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  1. 01 5月, 2019 1 次提交
  3. 26 4月, 2019 1 次提交
  5. 16 4月, 2019 1 次提交
  7. 07 4月, 2019 1 次提交
    • K
      fs: stream_open - opener for stream-like files so that read and write can run... · 10dce8af
      由 Kirill Smelkov 提交于 
      fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock

Commit 9c225f26 ("vfs: atomic f_pos accesses as per POSIX") added
locking for file.f_pos access and in particular made concurrent read and
write not possible - now both those functions take f_pos lock for the
whole run, and so if e.g. a read is blocked waiting for data, write will
deadlock waiting for that read to complete.

This caused regression for stream-like files where previously read and
write could run simultaneously, but after that patch could not do so
anymore. See e.g. commit 581d21a2 ("xenbus: fix deadlock on writes
to /proc/xen/xenbus") which fixes such regression for particular case of
/proc/xen/xenbus.

The patch that added f_pos lock in 2014 did so to guarantee POSIX thread
safety for read/write/lseek and added the locking to file descriptors of
all regular files. In 2014 that thread-safety problem was not new as it
was already discussed earlier in 2006.

However even though 2006'th version of Linus's patch was adding f_pos
locking "only for files that are marked seekable with FMODE_LSEEK (thus
avoiding the stream-like objects like pipes and sockets)", the 2014
version - the one that actually made it into the tree as 9c225f26 -
is doing so irregardless of whether a file is seekable or not.

See

    https://lore.kernel.org/lkml/53022DB1.4070805@gmail.com/
    https://lwn.net/Articles/180387
    https://lwn.net/Articles/180396

for historic context.

The reason that it did so is, probably, that there are many files that
are marked non-seekable, but e.g. their read implementation actually
depends on knowing current position to correctly handle the read. Some
examples:

	kernel/power/user.c		snapshot_read
	fs/debugfs/file.c		u32_array_read
	fs/fuse/control.c		fuse_conn_waiting_read + ...
	drivers/hwmon/asus_atk0110.c	atk_debugfs_ggrp_read
	arch/s390/hypfs/inode.c		hypfs_read_iter
	...

Despite that, many nonseekable_open users implement read and write with
pure stream semantics - they don't depend on passed ppos at all. And for
those cases where read could wait for something inside, it creates a
situation similar to xenbus - the write could be never made to go until
read is done, and read is waiting for some, potentially external, event,
for potentially unbounded time -> deadlock.

Besides xenbus, there are 14 such places in the kernel that I've found
with semantic patch (see below):

	drivers/xen/evtchn.c:667:8-24: ERROR: evtchn_fops: .read() can deadlock .write()
	drivers/isdn/capi/capi.c:963:8-24: ERROR: capi_fops: .read() can deadlock .write()
	drivers/input/evdev.c:527:1-17: ERROR: evdev_fops: .read() can deadlock .write()
	drivers/char/pcmcia/cm4000_cs.c:1685:7-23: ERROR: cm4000_fops: .read() can deadlock .write()
	net/rfkill/core.c:1146:8-24: ERROR: rfkill_fops: .read() can deadlock .write()
	drivers/s390/char/fs3270.c:488:1-17: ERROR: fs3270_fops: .read() can deadlock .write()
	drivers/usb/misc/ldusb.c:310:1-17: ERROR: ld_usb_fops: .read() can deadlock .write()
	drivers/hid/uhid.c:635:1-17: ERROR: uhid_fops: .read() can deadlock .write()
	net/batman-adv/icmp_socket.c:80:1-17: ERROR: batadv_fops: .read() can deadlock .write()
	drivers/media/rc/lirc_dev.c:198:1-17: ERROR: lirc_fops: .read() can deadlock .write()
	drivers/leds/uleds.c:77:1-17: ERROR: uleds_fops: .read() can deadlock .write()
	drivers/input/misc/uinput.c:400:1-17: ERROR: uinput_fops: .read() can deadlock .write()
	drivers/infiniband/core/user_mad.c:985:7-23: ERROR: umad_fops: .read() can deadlock .write()
	drivers/gnss/core.c:45:1-17: ERROR: gnss_fops: .read() can deadlock .write()

In addition to the cases above another regression caused by f_pos
locking is that now FUSE filesystems that implement open with
FOPEN_NONSEEKABLE flag, can no longer implement bidirectional
stream-like files - for the same reason as above e.g. read can deadlock
write locking on file.f_pos in the kernel.

