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authorKent Overstreet <koverstreet@google.com>2013-05-13 13:42:52 -0700
committerKent Overstreet <koverstreet@google.com>2013-06-17 19:37:06 -0700
commit88fae56176db1d8dc6793e13dcda79f765180410 (patch)
tree62c050cb9ac137146655c5ea02df8f8c42318e75
parentabcdc06aa97d6e0a85b14da7f76f60cc161f1447 (diff)
aio: Kill ki_users
The kiocb refcount is only needed for cancellation - to ensure a kiocb isn't freed while a ki_cancel callback is running. But if we restrict ki_cancel callbacks to not block (which they currently don't), we can simply drop the refcount. Signed-off-by: Kent Overstreet <koverstreet@google.com> Cc: Zach Brown <zab@redhat.com> Cc: Felipe Balbi <balbi@ti.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Jens Axboe <axboe@kernel.dk> Cc: Asai Thambi S P <asamymuthupa@micron.com> Cc: Selvan Mani <smani@micron.com> Cc: Sam Bradshaw <sbradshaw@micron.com> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Benjamin LaHaise <bcrl@kvack.org> Cc: Theodore Ts'o <tytso@mit.edu>
-rw-r--r--fs/aio.c47
-rw-r--r--include/linux/aio.h5
2 files changed, 12 insertions, 40 deletions
diff --git a/fs/aio.c b/fs/aio.c
index c3e16e845af2..0afa71e3e270 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -260,7 +260,6 @@ EXPORT_SYMBOL(kiocb_set_cancel_fn);
static int kiocb_cancel(struct kioctx *ctx, struct kiocb *kiocb)
{
kiocb_cancel_fn *old, *cancel;
- int ret = -EINVAL;
/*
* Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it
@@ -270,21 +269,13 @@ static int kiocb_cancel(struct kioctx *ctx, struct kiocb *kiocb)
cancel = ACCESS_ONCE(kiocb->ki_cancel);
do {
if (!cancel || cancel == KIOCB_CANCELLED)
- return ret;
+ return -EINVAL;
old = cancel;
cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED);
} while (cancel != old);
- atomic_inc(&kiocb->ki_users);
- spin_unlock_irq(&ctx->ctx_lock);
-
- ret = cancel(kiocb);
-
- spin_lock_irq(&ctx->ctx_lock);
- aio_put_req(kiocb);
-
- return ret;
+ return cancel(kiocb);
}
static void free_ioctx_rcu(struct rcu_head *head)
@@ -496,16 +487,16 @@ static void kill_ioctx(struct kioctx *ctx)
/* wait_on_sync_kiocb:
* Waits on the given sync kiocb to complete.
*/
-ssize_t wait_on_sync_kiocb(struct kiocb *iocb)
+ssize_t wait_on_sync_kiocb(struct kiocb *req)
{
- while (atomic_read(&iocb->ki_users)) {
+ while (!req->ki_ctx) {
set_current_state(TASK_UNINTERRUPTIBLE);
- if (!atomic_read(&iocb->ki_users))
+ if (req->ki_ctx)
break;
io_schedule();
}
__set_current_state(TASK_RUNNING);
- return iocb->ki_user_data;
+ return req->ki_user_data;
}
EXPORT_SYMBOL(wait_on_sync_kiocb);
@@ -584,14 +575,8 @@ out:
}
/* aio_get_req
- * Allocate a slot for an aio request. Increments the ki_users count
- * of the kioctx so that the kioctx stays around until all requests are
- * complete. Returns NULL if no requests are free.
- *
- * Returns with kiocb->ki_users set to 2. The io submit code path holds
- * an extra reference while submitting the i/o.
- * This prevents races between the aio code path referencing the
- * req (after submitting it) and aio_complete() freeing the req.
+ * Allocate a slot for an aio request.
+ * Returns NULL if no requests are free.
*/
static inline struct kiocb *aio_get_req(struct kioctx *ctx)
{
@@ -604,7 +589,6 @@ static inline struct kiocb *aio_get_req(struct kioctx *ctx)
if (unlikely(!req))
goto out_put;
- atomic_set(&req->ki_users, 1);
req->ki_ctx = ctx;
return req;
out_put:
@@ -623,13 +607,6 @@ static void kiocb_free(struct kiocb *req)
kmem_cache_free(kiocb_cachep, req);
}
-void aio_put_req(struct kiocb *req)
-{
- if (atomic_dec_and_test(&req->ki_users))
- kiocb_free(req);
-}
-EXPORT_SYMBOL(aio_put_req);
-
static struct kioctx *lookup_ioctx(unsigned long ctx_id)
{
struct mm_struct *mm = current->mm;
@@ -668,9 +645,9 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
* - the sync task helpfully left a reference to itself in the iocb
*/
if (is_sync_kiocb(iocb)) {
- BUG_ON(atomic_read(&iocb->ki_users) != 1);
iocb->ki_user_data = res;
- atomic_set(&iocb->ki_users, 0);
+ smp_wmb();
+ iocb->ki_ctx = ERR_PTR(-EXDEV);
wake_up_process(iocb->ki_obj.tsk);
return;
}
@@ -742,7 +719,7 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
eventfd_signal(iocb->ki_eventfd, 1);
/* everything turned out well, dispose of the aiocb. */
- aio_put_req(iocb);
+ kiocb_free(iocb);
/*
* We have to order our ring_info tail store above and test
@@ -1166,7 +1143,7 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
return 0;
out_put_req:
put_reqs_available(ctx, 1);
- aio_put_req(req);
+ kiocb_free(req);
return ret;
}
diff --git a/include/linux/aio.h b/include/linux/aio.h
index b570472355d1..c4f07ffa1cbb 100644
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -30,8 +30,6 @@ struct kiocb;
typedef int (kiocb_cancel_fn)(struct kiocb *);
struct kiocb {
- atomic_t ki_users;
-
struct file *ki_filp;
struct kioctx *ki_ctx; /* NULL for sync ops */
kiocb_cancel_fn *ki_cancel;
@@ -65,7 +63,6 @@ static inline bool is_sync_kiocb(struct kiocb *kiocb)
static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
{
*kiocb = (struct kiocb) {
- .ki_users = ATOMIC_INIT(1),
.ki_ctx = NULL,
.ki_filp = filp,
.ki_obj.tsk = current,
@@ -75,7 +72,6 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
/* prototypes */
#ifdef CONFIG_AIO
extern ssize_t wait_on_sync_kiocb(struct kiocb *iocb);
-extern void aio_put_req(struct kiocb *iocb);
extern void aio_complete(struct kiocb *iocb, long res, long res2);
struct mm_struct;
extern void exit_aio(struct mm_struct *mm);
@@ -84,7 +80,6 @@ extern long do_io_submit(aio_context_t ctx_id, long nr,
void kiocb_set_cancel_fn(struct kiocb *req, kiocb_cancel_fn *cancel);
#else
static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; }
-static inline void aio_put_req(struct kiocb *iocb) { }
static inline void aio_complete(struct kiocb *iocb, long res, long res2) { }
struct mm_struct;
static inline void exit_aio(struct mm_struct *mm) { }