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    Subject[PATCH] rcu: Fix wrong check in list_splice_init_rcu()
    Date
    Hi.

    If I don't miss something obvious, the following patch would
    be a good idea.

    There are currently two users of list_splice_init_rcu(): IPMI and btrfs.
    For these, list_splice_init_rcu() is currently a NOP.

    If I interpret the code correctly, this fixes a memory leak for
    IPMI and something probably worse for btrfs.

    The call from within btrfs was introduced only after v2.6.39 with commit
    1f78160 ("Btrfs: using rcu lock in the reader side of devices list") by
    converting a list_splice_init() call.

    Therefore, this patch might be a candidate for v3.0.

    Regards
    Jan

    ----8<----
    From: Jan H. Schönherr <schnhrr@cs.tu-berlin.de>

    Splicing something into an empty list should work, while there is
    nothing to do if the source list is empty.

    Signed-off-by: Jan H. Schönherr <schnhrr@cs.tu-berlin.de>
    ---
    include/linux/rculist.h | 2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)

    diff --git a/include/linux/rculist.h b/include/linux/rculist.h
    index e3beb31..d079290 100644
    --- a/include/linux/rculist.h
    +++ b/include/linux/rculist.h
    @@ -183,7 +183,7 @@ static inline void list_splice_init_rcu(struct list_head *list,
    struct list_head *last = list->prev;
    struct list_head *at = head->next;

    - if (list_empty(head))
    + if (list_empty(list))
    return;

    /* "first" and "last" tracking list, so initialize it. */
    --
    1.7.6
    --
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