On 05/14/10 02:37 PM, Trond Myklebust wrote:
On Fri, 2010-05-14 at 14:07 -0400, Trond Myklebust wrote:
On Fri, 2010-05-14 at 13:32 -0400, Chuck Lever wrote:
When mm calls with nr_to_scan set to zero, it doesn't expect a -1
return, it just uses the returned value. mm checks for a -1 return only
when a non-zero scan count argument is passed.
So the check you added here (and in the access cache shrinker) to return
-1 when the gfp_mask doesn't contain GFP_KERNEL could cause some
trouble. It would be safer if we return -1 _after_ checking for
nr_to_scan == 0.
Oh... You're referring to the change that was added in Patch 6/15
SUNRPC: Dont run rpcauth_cache_shrinker() when gfp_mask is GFP_NOFS? I
got confused...
Sorry.
I can perhaps rather add a check for nr_to_scan != 0 in that patch...
OK... How about the following? (and ditto for the access cache shrinker)
A comment that explains the choice of return codes might be nice, but
yeah, I guess that will work. It avoids the need to take the
rpc_credcache_lock in cases where you can't do any shrinkage anyway.
So, for the series:
Reviewed-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Looked at patch 2 and 3, but my understanding of gss and v4 reclaim
isn't terribly extensive. I didn't see anything egregious in those two,
but I can't really comment intelligently on the high-level logic changes.
--------------------------------------------------------------------------------------------
From 8048209c54b95046a23cd994b3d0520757ea5845 Mon Sep 17 00:00:00 2001
From: Trond Myklebust<Trond.Myklebust@xxxxxxxxxx>
Date: Thu, 13 May 2010 12:51:03 -0400
Subject: [PATCH 06/15] 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@xxxxxxxxxx>
---
net/sunrpc/auth.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index 95afe79..0667a36 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -270,6 +270,8 @@ rpcauth_cache_shrinker(int nr_to_scan, gfp_t gfp_mask)
LIST_HEAD(free);
int res;
+ if ((gfp_mask& GFP_KERNEL) != GFP_KERNEL)
+ return (nr_to_scan == 0) ? 0 : -1;
if (list_empty(&cred_unused))
return 0;
spin_lock(&rpc_credcache_lock);
--
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