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Filename Latest commit message Latest commit date
Tahsin Erdogan 7fc6b87a9f blkcg: allocate struct blkcg_gq outside request queue spinlock
blkg_conf_prep() currently calls blkg_lookup_create() while holding
request queue spinlock. This means allocating memory for struct
blkcg_gq has to be made non-blocking. This causes occasional -ENOMEM
failures in call paths like below:

  pcpu_alloc+0x68f/0x710
  __alloc_percpu_gfp+0xd/0x10
  __percpu_counter_init+0x55/0xc0
  cfq_pd_alloc+0x3b2/0x4e0
  blkg_alloc+0x187/0x230
  blkg_create+0x489/0x670
  blkg_lookup_create+0x9a/0x230
  blkg_conf_prep+0x1fb/0x240
  __cfqg_set_weight_device.isra.105+0x5c/0x180
  cfq_set_weight_on_dfl+0x69/0xc0
  cgroup_file_write+0x39/0x1c0
  kernfs_fop_write+0x13f/0x1d0
  __vfs_write+0x23/0x120
  vfs_write+0xc2/0x1f0
  SyS_write+0x44/0xb0
  entry_SYSCALL_64_fastpath+0x18/0xad

In the code path above, percpu allocator cannot call vmalloc() due to
queue spinlock.

A failure in this call path gives grief to tools which are trying to
configure io weights. We see occasional failures happen shortly after
reboots even when system is not under any memory pressure. Machines
with a lot of cpus are more vulnerable to this condition.

Update blkg_create() function to temporarily drop the rcu and queue
locks when it is allowed by gfp mask.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
2017-03-28 15:59:04 -06:00
arch powerpc fixes for 4.11 #5 2017-03-19 18:49:28 -07:00
block blkcg: allocate struct blkcg_gq outside request queue spinlock 2017-03-28 15:59:04 -06:00
certs
crypto net: Work around lockdep limitation in sockets that use sockets 2017-03-09 18:23:27 -08:00
Documentation blk-throttle: make throtl_slice tunable 2017-03-28 08:02:20 -06:00
drivers jsflash: stop sharing request queue across multiple gendisks 2017-03-28 15:06:58 -06:00
firmware
fs block: Fix oops in locked_inode_to_wb_and_lock_list() 2017-03-22 20:11:33 -06:00
include blkcg: allocate struct blkcg_gq outside request queue spinlock 2017-03-28 15:59:04 -06:00
init Change get_random_{int,log} to use the CRNG used by /dev/urandom and 2017-03-11 09:08:47 -08:00
ipc
kernel Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-18 08:33:44 -07:00
lib kobject: Export kobject_get_unless_zero() 2017-03-22 20:11:35 -06:00
mm bdi: Rename cgwb_bdi_destroy() to cgwb_bdi_unregister() 2017-03-22 20:11:31 -06:00
net NFS client fixes for 4.11 2017-03-17 14:16:22 -07:00
samples
scripts Merge branch 'akpm' (patches from Andrew) 2017-03-10 08:34:42 -08:00
security
sound scripts/spelling.txt: add "disble(d)" pattern and fix typo instances 2017-03-09 17:01:09 -08:00
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-17 13:59:52 -07:00
usr
virt KVM: arm/arm64: VGIC: Fix command handling while ITS being disabled 2017-03-07 15:44:08 +00:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS MAINTAINERS: usb251xb: remove reference inexistent file 2017-03-09 10:34:16 +01:00
Makefile Linux 4.11-rc3 2017-03-19 19:09:39 -07:00
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.