sizeof(struct kiocb) is dangerously large for a structure commonly
allocated on-stack. This patch converts the 24*sizeof(long) field,
->private, to a void pointer for use by file_operations entrypoints.
A ->dtor() method is added to the kiocb in order to support the release
of dynamically allocated structures referred to by ->private.
The sole in-tree users of ->private are async network read/write,
which are not, in fact, async, and so need not handle preallocated
->private as they would need to if ->ki_retry were ever used. The sole
truly async operations are direct IO pread()/pwrite() which do not
now use ->ki_retry(). All they would need to do in that case is to
check for ->private already being allocated for async kiocbs.
This rips 88B off the stack on 32-bit in the common case.
vs. 2.6.7-mm3
Index: mm3-2.6.7/include/net/sock.h
===================================================================
--- mm3-2.6.7.orig/include/net/sock.h 2004-06-27 15:44:42.365168400 -0700
+++ mm3-2.6.7/include/net/sock.h 2004-06-27 15:50:40.651700568 -0700
@@ -617,17 +617,17 @@
struct scm_cookie *scm;
struct msghdr *msg, async_msg;
struct iovec async_iov;
+ struct kiocb *kiocb;
};
static inline struct sock_iocb *kiocb_to_siocb(struct kiocb *iocb)
{
- BUG_ON(sizeof(struct sock_iocb) > KIOCB_PRIVATE_SIZE);
return (struct sock_iocb *)iocb->private;
}
static inline struct kiocb *siocb_to_kiocb(struct sock_iocb *si)
{
- return container_of((void *)si, struct kiocb, private);
+ return si->kiocb;
}
struct socket_alloc {
Index: mm3-2.6.7/include/linux/aio.h
===================================================================
--- mm3-2.6.7.orig/include/linux/aio.h 2004-06-15 22:18:54.000000000 -0700
+++ mm3-2.6.7/include/linux/aio.h 2004-06-27 15:50:40.654700112 -0700
@@ -23,8 +23,6 @@
#define KIOCB_SYNC_KEY (~0U)
-#define KIOCB_PRIVATE_SIZE (24 * sizeof(long))
-
/* ki_flags bits */
#define KIF_LOCKED 0
#define KIF_KICKED 1
@@ -55,6 +53,7 @@
struct kioctx *ki_ctx; /* may be NULL for sync ops */
int (*ki_cancel)(struct kiocb *, struct io_event *);
long (*ki_retry)(struct kiocb *);
+ void (*ki_dtor)(struct kiocb *);
struct list_head ki_list; /* the aio core uses this
* for cancellation */
@@ -65,8 +64,7 @@
} ki_obj;
__u64 ki_user_data; /* user's data for completion */
loff_t ki_pos;
-
- char private[KIOCB_PRIVATE_SIZE];
+ void *private;
};
#define is_sync_kiocb(iocb) ((iocb)->ki_key == KIOCB_SYNC_KEY)
@@ -79,6 +77,7 @@
(x)->ki_filp = (filp); \
(x)->ki_ctx = &tsk->active_mm->default_kioctx; \
(x)->ki_cancel = NULL; \
+ (x)->ki_dtor = NULL; \
(x)->ki_obj.tsk = tsk; \
} while (0)
Index: mm3-2.6.7/net/socket.c
===================================================================
--- mm3-2.6.7.orig/net/socket.c 2004-06-15 22:19:13.000000000 -0700
+++ mm3-2.6.7/net/socket.c 2004-06-27 15:50:40.662698896 -0700
@@ -548,9 +548,11 @@
int sock_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
{
struct kiocb iocb;
+ struct sock_iocb siocb;
int ret;
init_sync_kiocb(&iocb, NULL);
+ iocb.private = &siocb;
ret = __sock_sendmsg(&iocb, sock, msg, size);
if (-EIOCBQUEUED == ret)
ret = wait_on_sync_kiocb(&iocb);
@@ -581,15 +583,22 @@
size_t size, int flags)
{
struct kiocb iocb;
+ struct sock_iocb siocb;
int ret;
init_sync_kiocb(&iocb, NULL);
+ iocb.private = &siocb;
ret = __sock_recvmsg(&iocb, sock, msg, size, flags);
if (-EIOCBQUEUED == ret)
ret = wait_on_sync_kiocb(&iocb);
return ret;
}
+static void sock_aio_dtor(struct kiocb *iocb)
+{
+ kfree(iocb->private);
+}
+
/*
* Read data from a socket. ubuf is a user mode pointer. We make sure the
user
* area ubuf...ubuf+size-1 is writable before asking the protocol.
@@ -598,7 +607,7 @@
static ssize_t sock_aio_read(struct kiocb *iocb, char __user *ubuf,
size_t size, loff_t pos)
{
- struct sock_iocb *x = kiocb_to_siocb(iocb);
+ struct sock_iocb *x, siocb;
struct socket *sock;
int flags;
@@ -607,6 +616,16 @@
if (size==0) /* Match SYS5 behaviour */
return 0;
+ if (is_sync_kiocb(iocb))
+ x = &siocb;
+ else {
+ x = kmalloc(sizeof(struct sock_iocb), GFP_KERNEL);
+ if (!x)
+ return -ENOMEM;
+ iocb->ki_dtor = sock_aio_dtor;
+ }
+ iocb->private = x;
+ x->kiocb = iocb;
sock = SOCKET_I(iocb->ki_filp->f_dentry->d_inode);
x->async_msg.msg_name = NULL;
@@ -631,7 +650,7 @@
static ssize_t sock_aio_write(struct kiocb *iocb, const char __user *ubuf,
size_t size, loff_t pos)
{
- struct sock_iocb *x = kiocb_to_siocb(iocb);
+ struct sock_iocb *x, siocb;
struct socket *sock;
if (pos != 0)
@@ -639,6 +658,16 @@
if(size==0) /* Match SYS5 behaviour */
return 0;
+ if (is_sync_kiocb(iocb))
+ x = &siocb;
+ else {
+ x = kmalloc(sizeof(struct sock_iocb), GFP_KERNEL);
+ if (!x)
+ return -ENOMEM;
+ iocb->ki_dtor = sock_aio_dtor;
+ }
+ iocb->private = x;
+ x->kiocb = iocb;
sock = SOCKET_I(iocb->ki_filp->f_dentry->d_inode);
x->async_msg.msg_name = NULL;
Index: mm3-2.6.7/fs/aio.c
===================================================================
--- mm3-2.6.7.orig/fs/aio.c 2004-06-27 15:44:54.278357320 -0700
+++ mm3-2.6.7/fs/aio.c 2004-06-27 15:50:40.667698136 -0700
@@ -396,6 +396,8 @@
req->ki_cancel = NULL;
req->ki_retry = NULL;
req->ki_obj.user = NULL;
+ req->ki_dtor = NULL;
+ req->private = NULL;
/* Check if the completion queue has enough free space to
* accept an event from this io.
@@ -436,9 +438,13 @@
static inline void really_put_req(struct kioctx *ctx, struct kiocb *req)
{
+ if (req->ki_dtor)
+ req->ki_dtor(req);
req->ki_ctx = NULL;
req->ki_filp = NULL;
req->ki_obj.user = NULL;
+ req->ki_dtor = NULL;
+ req->private = NULL;
kmem_cache_free(kiocb_cachep, req);
ctx->reqs_active--;
|