From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by wx-out-0506.google.com with SMTP id h31so502003wxd.11 for ; Thu, 10 Jan 2008 07:56:08 -0800 (PST) Message-ID: <4df4ef0c0801100756v2a536cc5xa80d9d1cfdae073a@mail.gmail.com> Date: Thu, 10 Jan 2008 18:56:07 +0300 From: "Anton Salikhmetov" Subject: Re: [PATCH][RFC][BUG] updating the ctime and mtime time stamps in msync() In-Reply-To: <20080110104543.398baf5c@bree.surriel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <1199728459.26463.11.camel@codedot> <20080109155015.4d2d4c1d@cuia.boston.redhat.com> <26932.1199912777@turing-police.cc.vt.edu> <20080109170633.292644dc@cuia.boston.redhat.com> <20080109223340.GH25527@unthought.net> <20080109184141.287189b8@bree.surriel.com> <4df4ef0c0801091603y2bf507e1q2b99971c6028d1f3@mail.gmail.com> <20080110085120.GK25527@unthought.net> <4df4ef0c0801100253m6c08e4a3t917959c030533f80@mail.gmail.com> <20080110104543.398baf5c@bree.surriel.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: Jakob Oestergaard , Valdis.Kletnieks@vt.edu, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: 2008/1/10, Rik van Riel : > On Thu, 10 Jan 2008 13:53:59 +0300 > "Anton Salikhmetov" wrote: > > > Indeed, if msync() is called with MS_SYNC an explicit sync is > > triggered, and Rik's suggestion would work. However, the POSIX > > standard requires a call to msync() with MS_ASYNC to update the > > st_ctime and st_mtime stamps too. No explicit sync of the inode data > > is triggered in the current implementation of msync(). Hence Rik's > > suggestion would fail to satisfy POSIX in the latter case. > > Since your patch is already changing msync(), has it occurred > to you that your patch could change msync() to do the right > thing? No, not quite. Peter Staubach mentioned an issue in my solution: >>> > The patch adds a call to the file_update_time() function to change > the file metadata before syncing. The patch also contains > substantial code cleanup: consolidated error check > for function parameters, using the PAGE_ALIGN() macro instead of > "manual" alignment check, improved readability of the loop, > which traverses the process memory regions, updated comments. > > These changes catch the simple case, where the file is mmap'd, modified via the mmap'd region, and then an msync is done, all on a mostly quiet system. However, I don't see how they will work if there has been something like a sync(2) done after the mmap'd region is modified and the msync call. When the inode is written out as part of the sync process, I_DIRTY_PAGES will be cleared, thus causing a miss in this code. The I_DIRTY_PAGES check here is good, but I think that there needs to be some code elsewhere too, to catch the case where I_DIRTY_PAGES is being cleared, but the time fields still need to be updated. <<< So I'm working on my next solution for this bug now. > > -- > All rights reversed. > -- 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