On 17 Mar 2017, at 15:19, Konstantin Belousov <kostikbel_at_gmail.com> wrote: > > On Fri, Mar 17, 2017 at 01:53:46PM +0000, Rick Macklem wrote: >> Well, I don't mind adding ncl_flush(), but it shouldn't be >> necessary. I actually had it in the first >> rendition of the patch, but took it out because it should happen >> on the VOP_CLOSE() if any writing to the buffer cache happened >> and that code hasn't changed in many years. > Dirty pages are flushed by writes, so if we have a set of dirty pages and > async vm_object_page_clean() is called on the vnode' vm_object, we get > a bunch of delayed-write AKA dirty buffers. This is possible even after > VOP_CLOSE() was done, e.g. by syncer performing regular run involving > vfs_msync(). > > I agree that the patch would not create new dirty buffers, but it is possible > to get them by other means. > >> >> What the patch was missing was updating n_mtime after the dirty >> page flush. >> >> Btw, a flush without OBJPC_SYNC happens when the file is VOP_CLOSE()'d >> unless the default value of vfs.nfs.clean_[ages_on_close is changed, which >> I think is why the 1sec resolution always seemed to work, at least for the >> example where there was an munmap before close. >> >> Attached is an updated version with that in it, rick FWIW, Rick's patch seems to do the trick, both for my test case and lld itself. And even with vfs.timestamp_precision=3 on both server and client. -Dimitry
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