diff options
| -rw-r--r-- | fs/aio.c | 35 |
1 files changed, 24 insertions, 11 deletions
@@ -239,15 +239,23 @@ static void __put_ioctx(struct kioctx *ctx) call_rcu(&ctx->rcu_head, ctx_rcu_free); } -#define get_ioctx(kioctx) do { \ - BUG_ON(atomic_read(&(kioctx)->users) <= 0); \ - atomic_inc(&(kioctx)->users); \ -} while (0) -#define put_ioctx(kioctx) do { \ - BUG_ON(atomic_read(&(kioctx)->users) <= 0); \ - if (unlikely(atomic_dec_and_test(&(kioctx)->users))) \ - __put_ioctx(kioctx); \ -} while (0) +static inline void get_ioctx(struct kioctx *kioctx) +{ + BUG_ON(atomic_read(&kioctx->users) <= 0); + atomic_inc(&kioctx->users); +} + +static inline int try_get_ioctx(struct kioctx *kioctx) +{ + return atomic_inc_not_zero(&kioctx->users); +} + +static inline void put_ioctx(struct kioctx *kioctx) +{ + BUG_ON(atomic_read(&kioctx->users) <= 0); + if (unlikely(atomic_dec_and_test(&kioctx->users))) + __put_ioctx(kioctx); +} /* ioctx_alloc * Allocates and initializes an ioctx. Returns an ERR_PTR if it failed. @@ -601,8 +609,13 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id) rcu_read_lock(); hlist_for_each_entry_rcu(ctx, n, &mm->ioctx_list, list) { - if (ctx->user_id == ctx_id && !ctx->dead) { - get_ioctx(ctx); + /* + * RCU protects us against accessing freed memory but + * we have to be careful not to get a reference when the + * reference count already dropped to 0 (ctx->dead test + * is unreliable because of races). + */ + if (ctx->user_id == ctx_id && !ctx->dead && try_get_ioctx(ctx)){ ret = ctx; break; } |