FUSE's FOPEN_NONSEEKABLE was added in 2008 in a7c1b990 ("fuse:
implement nonseekable open") to support OSSPD. OSSPD implements /dev/dsp
in userspace with FOPEN_NONSEEKABLE flag, with corresponding read and
write routines not depending on current position at all, and with both
read and write being potentially blocking operations:

See

    https://github.com/libfuse/osspd
    https://lwn.net/Articles/308445

    https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1406
    https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1438-L1477
    https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1479-L1510

Corresponding libfuse example/test also describes FOPEN_NONSEEKABLE as
"somewhat pipe-like files ..." with read handler not using offset.
However that test implements only read without write and cannot exercise
the deadlock scenario:

    https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L124-L131
    https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L146-L163
    https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L209-L216

I've actually hit the read vs write deadlock for real while implementing
my FUSE filesystem where there is /head/watch file, for which open
creates separate bidirectional socket-like stream in between filesystem
and its user with both read and write being later performed
simultaneously. And there it is semantically not easy to split the
stream into two separate read-only and write-only channels:

    https://lab.nexedi.com/kirr/wendelin.core/blob/f13aa600/wcfs/wcfs.go#L88-169

Let's fix this regression. The plan is:

1. We can't change nonseekable_open to include &~FMODE_ATOMIC_POS -
   doing so would break many in-kernel nonseekable_open users which
   actually use ppos in read/write handlers.

2. Add stream_open() to kernel to open stream-like non-seekable file
   descriptors. Read and write on such file descriptors would never use
   nor change ppos. And with that property on stream-like files read and
   write will be running without taking f_pos lock - i.e. read and write
   could be running simultaneously.

3. With semantic patch search and convert to stream_open all in-kernel
   nonseekable_open users for which read and write actually do not
   depend on ppos and where there is no other methods in file_operations
   which assume @offset access.

4. Add FOPEN_STREAM to fs/fuse/ and open in-kernel file-descriptors via
   steam_open if that bit is present in filesystem open reply.

   It was tempting to change fs/fuse/ open handler to use stream_open
   instead of nonseekable_open on just FOPEN_NONSEEKABLE flags, but
   grepping through Debian codesearch shows users of FOPEN_NONSEEKABLE,
   and in particular GVFS which actually uses offset in its read and
   write handlers

	https://codesearch.debian.net/search?q=-%3Enonseekable+%3D
	https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1080
	https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1247-1346
	https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1399-1481

   so if we would do such a change it will break a real user.

5. Add stream_open and FOPEN_STREAM handling to stable kernels starting
   from v3.14+ (the kernel where 9c225f26 first appeared).

   This will allow to patch OSSPD and other FUSE filesystems that
   provide stream-like files to return FOPEN_STREAM | FOPEN_NONSEEKABLE
   in their open handler and this way avoid the deadlock on all kernel
   versions. This should work because fs/fuse/ ignores unknown open
   flags returned from a filesystem and so passing FOPEN_STREAM to a
   kernel that is not aware of this flag cannot hurt. In turn the kernel
   that is not aware of FOPEN_STREAM will be < v3.14 where just
   FOPEN_NONSEEKABLE is sufficient to implement streams without read vs
   write deadlock.

This patch adds stream_open, converts /proc/xen/xenbus to it and adds
semantic patch to automatically locate in-kernel places that are either
required to be converted due to read vs write deadlock, or that are just
safe to be converted because read and write do not use ppos and there
are no other funky methods in file_operations.

Regarding semantic patch I've verified each generated change manually -
that it is correct to convert - and each other nonseekable_open instance
left - that it is either not correct to convert there, or that it is not
converted due to current stream_open.cocci limitations.

The script also does not convert files that should be valid to convert,
but that currently have .llseek = noop_llseek or generic_file_llseek for
unknown reason despite file being opened with nonseekable_open (e.g.
drivers/input/mousedev.c)

Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Yongzhi Pan <panyongzhi@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Tejun Heo <tj@kernel.org>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: Nikolaus Rath <Nikolaus@rath.org>
Cc: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: NKirill Smelkov <kirr@nexedi.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      10dce8af
  9. 06 4月, 2019 4 次提交
    • G
      mm: writeback: use exact memcg dirty counts · 0b3d6e6f
      由 Greg Thelen 提交于 
      Since commit a983b5eb ("mm: memcontrol: fix excessive complexity in
memory.stat reporting") memcg dirty and writeback counters are managed
as:

 1) per-memcg per-cpu values in range of [-32..32]

 2) per-memcg atomic counter

When a per-cpu counter cannot fit in [-32..32] it's flushed to the
atomic.  Stat readers only check the atomic.  Thus readers such as
balance_dirty_pages() may see a nontrivial error margin: 32 pages per
cpu.

