> > This patch makes writing to shared memory mappings update st_ctime and > > st_mtime as defined by SUSv3: > > Boy this is complicated.
You tell me? > Is there a simpler way of doing all this? Say, we define a new page flag > PG_dirtiedbywrite and we do SetPageDirtiedByWrite() inside write() and > ClearPageDirtiedByWrite() whenever we propagate pte-dirtiness into > page-dirtiness. Then, when performing writeback we look to see if any of > the dirty pages are !PageDirtiedByWrite() and, if so, we update [mc]time to > current-time. I don't think a page flag gains anything over the address_space flag that this patch already has. The complexity is not about keeping track of the "data modified through mmap" state, but about msync() guarantees, that POSIX wants. And these requirements do in fact make some sense: msync() basically means: "I want the data written through mmaps to be visible to the world" And that obviously includes updating the timestamps. So how do we know if the data was modified between two msync() invocations? The only sane way I can think of is to walk the page tables in msync() and test/clear the pte dirty bit. Yes, this will make msync(MS_ASYNC) more heavyweight again. But if an application doesn't want to update the timestamps, it should just omit this call, since it does nothing else. There shouldn't be any other side effect. Miklos - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
