i_shared_lock is held for a very long time during vmtruncate() and causes
high scheduling latencies when truncating a file which is mmapped.  I've seen
100 milliseconds.

So turn it into a semaphore.  It nests inside mmap_sem.

This change is also needed by the shared pagetable patch, which needs to
unshare pte's on the vmtruncate path - lots of pagetable pages need to
be allocated and they are using __GFP_WAIT.

The patch also makes unmap_vma() static.

This patch from Roland McGrath fixes a threading related ptrace bug:
PTRACE_ATTACH should not stop everybody for each thread attached.

This is needed by some includers of <asm/stat.h>.

Implementing hash_str as hash_mem(..., strlen()) is actually quite slow,
so create a separate hash_str.

Now hash_mem has only one call site, and both are quite small, so we make them
both inline.

blk_plug_device and blk_remove_plug want irqs_disabled,
so we give it to them.

I think this is finally right:
 - we always wake_up when curr_resync decreases.
 - we wait for the other guys curr_resync to be less than ours
 - if we ever wait for someone who might yield, we start checking
   again from the start.

Currently nfsd only worries about read-only exports for
directories and files, which allows device special files
to be chmodded (for example).

This patch extends the test to cover all files, but is careful
to avoid it when an IRIX client is doing an write-permission test
against a pre-existing device special file.

We encode that status in the return value.

Also, don't pass 'proc' parameter to ->accept, as it is
implicit in rqstp.

If one of the callback (e.g. data ready) is called
before socket setup is complete, oops may occur.

With this patch, socket is kept SK_BUSY until all is
ready to avoid this.

Also some code is moved around to make it cleaner.

into home.transmeta.com:/home/torvalds/v2.5/linux