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If an array consists of two drives and the first drive has the bad block, the read request to the region overlapping the bad block chooses the same disk (with bad block) as device to read from over and over and the request gets stuck. If the first disk only partially overlaps with bad block, it becomes a candidate ("best disk") for shorter range of sectors. The second disk is capable of reading the entire requested range and it is updated accordingly, however it is not recorded as a best device for the request. In the end the request is sent to the first disk to read entire range of sectors. It fails and is re-tried in a moment but with the same outcome. Actually it is quite likely scenario but it had little exposure in my test until commit 715d40b93b10 ("md/raid1: add failfast handling for reads.") removed preference for idle disk. Such scenario had been passing as second disk was always chosen when idle. Reset a candidate ("best disk") to read from if disk can read entire range. Do it only if other disk has already been chosen as a candidate for a smaller range. The head position / disk type logic will select the best disk to read from - it is fine as disk with bad block won't be considered for it. Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com> Signed-off-by: Shaohua Li <shli@fb.com> |
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arch | ||
block | ||
certs | ||
crypto | ||
Documentation | ||
drivers | ||
firmware | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.cocciconfig | ||
.get_maintainer.ignore | ||
.gitattributes | ||
.gitignore | ||
.mailmap | ||
COPYING | ||
CREDITS | ||
Kbuild | ||
Kconfig | ||
MAINTAINERS | ||
Makefile | ||
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.