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NeilBrown 7471fb77ce md/raid6: Fix anomily when recovering a single device in RAID6.
When recoverying a single missing/failed device in a RAID6,
those stripes where the Q block is on the missing device are
handled a bit differently.  In these cases it is easy to
check that the P block is correct, so we do.  This results
in the P block be destroy.  Consequently the P block needs
to be read a second time in order to compute Q.  This causes
lots of seeks and hurts performance.

It shouldn't be necessary to re-read P as it can be computed
from the DATA.  But we only compute blocks on missing
devices, since c337869d95 ("md: do not compute parity
unless it is on a failed drive").

So relax the change made in that commit to allow computing
of the P block in a RAID6 which it is the only missing that
block.

This makes RAID6 recovery run much faster as the disk just
"before" the recovering device is no longer seeking
back-and-forth.

Reported-by-tested-by: Brad Campbell <lists2009@fnarfbargle.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
2017-04-10 10:35:27 -07:00
Documentation md: add sysfs entries for PPL 2017-03-16 16:55:55 -07:00
arch arm64 fixes/cleanups: 2017-03-16 11:47:28 -07:00
block block: remove bio_clone_bioset_partial() 2017-03-25 09:18:37 -07:00
certs certs: Add a secondary system keyring that can be added to dynamically 2016-04-11 22:48:09 +01:00
crypto net: Work around lockdep limitation in sockets that use sockets 2017-03-09 18:23:27 -08:00
drivers md/raid6: Fix anomily when recovering a single device in RAID6. 2017-04-10 10:35:27 -07:00
firmware WHENCE: use https://linuxtv.org for LinuxTV URLs 2015-12-04 10:35:11 -02:00
fs Changes since last time: 2017-03-16 12:30:43 -07:00
include block: remove bio_clone_bioset_partial() 2017-03-25 09:18:37 -07:00
init Change get_random_{int,log} to use the CRNG used by /dev/urandom and 2017-03-11 09:08:47 -08:00
ipc Merge branch 'WIP.sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-03 10:16:38 -08:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-03-14 21:31:23 -07:00
lib percpu-refcount: support synchronous switch to atomic mode. 2017-03-22 19:18:43 -07:00
mm Merge branch 'for-4.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2017-03-14 14:48:50 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-03-14 21:31:23 -07:00
samples Merge branch 'rebased-statx' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-03-03 11:38:56 -08:00
scripts Merge branch 'akpm' (patches from Andrew) 2017-03-10 08:34:42 -08:00
security Merge branch 'WIP.sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-03 10:16:38 -08:00
sound scripts/spelling.txt: add "disble(d)" pattern and fix typo instances 2017-03-09 17:01:09 -08:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-03-14 21:31:23 -07:00
usr kbuild: initramfs cleanup, set target from Kconfig 2017-01-05 09:40:16 -08:00
virt KVM: arm/arm64: VGIC: Fix command handling while ITS being disabled 2017-03-07 15:44:08 +00:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Merge branch 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild 2016-08-02 16:48:52 -04:00
.mailmap mailmap: add codeaurora.org names for nameless email commits 2017-01-10 18:31:55 -08:00
COPYING
CREDITS MAINTAINERS: Remove old e-mail address 2017-02-13 12:24:56 -05:00
Kbuild scripts/gdb: provide linux constants 2016-05-23 17:04:14 -07:00
Kconfig
MAINTAINERS MAINTAINERS: usb251xb: remove reference inexistent file 2017-03-09 10:34:16 +01:00
Makefile Linux 4.11-rc2 2017-03-12 14:47:08 -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.