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Tetsuo Handa 2e517d6816 lockdep: fix fs_reclaim warning 
Dave Jones reported fs_reclaim lockdep warnings.

  ============================================
  WARNING: possible recursive locking detected
  4.15.0-rc9-backup-debug+ #1 Not tainted
  --------------------------------------------
  sshd/24800 is trying to acquire lock:
   (fs_reclaim){+.+.}, at: [<0000000084f438c2>] fs_reclaim_acquire.part.102+0x5/0x30

  but task is already holding lock:
   (fs_reclaim){+.+.}, at: [<0000000084f438c2>] fs_reclaim_acquire.part.102+0x5/0x30

  other info that might help us debug this:
   Possible unsafe locking scenario:

         CPU0
         ----
    lock(fs_reclaim);
    lock(fs_reclaim);

   *** DEADLOCK ***

   May be due to missing lock nesting notation

  2 locks held by sshd/24800:
   #0:  (sk_lock-AF_INET6){+.+.}, at: [<000000001a069652>] tcp_sendmsg+0x19/0x40
   #1:  (fs_reclaim){+.+.}, at: [<0000000084f438c2>] fs_reclaim_acquire.part.102+0x5/0x30

  stack backtrace:
  CPU: 3 PID: 24800 Comm: sshd Not tainted 4.15.0-rc9-backup-debug+ #1
  Call Trace:
   dump_stack+0xbc/0x13f
   __lock_acquire+0xa09/0x2040
   lock_acquire+0x12e/0x350
   fs_reclaim_acquire.part.102+0x29/0x30
   kmem_cache_alloc+0x3d/0x2c0
   alloc_extent_state+0xa7/0x410
   __clear_extent_bit+0x3ea/0x570
   try_release_extent_mapping+0x21a/0x260
   __btrfs_releasepage+0xb0/0x1c0
   btrfs_releasepage+0x161/0x170
   try_to_release_page+0x162/0x1c0
   shrink_page_list+0x1d5a/0x2fb0
   shrink_inactive_list+0x451/0x940
   shrink_node_memcg.constprop.88+0x4c9/0x5e0
   shrink_node+0x12d/0x260
   try_to_free_pages+0x418/0xaf0
   __alloc_pages_slowpath+0x976/0x1790
   __alloc_pages_nodemask+0x52c/0x5c0
   new_slab+0x374/0x3f0
   ___slab_alloc.constprop.81+0x47e/0x5a0
   __slab_alloc.constprop.80+0x32/0x60
   __kmalloc_track_caller+0x267/0x310
   __kmalloc_reserve.isra.40+0x29/0x80
   __alloc_skb+0xee/0x390
   sk_stream_alloc_skb+0xb8/0x340
   tcp_sendmsg_locked+0x8e6/0x1d30
   tcp_sendmsg+0x27/0x40
   inet_sendmsg+0xd0/0x310
   sock_write_iter+0x17a/0x240
   __vfs_write+0x2ab/0x380
   vfs_write+0xfb/0x260
   SyS_write+0xb6/0x140
   do_syscall_64+0x1e5/0xc05
   entry_SYSCALL64_slow_path+0x25/0x25

This warning is caused by commit d92a8cfcb3 ("locking/lockdep:
Rework FS_RECLAIM annotation") which replaced the use of
lockdep_{set,clear}_current_reclaim_state() in __perform_reclaim()
and lockdep_trace_alloc() in slab_pre_alloc_hook() with
fs_reclaim_acquire()/ fs_reclaim_release().

Since __kmalloc_reserve() from __alloc_skb() adds __GFP_NOMEMALLOC |
__GFP_NOWARN to gfp_mask, and all reclaim path simply propagates
__GFP_NOMEMALLOC, fs_reclaim_acquire() in slab_pre_alloc_hook() is
trying to grab the 'fake' lock again when __perform_reclaim() already
grabbed the 'fake' lock.

The

  /* this guy won't enter reclaim */
  if ((current->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
          return false;

test which causes slab_pre_alloc_hook() to try to grab the 'fake' lock
was added by commit cf40bd16fd ("lockdep: annotate reclaim context
(__GFP_NOFS)").  But that test is outdated because PF_MEMALLOC thread
won't enter reclaim regardless of __GFP_NOMEMALLOC after commit
341ce06f69 ("page allocator: calculate the alloc_flags for allocation
only once") added the PF_MEMALLOC safeguard (

  /* Avoid recursion of direct reclaim */
  if (p->flags & PF_MEMALLOC)
          goto nopage;

in __alloc_pages_slowpath()).

Thus, let's fix outdated test by removing __GFP_NOMEMALLOC test and
allow __need_fs_reclaim() to return false.

Link: http://lkml.kernel.org/r/201802280650.FJC73911.FOSOMLJVFFQtHO@I-love.SAKURA.ne.jp
Fixes: d92a8cfcb3 ("locking/lockdep: Rework FS_RECLAIM annotation")
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Tested-by: Dave Jones <davej@codemonkey.org.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Nick Piggin <npiggin@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nikolay Borisov <nborisov@suse.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: <stable@vger.kernel.org>	[4.14+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-03-22 17:07:01 -07:00
arch kvm/x86: fix icebp instruction handling 2018-03-20 14:58:34 -07:00
block for-linus-20180302 2018-03-02 09:35:36 -08:00
certs certs/blacklist_nohashes.c: fix const confusion in certs blacklist 2018-02-21 15:35:43 -08:00
crypto X.509: fix NULL dereference when restricting key with unsupported_sig 2018-02-22 14:38:34 +00:00
Documentation Merge branch 'for-4.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata 2018-03-19 14:23:30 -07:00
drivers A late collection of fixes for regressions seen this release cycle. 2018-03-20 17:44:27 -07:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Just one fix for an occasional panic from Jeff Layton. 2018-03-20 16:10:26 -07:00
include Fourth pull request for 4.16-rc 2018-03-20 17:39:07 -07:00
init jump_label: Explicitly disable jump labels in __init code 2018-02-21 16:54:05 +01:00
ipc vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
kernel Merge branch 'for-4.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2018-03-19 15:39:02 -07:00
lib Merge branch 'for-4.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2018-03-19 14:48:35 -07:00
LICENSES LICENSES: Add MPL-1.1 license 2018-01-06 10:59:44 -07:00
mm lockdep: fix fs_reclaim warning 2018-03-22 17:07:01 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-03-05 11:29:24 -08:00
samples - do not build samples when cross compiling (Michal Hocko) 2018-02-27 10:39:29 -08:00
scripts kbuild: Handle builtin dtb file names containing hyphens 2018-03-09 01:14:38 +09:00
security integrity/security: fix digsig.c build error with header file 2018-02-22 20:09:08 -08:00
sound ASoC: Fixes for v4.16 2018-03-12 17:30:38 +01:00
tools Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-03-18 12:03:15 -07:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt kvm/arm fixes for 4.16, take 2 2018-03-15 21:45:37 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore .gitignore: ignore ASN.1 auto generated files 2018-02-14 21:05:38 +01:00
.mailmap mailmap: update Mark Yao's email address 2018-01-04 16:45:09 -08:00
COPYING
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS MAINTAINERS: update Mark Fasheh's e-mail 2018-03-22 17:07:01 -07:00
Makefile Linux 4.16-rc6 2018-03-18 17:48:42 -07:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.