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Date: Fri, 18 Jan 2008 18:50:03 -0600 From: Matt Mackall <mpm@...enic.com> To: Rik van Riel <riel@...hat.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Ingo Oeser <ioe-lkml@...eria.de>, Miklos Szeredi <miklos@...redi.hu>, peterz@...radead.org, salikhmetov@...il.com, linux-mm@...ck.org, jakob@...hought.net, linux-kernel@...r.kernel.org, valdis.kletnieks@...edu, ksm@...dk, staubach@...hat.com, jesper.juhl@...il.com, akpm@...ux-foundation.org, protasnb@...il.com, r.e.wolff@...wizard.nl, hidave.darkstar@...il.com, hch@...radead.org Subject: Re: [PATCH -v6 2/2] Updating ctime and mtime for memory-mapped files On Fri, 2008-01-18 at 17:54 -0500, Rik van Riel wrote: > On Fri, 18 Jan 2008 14:47:33 -0800 (PST) > Linus Torvalds <torvalds@...ux-foundation.org> wrote: > > > - keep it simple. Let's face it, Linux has never ever given those > > guarantees before, and it's not is if anybody has really cared. Even > > now, the issue seems to be more about paper standards conformance than > > anything else. > > There is one issue which is way more than just standards conformance. > > When a program changes file data through mmap(), at some point the > mtime needs to be update so that backup programs know to back up the > new version of the file. > > Backup programs not seeing an updated mtime is a really big deal. And that's fixed with the 4-line approach. Reminds me, I've got a patch here for addressing that problem with loop mounts: Writes to loop should update the mtime of the underlying file. Signed-off-by: Matt Mackall <mpm@...enic.com> Index: l/drivers/block/loop.c =================================================================== --- l.orig/drivers/block/loop.c 2007-11-05 17:50:07.000000000 -0600 +++ l/drivers/block/loop.c 2007-11-05 19:03:51.000000000 -0600 @@ -221,6 +221,7 @@ static int do_lo_send_aops(struct loop_d offset = pos & ((pgoff_t)PAGE_CACHE_SIZE - 1); bv_offs = bvec->bv_offset; len = bvec->bv_len; + file_update_time(file); while (len > 0) { sector_t IV; unsigned size; @@ -299,6 +300,7 @@ static int __do_lo_send_write(struct fil set_fs(get_ds()); bw = file->f_op->write(file, buf, len, &pos); + file_update_time(file); set_fs(old_fs); if (likely(bw == len)) return 0; -- Mathematics is the supreme nostalgia of our time. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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