Revision 6460495709aeb651896bc8e5c134b2e4ca7d34a8 authored by James Wang on 08 June 2017, 06:52:51 UTC, committed by Jens Axboe on 08 June 2017, 14:04:18 UTC
While installing SLES-12 (based on v4.4), I found that the installer
will stall for 60+ seconds during LVM disk scan. The root cause was
determined to be the removal of a bound device check in loop_flush()
by commit b5dd2f6047ca ("block: loop: improve performance via blk-mq").
Restoring this check, examining ->lo_state as set by loop_set_fd()
eliminates the bad behavior.
Test method:
modprobe loop max_loop=64
dd if=/dev/zero of=disk bs=512 count=200K
for((i=0;i<4;i++))do losetup -f disk; done
mkfs.ext4 -F /dev/loop0
for((i=0;i<4;i++))do mkdir t$i; mount /dev/loop$i t$i;done
for f in `ls /dev/loop[0-9]*|sort`; do \
echo $f; dd if=$f of=/dev/null bs=512 count=1; \
done
Test output: stock patched
/dev/loop0 18.1217e-05 8.3842e-05
/dev/loop1 6.1114e-05 0.000147979
/dev/loop10 0.414701 0.000116564
/dev/loop11 0.7474 6.7942e-05
/dev/loop12 0.747986 8.9082e-05
/dev/loop13 0.746532 7.4799e-05
/dev/loop14 0.480041 9.3926e-05
/dev/loop15 1.26453 7.2522e-05
Note that from loop10 onward, the device is not mounted, yet the
stock kernel consumes several orders of magnitude more wall time
than it does for a mounted device.
(Thanks for Mike Galbraith <efault@gmx.de>, give a changelog review.)
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: James Wang <jnwang@suse.com>
Fixes: b5dd2f6047ca ("block: loop: improve performance via blk-mq")
Signed-off-by: Jens Axboe <axboe@fb.com>
1 parent 6679a90
Kconfig
menuconfig SAMPLES
bool "Sample kernel code"
help
You can build and test sample kernel code here.
if SAMPLES
config SAMPLE_TRACE_EVENTS
tristate "Build trace_events examples -- loadable modules only"
depends on EVENT_TRACING && m
help
This build trace event example modules.
config SAMPLE_TRACE_PRINTK
tristate "Build trace_printk module - tests various trace_printk formats"
depends on EVENT_TRACING && m
help
This builds a module that calls trace_printk() and can be used to
test various trace_printk() calls from a module.
config SAMPLE_KOBJECT
tristate "Build kobject examples -- loadable modules only"
depends on m
help
This config option will allow you to build a number of
different kobject sample modules showing how to use kobjects,
ksets, and ktypes properly.
If in doubt, say "N" here.
config SAMPLE_KPROBES
tristate "Build kprobes examples -- loadable modules only"
depends on KPROBES && m
help
This build several kprobes example modules.
config SAMPLE_KRETPROBES
tristate "Build kretprobes example -- loadable modules only"
default m
depends on SAMPLE_KPROBES && KRETPROBES
config SAMPLE_HW_BREAKPOINT
tristate "Build kernel hardware breakpoint examples -- loadable module only"
depends on HAVE_HW_BREAKPOINT && m
help
This builds kernel hardware breakpoint example modules.
config SAMPLE_KFIFO
tristate "Build kfifo examples -- loadable modules only"
depends on m
help
This config option will allow you to build a number of
different kfifo sample modules showing how to use the
generic kfifo API.
If in doubt, say "N" here.
config SAMPLE_KDB
tristate "Build kdb command example -- loadable modules only"
depends on KGDB_KDB && m
help
Build an example of how to dynamically add the hello
command to the kdb shell.
config SAMPLE_RPMSG_CLIENT
tristate "Build rpmsg client sample -- loadable modules only"
depends on RPMSG && m
help
Build an rpmsg client sample driver, which demonstrates how
to communicate with an AMP-configured remote processor over
the rpmsg bus.
config SAMPLE_LIVEPATCH
tristate "Build live patching sample -- loadable modules only"
depends on LIVEPATCH && m
help
Builds a sample live patch that replaces the procfs handler
for /proc/cmdline to print "this has been live patched".
config SAMPLE_CONFIGFS
tristate "Build configfs patching sample -- loadable modules only"
depends on CONFIGFS_FS && m
help
Builds a sample configfs interface.
config SAMPLE_CONNECTOR
tristate "Build connector sample -- loadable modules only"
depends on CONNECTOR && m
help
When enabled, this builds both a sample kernel module for
the connector interface and a user space tool to communicate
with it.
See also Documentation/connector/connector.txt
config SAMPLE_SECCOMP
tristate "Build seccomp sample code -- loadable modules only"
depends on SECCOMP_FILTER && m
help
Build samples of seccomp filters using various methods of
BPF filter construction.
config SAMPLE_BLACKFIN_GPTIMERS
tristate "Build blackfin gptimers sample code -- loadable modules only"
depends on BLACKFIN && BFIN_GPTIMERS && m
help
Build samples of blackfin gptimers sample module.
config SAMPLE_VFIO_MDEV_MTTY
tristate "Build VFIO mtty example mediated device sample code -- loadable modules only"
depends on VFIO_MDEV_DEVICE && m
help
Build a virtual tty sample driver for use as a VFIO
mediated device
config SAMPLE_STATX
bool "Build example extended-stat using code"
depends on BROKEN
help
Build example userspace program to use the new extended-stat syscall.
endif # SAMPLES
Computing file changes ...
