From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: moiz_kohari@yahoo.com
Cc: NFS maillist <nfs@lists.sourceforge.net>
Subject: Re: posix record locking?
Date: 25 Nov 2003 19:50:23 -0500 [thread overview]
Message-ID: <shsoev0uf5c.fsf@charged.uio.no> (raw)
In-Reply-To: <3FC2781E.4010107@yahoo.com>
>>>>> " " == moiz kohari <moiz_kohari@yahoo.com> writes:
> Hi, I am looking at posix record locking with nfs and I have a
> couple of questions:
> 1. The fcntl_setlk() calls nfs_lock() (towards the end of fcntl_setlk
> by calling filp->f_op->lock), fcntl_setlk() then calls
> posix_lock_file() (where all the vfs magic happens for file
> locks). If nfs_lock() returns successful (server has
> granted the lock) but the subsequent posix_lock_file() fails
> (due to deadlock, conflict or low memory), we never go back
> to the server to clean up this lock. Is this a problem or
> am I missing something?
Low memory is a problem, but how are you going to solve that (RPC
calls require memory too)?
As for the rest: why would the VFS tell us we're
deadlocked/conflicting if the server says we aren't? That would
clearly be a bug.
> 2. nfs_lock() calls nlmclnt_proc() after we pick up the kernel lock
> (lock_kernel()). The nlmclnt_proc() goes on to call:
> nlmclnt_lock() nlmclnt_call() rpc...
> Is this OK? Are we going over the wire while holding the
> kernel lock?
Yes. The BKL is unique as far as spinlocks go in that it allows this
sort of thing.
Cheers,
Trond
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prev parent reply other threads:[~2003-11-26 0:50 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-24 21:29 posix record locking? moiz kohari
2003-11-26 0:50 ` Trond Myklebust [this message]
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