@@ -378,9 +378,7 @@ static ssize_t userfaultfd_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
struct userfaultfd_ctx *ctx = file->private_data;
- ssize_t res;
__u64 range[2];
- DECLARE_WAITQUEUE(wait, current);
if (ctx->state == USERFAULTFD_STATE_ASK_PROTOCOL) {
__u64 protocol;
@@ -408,34 +406,12 @@ static ssize_t userfaultfd_write(struct file *file, const char __user *buf,
if (range[0] >= range[1])
return -ERANGE;
- spin_lock(&ctx->fd_wqh.lock);
- __add_wait_queue(&ctx->fd_wqh, &wait);
- for (;;) {
- set_current_state(TASK_INTERRUPTIBLE);
- /* always take the fd_wqh lock before the fault_wqh lock */
- if (find_userfault(ctx, NULL, POLLOUT)) {
- if (!wake_userfault(ctx, range)) {
- res = sizeof(range);
- break;
- }
- }
- if (signal_pending(current)) {
- res = -ERESTARTSYS;
- break;
- }
- if (file->f_flags & O_NONBLOCK) {
- res = -EAGAIN;
- break;
- }
- spin_unlock(&ctx->fd_wqh.lock);
- schedule();
- spin_lock(&ctx->fd_wqh.lock);
- }
- __remove_wait_queue(&ctx->fd_wqh, &wait);
- __set_current_state(TASK_RUNNING);
- spin_unlock(&ctx->fd_wqh.lock);
+ /* always take the fd_wqh lock before the fault_wqh lock */
+ if (find_userfault(ctx, NULL, POLLOUT))
+ if (!wake_userfault(ctx, range))
+ return sizeof(range);
- return res;
+ return -ENOENT;
}
#ifdef CONFIG_PROC_FS
It is generally inefficient to ask the wakeup of userfault ranges where there's not a single userfault address read through userfaultfd_read earlier and in turn waiting a wakeup. However it may come handy to wakeup the same userfault range twice in case of multiple thread faulting on the same address. But we should still return an error so if the application thinks this occurrence can never happen it will know it hit a bug. So just return -ENOENT instead of blocking. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> --- fs/userfaultfd.c | 34 +++++----------------------------- 1 file changed, 5 insertions(+), 29 deletions(-)