get_futex_key — Get parameters which are the keys for a futex
|u32 __user * uaddr,|
|union futex_key * key,|
u32 __user * uaddr
virtual address of the futex
0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED
union futex_key * key
address where result is stored.
mapping needs to be read/write (values: VERIFY_READ, VERIFY_WRITE)
a negative error code or 0
The key words are stored in *key on success.
For shared mappings, it's (page->index, file_inode(vma->vm_file), offset_within_page). For private mappings, it's (uaddr, current->mm). We can usually work out the index without swapping in the page.
lock_page might sleep, the caller should not hold a spinlock.