linux-kernel - [155/244] blk-cgroup: be able to remove the record of unplugged device

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Date:	Wed, 28 Sep 2011 15:01:59 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Wanlong Gao <gaowanlong@...fujitsu.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Paul Menage <paul@...lmenage.org>,
	Vivek Goyal <vgoyal@...hat.com>, Jens Axboe <axboe@...nel.dk>
Subject: [155/244] blk-cgroup: be able to remove the record of unplugged device

3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Wanlong Gao <gaowanlong@...fujitsu.com>

commit d11bb4462c4cc6ddd45c6927c617ad79fa6fb8fc upstream.

The bug is we're not able to remove the device from blkio cgroup's
per-device control files if it gets unplugged.

To reproduce the bug:

  # mount -t cgroup -o blkio xxx /cgroup
  # cd /cgroup
  # echo "8:0 1000" > blkio.throttle.read_bps_device
  # unplug the device
  # cat blkio.throttle.read_bps_device
  8:0	1000
  # echo "8:0 0" > blkio.throttle.read_bps_device
  -bash: echo: write error: No such device

After patching, the device removal will succeed.

Thanks for the comments of Paul, Zefan, and Vivek.

Signed-off-by: Wanlong Gao <gaowanlong@...fujitsu.com>
Cc: Li Zefan <lizf@...fujitsu.com>
Cc: Paul Menage <paul@...lmenage.org>
Acked-by: Vivek Goyal <vgoyal@...hat.com>
Cc: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 block/blk-cgroup.c |   37 ++++++++++++++++---------------------
 1 file changed, 16 insertions(+), 21 deletions(-)

--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -785,10 +785,10 @@ static int blkio_policy_parse_and_set(ch
 {
 	char *s[4], *p, *major_s = NULL, *minor_s = NULL;
 	int ret;
-	unsigned long major, minor, temp;
+	unsigned long major, minor;
 	int i = 0;
 	dev_t dev;
-	u64 bps, iops;
+	u64 temp;
 
 	memset(s, 0, sizeof(s));
 
@@ -826,20 +826,23 @@ static int blkio_policy_parse_and_set(ch
 
 	dev = MKDEV(major, minor);
 
-	ret = blkio_check_dev_num(dev);
+	ret = strict_strtoull(s[1], 10, &temp);
 	if (ret)
-		return ret;
+		return -EINVAL;
 
-	newpn->dev = dev;
+	/* For rule removal, do not check for device presence. */
+	if (temp) {
+		ret = blkio_check_dev_num(dev);
+		if (ret)
+			return ret;
+	}
 
-	if (s[1] == NULL)
-		return -EINVAL;
+	newpn->dev = dev;
 
 	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 ((temp < BLKIO_WEIGHT_MIN && temp > 0) ||
+		     temp > BLKIO_WEIGHT_MAX)
 			return -EINVAL;
 
 		newpn->plid = plid;
@@ -850,26 +853,18 @@ static int blkio_policy_parse_and_set(ch
 		switch(fileid) {
 		case BLKIO_THROTL_read_bps_device:
 		case BLKIO_THROTL_write_bps_device:
-			ret = strict_strtoull(s[1], 10, &bps);
-			if (ret)
-				return -EINVAL;
-
 			newpn->plid = plid;
 			newpn->fileid = fileid;
-			newpn->val.bps = bps;
+			newpn->val.bps = temp;
 			break;
 		case BLKIO_THROTL_read_iops_device:
 		case BLKIO_THROTL_write_iops_device:
-			ret = strict_strtoull(s[1], 10, &iops);
-			if (ret)
-				return -EINVAL;
-
-			if (iops > THROTL_IOPS_MAX)
+			if (temp > THROTL_IOPS_MAX)
 				return -EINVAL;
 
 			newpn->plid = plid;
 			newpn->fileid = fileid;
-			newpn->val.iops = (unsigned int)iops;
+			newpn->val.iops = (unsigned int)temp;
 			break;
 		}
 		break;


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