Re: [PATCH v3 02/10] zram: use zram->lock to protect zram_free_page()in swap free notify path

From: Jerome Marchand
Date: Fri Jun 07 2013 - 05:32:41 EST

On 06/06/2013 06:07 PM, Jiang Liu wrote:
> zram_slot_free_notify() is free-running without any protection from
> concurrent operations. So there are race conditions between
> zram_bvec_read()/zram_bvec_write() and zram_slot_free_notify(),
> and possible consequences include:
> 1) Trigger BUG_ON(!handle) on zram_bvec_write() side.
> 2) Access to freed pages on zram_bvec_read() side.
> 3) Break some fields (bad_compress, good_compress, pages_stored)
> in zram->stats if the swap layer makes concurrently call to
> zram_slot_free_notify().
> So enhance zram_slot_free_notify() to acquire writer lock on zram->lock
> before calling zram_free_page().
> Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

Acked-by: Jerome Marchand <jmarchand@xxxxxxxxxx>

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