On Dec 30, 2015 4:24 AM, "Martin Uecker" <muecker@xxxxxxx> wrote: > > > > Hi all, > > I want to reliably detect changes to a file even when > written to using mmap. Surprisingly, there seems to be > no API which would make this possible. Or at least I > haven't found a way to do it... > > > I looked at: > > - mtime. What is missing here is an API which would > force mtime to be updated if there are dirty PTEs > in some mapping (which need to be cleared/transferred > to struct page at this point). This would allow to > reliably detect changes to the file. If I understand it > correctly, there was patch from Andy Lutomirski which > made msync(ASYNC) do exactly this: > > http://oss.sgi.com/archives/xfs/2013-08/msg00748.html > > But it seems this never got in. The other problem with > this is that mtime has limited granularity. > (but maybe that could be worked around by having some > kind of counter + API which tells how often mtime has > been updated without changing its nominal value) Those patches plus nanosecond granularity should do it, I think. I keep meaning to dust them off. You could do it :) --Andy -- 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>