Date: Wed, 13 Oct 2010 12:54:56 +0400 From: "Andrey V. Elsukov" <bu7cher@yandex.ru> To: Stefan Bethke <stb@lassitu.de> Cc: stable@freebsd.org Subject: Re: Label question...why does ufs label vanish on mount? Message-ID: <4CB573E0.1030104@yandex.ru> In-Reply-To: <B6AAC89E-5651-4B4B-B770-11443A7BCC22@lassitu.de> References: <20101012185100.5AA661CC3E@ptavv.es.net> <4CB53BF7.1020408@yandex.ru> <B6AAC89E-5651-4B4B-B770-11443A7BCC22@lassitu.de>
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[-- Attachment #1 --] On 13.10.2010 10:29, Stefan Bethke wrote: >> When you are opening provider for writing (i.e. mount FS) GEOM(4) >> initiates SPOILING and all consumers that are attached to this provider >> except one will self-destroyed. When you are closing provider GEOM(4) >> initiates TASTING and consumers can return back. Look at man 4 geom >> for details. > > That explains the mechanism, but not the rationale. Or is it just an > unintended consequence? And how is da2p1 different from ufs/mylabel? > (Mount da2p1 and ufs/mylabel is removed, but not the other way around.) This is by design. Any provider's entries in /dev are created by GEOM_DEV class. GEOM_PART serves partition tables. GEOM_PART_GPT as part of GEOM_PART serves GPT. GEOM_PART creates new provider for each entry in GPT. For example: da2 has GPT. da2p1 - first entry in GPT. GEOM_PART creates da2p1 provider and GEOM initiate tasting. GEOM_DEV creates new consumer for da2p1 and /dev/da2p1 entry in devfs. At the same time GEOM_LABEL checks this provider and if it found "labels" it creates new consumer and new provider with name ufs/mylabel via slicer interface. After creating new provider GEOM initiate tasting again. And GEOM_DEV creates new consumer and /dev/ufs/mylabel entry. So, now we have two providers through we can get access to one device. But ufs/mylabel's is on top of da2p1. When we do first open one of them for writing GEOM initiate spoiling for protecting from stale metadata. When we do open da2p1 then GEOM_LABEL receives spoil event and destroys own provider. If I'm wrong Pawel can correct me. -- WBR, Andrey V. Elsukov [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (MingW32) iQEcBAEBAgAGBQJMtXPjAAoJEAHF6gQQyKF6CY0H/0N2S7hsxzIdyg8uSKDrWpQ+ laAFM8AOhVArtNv0/KfPQnNm670rEeNZYfZhwNnutblhvBnNR3J/ZctgwE5mrmx6 6xXwKKz5Md/FCeZolgFAy74LL+9CFiqws6tfTffUqXpuEY5o0OZb0cnxeaN1xLQS G/cLQ1V2oHufOm1Fd1dIQVzJ0iHkNbLXT1TgiWzPHTrkWj1w3Ke2azRhQFxxLb/9 6FUUtIbkRcJH/4Elk/TJ3aMUfQ1hmPIx6Ih0+Gfhs9gThK860f4nSneZxD4V9Whr 6l/0Q0ZBljru0MJ+/eSmPbATkeB6YLmBiDuDV79icUiNF8RXLb0XTaRcCypXzO4= =j7M0 -----END PGP SIGNATURE-----
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