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  1. 29 5月, 2016 8 次提交
    • G
      m68k: Add <asm/hash.h> · 14c44b95
      由 George Spelvin 提交于 
      This provides a multiply by constant GOLDEN_RATIO_32 = 0x61C88647
for the original mc68000, which lacks a 32x32-bit multiply instruction.

Yes, the amount of optimization effort put in is excessive. :-)

Shift-add chain found by Yevgen Voronenko's Hcub algorithm at
http://spiral.ece.cmu.edu/mcm/gen.htmlSigned-off-by: NGeorge Spelvin <linux@sciencehorizons.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Cc: Philippe De Muyter <phdm@macq.eu>
Cc: linux-m68k@lists.linux-m68k.org
      14c44b95
    • G
      <linux/hash.h>: Add support for architecture-specific functions · 468a9428
      由 George Spelvin 提交于 
      This is just the infrastructure; there are no users yet.

This is modelled on CONFIG_ARCH_RANDOM; a CONFIG_ symbol declares
the existence of <asm/hash.h>.

That file may define its own versions of various functions, and define
HAVE_* symbols (no CONFIG_ prefix!) to suppress the generic ones.

Included is a self-test (in lib/test_hash.c) that verifies the basics.
It is NOT in general required that the arch-specific functions compute
the same thing as the generic, but if a HAVE_* symbol is defined with
the value 1, then equality is tested.
Signed-off-by: NGeorge Spelvin <linux@sciencehorizons.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Cc: Philippe De Muyter <phdm@macq.eu>
Cc: linux-m68k@lists.linux-m68k.org
Cc: Alistair Francis <alistai@xilinx.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: uclinux-h8-devel@lists.sourceforge.jp
      468a9428
    • G
      fs/namei.c: Improve dcache hash function · 2a18da7a
      由 George Spelvin 提交于 
      Patch 0fed3ac8 improved the hash mixing, but the function is slower
than necessary; there's a 7-instruction dependency chain (10 on x86)
each loop iteration.

Word-at-a-time access is a very tight loop (which is good, because
link_path_walk() is one of the hottest code paths in the entire kernel),
and the hash mixing function must not have a longer latency to avoid
slowing it down.

There do not appear to be any published fast hash functions that:
1) Operate on the input a word at a time, and
2) Don't need to know the length of the input beforehand, and
3) Have a single iterated mixing function, not needing conditional
   branches or unrolling to distinguish different loop iterations.

One of the algorithms which comes closest is Yann Collet's xxHash, but
that's two dependent multiplies per word, which is too much.

The key insights in this design are:

1) Barring expensive ops like multiplies, to diffuse one input bit
   across 64 bits of hash state takes at least log2(64) = 6 sequentially
   dependent instructions.  That is more cycles than we'd like.
2) An operation like "hash ^= hash << 13" requires a second temporary
   register anyway, and on a 2-operand machine like x86, it's three
   instructions.
3) A better use of a second register is to hold a two-word hash state.
   With careful design, no temporaries are needed at all, so it doesn't
   increase register pressure.  And this gets rid of register copying
   on 2-operand machines, so the code is smaller and faster.
4) Using two words of state weakens the requirement for one-round mixing;
   we now have two rounds of mixing before cancellation is possible.
5) A two-word hash state also allows operations on both halves to be
   done in parallel, so on a superscalar processor we get more mixing
   in fewer cycles.

I ended up using a mixing function inspired by the ChaCha and Speck
round functions.  It is 6 simple instructions and 3 cycles per iteration
(assuming multiply by 9 can be done by an "lea" instruction):

		x ^= *input++;
	y ^= x;	x = ROL(x, K1);
	x += y;	y = ROL(y, K2);
	y *= 9;

Not only is this reversible, two consecutive rounds are reversible:
if you are given the initial and final states, but not the intermediate
state, it is possible to compute both input words.  This means that at
least 3 words of input are required to create a collision.

(It also has the property, used by hash_name() to avoid a branch, that
it hashes all-zero to all-zero.)

The rotate constants K1 and K2 were found by experiment.  The search took
a sample of random initial states (I used 1023) and considered the effect
of flipping each of the 64 input bits on each of the 128 output bits two
rounds later.  Each of the 8192 pairs can be considered a biased coin, and
adding up the Shannon entropy of all of them produces a score.

The best-scoring shifts also did well in other tests (flipping bits in y,
trying 3 or 4 rounds of mixing, flipping all 64*63/2 pairs of input bits),
so the choice was made with the additional constraint that the sum of the
shifts is odd and not too close to the word size.

The final state is then folded into a 32-bit hash value by a less carefully
optimized multiply-based scheme.  This also has to be fast, as pathname
components tend to be short (the most common case is one iteration!), but
there's some room for latency, as there is a fair bit of intervening logic
before the hash value is used for anything.

