From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <45DC9581.4070909@redhat.com> Date: Wed, 21 Feb 2007 13:54:57 -0500 From: Peter Staubach MIME-Version: 1.0 Subject: Re: [PATCH] update ctime and mtime for mmaped write References: <45DC8A47.5050900@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: >>> Inspired by Peter Staubach's patch and the resulting comments. >>> >>> >>> >> An updated version of the original patch was submitted to LKML >> yesterday... :-) >> > > Strange coincidence :) > > >>> file = vma->vm_file; >>> start = vma->vm_end; >>> + mapping_update_time(file); >>> if ((flags & MS_SYNC) && file && >>> (vma->vm_flags & VM_SHARED)) { >>> get_file(file); >>> >>> >> It seems to me that this might lead to file times being updated for >> non-MAP_SHARED mappings. >> > > In theory no, because the COW-ed pages become anonymous and are not > part of the original mapping any more. > > I must profess to having a incomplete understanding of all of this support, but then why would it be necessary to test VM_SHARED at this point in msync()? I ran into problems early on with file times being updated incorrectly so I am a little sensitive this aspect. >>> +int set_page_dirty_mapping(struct page *page); >>> >>> >> This aspect of the design seems intrusive to me. I didn't see a strong >> reason to introduce new versions of many of the routines just to handle >> these semantics. What motivated this part of your design? Why the new >> _mapping versions of routines? >> > > Because there's no way to know inside the set_page_dirty() functions > if the dirtying comes from a memory mapping or from a modification > through a normal write(). And they have different semantics, for > write() the modification times are updated immediately. Perhaps I didn't understand what page_mapped() does, but it does seem to have the right semantics as far as I could see. 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