Date: Thu, 1 Mar 2012 18:45:11 +0200 From: Gleb Kurtsou <gleb.kurtsou@gmail.com> To: Christoph Hellwig <hch@infradead.org> 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: <20120301164511.GA1501@reks> In-Reply-To: <20120301141010.GA7079@infradead.org> 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> <20120301141010.GA7079@infradead.org>
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On (01/03/2012 09:10), Christoph Hellwig wrote: > 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 > My bad. I thought s_vfs_rename_mutex can be optional. Quite unfortunate linux doesn't support concurrent cross-directory renames :) Thanks, Gleb.
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