Date: Wed, 18 Jan 2006 19:43:21 -0500 From: Kris Kennaway <kris@obsecurity.org> To: "Shin,Hee-Sub" <heesub.shin@samsung.com> Cc: freebsd-questions@FreeBSD.org Subject: Re: About VFS locking strategy... Message-ID: <20060119004321.GA58284@xor.obsecurity.org> In-Reply-To: <000001c61c89$0da481a0$19a5580a@swcenter.sec.samsung.co.kr> References: <000001c61c89$0da481a0$19a5580a@swcenter.sec.samsung.co.kr>
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--9amGYk9869ThD9tj Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jan 19, 2006 at 08:43:55AM +0900, Shin,Hee-Sub wrote: > Hi all.=20 >=20 > =20 >=20 > I'm speluking with source code of FreeBSD now, comparing VFS of FBSD and > the linux's.=20 >=20 > =20 >=20 > I have a question related with concurrent accesses to the file system. It > is seemed that VFS locks and unlocks each VNODEs before calling VNODE OPS > provided by underlying FS. For example, it calls vn_lock(vp, ...) before > jumps to VOP_READ() in vn_read().=20 >=20 > =20 >=20 > WindowsCE kernel also has a component that is responsible for switching FS > requests to appropriate file-system underlying and similar with VFS of ma= ny > UNIX variants, but it's not perfectly same. In WindowsCE world, file syst= em > driver code can be called on re-entry and file system programmer should > keep this in mind. The manager does not manage any synchronization proble= ms > that can be occurred when multiple threads access to the file system. It > has only a few locks for protecting its own data structures.=20 >=20 > =20 >=20 > How does it manage synchronization problems in the VFS of FreeBSD?=20 >=20 > =20 >=20 > Please give me a detailed description about lock strategy the FreeBSD use= s.=20 This question might be too general to get any replies, but it would still be better asked on fs@ or hackers@. Kris --9amGYk9869ThD9tj Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) iD8DBQFDzuCpWry0BWjoQKURAgsJAKCm5XsvtC34txjnfOx7IO7X54dymgCeMDIc BejZJeE9I9s/IK67DRL4ZTc= =loE4 -----END PGP SIGNATURE----- --9amGYk9869ThD9tj--
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