Date: Thu, 1 Aug 2013 12:33:18 +0200 From: "dawidek.net" <pawel@dawidek.net> To: Luca Ferrari <fluca1978@infinito.it> Cc: Rotate 13 <rabgvzr@gmail.com>, "lev@freebsd.org" <lev@freebsd.org>, Brooks Davis <brooks@freebsd.org>, "freebsd-geom@freebsd.org" <freebsd-geom@freebsd.org> Subject: Re: How to disable all GEOM tasting? Message-ID: <E03B38B6-F6AC-40F7-92A5-7762D40F3EF8@dawidek.net> In-Reply-To: <CAKoxK%2B6L-AT_j=Z6w_VDeoTsh=Uo73pgXw-gSL1Vj0viO_OJUg@mail.gmail.com> References: <CADBSp1fcO9Eb7nQXDQPghd0ModKuAtKBiwHfS80h_njn10U8Gg@mail.gmail.com> <20130730214114.GL13659@lor.one-eyed-alien.net> <CADBSp1dH01%2B1i1ydq-nWtivq30vxfjnnnJPnH%2Bqb0XycsbbjcA@mail.gmail.com> <CAKoxK%2B6oP2e4YfBLRtz3AWbMJxQSJW-LpB2QjHAYd55%2BCkBs2Q@mail.gmail.com> <331012162.20130801122156@serebryakov.spb.ru> <CAKoxK%2B6L-AT_j=Z6w_VDeoTsh=Uo73pgXw-gSL1Vj0viO_OJUg@mail.gmail.com>
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Dnia 1 sie 2013 o godz. 11:16 Luca Ferrari <fluca1978@infinito.it> napisa=C5= =82(a): > On Thu, Aug 1, 2013 at 10:21 AM, Lev Serebryakov <lev@freebsd.org> wrote: >> Hello, Luca. >> You wrote 1 =D0=B0=D0=B2=D0=B3=D1=83=D1=81=D1=82=D0=B0 2013 =D0=B3., 11:3= 1:21: >>=20 >> LF> However, I don't get the whole point in disabling tasting: it is >> LF> required for proper system functioning. >> Presence of a lot (and "a lot" could mean THOUSANDS -- think about regu= lar ZVOLs >> snapshots on iSCSI-used NAS) of "foreign" "block devices". >=20 > Uhm...but in such case the class should have a g_taste set to NULL to > avoid tasting on itself. What I was saying is that disabling taste > system wide (i.e., in the geom subsystem) cannot work. > Am I wrong? The biggest problem with disabling tasting is that the corresponding entries= won't be created in /dev/. There is the DEV GEOM class, which create those e= ntries from its taste method. I do see a value in being able to temporairly disable tasting in some emerge= ncy situations, but there is no way to do that now. Taste methods are called from three different places: 1. When new provider is created all GEOM classes are noticed. 2. When new GEOM class is loaded it gets all existing providers for tasting.= 3. When the last consumer that had provider open for writing closes its acce= ss, GEOM notices all the classes again, as writes might have changed provide= r's metadata and classes may be able to find something interesting now. --=20 Pawe=C5=82 Jakub Dawidek=
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