On Fri, 2011-05-27 at 12:07 -0700, Andy Grover wrote:
> Apparently C supports variable arrays on the stack now, pretty sweet.
> Perfect for the iovec array.
>
> Signed-off-by: Andy Grover <agrover@xxxxxxxxxx>
> ---
So as Christoph mentioned, this is really not safe to do for all cases..
What about something along the lines of the following..? Christoph, is
there a smarter way to determine when *_onstack() should be getting
called..?
Thanks,
--nab
--------------------------------------------------------------------
diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index 5c47f42..f437c51 100644
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -284,23 +284,16 @@ fd_alloc_task(struct se_cmd *cmd)
return &fd_req->fd_task;
}
-static int fd_do_readv(struct se_task *task)
+static int __fd_do_readv(struct se_task *task, struct iovec *iov)
{
struct fd_request *req = FILE_REQ(task);
struct file *fd = req->fd_dev->fd_file;
struct scatterlist *sg = task->task_sg;
- struct iovec *iov;
mm_segment_t old_fs;
loff_t pos = (task->task_lba *
task->se_dev->se_sub_dev->se_dev_attrib.block_size);
int ret = 0, i;
- iov = kzalloc(sizeof(struct iovec) * task->task_sg_num, GFP_KERNEL);
- if (!(iov)) {
- printk(KERN_ERR "Unable to allocate fd_do_readv iov[]\n");
- return -ENOMEM;
- }
-
for (i = 0; i < task->task_sg_num; i++) {
iov[i].iov_len = sg[i].length;
iov[i].iov_base = sg_virt(&sg[i]);
@@ -310,8 +303,6 @@ static int fd_do_readv(struct se_task *task)
set_fs(get_ds());
ret = vfs_readv(fd, &iov[0], task->task_sg_num, &pos);
set_fs(old_fs);
-
- kfree(iov);
/*
* Return zeros and GOOD status even if the READ did not return
* the expected virt_size for struct file w/o a backing struct
@@ -335,23 +326,39 @@ static int fd_do_readv(struct se_task *task)
return 1;
}
-static int fd_do_writev(struct se_task *task)
+static int fd_do_readv_onstack(struct se_task *task)
+{
+ struct iovec iov[task->task_sg_num];
+
+ return __fd_do_readv(task, &iov[0]);
+}
+
+static int fd_do_readv_offstack(struct se_task *task)
+{
+ struct iovec *iov;
+ int ret;
+
+ iov = kzalloc(sizeof(struct iovec) * task->task_sg_num, GFP_KERNEL);
+ if (!iov) {
+ printk(KERN_ERR "Unable to allocate fd_do_readv iov[]\n");
+ return -ENOMEM;
+ }
+
+ ret = __fd_do_readv(task, iov);
+ kfree(iov);
+ return ret;
+}
+
+static int __fd_do_writev(struct se_task *task, struct iovec *iov)
{
struct fd_request *req = FILE_REQ(task);
struct file *fd = req->fd_dev->fd_file;
struct scatterlist *sg = task->task_sg;
- struct iovec *iov;
mm_segment_t old_fs;
loff_t pos = (task->task_lba *
task->se_dev->se_sub_dev->se_dev_attrib.block_size);
int ret, i = 0;
- iov = kzalloc(sizeof(struct iovec) * task->task_sg_num, GFP_KERNEL);
- if (!(iov)) {
- printk(KERN_ERR "Unable to allocate fd_do_writev iov[]\n");
- return -ENOMEM;
- }
-
for (i = 0; i < task->task_sg_num; i++) {
iov[i].iov_len = sg[i].length;
iov[i].iov_base = sg_virt(&sg[i]);
@@ -362,8 +369,6 @@ static int fd_do_writev(struct se_task *task)
ret = vfs_writev(fd, &iov[0], task->task_sg_num, &pos);
set_fs(old_fs);
- kfree(iov);
-
if (ret < 0 || ret != task->task_size) {
printk(KERN_ERR "vfs_writev() returned %d\n", ret);
return (ret < 0 ? ret : -EINVAL);
@@ -372,6 +377,29 @@ static int fd_do_writev(struct se_task *task)
return 1;
}
+static int fd_do_writev_onstack(struct se_task *task)
+{
+ struct iovec iov[task->task_sg_num];
+
+ return __fd_do_writev(task, &iov[0]);
+}
+
+static int fd_do_writev_offstack(struct se_task *task)
+{
+ struct iovec *iov;
+ int ret;
+
+ iov = kzalloc(sizeof(struct iovec) * task->task_sg_num, GFP_KERNEL);
+ if (!iov) {
+ printk(KERN_ERR "Unable to allocate fd_do_writev iov[]\n");
+ return -ENOMEM;
+ }
+
+ ret = __fd_do_writev(task, iov);
+ kfree(iov);
+ return ret;
+}
+
static void fd_emulate_sync_cache(struct se_task *task)
{
struct se_cmd *cmd = task->task_se_cmd;
@@ -461,6 +489,7 @@ static int fd_do_task(struct se_task *task)
{
struct se_cmd *cmd = task->task_se_cmd;
struct se_device *dev = cmd->se_dev;
+ u32 iovec_bytes = task->task_sg_num * sizeof(struct iovec);
int ret = 0;
/*
@@ -468,9 +497,15 @@ static int fd_do_task(struct se_task *task)
* physical memory addresses to struct iovec virtual memory.
*/
if (task->task_data_direction == DMA_FROM_DEVICE) {
- ret = fd_do_readv(task);
+ if (iovec_bytes < (THREAD_SIZE / 2))
+ ret = fd_do_readv_onstack(task);
+ else
+ ret = fd_do_readv_offstack(task);
} else {
- ret = fd_do_writev(task);
+ if (iovec_bytes < (THREAD_SIZE / 2))
+ ret = fd_do_writev_onstack(task);
+ else
+ ret = fd_do_writev_offstack(task);
if (ret > 0 &&
dev->se_sub_dev->se_dev_attrib.emulate_write_cache > 0 &&
--
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