On Wed, Apr 09, 2014 at 10:55:29PM +0200, Jan Kara wrote: > > In addition to writing back dirty pages, filemap_write_and_wait_range() > > will evict clean pages. Unintuitive, I know, but it matches what the > > direct I/O path does. Plus, if we fall back to buffered I/O for holes > > (see above), then this will do the right thing at that time. > Ugh, I'm pretty certain filemap_write_and_wait_range() doesn't evict > anything ;). Direct IO path calls that function so that direct IO read > after buffered write returns the written data. In that case we don't evict > anything from page cache because direct IO read doesn't invalidate any > information we have cached. Only direct IO write does that and for that we > call invalidate_inode_pages2_range() after writing the pages. So I maintain > that what you do doesn't make sense to me. You might need to do some > invalidation of hole pages. But note that generic_file_direct_write() does > that for you and even though that isn't serialized in any way with page > faults which can instantiate the hole pages again, things should work out > fine for you since that function also invalidates the range again after > ->direct_IO callback is done. So AFAICT you don't have to do anything > except writing some nice comment about this ;). You're right. I'm not sure what I got confused with there. I don't think there's a race I need to worry about ... even if another page gets instantiated (consider one thread furiously loading from a hole as fast as it can while another thread does a write), we'll shoot it down again. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
