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    Subject[PATCH AUTOSEL 5.5 511/542] bcache: fix incorrect data type usage in btree_flush_write()
    Date
    From: Coly Li <colyli@suse.de>

    [ Upstream commit d1c3cc34f5a78b38d2b809b289d912c3560545df ]

    Dan Carpenter points out that from commit 2aa8c529387c ("bcache: avoid
    unnecessary btree nodes flushing in btree_flush_write()"), there is a
    incorrect data type usage which leads to the following static checker
    warning:
    drivers/md/bcache/journal.c:444 btree_flush_write()
    warn: 'ref_nr' unsigned <= 0

    drivers/md/bcache/journal.c
    422 static void btree_flush_write(struct cache_set *c)
    423 {
    424 struct btree *b, *t, *btree_nodes[BTREE_FLUSH_NR];
    425 unsigned int i, nr, ref_nr;
    ^^^^^^

    426 atomic_t *fifo_front_p, *now_fifo_front_p;
    427 size_t mask;
    428
    429 if (c->journal.btree_flushing)
    430 return;
    431
    432 spin_lock(&c->journal.flush_write_lock);
    433 if (c->journal.btree_flushing) {
    434 spin_unlock(&c->journal.flush_write_lock);
    435 return;
    436 }
    437 c->journal.btree_flushing = true;
    438 spin_unlock(&c->journal.flush_write_lock);
    439
    440 /* get the oldest journal entry and check its refcount */
    441 spin_lock(&c->journal.lock);
    442 fifo_front_p = &fifo_front(&c->journal.pin);
    443 ref_nr = atomic_read(fifo_front_p);
    444 if (ref_nr <= 0) {
    ^^^^^^^^^^^
    Unsigned can't be less than zero.

    445 /*
    446 * do nothing if no btree node references
    447 * the oldest journal entry
    448 */
    449 spin_unlock(&c->journal.lock);
    450 goto out;
    451 }
    452 spin_unlock(&c->journal.lock);

    As the warning information indicates, local varaible ref_nr in unsigned
    int type is wrong, which does not matche atomic_read() and the "<= 0"
    checking.

    This patch fixes the above error by defining local variable ref_nr as
    int type.

    Fixes: 2aa8c529387c ("bcache: avoid unnecessary btree nodes flushing in btree_flush_write()")
    Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
    Signed-off-by: Coly Li <colyli@suse.de>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/md/bcache/journal.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
    index 33ddc5269e8dc..6730820780b06 100644
    --- a/drivers/md/bcache/journal.c
    +++ b/drivers/md/bcache/journal.c
    @@ -422,7 +422,8 @@ int bch_journal_replay(struct cache_set *s, struct list_head *list)
    static void btree_flush_write(struct cache_set *c)
    {
    struct btree *b, *t, *btree_nodes[BTREE_FLUSH_NR];
    - unsigned int i, nr, ref_nr;
    + unsigned int i, nr;
    + int ref_nr;
    atomic_t *fifo_front_p, *now_fifo_front_p;
    size_t mask;

    --
    2.20.1
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