linux-kernel - Re: [GIT PULL] Please pull NFS client changes

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Message-ID: <20100518085917.GH14172@ics.muni.cz>
Date:	Tue, 18 May 2010 10:59:17 +0200
From:	Lukas Hejtmanek <xhejtman@....muni.cz>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org
Subject: Re: [GIT PULL] Please pull NFS client changes

Hi Trond,

On Mon, May 17, 2010 at 06:28:01PM -0400, Trond Myklebust wrote:
> commit 9c7e7e23371e629dbb3b341610a418cdf1c19d91
> Author: Trond Myklebust <Trond.Myklebust@...app.com>
> Date:   Thu May 13 12:51:06 2010 -0400
> 
>     NFS: Don't call iput() in nfs_access_cache_shrinker
>     
>     iput() can potentially attempt to allocate memory, so we should avoid
>     calling it in a memory shrinker. Instead, rely on the fact that iput() will
>     call nfs_access_zap_cache().
>     
>     Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
> 
> commit 1a81bb8a1fa62ccb9b2411ac10ce702ca4ed302a
> Author: Trond Myklebust <Trond.Myklebust@...app.com>
> Date:   Thu May 13 12:51:06 2010 -0400
> 
>     NFS: Clean up nfs_access_zap_cache()
>     
>     Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
> 
> commit 61d5eb2985b3b1d69fd53d7dc9789037c27f8d91
> Author: Trond Myklebust <Trond.Myklebust@...app.com>
> Date:   Thu May 13 12:51:06 2010 -0400
> 
>     NFS: Don't run nfs_access_cache_shrinker() when the mask is GFP_NOFS
>     
>     Both iput() and put_rpccred() might allocate memory under certain
>     circumstances, so make sure that we don't recurse and deadlock...
>     
>     Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
> 
> commit 93a05e65c090dda9cbd79d0cf57b65c4dbd8da55
> Author: Trond Myklebust <Trond.Myklebust@...app.com>
> Date:   Thu May 13 12:51:06 2010 -0400
> 
>     SUNRPC: Ensure memory shrinker doesn't waste time in rpcauth_prune_expired()
>     
>     The 'cred_unused' list, that is traversed by rpcauth_cache_shrinker is
>     ordered by time. If we hit a credential that is under the 60 second garbage
>     collection moratorium, we should exit because we know at that point that
>     all successive credentials are subject to the same moratorium...
>     
>     Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
> 
> commit d300a41ef1c39cc5e6b90fd8834ea7ab16b5c48f
> Author: Trond Myklebust <Trond.Myklebust@...app.com>
> Date:   Thu May 13 12:51:03 2010 -0400
> 
>     SUNRPC: Dont run rpcauth_cache_shrinker() when gfp_mask is GFP_NOFS
>     
>     Under some circumstances, put_rpccred() can end up allocating memory, so
>     check the gfp_mask to prevent deadlocks.
>     
>     Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
> 
> commit 93870d76fee22e887aa6e7e1fc904dbeca976928
> Author: Trond Myklebust <Trond.Myklebust@...app.com>
> Date:   Thu May 13 12:51:03 2010 -0400
> 
>     NFS: Read requests can use GFP_KERNEL.
>     
>     There is no danger of deadlock should the allocation trigger page
>     writeback.
>     
>     Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
> 
> commit 1f4c86c0be9064ab4eebd9e67c84606c1cfeec4b
> Author: Trond Myklebust <Trond.Myklebust@...app.com>
> Date:   Thu May 13 12:51:02 2010 -0400
> 
>     NFS: Don't use GFP_KERNEL in rpcsec_gss downcalls
>     
>     Again, we can deadlock if the memory reclaim triggers a writeback that
>     requires a rpcsec_gss credential lookup.
>     
>     Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
> 
> commit 8535b2be5181fc3019e4150567ef53210fe3b04f
> Author: Trond Myklebust <Trond.Myklebust@...app.com>
> Date:   Thu May 13 12:51:01 2010 -0400
> 
>     NFSv4: Don't use GFP_KERNEL allocations in state recovery
>     
>     We do not want to have the state recovery thread kick off and wait for a
>     memory reclaim, since that may deadlock when the writebacks end up
>     waiting for the state recovery thread to complete.
>     
>     The safe thing is therefore to use GFP_NOFS in all open, close,
>     delegation return, lock, etc. operations that may be called by the
>     state recovery thread.
>     
>     Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>

do these solve also cases when rpc.gssd itself needs memory and there is no
free memory because there is a lot of dirty pages as NFS cache?

rpc.gssd needs memory whenever it needs to create a new kerberos context (in
particular, fread needs it).

-- 
Lukáš Hejtmánek
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