From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <45DE01FB.2010204@redhat.com> Date: Thu, 22 Feb 2007 15:50:03 -0500 From: Peter Staubach MIME-Version: 1.0 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> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Miklos Szeredi Cc: akpm@linux-foundation.org, hugh@veritas.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: Miklos Szeredi wrote: >>> 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 ;) Interesting. No, I wouldn't want to get into worrying about set_page_dirty() calls. Life is short and people have too much imagination... :-) Thanx... ps -- 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