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  1. 05 Jan, 2019 5 commits
    • Linus Torvalds's avatar
      Merge branch 'akpm' (patches from Andrew) · a6598110
      Linus Torvalds authored 
      Merge more updates from Andrew Morton:

 - procfs updates

 - various misc bits

 - lib/ updates

 - epoll updates

 - autofs

 - fatfs

 - a few more MM bits

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (58 commits)
  mm/page_io.c: fix polled swap page in
  checkpatch: add Co-developed-by to signature tags
  docs: fix Co-Developed-by docs
  drivers/base/platform.c: kmemleak ignore a known leak
  fs: don't open code lru_to_page()
  fs/: remove caller signal_pending branch predictions
  mm/: remove caller signal_pending branch predictions
  arch/arc/mm/fault.c: remove caller signal_pending_branch predictions
  kernel/sched/: remove caller signal_pending branch predictions
  kernel/locking/mutex.c: remove caller signal_pending branch predictions
  mm: select HAVE_MOVE_PMD on x86 for faster mremap
  mm: speed up mremap by 20x on large regions
  mm: treewide: remove unused address argument from pte_alloc functions
  initramfs: cleanup incomplete rootfs
  scripts/gdb: fix lx-version string output
  kernel/kcov.c: mark write_comp_data() as notrace
  kernel/sysctl: add panic_print into sysctl
  panic: add options to print system info when panic happens
  bfs: extra sanity checking and static inode bitmap
  exec: separate MM_ANONPAGES and RLIMIT_STACK accounting
  ...
      a6598110
    • Christoph Hellwig's avatar
      ia64: fix compile without swiotlb · 3fed6ae4
      Christoph Hellwig authored 
      Some non-generic ia64 configs don't build swiotlb, and thus should not
pull in the generic non-coherent DMA infrastructure.

Fixes: 68c60834 ("swiotlb: remove dma_mark_clean")
Reported-by: default avatarTony Luck <tony.luck@gmail.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      3fed6ae4
    • Linus Torvalds's avatar
      x86: re-introduce non-generic memcpy_{to,from}io · 170d13ca
      Linus Torvalds authored 
      This has been broken forever, and nobody ever really noticed because
it's purely a performance issue.

Long long ago, in commit 6175ddf0 ("x86: Clean up mem*io functions")
Brian Gerst simplified the memory copies to and from iomem, since on
x86, the instructions to access iomem are exactly the same as the
regular instructions.

That is technically true, and things worked, and nobody said anything.
Besides, back then the regular memcpy was pretty simple and worked fine.

Nobody noticed except for David Laight, that is.  David has a testing a
TLP monitor he was writing for an FPGA, and has been occasionally
complaining about how memcpy_toio() writes things one byte at a time.

Which is completely unacceptable from a performance standpoint, even if
it happens to technically work.

The reason it's writing one byte at a time is because while it's
technically true that accesses to iomem are the same as accesses to
regular memory on x86, the _granularity_ (and ordering) of accesses
matter to iomem in ways that they don't matter to regular cached memory.

In particular, when ERMS is set, we default to using "rep movsb" for
larger memory copies.  That is indeed perfectly fine for real memory,
since the whole point is that the CPU is going to do cacheline
optimizations and executes the memory copy efficiently for cached
memory.

With iomem? Not so much.  With iomem, "rep movsb" will indeed work, but
it will copy things one byte at a time. Slowly and ponderously.

Now, originally, back in 2010 when commit 6175ddf0 was done, we
didn't use ERMS, and this was much less noticeable.

Our normal memcpy() was simpler in other ways too.

Because in fact, it's not just about using the string instructions.  Our
memcpy() these days does things like "read and write overlapping values"
to handle the last bytes of the copy.  Again, for normal memory,
overlapping accesses isn't an issue.  For iomem? It can be.

So this re-introduces the specialized memcpy_toio(), memcpy_fromio() and
memset_io() functions.  It doesn't particularly optimize them, but it
tries to at least not be horrid, or do overlapping accesses.  In fact,
this uses the existing __inline_memcpy() function that we still had
lying around that uses our very traditional "rep movsl" loop followed by
movsw/movsb for the final bytes.

Somebody may decide to try to improve on it, but if we've gone almost a
decade with only one person really ever noticing and complaining, maybe
it's not worth worrying about further, once it's not _completely_ broken?
Reported-by: default avatarDavid Laight <David.Laight@aculab.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      170d13ca
    • Linus Torvalds's avatar
      Use __put_user_goto in __put_user_size() and unsafe_put_user() · a959dc88
      Linus Torvalds authored 
      This actually enables the __put_user_goto() functionality in
unsafe_put_user().

For an example of the effect of this, this is the code generated for the

        unsafe_put_user(signo, &infop->si_signo, Efault);

in the waitid() system call:

	movl %ecx,(%rbx)        # signo, MEM[(struct __large_struct *)_2]

It's just one single store instruction, along with generating an
exception table entry pointing to the Efault label case in case that
instruction faults.

Before, we would generate this:

	xorl    %edx, %edx
	movl %ecx,(%rbx)        # signo, MEM[(struct __large_struct *)_3]
        testl   %edx, %edx
        jne     .L309

with the exception table generated for that 'mov' instruction causing us
to jump to a stub that set %edx to -EFAULT and then jumped back to the
'testl' instruction.

So not only do we now get rid of the extra code in the normal sequence,
we also avoid unnecessarily keeping that extra error register live
across it all.
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a959dc88
    • Linus Torvalds's avatar
      x86 uaccess: Introduce __put_user_goto · 4a789213
      Linus Torvalds authored 
      This is finally the actual reason for the odd error handling in the
"unsafe_get/put_user()" functions, introduced over three years ago.

Using a "jump to error label" interface is somewhat odd, but very
convenient as a programming interface, and more importantly, it fits
very well with simply making the target be the exception handler address
directly from the inline asm.

The reason it took over three years to actually do this? We need "asm
goto" support for it, which only became the default on x86 last year.
It's now been a year that we've forced asm goto support (see commit
e501ce95 "x86: Force asm-goto"), and so let's just do it here too.

[ Side note: this commit was originally done back in 2016. The above
  commentary about timing is obviously about it only now getting merged
  into my real upstream tree     - Linus ]

Sadly, gcc still only supports "asm goto" with asms that do not have any
outputs, so we are limited to only the put_user case for this.  Maybe in
several more years we can do the get_user case too.
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      4a789213
  3. 04 Jan, 2019 35 commits
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