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    Subject[PATCH] dm thin: reinstate missing mempool_free in cell_release_singleton
    Hi Greg,

    3.3-stable pulled in upstream commit
    6f94a4c45a6f744383f9f695dde019998db3df55 (dm thin: fix stacked bi_next usage)

    But later in the 3.4 development window it was determined that that
    commit introduced a significant leak. The following upstream commit
    fixes it (but unfortunately didn't cc: stable).

    -------------------

    From: Mike Snitzer <snitzer@redhat.com>

    commit 03aaae7cdc71bc306888440b1f569d463e917b6d upstream.

    Fix a significant memory leak inadvertently introduced during
    simplification of cell_release_singleton() in commit
    6f94a4c45a6f744383f9f695dde019998db3df55 ("dm thin: fix stacked bi_next
    usage").

    A cell's hlist_del() must be accompanied by a mempool_free().
    Use __cell_release() to do this, like before.

    Signed-off-by: Mike Snitzer <snitzer@redhat.com>
    Signed-off-by: Alasdair G Kergon <agk@redhat.com>
    ---
    drivers/md/dm-thin.c | 9 ++++++---
    1 files changed, 6 insertions(+), 3 deletions(-)

    diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
    index 213ae32..301db0f 100644
    --- a/drivers/md/dm-thin.c
    +++ b/drivers/md/dm-thin.c
    @@ -279,8 +279,10 @@ static void __cell_release(struct cell *cell, struct bio_list *inmates)

    hlist_del(&cell->list);

    - bio_list_add(inmates, cell->holder);
    - bio_list_merge(inmates, &cell->bios);
    + if (inmates) {
    + bio_list_add(inmates, cell->holder);
    + bio_list_merge(inmates, &cell->bios);
    + }

    mempool_free(cell, prison->cell_pool);
    }
    @@ -303,9 +305,10 @@ static void cell_release(struct cell *cell, struct bio_list *bios)
    */
    static void __cell_release_singleton(struct cell *cell, struct bio *bio)
    {
    - hlist_del(&cell->list);
    BUG_ON(cell->holder != bio);
    BUG_ON(!bio_list_empty(&cell->bios));
    +
    + __cell_release(cell, NULL);
    }

    static void cell_release_singleton(struct cell *cell, struct bio *bio)
    --
    1.7.4.4

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