Re: [patch] splice mmap_sem deadlock

[Linus Torvalds <torvalds@linux-foundation.org>]

On Fri, 28 Sep 2007, Linus Torvalds wrote:
> 
> So something like the appended might work. Untested.

Btw, it migth be cleaner to separate out this thing as a function of it's 
own, ie something like

  /*
   * Do a copy-from-user while holding the mmap_semaphore for reading
   */
  int copy_from_user_mmap_sem(void *dst, const void __user *src, size_t n)
  {
	int partial;

	pagefault_disable();
	partial = __copy_from_user_inatomic(dst, src, n);
	pagefault_enable();

	if (!partial)
		return 0;
	up_read(&current->mm->mmap_sem);
	partial = copy_from_user(dst, src, n);
	down_read(&current->mm->mmap_sem);

	return partial ? -EFAULT : 0;
  }

in case anybody else needs it. And even if nobody else does, making it a 
static inline function in fs/splice.c would at least separate out this 
thing from the core functionality, and just help keep things clear.

Wanna test that thing?

		Linus

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