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authorZach Brown <zach.brown@oracle.com>2005-11-13 16:07:33 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2005-11-13 18:14:16 -0800
commit20dcae32439384b6863c626bb3b2a09bed65b33e (patch)
tree9750c39119447fb32963448bf1935e1ba22b2f9d
parent4557398f8cbaf9f254cff747534b4724c7f75c4f (diff)
[PATCH] aio: remove kioctx from mm_struct
Sync iocbs have a life cycle that don't need a kioctx. Their retrying, if any, is done in the context of their owner who has allocated them on the stack. The sole user of a sync iocb's ctx reference was aio_complete() checking for an elevated iocb ref count that could never happen. No path which grabs an iocb ref has access to sync iocbs. If we were to implement sync iocb cancelation it would be done by the owner of the iocb using its on-stack reference. Removing this chunk from aio_complete allows us to remove the entire kioctx instance from mm_struct, reducing its size by a third. On a i386 testing box the slab size went from 768 to 504 bytes and from 5 to 8 per page. Signed-off-by: Zach Brown <zach.brown@oracle.com> Acked-by: Benjamin LaHaise <bcrl@kvack.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--fs/aio.c27
-rw-r--r--include/linux/aio.h2
-rw-r--r--include/linux/init_task.h1
-rw-r--r--include/linux/sched.h1
-rw-r--r--kernel/fork.c1
5 files changed, 10 insertions, 22 deletions
diff --git a/fs/aio.c b/fs/aio.c
index 20bb919eb19..e7cd40b626b 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -937,28 +937,19 @@ int fastcall aio_complete(struct kiocb *iocb, long res, long res2)
unsigned long tail;
int ret;
- /* Special case handling for sync iocbs: events go directly
- * into the iocb for fast handling. Note that this will not
- * work if we allow sync kiocbs to be cancelled. in which
- * case the usage count checks will have to move under ctx_lock
- * for all cases.
+ /*
+ * Special case handling for sync iocbs:
+ * - events go directly into the iocb for fast handling
+ * - the sync task with the iocb in its stack holds the single iocb
+ * ref, no other paths have a way to get another ref
+ * - the sync task helpfully left a reference to itself in the iocb
*/
if (is_sync_kiocb(iocb)) {
- int ret;
-
+ BUG_ON(iocb->ki_users != 1);
iocb->ki_user_data = res;
- if (iocb->ki_users == 1) {
- iocb->ki_users = 0;
- ret = 1;
- } else {
- spin_lock_irq(&ctx->ctx_lock);
- iocb->ki_users--;
- ret = (0 == iocb->ki_users);
- spin_unlock_irq(&ctx->ctx_lock);
- }
- /* sync iocbs put the task here for us */
+ iocb->ki_users = 0;
wake_up_process(iocb->ki_obj.tsk);
- return ret;
+ return 1;
}
info = &ctx->ring_info;
diff --git a/include/linux/aio.h b/include/linux/aio.h
index 403d71dcb7c..9e0ae871127 100644
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -124,7 +124,7 @@ struct kiocb {
(x)->ki_users = 1; \
(x)->ki_key = KIOCB_SYNC_KEY; \
(x)->ki_filp = (filp); \
- (x)->ki_ctx = &tsk->active_mm->default_kioctx; \
+ (x)->ki_ctx = NULL; \
(x)->ki_cancel = NULL; \
(x)->ki_dtor = NULL; \
(x)->ki_obj.tsk = tsk; \
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 68ab5f2ab9c..dcfd2ecccb5 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -51,7 +51,6 @@
.page_table_lock = SPIN_LOCK_UNLOCKED, \
.mmlist = LIST_HEAD_INIT(name.mmlist), \
.cpu_vm_mask = CPU_MASK_ALL, \
- .default_kioctx = INIT_KIOCTX(name.default_kioctx, name), \
}
#define INIT_SIGNALS(sig) { \
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 41df8139571..2038bd27b04 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -357,7 +357,6 @@ struct mm_struct {
/* aio bits */
rwlock_t ioctx_list_lock;
struct kioctx *ioctx_list;
- struct kioctx default_kioctx;
};
struct sighand_struct {
diff --git a/kernel/fork.c b/kernel/fork.c
index 2c70c9cdf5d..e0d0b77343f 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -323,7 +323,6 @@ static struct mm_struct * mm_init(struct mm_struct * mm)
spin_lock_init(&mm->page_table_lock);
rwlock_init(&mm->ioctx_list_lock);
mm->ioctx_list = NULL;
- mm->default_kioctx = (struct kioctx)INIT_KIOCTX(mm->default_kioctx, *mm);
mm->free_area_cache = TASK_UNMAPPED_BASE;
mm->cached_hole_size = ~0UL;