(Performance verified with "bonnie++ -s 0 -n 1536:-2" on tmpfs.  I need
a better benchmark; the numbers seem to show a slight dip in performance
between 4.6.0 and this patch, but they're too noisy to quote.)

Special thanks to Bruce fields for diligent testing which uncovered a
nasty fencepost error in an earlier version of this patch.

[checkpatch.pl formatting complaints noted and respectfully disagreed with.]
Signed-off-by: NGeorge Spelvin <linux@sciencehorizons.net>
Tested-by: NJ. Bruce Fields <bfields@redhat.com>
      2a18da7a
    • G
      Eliminate bad hash multipliers from hash_32() and hash_64() · ef703f49
      由 George Spelvin 提交于 
      The "simplified" prime multipliers made very bad hash functions, so get rid
of them.  This completes the work of 689de1d6.

To avoid the inefficiency which was the motivation for the "simplified"
multipliers, hash_64() on 32-bit systems is changed to use a different
algorithm.  It makes two calls to hash_32() instead.

drivers/media/usb/dvb-usb-v2/af9015.c uses the old GOLDEN_RATIO_PRIME_32
for some horrible reason, so it inherits a copy of the old definition.
Signed-off-by: NGeorge Spelvin <linux@sciencehorizons.net>
Cc: Antti Palosaari <crope@iki.fi>
Cc: Mauro Carvalho Chehab <m.chehab@samsung.com>
      ef703f49
    • G
      Change hash_64() return value to 32 bits · 92d56774
      由 George Spelvin 提交于 
      That's all that's ever asked for, and it makes the return
type of hash_long() consistent.

It also allows (upcoming patch) an optimized implementation
of hash_64 on 32-bit machines.

I tried adding a BUILD_BUG_ON to ensure the number of bits requested
was never more than 32 (most callers use a compile-time constant), but
adding <linux/bug.h> to <linux/hash.h> breaks the tools/perf compiler
unless tools/perf/MANIFEST is updated, and understanding that code base
well enough to update it is too much trouble.  I did the rest of an
allyesconfig build with such a check, and nothing tripped.
Signed-off-by: NGeorge Spelvin <linux@sciencehorizons.net>
      92d56774
    • G
      <linux/sunrpc/svcauth.h>: Define hash_str() in terms of hashlen_string() · 917ea166
      由 George Spelvin 提交于 
      Finally, the first use of previous two patches: eliminate the
separate ad-hoc string hash functions in the sunrpc code.

Now hash_str() is a wrapper around hash_string(), and hash_mem() is
likewise a wrapper around full_name_hash().

Note that sunrpc code *does* call hash_mem() with a zero length, which
is why the previous patch needed to handle that in full_name_hash().
(Thanks, Bruce, for finding that!)

This also eliminates the only caller of hash_long which asks for
more than 32 bits of output.

The comment about the quality of hashlen_string() and full_name_hash()
is jumping the gun by a few patches; they aren't very impressive now,
but will be improved greatly later in the series.
Signed-off-by: NGeorge Spelvin <linux@sciencehorizons.net>
Tested-by: NJ. Bruce Fields <bfields@redhat.com>
Acked-by: NJ. Bruce Fields <bfields@redhat.com>
Cc: Jeff Layton <jlayton@poochiereds.net>
Cc: linux-nfs@vger.kernel.org
      917ea166
    • G
      fs/namei.c: Add hashlen_string() function · fcfd2fbf
      由 George Spelvin 提交于 
      We'd like to make more use of the highly-optimized dcache hash functions
throughout the kernel, rather than have every subsystem create its own,
and a function that hashes basic null-terminated strings is required
for that.

(The name is to emphasize that it returns both hash and length.)

It's actually useful in the dcache itself, specifically d_alloc_name().
Other uses in the next patch.

full_name_hash() is also tweaked to make it more generally useful:
1) Take a "char *" rather than "unsigned char *" argument, to
   be consistent with hash_name().
2) Handle zero-length inputs.  If we want more callers, we don't want
   to make them worry about corner cases.
Signed-off-by: NGeorge Spelvin <linux@sciencehorizons.net>
      fcfd2fbf
    • G
      Pull out string hash to <linux/stringhash.h> · f4bcbe79
      由 George Spelvin 提交于 
      ... so they can be used without the rest of <linux/dcache.h>

The hashlen_* macros will make sense next patch.
Signed-off-by: NGeorge Spelvin <linux@sciencehorizons.net>
      f4bcbe79
  3. 17 5月, 2016 1 次提交
  5. 16 5月, 2016 1 次提交
  7. 15 5月, 2016 6 次提交
    • L
      Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · 5f95063c
      由 Linus Torvalds 提交于 
      Pull x86 fix from Thomas Gleixner:
 "Just the missing compat entry for the new pread/writev2"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86: Use compat version for preadv2 and pwritev2
      5f95063c
    • L
      Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net · 272911b8
      由 Linus Torvalds 提交于 
      Pull networking fixes from David Miller:

 1) Fix mvneta/bm dependencies, from Arnd Bergmann.

