[PATCH v3] blk-cgroup:be able to remove the record of unplugged device

[Wanlong Gao]

Write a record like:
echo 8:0 1000 > blkio.throttle.read_bps_device
to control the bps of the device.
And then unplug this device without doing
"8:0 0 > blkio.throttle.read_bps_device" to remove the record,
it will not be removed until reboot, because if the device is removed,
write some record will return "-ENODEV".

With this patch, when the device is removed, then if we want to remove
the record for this removed device, just write "0" then it'll not check
if it is a present device, just remove the present record.

Below is my test:
1. Test native.
[root@test ~]# mount -t cgroup -o blkio nodev /cgroup/
[root@test ~]# cd /cgroup/
[root@test cgroup]# ll /dev/sd*
brw-rw---- 1 root disk 8, 0 Jul 25 13:27 /dev/sda
brw-rw---- 1 root disk 8, 1 Jul 25 13:27 /dev/sda1
[root@test cgroup]# cat blkio.throttle.read_bps_device
[root@test cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
[root@test cgroup]# cat blkio.throttle.read_bps_device
8:0	1000
[root@test cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
[root@test cgroup]# cat blkio.throttle.read_bps_device
[root@test cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
[root@test cgroup]# cat blkio.throttle.read_bps_device
8:0	1000
[root@test cgroup]# ll /dev/sd*
ls: cannot access /dev/sd*: No such file or directory
[root@test cgroup]# cat blkio.throttle.read_bps_device
8:0	1000
[root@test cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
-bash: echo: write error: No such device
[root@test cgroup]# cat blkio.throttle.read_bps_device
8:0	1000

2.Test with this patch:

[root@test ~]# mount -t cgroup -o blkio nodev /cgroup/
[root@test ~]# ll /dev/sd*
brw-rw---- 1 root disk 8, 0 Jul 25 13:11 /dev/sda
brw-rw---- 1 root disk 8, 1 Jul 25 13:11 /dev/sda1
[root@test ~]# cd /cgroup/
[root@test cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
[root@test cgroup]# cat blkio.throttle.read_bps_device
8:0	1000
[root@test cgroup]# ll /dev/sd*
brw-rw---- 1 root disk 8, 0 Jul 25 13:11 /dev/sda
brw-rw---- 1 root disk 8, 1 Jul 25 13:11 /dev/sda1
[root@test cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
[root@test cgroup]# cat blkio.throttle.read_bps_device
[root@test cgroup]# ll /dev/sd*
brw-rw---- 1 root disk 8, 0 Jul 25 13:11 /dev/sda
brw-rw---- 1 root disk 8, 1 Jul 25 13:11 /dev/sda1
[root@test cgroup]# echo 8:0 2000 > blkio.throttle.read_bps_device
[root@test cgroup]# cat blkio.throttle.read_bps_device
8:0	2000

[root@test cgroup]# ll /dev/sd*
ls: cannot access /dev/sd*: No such file or directory
[root@test cgroup]# cat blkio.throttle.read_bps_device
8:0	2000
[root@test cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
[root@test cgroup]# cat blkio.throttle.read_bps_device
[root@test cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
-bash: echo: write error: No such device
[root@test cgroup]# echo 8:0 01100 > blkio.throttle.read_bps_device
-bash: echo: write error: No such device
[root@test cgroup]#

Signed-off-by: Wanlong Gao <gaowanlong@xxxxxxxxxxxxxx>
---
 block/blk-cgroup.c |   18 +++++++++---------
 1 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index bcaf16e..246645c 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -785,7 +785,7 @@ static int blkio_policy_parse_and_set(char *buf,
 {
 	char *s[4], *p, *major_s = NULL, *minor_s = NULL;
 	int ret;
-	unsigned long major, minor, temp;
+	unsigned long major, minor, weight;
 	int i = 0;
 	dev_t dev;
 	u64 bps, iops;
@@ -826,25 +826,25 @@ static int blkio_policy_parse_and_set(char *buf,
 
 	dev = MKDEV(major, minor);
 
-	ret = blkio_check_dev_num(dev);
+	ret = strict_strtoul(s[1], 10, &weight);
 	if (ret)
+		return -EINVAL;
+
+	ret = blkio_check_dev_num(dev);
+	if (ret && (weight != 0))
 		return ret;
 
 	newpn->dev = dev;
 
-	if (s[1] == NULL)
-		return -EINVAL;
-
 	switch (plid) {
 	case BLKIO_POLICY_PROP:
-		ret = strict_strtoul(s[1], 10, &temp);
-		if (ret || (temp < BLKIO_WEIGHT_MIN && temp > 0) ||
-			temp > BLKIO_WEIGHT_MAX)
+		if ((weight < BLKIO_WEIGHT_MIN && weight > 0) ||
+			weight > BLKIO_WEIGHT_MAX)
 			return -EINVAL;
 
 		newpn->plid = plid;
 		newpn->fileid = fileid;
-		newpn->val.weight = temp;
+		newpn->val.weight = weight;
 		break;
 	case BLKIO_POLICY_THROTL:
 		switch(fileid) {
-- 
1.7.6

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