Reference counters are preferred to use refcount_t instead of atomic_t. This is because the implementation of refcount_t can prevent overflows and detect possible use-after-free. So convert atomic_t ref counters to refcount_t.
Signed-off-by: Chuhong Yuan <[email protected]> --- drivers/block/rbd.c | 57 ++++++++------------------------------------- 1 file changed, 10 insertions(+), 47 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 3327192bb71f..74d2dddbe108 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -46,44 +46,12 @@ #include <linux/slab.h> #include <linux/idr.h> #include <linux/workqueue.h> +#include <linux/refcount.h> #include "rbd_types.h" #define RBD_DEBUG /* Activate rbd_assert() calls */ -/* - * Increment the given counter and return its updated value. - * If the counter is already 0 it will not be incremented. - * If the counter is already at its maximum value returns - * -EINVAL without updating it. - */ -static int atomic_inc_return_safe(atomic_t *v) -{ - unsigned int counter; - - counter = (unsigned int)atomic_fetch_add_unless(v, 1, 0); - if (counter <= (unsigned int)INT_MAX) - return (int)counter; - - atomic_dec(v); - - return -EINVAL; -} - -/* Decrement the counter. Return the resulting value, or -EINVAL */ -static int atomic_dec_return_safe(atomic_t *v) -{ - int counter; - - counter = atomic_dec_return(v); - if (counter >= 0) - return counter; - - atomic_inc(v); - - return -EINVAL; -} - #define RBD_DRV_NAME "rbd" #define RBD_MINORS_PER_MAJOR 256 @@ -438,7 +406,7 @@ struct rbd_device { struct rbd_spec *parent_spec; u64 parent_overlap; - atomic_t parent_ref; + refcount_t parent_ref; struct rbd_device *parent; /* Block layer tags. */ @@ -1680,21 +1648,19 @@ static void rbd_dev_unparent(struct rbd_device *rbd_dev) */ static void rbd_dev_parent_put(struct rbd_device *rbd_dev) { - int counter; + bool is_dec_to_zero; if (!rbd_dev->parent_spec) return; - counter = atomic_dec_return_safe(&rbd_dev->parent_ref); - if (counter > 0) + is_dec_to_zero = refcount_dec_and_test_checked(&rbd_dev->parent_ref); + if (!is_dec_to_zero) return; /* Last reference; clean up parent data structures */ - if (!counter) + if (is_dec_to_zero) rbd_dev_unparent(rbd_dev); - else - rbd_warn(rbd_dev, "parent reference underflow"); } /* @@ -1707,20 +1673,17 @@ static void rbd_dev_parent_put(struct rbd_device *rbd_dev) */ static bool rbd_dev_parent_get(struct rbd_device *rbd_dev) { - int counter = 0; + bool is_inc_suc = false; if (!rbd_dev->parent_spec) return false; down_read(&rbd_dev->header_rwsem); if (rbd_dev->parent_overlap) - counter = atomic_inc_return_safe(&rbd_dev->parent_ref); + is_inc_suc = refcount_inc_not_zero_checked(&rbd_dev->parent_ref); up_read(&rbd_dev->header_rwsem); - if (counter < 0) - rbd_warn(rbd_dev, "parent reference overflow"); - - return counter > 0; + return is_inc_suc; } /* @@ -6823,7 +6786,7 @@ static int rbd_dev_probe_parent(struct rbd_device *rbd_dev, int depth) goto out_err; rbd_dev->parent = parent; - atomic_set(&rbd_dev->parent_ref, 1); + refcount_set(&rbd_dev->parent_ref, 1); return 0; out_err: -- 2.20.1
