Date: Tue, 16 Apr 2013 06:50:13 -0500 From: Kevin Day <toasty@dragondata.com> To: Bruce Evans <brde@optusnet.com.au> Cc: "freebsd-fs@FreeBSD.org Filesystems" <freebsd-fs@FreeBSD.org> Subject: Re: Does sync(8) really flush everything? Lost writes with journaled SU after sync+power cycle Message-ID: <E227CDC9-4DCE-4050-BAEC-6350D8E1B6F0@dragondata.com> In-Reply-To: <20130411160253.V1041@besplex.bde.org> References: <87CC14D8-7DC6-481A-8F85-46629F6D2249@dragondata.com> <20130411160253.V1041@besplex.bde.org>
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On Apr 11, 2013, at 1:30 AM, Bruce Evans <brde@optusnet.com.au> wrote: > sync(2) only schedules all writing of all modified buffers to disk. = Its > man page even says this. It doesn't wait for any of the writes to = complete. A very kind person has pointed out to me (off-list) that doing: mount -u -o ro / (without -f) causes mount to force a flush, waits for completion, THEN bails out = because there are open files preventing the read-only downgrade. We've = been testing this here and it seems to be a usable workaround. I'm also pointing out for at least our purposes, this problem (sync(2) = doesn't seem to actually cause any writes) only seems to be causing lost = directories if I'm using journaling. I'm attempting to narrow down why = journaling appears to make sync into a no-op.=20 -- Kevin
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