From: Theodore Ts'o <tytso@mit.edu>
To: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Jiang Biao <jiang.biao2@zte.com.cn>,
linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
ebiggers@google.com, zhong.weidong@zte.com.cn
Subject: Re: [PATCH v2] fs/mbcache: make sure mb_cache_count() not return negative value.
Date: Wed, 10 Jan 2018 15:11:37 -0500 [thread overview]
Message-ID: <20180110201137.GB6499@thunk.org> (raw)
In-Reply-To: <20180110150223.axkqucrhzef2n64u@quack2.suse.cz>
On Wed, Jan 10, 2018 at 04:02:23PM +0100, Jan Kara wrote:
> So I don't think this can be a problem. Look, mb_cache_shrink() holds
> c_list_lock. It will take first entry from cache->c_list - this list is
> using list_head entry->e_list and so we are guaranteed entry->e_list is
> non-empty.
>
> The other place deleting entry - mb_cache_entry_delete() - which is using
> different list to grab the entry is properly checking for
> !list_empty(entry->e_list) after acquiring c_list_lock.
Hmm... you're right. How we handle the hlist_bl_lock and c_list_lock
still creeps me out a bit, but it's not going to cause the potential
problem. I think there is a problem if mb_cache_entry_create() races
with mb_cache_delete(), but that will result in an entry being on the
c_list while not being on the hash list, and it doesn't cause the
c_entry_count to get out of sync with reality.
Drat....
- Ted
next prev parent reply other threads:[~2018-01-10 20:11 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-08 23:38 [PATCH v2] fs/mbcache: make sure mb_cache_count() not return negative value Jiang Biao
2018-01-09 0:13 ` Andrew Morton
2018-01-10 4:26 ` Theodore Ts'o
2018-01-10 15:02 ` Jan Kara
2018-01-10 20:11 ` Theodore Ts'o [this message]
2018-01-11 9:04 ` Jan Kara
2018-01-10 4:58 ` Theodore Ts'o
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