Assuming 100 cpus:
   4k x86 page_size:  13 MiB error per memcg
  64k ppc page_size: 200 MiB error per memcg

Considering that dirty+writeback are used together for some decisions the
errors double.

This inaccuracy can lead to undeserved oom kills.  One nasty case is
when all per-cpu counters hold positive values offsetting an atomic
negative value (i.e.  per_cpu[*]=32, atomic=n_cpu*-32).
balance_dirty_pages() only consults the atomic and does not consider
throttling the next n_cpu*32 dirty pages.  If the file_lru is in the
13..200 MiB range then there's absolutely no dirty throttling, which
burdens vmscan with only dirty+writeback pages thus resorting to oom
kill.

It could be argued that tiny containers are not supported, but it's more
subtle.  It's the amount the space available for file lru that matters.
If a container has memory.max-200MiB of non reclaimable memory, then it
will also suffer such oom kills on a 100 cpu machine.

The following test reliably ooms without this patch.  This patch avoids
oom kills.

  $ cat test
  mount -t cgroup2 none /dev/cgroup
  cd /dev/cgroup
  echo +io +memory > cgroup.subtree_control
  mkdir test
  cd test
  echo 10M > memory.max
  (echo $BASHPID > cgroup.procs && exec /memcg-writeback-stress /foo)
  (echo $BASHPID > cgroup.procs && exec dd if=/dev/zero of=/foo bs=2M count=100)

  $ cat memcg-writeback-stress.c
  /*
   * Dirty pages from all but one cpu.
   * Clean pages from the non dirtying cpu.
   * This is to stress per cpu counter imbalance.
   * On a 100 cpu machine:
   * - per memcg per cpu dirty count is 32 pages for each of 99 cpus
   * - per memcg atomic is -99*32 pages
   * - thus the complete dirty limit: sum of all counters 0
   * - balance_dirty_pages() only sees atomic count -99*32 pages, which
   *   it max()s to 0.
   * - So a workload can dirty -99*32 pages before balance_dirty_pages()
   *   cares.
   */
  #define _GNU_SOURCE
  #include <err.h>
  #include <fcntl.h>
  #include <sched.h>
  #include <stdlib.h>
  #include <stdio.h>
  #include <sys/stat.h>
  #include <sys/sysinfo.h>
  #include <sys/types.h>
  #include <unistd.h>

  static char *buf;
  static int bufSize;

  static void set_affinity(int cpu)
  {
  	cpu_set_t affinity;

  	CPU_ZERO(&affinity);
  	CPU_SET(cpu, &affinity);
  	if (sched_setaffinity(0, sizeof(affinity), &affinity))
  		err(1, "sched_setaffinity");
  }

  static void dirty_on(int output_fd, int cpu)
  {
  	int i, wrote;

  	set_affinity(cpu);
  	for (i = 0; i < 32; i++) {
  		for (wrote = 0; wrote < bufSize; ) {
  			int ret = write(output_fd, buf+wrote, bufSize-wrote);
  			if (ret == -1)
  				err(1, "write");
  			wrote += ret;
  		}
  	}
  }

  int main(int argc, char **argv)
  {
  	int cpu, flush_cpu = 1, output_fd;
  	const char *output;

  	if (argc != 2)
  		errx(1, "usage: output_file");

  	output = argv[1];
  	bufSize = getpagesize();
  	buf = malloc(getpagesize());
  	if (buf == NULL)
  		errx(1, "malloc failed");

  	output_fd = open(output, O_CREAT|O_RDWR);
  	if (output_fd == -1)
  		err(1, "open(%s)", output);

  	for (cpu = 0; cpu < get_nprocs(); cpu++) {
  		if (cpu != flush_cpu)
  			dirty_on(output_fd, cpu);
  	}

  	set_affinity(flush_cpu);
  	if (fsync(output_fd))
  		err(1, "fsync(%s)", output);
  	if (close(output_fd))
  		err(1, "close(%s)", output);
  	free(buf);
  }

Make balance_dirty_pages() and wb_over_bg_thresh() work harder to
collect exact per memcg counters.  This avoids the aforementioned oom
kills.

