Re: [PATCH 5/6] lightnvm: pblk: free up mempool allocation for erases correctly
From: Rakesh Pandit
Date: Mon Oct 02 2017 - 08:25:19 EST
On Mon, Oct 02, 2017 at 02:09:35PM +0200, Javier González wrote:
> > On 1 Oct 2017, at 15.25, Rakesh Pandit <rakesh@xxxxxxxxxx> wrote:
> > While separating read and erase mempools in 22da65a1b pblk_g_rq_cache
> > was used two times to set aside memory both for erase and read
> > requests. Because same kmem cache is used repeatedly a single call to
> > kmem_cache_destroy wouldn't deallocate everything. Repeatedly doing
> > loading and unloading of pblk modules would eventually result in some
> > leak.
> > The fix is to really use separate kmem cache and track it
> > appropriately.
> > Fixes: 22da65a1b ("lightnvm: pblk: decouple read/erase mempools")
> > Signed-off-by: Rakesh Pandit <rakesh@xxxxxxxxxx>
> I'm not sure I follow this logic. I assume that you're thinking of the
> refcount on kmem_cache. During cache creation, all is good; if a
> different cache creation fails, destruction is guaranteed, since the
> refcount is 0. On tear down (pblk_core_free), we destroy the mempools
> associated to the caches. In this case, the refcount goes to 0 too, as
> we destroy the 2 mempools. So I don't see where the leak can happen. Am
> I missing something?
> In any case, Jens reported some bugs on the mempools, where we did not
> guarantee forward progress. Here you can find the original discussion
> and the mempool audit . Would be good if you reviewed these.
>  https://www.spinics.net/lists/kernel/msg2602274.html
Thanks, yes makes sense to follow up in patch thread. I will respond
to above questions there later today.