From mboxrd@z Thu Jan 1 00:00:00 1970 In-reply-to: <45DDF8F3.2020304@redhat.com> (message from Peter Staubach on Thu, 22 Feb 2007 15:11:31 -0500) Subject: Re: [PATCH] update ctime and mtime for mmaped write References: <45DC8A47.5050900@redhat.com> <45DC9581.4070909@redhat.com> <45DDD498.9050202@redhat.com> <45DDF8F3.2020304@redhat.com> Message-Id: From: Miklos Szeredi Date: Thu, 22 Feb 2007 21:43:29 +0100 Sender: owner-linux-mm@kvack.org Return-Path: To: staubach@redhat.com Cc: miklos@szeredi.hu, akpm@linux-foundation.org, hugh@veritas.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: > > Take this example: > > > > fd = open() > > addr = mmap(.., fd) > > write(fd, ...) > > close(fd) > > sleep(100) > > msync(addr,...) > > munmap(addr) > > > > The file times will be updated in write(), but with your patch, the > > bit in the mapping will also be set. > > > > Then in msync() the file times will be updated again, which is wrong, > > since the memory was _not_ modified through the mapping. > > This is correct. I have updated my proposed patch to include the clearing > of AS_MCTIME in the routine which updates the mtime field. That doesn't really help. Look at __generic_file_aio_write_nolock(). file_update_time() is called before the data is written, so after the last write, there will be nothing to clear the flag. And even if fixed this case by moving the file_update_time() call to the end of the function, there's no guarantee, that some filesystem won't do something exotic and call set_page_dirty() indenpendently of write(). Good luck auditing all the set_page_dirty() calls ;) Thanks, Miklos -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org