This does not affect the overhead of memory.stat, which still reads the
single atomic counter.

Why not use percpu_counter? memcg already handles cpus going offline, so
no need for that overhead from percpu_counter.  And the percpu_counter
spinlocks are more heavyweight than is required.

It probably also makes sense to use exact dirty and writeback counters
in memcg oom reports.  But that is saved for later.

Link: http://lkml.kernel.org/r/20190329174609.164344-1-gthelen@google.comSigned-off-by: NGreg Thelen <gthelen@google.com>
Reviewed-by: NRoman Gushchin <guro@fb.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>	[4.16+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      0b3d6e6f
    • J
      mm: fix vm_fault_t cast in VM_FAULT_GET_HINDEX() · fcae96ff
      由 Jann Horn 提交于 
      Symmetrically to VM_FAULT_SET_HINDEX(), we need a force-cast in
VM_FAULT_GET_HINDEX() to tell sparse that this is intentional.

Sparse complains about the current code when building a kernel with
CONFIG_MEMORY_FAILURE:

  arch/x86/mm/fault.c:1058:53: warning: restricted vm_fault_t degrades to integer

Link: http://lkml.kernel.org/r/20190327204117.35215-1-jannh@google.com
Fixes: 3d353901 ("mm: create the new vm_fault_t type")
Signed-off-by: NJann Horn <jannh@google.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      fcae96ff
    • A
      include/linux/bitrev.h: fix constant bitrev · 6147e136
      由 Arnd Bergmann 提交于 
      clang points out with hundreds of warnings that the bitrev macros have a
problem with constant input:

  drivers/hwmon/sht15.c:187:11: error: variable '__x' is uninitialized when used within its own initialization
        [-Werror,-Wuninitialized]
          u8 crc = bitrev8(data->val_status & 0x0F);
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  include/linux/bitrev.h:102:21: note: expanded from macro 'bitrev8'
          __constant_bitrev8(__x) :                       \
          ~~~~~~~~~~~~~~~~~~~^~~~
  include/linux/bitrev.h:67:11: note: expanded from macro '__constant_bitrev8'
          u8 __x = x;                     \
             ~~~   ^

Both the bitrev and the __constant_bitrev macros use an internal
variable named __x, which goes horribly wrong when passing one to the
other.

The obvious fix is to rename one of the variables, so this adds an extra
'_'.

It seems we got away with this because

 - there are only a few drivers using bitrev macros

 - usually there are no constant arguments to those

 - when they are constant, they tend to be either 0 or (unsigned)-1
   (drivers/isdn/i4l/isdnhdlc.o, drivers/iio/amplifiers/ad8366.c) and
   give the correct result by pure chance.

In fact, the only driver that I could find that gets different results
with this is drivers/net/wan/slic_ds26522.c, which in turn is a driver
for fairly rare hardware (adding the maintainer to Cc for testing).

Link: http://lkml.kernel.org/r/20190322140503.123580-1-arnd@arndb.de
Fixes: 556d2f05 ("ARM: 8187/1: add CONFIG_HAVE_ARCH_BITREVERSE to support rbit instruction")
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
Cc: Zhao Qiang <qiang.zhao@nxp.com>
Cc: Yalin Wang <yalin.wang@sonymobile.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      6147e136
    • N
      lib/string.c: implement a basic bcmp · 5f074f3e
      由 Nick Desaulniers 提交于 
      A recent optimization in Clang (r355672) lowers comparisons of the
return value of memcmp against zero to comparisons of the return value
of bcmp against zero.  This helps some platforms that implement bcmp
more efficiently than memcmp.  glibc simply aliases bcmp to memcmp, but
an optimized implementation is in the works.

This results in linkage failures for all targets with Clang due to the
undefined symbol.  For now, just implement bcmp as a tailcail to memcmp
to unbreak the build.  This routine can be further optimized in the
future.

Other ideas discussed:

 * A weak alias was discussed, but breaks for architectures that define
   their own implementations of memcmp since aliases to declarations are
   not permitted (only definitions). Arch-specific memcmp
   implementations typically declare memcmp in C headers, but implement
   them in assembly.

 * -ffreestanding also is used sporadically throughout the kernel.

