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| author | James Wang <jnwang@suse.com> | 2017-06-08 14:52:51 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2017-06-08 08:04:18 -0600 |
| commit | 6460495709aeb651896bc8e5c134b2e4ca7d34a8 (patch) | |
| tree | 94bb68a2febbf13aa2295e4161a9c61692bd2441 /drivers | |
| parent | 6679a90c4b0dc2563383df1fe0eb170736952a2e (diff) | |
| download | linux-6460495709aeb651896bc8e5c134b2e4ca7d34a8.tar.bz2 | |
Fix loop device flush before configure v3
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>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/block/loop.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 28d932906f24..ebbd0c3fe0ed 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -608,6 +608,9 @@ static int loop_switch(struct loop_device *lo, struct file *file) */ static int loop_flush(struct loop_device *lo) { + /* loop not yet configured, no running thread, nothing to flush */ + if (lo->lo_state != Lo_bound) + return 0; return loop_switch(lo, NULL); } |