On 09/01/2015 02:10 PM, Kirill A. Shutemov wrote:
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
I found it examining Dave's complain on generic/080:
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
Ha right we have both as well, and so should xfs I think (because of the
zero pages thing, in fact any dax.c user should).
Thanks so this verifies why we could not see any such breakage.
ACK-by: Boaz Harrosh <boaz(a)plexistor.com>