On Tue, Sep 01, 2015 at 01:54:26PM +0300, Boaz Harrosh wrote: > On 09/01/2015 01:22 PM, Kirill A. Shutemov wrote: > > For VM_PFNMAP and VM_MIXEDMAP we use vm_ops->pfn_mkwrite instead of > > vm_ops->page_mkwrite to notify abort write access. This means we want > > vma->vm_page_prot to be write-protected if the VMA provides this vm_ops. > > > > Hi Kirill > > I will test with this right away and ACK on this. > > Hmm so are you saying we might be missing some buffer modifications right now. > > What would be a theoretical scenario that will cause these missed events? On writable mapping with vm_ops->pfn_mkwrite, but without vm_ops->page_mkwrite: read fault followed by write access to the pfn. Writable pte will be set up on read fault and write fault will not be generated. I found it examining Dave's complain on generic/080: http://lkml.kernel.org/g/20150831233803.GO3902@dastard Although I don't think it's the reason. > I would like to put a test in our test rigs that should fail today and this > patch fixes. > > [In our system every modified pmem block is also RDMAed to a remote > pmem for HA, a missed modification will make the two copies unsynced] It shouldn't be a problem for ext2/ext4 as they provide both pfn_mkwrite and page_mkwrite. -- Kirill A. Shutemov -- 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>