 * -fno-builtin-bcmp doesn't work when doing LTO.

Link: https://bugs.llvm.org/show_bug.cgi?id=41035
Link: https://code.woboq.org/userspace/glibc/string/memcmp.c.html#bcmp
Link: https://github.com/llvm/llvm-project/commit/8e16d73346f8091461319a7dfc4ddd18eedcff13
Link: https://github.com/ClangBuiltLinux/linux/issues/416
Link: http://lkml.kernel.org/r/20190313211335.165605-1-ndesaulniers@google.comSigned-off-by: NNick Desaulniers <ndesaulniers@google.com>
Reported-by: NNathan Chancellor <natechancellor@gmail.com>
Reported-by: NAdhemerval Zanella <adhemerval.zanella@linaro.org>
Suggested-by: NArnd Bergmann <arnd@arndb.de>
Suggested-by: NJames Y Knight <jyknight@google.com>
Suggested-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Suggested-by: NNathan Chancellor <natechancellor@gmail.com>
Suggested-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: NNathan Chancellor <natechancellor@gmail.com>
Tested-by: NNathan Chancellor <natechancellor@gmail.com>
Reviewed-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      5f074f3e
  11. 04 4月, 2019 1 次提交
    • S
      ptrace: Remove maxargs from task_current_syscall() · 631b7aba
      由 Steven Rostedt (Red Hat) 提交于 
      task_current_syscall() has a single user that passes in 6 for maxargs, which
is the maximum arguments that can be used to get system calls from
syscall_get_arguments(). Instead of passing in a number of arguments to
grab, just get 6 arguments. The args argument even specifies that it's an
array of 6 items.

This will also allow changing syscall_get_arguments() to not get a variable
number of arguments, but always grab 6.

Linus also suggested not passing in a bunch of arguments to
task_current_syscall() but to instead pass in a pointer to a structure, and
just fill the structure. struct seccomp_data has almost all the parameters
that is needed except for the stack pointer (sp). As seccomp_data is part of
uapi, and I'm afraid to change it, a new structure was created
"syscall_info", which includes seccomp_data and adds the "sp" field.

Link: http://lkml.kernel.org/r/20161107213233.466776454@goodmis.org

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
      631b7aba
  13. 30 3月, 2019 6 次提交
  15. 28 3月, 2019 2 次提交
  17. 27 3月, 2019 1 次提交
  19. 26 3月, 2019 2 次提交
    • B
      proc/kcore: Remove unused kclist_add_remap() · db779ef6
      由 Bhupesh Sharma 提交于 
      Commit

  bf904d27 ("x86/pti/64: Remove the SYSCALL64 entry trampoline")

removed the sole usage of kclist_add_remap() but it did not remove the
left-over definition from the include file.

Fix the same.
Signed-off-by: NBhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Anderson <anderson@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Kairui Song <kasong@redhat.com>
Cc: kexec@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Omar Sandoval <osandov@fb.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/1553583028-17804-1-git-send-email-bhsharma@redhat.com
      db779ef6
    • L
      Revert "parport: daisy: use new parport device model" · a3ac7917
      由 Linus Torvalds 提交于 
      This reverts commit 1aec4211.

Steven Rostedt reports that it causes a hang at bootup and bisected it
to this commit.

The troigger is apparently a module alias for "parport_lowlevel" that
points to "parport_pc", which causes a hang with

    modprobe -q -- parport_lowlevel

blocking forever with a backtrace like this:

    wait_for_completion_killable+0x1c/0x28
    call_usermodehelper_exec+0xa7/0x108
    __request_module+0x351/0x3d8
    get_lowlevel_driver+0x28/0x41 [parport]
    __parport_register_driver+0x39/0x1f4 [parport]
    daisy_drv_init+0x31/0x4f [parport]
    parport_bus_init+0x5d/0x7b [parport]
    parport_default_proc_register+0x26/0x1000 [parport]
    do_one_initcall+0xc2/0x1e0
    do_init_module+0x50/0x1d4
    load_module+0x1c2e/0x21b3
    sys_init_module+0xef/0x117

Supid says:
 "Due to the new device model daisy driver will now try to find the
  parallel ports while trying to register its driver so that it can bind
  with them. Now, since daisy driver is loaded while parport bus is
  initialising the list of parport is still empty and it tries to load
  the lowlevel driver, which has an alias set to parport_pc, now causes
  a deadlock"

But I don't think the daisy driver should be loaded by the parport
initialization in the first place, so let's revert the whole change.

