old_size == 0) behavior. -- Mike Kravetz > >> --- >> mm/mremap.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/mm/mremap.c b/mm/mremap.c >> index cd8a1b1..076f506 100644 >> --- a/mm/mremap.c >> +++ b/mm/mremap.c >> @@ -383,6 +383,13 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr, >> if (!vma || vma->vm_start > addr) >> return ERR_PTR(-EFAULT); >> >> + /* >> + * !old_len is a special case where a mapping is 'duplicated'. >> + * Do not allow this for private mappings. >> + */ >> + if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) >> + return ERR_PTR(-EINVAL); >> + >> if (is_vm_hugetlb_page(vma)) >> return ERR_PTR(-EINVAL); >> >> > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
