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From: David Miller <davem@davemloft.net>
To: npiggin@kernel.dk
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [patch 01/28] fs: d_validate fixes
Date: Thu, 18 Nov 2010 12:59:13 -0800 (PST)	[thread overview]
Message-ID: <20101118.125913.13739447.davem@davemloft.net> (raw)
In-Reply-To: <20101118.125123.241932424.davem@davemloft.net>

From: David Miller <davem@davemloft.net>
Date: Thu, 18 Nov 2010 12:51:23 -0800 (PST)

> From: Nick Piggin <npiggin@kernel.dk>
> Date: Wed, 17 Nov 2010 01:09:01 +1100
> 
>> d_validate has been broken for a long time.
>> 
>> kmem_ptr_validate does not guarantee that a pointer can be dereferenced
>> if it can go away at any time. Even rcu_read_lock doesn't help, because
>> the pointer might be queued in RCU callbacks but not executed yet.
>> 
>> So the parent cannot be checked, nor the name hashed. The dentry pointer
>> can not be touched until it can be verified under lock. Hashing simply
>> cannot be used.
>> 
>> Instead, verify the parent/child relationship by traversing parent's
>> d_child list. It's slow, but only ncpfs and the destaged smbfs care
>> about it, at this point.
>> 
>> Signed-off-by: Nick Piggin <npiggin@kernel.dk>
> 
> This won't apply because is conflicts with Christoph Hellwig's
> RCU conversion of d_validate().
> 
> Which is a change that went in more than a month ago.

In fact the conflicts of your patch set are even more pervasive, since
all dcache hash traversals are essentially RCU protected instead of
dcache_lock protected right now.

This makes it very difficult to test or analyze your patches for those
of us on mainline or similar.

  reply	other threads:[~2010-11-18 20:58 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-11-16 14:09 [patch 00/28] [rfc] dcache scaling part 1 Nick Piggin
2010-11-16 14:09 ` [patch 01/28] fs: d_validate fixes Nick Piggin
2010-11-17 10:44   ` Andi Kleen
2010-11-17 10:44     ` Andi Kleen
2010-11-18 20:51   ` David Miller
2010-11-18 20:59     ` David Miller [this message]
2010-11-19  5:05       ` Nick Piggin
2010-11-19  5:01     ` Nick Piggin
2010-11-16 14:09 ` [patch 02/28] kernel: kmem_ptr_validate considered harmful Nick Piggin
2010-11-16 14:09 ` [patch 03/28] fs: dcache documentation cleanup Nick Piggin
2010-11-16 14:09 ` [patch 04/28] fs: change d_delete semantics Nick Piggin
2010-11-17  0:16   ` Tim Pepper
2010-11-16 14:09 ` [patch 05/28] cifs: dont overwrite dentry name in d_revalidate Nick Piggin
2010-11-16 14:09 ` [patch 06/28] jfs: " Nick Piggin
2010-11-16 14:09 ` [patch 07/28] fs: change d_compare for rcu-walk Nick Piggin
2010-11-17  0:44   ` Tim Pepper
2010-11-16 14:09 ` [patch 08/28] fs: change d_hash " Nick Piggin
2010-11-17  0:50   ` Tim Pepper
2010-11-16 14:09 ` [patch 09/28] hostfs: simplify locking Nick Piggin
2010-11-16 14:09 ` [patch 10/28] fs: dcache scale hash Nick Piggin
2010-11-16 14:09 ` [patch 11/28] fs: dcache scale lru Nick Piggin
2010-11-16 14:09 ` [patch 12/28] fs: dcache scale dentry refcount Nick Piggin
2010-11-16 14:09 ` [patch 13/28] fs: dcache scale d_unhashed Nick Piggin
2010-11-19 19:41   ` Tim Pepper
2010-11-16 14:09 ` [patch 14/28] fs: dcache scale subdirs Nick Piggin
2010-11-19 19:41   ` Tim Pepper
2010-11-19 19:41     ` Tim Pepper
2010-11-16 14:09 ` [patch 15/28] fs: scale inode alias list Nick Piggin
2010-11-19 19:41   ` Tim Pepper
2010-11-19 19:41     ` Tim Pepper
2010-11-16 14:09 ` [patch 16/28] fs: Use rename lock and RCU for multi-step operations Nick Piggin
2010-11-19 19:42   ` Tim Pepper
2010-11-16 14:09 ` [patch 17/28] fs: increase d_name lock coverage Nick Piggin
2010-11-16 14:09 ` [patch 18/28] fs: dcache remove dcache_lock Nick Piggin
2010-11-16 14:09 ` [patch 19/28] fs: dcache avoid starvation in dcache multi-step operations Nick Piggin
2010-11-16 14:09 ` [patch 20/28] fs: dcache reduce dput locking Nick Piggin
2010-11-16 14:09 ` [patch 21/28] fs: dcache reduce locking in d_alloc Nick Piggin
2010-11-16 14:09 ` [patch 22/28] fs: dcache reduce dcache_inode_lock Nick Piggin
2010-11-16 14:09 ` [patch 23/28] fs: dcache rationalise dget variants Nick Piggin
2010-11-16 14:09 ` [patch 24/28] fs: dcache reduce d_parent locking Nick Piggin
2010-11-16 14:09 ` [patch 25/28] fs: dcache reduce prune_one_dentry locking Nick Piggin
2010-11-16 14:09 ` [patch 26/28] fs: reduce dcache_inode_lock width in lru scanning Nick Piggin
2010-11-16 14:09 ` [patch 27/28] fs: use RCU in shrink_dentry_list to reduce lock nesting Nick Piggin
2010-11-16 14:09 ` [patch 28/28] fs: consolidate dentry kill sequence Nick Piggin
2010-11-17  2:12 ` [patch 00/28] [rfc] dcache scaling part 1 Dave Chinner
2010-11-17 10:56 ` Andi Kleen
2010-11-17 11:19   ` Nick Piggin
2010-11-17 12:01     ` Andi Kleen
2010-11-19 19:43 ` Tim Pepper

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