If the daisy driver can just initialize separately on its own (like a
driver should), instead of hooking into the parport init sequence
directly, this issue probably would go away.
Reported-and-bisected-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Reported-by: NMichal Kubecek <mkubecek@suse.cz>
Acked-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a3ac7917
  21. 23 3月, 2019 2 次提交
  23. 22 3月, 2019 1 次提交
    • T
      gpio: amd-fch: Fix bogus SPDX identifier · b45a02e1
      由 Thomas Gleixner 提交于 
      spdxcheck.py complains:

 include/linux/platform_data/gpio/gpio-amd-fch.h: 1:28 Invalid License ID: GPL+

which is correct because GPL+ is not a valid identifier. Of course this
could have been caught by checkpatch.pl _before_ submitting or merging the
patch.

 WARNING: 'SPDX-License-Identifier: GPL+ */' is not supported in LICENSES/...
 #271: FILE: include/linux/platform_data/gpio/gpio-amd-fch.h:1:
 +/* SPDX-License-Identifier: GPL+ */

Fix it under the assumption that the author meant GPL-2.0+, which makes
sense as the corresponding C file is using that identifier.

Fixes: e09d168f ("gpio: AMD G-Series PCH gpio driver")
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NBartosz Golaszewski <bgolaszewski@baylibre.com>
      b45a02e1
  25. 21 3月, 2019 3 次提交
  27. 20 3月, 2019 1 次提交
    • I
      libceph: wait for latest osdmap in ceph_monc_blacklist_add() · bb229bbb
      由 Ilya Dryomov 提交于 
      Because map updates are distributed lazily, an OSD may not know about
the new blacklist for quite some time after "osd blacklist add" command
is completed.  This makes it possible for a blacklisted but still alive
client to overwrite a post-blacklist update, resulting in data
corruption.

Waiting for latest osdmap in ceph_monc_blacklist_add() and thus using
the post-blacklist epoch for all post-blacklist requests ensures that
all such requests "wait" for the blacklist to come into force on their
respective OSDs.

Cc: stable@vger.kernel.org
Fixes: 6305a3b4 ("libceph: support for blacklisting clients")
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>
Reviewed-by: NJason Dillaman <dillaman@redhat.com>
      bb229bbb
  29. 19 3月, 2019 3 次提交
    • D
      blk-mq: remove unused 'nr_expired' from blk_mq_hw_ctx · 9496c015
      由 Dongli Zhang 提交于 
      There is no usage of 'nr_expired'.

The 'nr_expired' was introduced by commit 1d9bd516 ("blk-mq: replace
timeout synchronization with a RCU and generation based scheme"). Its usage
was removed since commit 12f5b931 ("blk-mq: Remove generation
seqeunce").
Signed-off-by: NDongli Zhang <dongli.zhang@oracle.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      9496c015
    • J
      block: add BIO_NO_PAGE_REF flag · 399254aa
      由 Jens Axboe 提交于 
      If bio_iov_iter_get_pages() is called on an iov_iter that is flagged
with NO_REF, then we don't need to add a page reference for the pages
that we add.

Add BIO_NO_PAGE_REF to track this in the bio, so IO completion knows
not to drop a reference to these pages.
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      399254aa
    • J
      iov_iter: add ITER_BVEC_FLAG_NO_REF flag · 875f1d07
      由 Jens Axboe 提交于 
      For ITER_BVEC, if we're holding on to kernel pages, the caller
doesn't need to grab a reference to the bvec pages, and drop that
same reference on IO completion. This is essentially safe for any
ITER_BVEC, but some use cases end up reusing pages and uncondtionally
dropping a page reference on completion. And example of that is
sendfile(2), that ends up being a splice_in + splice_out on the
pipe pages.

Add a flag that tells us it's fine to not grab a page reference
to the bvec pages, since that caller knows not to drop a reference
when it's done with the pages.
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      875f1d07
  31. 18 3月, 2019 2 次提交
  33. 16 3月, 2019 3 次提交
    • P
      net: add documentation to socket.c · 8a3c245c
      由 Pedro Tammela 提交于 
      Adds missing sphinx documentation to the
socket.c's functions. Also fixes some whitespaces.

