callers of iov_copy_from_user_atomic() don't need pagecache_disable()

... it does that itself (via kmap_atomic())

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/btrfs/file.c
Simple merge

diff --cc fs/fuse/file.c
Simple merge

diff --cc mm/filemap.c
Simple merge