Re: [PATCH] mm: get_user_pages(write,force) refuse to COW in shared areas

2014-04-25 Thread Oleg Nesterov
On 04/24, Hugh Dickins wrote: On Thu, 24 Apr 2014, Oleg Nesterov wrote: So, what do you think about the patch below? It is probably fine in any case, but is there any strong reason to follow the gup's behaviour and forbid the anon page in VM_MAYSHARE !VM_MAYWRITE vma? I don't

Re: [PATCH] mm: get_user_pages(write,force) refuse to COW in shared areas

2014-04-25 Thread Hugh Dickins
On Fri, 25 Apr 2014, Oleg Nesterov wrote: And I forgot to mention, there is another reason why I would like to change uprobes to follow the same convention. I still think it would be better to kill __replace_page() and use gup(FOLL_WRITE | FORCE) in uprobe_write_opcode(). Oh, please please

Re: [PATCH] mm: get_user_pages(write,force) refuse to COW in shared areas

2014-04-24 Thread Oleg Nesterov
Hi Hugh, Sorry for late reply. First of all, to avoid the confusion, I think the patch is fine. When I saw this patch I decided that uprobes should be updated accordingly, but I just realized that I do not understand what should I write in the changelog. On 04/04, Hugh Dickins wrote: +

Re: [PATCH] mm: get_user_pages(write,force) refuse to COW in shared areas

2014-04-24 Thread Hugh Dickins
On Thu, 24 Apr 2014, Oleg Nesterov wrote: Hi Hugh, Sorry for late reply. First of all, to avoid the confusion, I think the patch is fine. When I saw this patch I decided that uprobes should be updated accordingly, but I just realized that I do not understand what should I write in the

[PATCH] mm: get_user_pages(write,force) refuse to COW in shared areas

2014-04-04 Thread Hugh Dickins
get_user_pages(write=1, force=1) has always had odd behaviour on write- protected shared mappings: although it demands FMODE_WRITE-access to the underlying object (do_mmap_pgoff sets neither VM_SHARED nor VM_MAYWRITE without that), it ends up with do_wp_page substituting private anonymous

Re: [PATCH] mm: get_user_pages(write,force) refuse to COW in shared areas

2014-04-04 Thread Kirill A. Shutemov
On Fri, Apr 04, 2014 at 01:28:22AM -0700, Hugh Dickins wrote: get_user_pages(write=1, force=1) has always had odd behaviour on write- protected shared mappings: although it demands FMODE_WRITE-access to the underlying object (do_mmap_pgoff sets neither VM_SHARED nor VM_MAYWRITE without that),

Re: [PATCH] mm: get_user_pages(write,force) refuse to COW in shared areas

2014-04-04 Thread Hugh Dickins
On Fri, 4 Apr 2014, Kirill A. Shutemov wrote: There's comment in do_wp_page() which is not true anymore with patch applied. It should be fixed. The * Only catch write-faults on shared writable pages, * read-only shared pages can get COWed by * get_user_pages(.write=1, .force=1). Yes,