Date: Thu, 1 Mar 2012 09:10:10 -0500 From: Christoph Hellwig <hch@infradead.org> To: Gleb Kurtsou <gleb.kurtsou@gmail.com> Cc: Attilio Rao <attilio@freebsd.org>, Konstantin Belousov <kostikbel@gmail.com>, Pawel Jakub Dawidek <pjd@FreeBSD.org>, arch@freebsd.org Subject: Re: Prefaulting for i/o buffers Message-ID: <20120301141010.GA7079@infradead.org> In-Reply-To: <20120301111624.GB30991@reks> References: <20120203193719.GB3283@deviant.kiev.zoral.com.ua> <CAJ-FndABi21GfcCRTZizCPc_Mnxm1EY271BiXcYt9SD_zXFpXw@mail.gmail.com> <20120225151334.GH1344@garage.freebsd.pl> <CAJ-FndBBKHrpB1MNJTXx8gkFXR2d-O6k5-HJeOAyv2DznpN-QQ@mail.gmail.com> <20120225194630.GI1344@garage.freebsd.pl> <20120301111624.GB30991@reks>
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On Thu, Mar 01, 2012 at 01:16:24PM +0200, Gleb Kurtsou wrote: > Are you aware of a real "libraries for file systems" VFS example? It > sounds very interesting but I'm afraid it's going to look good only in > theory. E.g. locking at file system level (Darwin, Dragonfly BSD) looks > rather messy (IMHO) and more likely to be bug prone. On the other side > Linux has optional per file system rename lock making VOP_RENAME > implementation much easier, while ours is tremendously difficult to do > right. All namespace locking in Linux is in the VFS, and it mandatory. A filesystem wide lock is only used for cross-directory renames. A more detailed description is here: http://git.kernel.dk/?p=linux.git;a=blob;f=Documentation/filesystems/directory-locking
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