md: allow suspend_lo and suspend_hi to decrease as well as increase.

The sysfs attributes 'suspend_lo' and 'suspend_hi' describe a region
to which read/writes are suspended so that the under lying data can be
manipulated without user-space noticing.
Currently the window they describe can only move forwards along the
device.  However this is an unnecessary restriction which will cause
problems with planned developments.
So relax this restriction and allow these endpoints to move
arbitrarily.

Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 42b1d9ead7f2b379fbaea955361557f8315e692f..dd64ad30a0fe0d405d84c4fae1018f967d4797f2 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4016,19 +4016,24 @@ suspend_lo_store(mddev_t *mddev, const char *buf, size_t len)
 {
        char *e;
        unsigned long long new = simple_strtoull(buf, &e, 10);
+       unsigned long long old = mddev->suspend_lo;
 
        if (mddev->pers == NULL || 
            mddev->pers->quiesce == NULL)
                return -EINVAL;
        if (buf == e || (*e && *e != '\n'))
                return -EINVAL;
-       if (new >= mddev->suspend_hi ||
-           (new > mddev->suspend_lo && new < mddev->suspend_hi)) {
-               mddev->suspend_lo = new;
+
+       mddev->suspend_lo = new;
+       if (new >= old)
+               /* Shrinking suspended region */
                mddev->pers->quiesce(mddev, 2);
-               return len;
-       } else
-               return -EINVAL;
+       else {
+               /* Expanding suspended region - need to wait */
+               mddev->pers->quiesce(mddev, 1);
+               mddev->pers->quiesce(mddev, 0);
+       }
+       return len;
 }
 static struct md_sysfs_entry md_suspend_lo =
 __ATTR(suspend_lo, S_IRUGO|S_IWUSR, suspend_lo_show, suspend_lo_store);
@@ -4045,20 +4050,24 @@ suspend_hi_store(mddev_t *mddev, const char *buf, size_t len)
 {
        char *e;
        unsigned long long new = simple_strtoull(buf, &e, 10);
+       unsigned long long old = mddev->suspend_hi;
 
        if (mddev->pers == NULL ||
            mddev->pers->quiesce == NULL)
                return -EINVAL;
        if (buf == e || (*e && *e != '\n'))
                return -EINVAL;
-       if ((new <= mddev->suspend_lo && mddev->suspend_lo >= mddev->suspend_hi) ||
-           (new > mddev->suspend_lo && new > mddev->suspend_hi)) {
-               mddev->suspend_hi = new;
+
+       mddev->suspend_hi = new;
+       if (new <= old)
+               /* Shrinking suspended region */
+               mddev->pers->quiesce(mddev, 2);
+       else {
+               /* Expanding suspended region - need to wait */
                mddev->pers->quiesce(mddev, 1);
                mddev->pers->quiesce(mddev, 0);
-               return len;
-       } else
-               return -EINVAL;
+       }
+       return len;
 }
 static struct md_sysfs_entry md_suspend_hi =
 __ATTR(suspend_hi, S_IRUGO|S_IWUSR, suspend_hi_show, suspend_hi_store);