I also changed the style of older documentation as an
effort to have an uniform documentation style.
Signed-off-by: NPedro Tammela <pctammela@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      8a3c245c
    • Y
      appletalk: Fix potential NULL pointer dereference in unregister_snap_client · 9804501f
      由 YueHaibing 提交于 
      register_snap_client may return NULL, all the callers
check it, but only print a warning. This will result in
NULL pointer dereference in unregister_snap_client and other
places.

It has always been used like this since v2.6
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      9804501f
    • J
      filemap: kill page_cache_read usage in filemap_fault · a75d4c33
      由 Josef Bacik 提交于 
      Patch series "drop the mmap_sem when doing IO in the fault path", v6.

Now that we have proper isolation in place with cgroups2 we have started
going through and fixing the various priority inversions.  Most are all
gone now, but this one is sort of weird since it's not necessarily a
priority inversion that happens within the kernel, but rather because of
something userspace does.

We have giant applications that we want to protect, and parts of these
giant applications do things like watch the system state to determine how
healthy the box is for load balancing and such.  This involves running
'ps' or other such utilities.  These utilities will often walk
/proc/<pid>/whatever, and these files can sometimes need to
down_read(&task->mmap_sem).  Not usually a big deal, but we noticed when
we are stress testing that sometimes our protected application has latency
spikes trying to get the mmap_sem for tasks that are in lower priority
cgroups.

This is because any down_write() on a semaphore essentially turns it into
a mutex, so even if we currently have it held for reading, any new readers
will not be allowed on to keep from starving the writer.  This is fine,
except a lower priority task could be stuck doing IO because it has been
throttled to the point that its IO is taking much longer than normal.  But
because a higher priority group depends on this completing it is now stuck
behind lower priority work.

In order to avoid this particular priority inversion we want to use the
existing retry mechanism to stop from holding the mmap_sem at all if we
are going to do IO.  This already exists in the read case sort of, but
needed to be extended for more than just grabbing the page lock.  With
io.latency we throttle at submit_bio() time, so the readahead stuff can
block and even page_cache_read can block, so all these paths need to have
the mmap_sem dropped.

The other big thing is ->page_mkwrite.  btrfs is particularly shitty here
because we have to reserve space for the dirty page, which can be a very
expensive operation.  We use the same retry method as the read path, and
simply cache the page and verify the page is still setup properly the next
pass through ->page_mkwrite().

I've tested these patches with xfstests and there are no regressions.

This patch (of 3):

If we do not have a page at filemap_fault time we'll do this weird forced
page_cache_read thing to populate the page, and then drop it again and
loop around and find it.  This makes for 2 ways we can read a page in
filemap_fault, and it's not really needed.  Instead add a FGP_FOR_MMAP
flag so that pagecache_get_page() will return a unlocked page that's in
pagecache.  Then use the normal page locking and readpage logic already in
filemap_fault.  This simplifies the no page in page cache case
significantly.

[akpm@linux-foundation.org: fix comment text]
[josef@toxicpanda.com: don't unlock null page in FGP_FOR_MMAP case]
  Link: http://lkml.kernel.org/r/20190312201742.22935-1-josef@toxicpanda.com
Link: http://lkml.kernel.org/r/20181211173801.29535-2-josef@toxicpanda.comSigned-off-by: NJosef Bacik <josef@toxicpanda.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a75d4c33
  35. 15 3月, 2019 1 次提交
  37. 14 3月, 2019 1 次提交
    • M
      bpf: Fix bpf_tcp_sock and bpf_sk_fullsock issue related to bpf_sk_release · 1b986589
      由 Martin KaFai Lau 提交于 
      Lorenz Bauer [thanks!] reported that a ptr returned by bpf_tcp_sock(sk)
can still be accessed after bpf_sk_release(sk).
Both bpf_tcp_sock() and bpf_sk_fullsock() have the same issue.
This patch addresses them together.

A simple reproducer looks like this:

	sk = bpf_sk_lookup_tcp();
	/* if (!sk) ... */
	tp = bpf_tcp_sock(sk);
	/* if (!tp) ... */
	bpf_sk_release(sk);
	snd_cwnd = tp->snd_cwnd; /* oops! The verifier does not complain. */

The problem is the verifier did not scrub the register's states of
the tcp_sock ptr (tp) after bpf_sk_release(sk).

