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    SubjectRe: [PATCH] staging: zcache: fix cleancache race condition with shrinker
    On Wed, Aug 29, 2012 at 04:58:45PM -0500, Seth Jennings wrote:
    > This patch fixes a race condition that results in memory
    > corruption when using cleancache.
    > The race exists between the zcache shrinker handler,
    > shrink_zcache_memory() and cleancache_get_page().
    > In most cases, the shrinker will both evict a zbpg
    > from its buddy list and flush it from tmem before a
    > cleancache_get_page() occurs on that page. A subsequent
    > cleancache_get_page() will fail in the tmem layer.
    > In the rare case that two occur together and the
    > cleancache_get_page() path gets through the tmem
    > layer before the shrinker path can flush tmem,
    > zbud_decompress() does a check to see if the zbpg is a
    > "zombie", i.e. not on a buddy list, which means the shrinker
    > is in the process of reclaiming it. If the zbpg is a zombie,
    > zbud_decompress() returns -EINVAL.
    > However, this return code is being ignored by the caller,
    > zcache_pampd_get_data_and_free(), which results in the
    > caller of cleancache_get_page() thinking that the page has
    > been properly retrieved when it has not.
    > This patch modifies zcache_pampd_get_data_and_free() to
    > convey the failure up the stack so that the caller of
    > cleancache_get_page() knows the page retrieval failed.
    > ---
    > Based on v3.6-rc3.
    > This needs to be applied to stable trees as well.
    > zcache-main.c was named zcache.c before v3.1, so
    > I'm not sure how you want to handle trees earlier
    > than that.
    > Signed-off-by: Seth Jennings <>
    Reviewed-by: Minchan Kim <>


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