Date: Wed, 20 Apr 2005 13:59:46 -0400 From: Brian Fundakowski Feldman <green@FreeBSD.ORG> To: Garrett Wollman <wollman@csail.mit.edu> Cc: freebsd-current@FreeBSD.ORG Subject: Re: NFS client/buffer cache deadlock Message-ID: <20050420175946.GL1157@green.homeunix.org> In-Reply-To: <16998.37222.529748.205885@khavrinen.csail.mit.edu> References: <20050419160900.GB12287@stack.nl> <20050419161616.GF1157@green.homeunix.org> <20050419204723.GG1157@green.homeunix.org> <20050420140409.GA77731@stack.nl> <20050420142448.GH1157@green.homeunix.org> <20050420143842.GB77731@stack.nl> <20050420152038.GI1157@green.homeunix.org> <20050420153528.GC77731@stack.nl> <20050420155233.GJ1157@green.homeunix.org> <16998.37222.529748.205885@khavrinen.csail.mit.edu>
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On Wed, Apr 20, 2005 at 01:29:10PM -0400, Garrett Wollman wrote: > <<On Wed, 20 Apr 2005 11:52:33 -0400, Brian Fundakowski Feldman <green@FreeBSD.ORG> said: > > > I think the first is more useful behavior than the last. Supporting it > > should be exactly the same as supporting what happens if the actual > > filesystem fills up. In this case, the filesystem is being requested to > > write more "than there is room for." > > Returning a short write for operations on regular files would > definitely be considered astonishing. The changes that you have made > should be considered flow control, not admission control, and should > appear to the user no differently than if we were waiting for a slow > disk to write something; i.e., the user thread should be blocked until > either the entire write completes, or the process is interrupted by a > signal. So what _would_ be consistent for nfs_bio.c::nfs_write()? IO_UNIT is set for all write calls which means "atomic", and nfs_rslock() and O_APPEND appear to at least attempt this. Please take a detailed look at the current system and the changes... it's far less clear-cut than POLA dictates. -- Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\ <> green@FreeBSD.org \ The Power to Serve! \ Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
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