[ Note that when calling bpf_tcp_sock(sk), the sk is not always
  refcount-acquired. e.g. bpf_tcp_sock(skb->sk). The verifier works
  fine for this case. ]

Currently, the verifier does not track if a helper's return ptr (in REG_0)
is "carry"-ing one of its argument's refcount status. To carry this info,
the reg1->id needs to be stored in reg0.

One approach was tried, like "reg0->id = reg1->id", when calling
"bpf_tcp_sock()".  The main idea was to avoid adding another "ref_obj_id"
for the same reg.  However, overlapping the NULL marking and ref
tracking purpose in one "id" does not work well:

	ref_sk = bpf_sk_lookup_tcp();
	fullsock = bpf_sk_fullsock(ref_sk);
	tp = bpf_tcp_sock(ref_sk);
	if (!fullsock) {
	     bpf_sk_release(ref_sk);
	     return 0;
	}
	/* fullsock_reg->id is marked for NOT-NULL.
	 * Same for tp_reg->id because they have the same id.
	 */

	/* oops. verifier did not complain about the missing !tp check */
	snd_cwnd = tp->snd_cwnd;

Hence, a new "ref_obj_id" is needed in "struct bpf_reg_state".
With a new ref_obj_id, when bpf_sk_release(sk) is called, the verifier can
scrub all reg states which has a ref_obj_id match.  It is done with the
changes in release_reg_references() in this patch.

While fixing it, sk_to_full_sk() is removed from bpf_tcp_sock() and
bpf_sk_fullsock() to avoid these helpers from returning
another ptr. It will make bpf_sk_release(tp) possible:

	sk = bpf_sk_lookup_tcp();
	/* if (!sk) ... */
	tp = bpf_tcp_sock(sk);
	/* if (!tp) ... */
	bpf_sk_release(tp);

A separate helper "bpf_get_listener_sock()" will be added in a later
patch to do sk_to_full_sk().

Misc change notes:
- To allow bpf_sk_release(tp), the arg of bpf_sk_release() is changed
  from ARG_PTR_TO_SOCKET to ARG_PTR_TO_SOCK_COMMON.  ARG_PTR_TO_SOCKET
  is removed from bpf.h since no helper is using it.

- arg_type_is_refcounted() is renamed to arg_type_may_be_refcounted()
  because ARG_PTR_TO_SOCK_COMMON is the only one and skb->sk is not
  refcounted.  All bpf_sk_release(), bpf_sk_fullsock() and bpf_tcp_sock()
  take ARG_PTR_TO_SOCK_COMMON.

- check_refcount_ok() ensures is_acquire_function() cannot take
  arg_type_may_be_refcounted() as its argument.

- The check_func_arg() can only allow one refcount-ed arg.  It is
  guaranteed by check_refcount_ok() which ensures at most one arg can be
  refcounted.  Hence, it is a verifier internal error if >1 refcount arg
  found in check_func_arg().

- In release_reference(), release_reference_state() is called
  first to ensure a match on "reg->ref_obj_id" can be found before
  scrubbing the reg states with release_reg_references().

- reg_is_refcounted() is no longer needed.
  1. In mark_ptr_or_null_regs(), its usage is replaced by
     "ref_obj_id && ref_obj_id == id" because,
     when is_null == true, release_reference_state() should only be
     called on the ref_obj_id obtained by a acquire helper (i.e.
     is_acquire_function() == true).  Otherwise, the following
     would happen:

	sk = bpf_sk_lookup_tcp();
	/* if (!sk) { ... } */
	fullsock = bpf_sk_fullsock(sk);
	if (!fullsock) {
		/*
		 * release_reference_state(fullsock_reg->ref_obj_id)
		 * where fullsock_reg->ref_obj_id == sk_reg->ref_obj_id.
		 *
		 * Hence, the following bpf_sk_release(sk) will fail
		 * because the ref state has already been released in the
		 * earlier release_reference_state(fullsock_reg->ref_obj_id).
		 */
		bpf_sk_release(sk);
	}

  2. In release_reg_references(), the current reg_is_refcounted() call
     is unnecessary because the id check is enough.

- The type_is_refcounted() and type_is_refcounted_or_null()
  are no longer needed also because reg_is_refcounted() is removed.

Fixes: 655a51e5 ("bpf: Add struct bpf_tcp_sock and BPF_FUNC_tcp_sock")
Reported-by: NLorenz Bauer <lmb@cloudflare.com>
Signed-off-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
      1b986589
  39. 13 3月, 2019 3 次提交