 2) RX completion hw bug workaround in bnxt_en, from Michael Chan.

 3) Kernel pointer leak in nf_conntrack, from Linus.

 4) Hoplimit route attribute limits not enforced properly, from Paolo
    Abeni.

 5) qlcnic driver NULL deref fix from Dan Carpenter.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net:
  arm64: bpf: jit JMP_JSET_{X,K}
  net/route: enforce hoplimit max value
  nf_conntrack: avoid kernel pointer value leak in slab name
  drivers: net: xgene: fix register offset
  drivers: net: xgene: fix statistics counters race condition
  drivers: net: xgene: fix ununiform latency across queues
  drivers: net: xgene: fix sharing of irqs
  drivers: net: xgene: fix IPv4 forward crash
  xen-netback: fix extra_info handling in xenvif_tx_err()
  net: mvneta: bm: fix dependencies again
  bnxt_en: Add workaround to detect bad opaque in rx completion (part 2)
  bnxt_en: Add workaround to detect bad opaque in rx completion (part 1)
  qlcnic: potential NULL dereference in qlcnic_83xx_get_minidump_template()
      272911b8
    • Z
      arm64: bpf: jit JMP_JSET_{X,K} · 98397fc5
      由 Zi Shen Lim 提交于 
      Original implementation commit e54bcde3 ("arm64: eBPF JIT compiler")
had the relevant code paths, but due to an oversight always fail jiting.

As a result, we had been falling back to BPF interpreter whenever a BPF
program has JMP_JSET_{X,K} instructions.

With this fix, we confirm that the corresponding tests in lib/test_bpf
continue to pass, and also jited.

...
[    2.784553] test_bpf: #30 JSET jited:1 188 192 197 PASS
[    2.791373] test_bpf: #31 tcpdump port 22 jited:1 325 677 625 PASS
[    2.808800] test_bpf: #32 tcpdump complex jited:1 323 731 991 PASS
...
[    3.190759] test_bpf: #237 JMP_JSET_K: if (0x3 & 0x2) return 1 jited:1 110 PASS
[    3.192524] test_bpf: #238 JMP_JSET_K: if (0x3 & 0xffffffff) return 1 jited:1 98 PASS
[    3.211014] test_bpf: #249 JMP_JSET_X: if (0x3 & 0x2) return 1 jited:1 120 PASS
[    3.212973] test_bpf: #250 JMP_JSET_X: if (0x3 & 0xffffffff) return 1 jited:1 89 PASS
...

Fixes: e54bcde3 ("arm64: eBPF JIT compiler")
Signed-off-by: NZi Shen Lim <zlim.lnx@gmail.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Acked-by: NYang Shi <yang.shi@linaro.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      98397fc5
    • P
      net/route: enforce hoplimit max value · 626abd59
      由 Paolo Abeni 提交于 
      Currently, when creating or updating a route, no check is performed
in both ipv4 and ipv6 code to the hoplimit value.

The caller can i.e. set hoplimit to 256, and when such route will
 be used, packets will be sent with hoplimit/ttl equal to 0.

This commit adds checks for the RTAX_HOPLIMIT value, in both ipv4
ipv6 route code, substituting any value greater than 255 with 255.

This is consistent with what is currently done for ADVMSS and MTU
in the ipv4 code.
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      626abd59
    • L
      nf_conntrack: avoid kernel pointer value leak in slab name · 31b0b385
      由 Linus Torvalds 提交于 
      The slab name ends up being visible in the directory structure under
/sys, and even if you don't have access rights to the file you can see
the filenames.

Just use a 64-bit counter instead of the pointer to the 'net' structure
to generate a unique name.

This code will go away in 4.7 when the conntrack code moves to a single
kmemcache, but this is the backportable simple solution to avoiding
leaking kernel pointers to user space.

Fixes: 5b3501fa ("netfilter: nf_conntrack: per netns nf_conntrack_cachep")
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Acked-by: NEric Dumazet <eric.dumazet@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      31b0b385
    • L
      Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs · 6ba5b85f
      由 Linus Torvalds 提交于 
      Pull vfs fixes from Al Viro:
 "Overlayfs fixes from Miklos, assorted fixes from me.

  Stable fodder of varying severity, all sat in -next for a while"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  ovl: ignore permissions on underlying lookup
  vfs: add lookup_hash() helper
  vfs: rename: check backing inode being equal
  vfs: add vfs_select_inode() helper
  get_rock_ridge_filename(): handle malformed NM entries
  ecryptfs: fix handling of directory opening
  atomic_open(): fix the handling of create_error
  fix the copy vs. map logics in blk_rq_map_user_iov()
  do_splice_to(): cap the size before passing to ->splice_read()
      6ba5b85f
  9. 14 5月, 2016 16 次提交
  11. 13 5月, 2016 8 次提交