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authorNeilBrown <neilb@suse.de>2008-03-04 14:29:33 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-03-04 16:35:18 -0800
commit27c529bb8e906d5d692152bc127cc09477d3629e (patch)
tree1bcfa43a45206e03bbc729c5d3af4bed830d4439
parent25156198235325805cd7295ed694509fd6e3a29e (diff)
downloadkernel-27c529bb8e906d5d692152bc127cc09477d3629e.tar.gz
md: lock access to rdev attributes properly
When we access attributes of an rdev (component device on an md array) through sysfs, we really need to lock the array against concurrent changes. We currently do that when we change an attribute, but not when we read an attribute. We need to lock when reading as well else rdev->mddev could become NULL while we are accessing it. So add appropriate locking (mddev_lock) to rdev_attr_show. rdev_size_store requires some extra care as well as it needs to unlock the mddev while scanning other mddevs for overlapping regions. We currently assume that rdev->mddev will still be unchanged after the scan, but that cannot be certain. So take a copy of rdev->mddev for use at the end of the function. Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--drivers/md/md.c35
1 files changed, 26 insertions, 9 deletions
diff --git a/drivers/md/md.c b/drivers/md/md.c
index a986845ea0c3..827824a9f3e9 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2001,9 +2001,11 @@ rdev_size_store(mdk_rdev_t *rdev, const char *buf, size_t len)
char *e;
unsigned long long size = simple_strtoull(buf, &e, 10);
unsigned long long oldsize = rdev->size;
+ mddev_t *my_mddev = rdev->mddev;
+
if (e==buf || (*e && *e != '\n'))
return -EINVAL;
- if (rdev->mddev->pers)
+ if (my_mddev->pers)
return -EBUSY;
rdev->size = size;
if (size > oldsize && rdev->mddev->external) {
@@ -2016,7 +2018,7 @@ rdev_size_store(mdk_rdev_t *rdev, const char *buf, size_t len)
int overlap = 0;
struct list_head *tmp, *tmp2;
- mddev_unlock(rdev->mddev);
+ mddev_unlock(my_mddev);
for_each_mddev(mddev, tmp) {
mdk_rdev_t *rdev2;
@@ -2036,7 +2038,7 @@ rdev_size_store(mdk_rdev_t *rdev, const char *buf, size_t len)
break;
}
}
- mddev_lock(rdev->mddev);
+ mddev_lock(my_mddev);
if (overlap) {
/* Someone else could have slipped in a size
* change here, but doing so is just silly.
@@ -2048,8 +2050,8 @@ rdev_size_store(mdk_rdev_t *rdev, const char *buf, size_t len)
return -EBUSY;
}
}
- if (size < rdev->mddev->size || rdev->mddev->size == 0)
- rdev->mddev->size = size;
+ if (size < my_mddev->size || my_mddev->size == 0)
+ my_mddev->size = size;
return len;
}
@@ -2070,10 +2072,21 @@ rdev_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
{
struct rdev_sysfs_entry *entry = container_of(attr, struct rdev_sysfs_entry, attr);
mdk_rdev_t *rdev = container_of(kobj, mdk_rdev_t, kobj);
+ mddev_t *mddev = rdev->mddev;
+ ssize_t rv;
if (!entry->show)
return -EIO;
- return entry->show(rdev, page);
+
+ rv = mddev ? mddev_lock(mddev) : -EBUSY;
+ if (!rv) {
+ if (rdev->mddev == NULL)
+ rv = -EBUSY;
+ else
+ rv = entry->show(rdev, page);
+ mddev_unlock(mddev);
+ }
+ return rv;
}
static ssize_t
@@ -2082,15 +2095,19 @@ rdev_attr_store(struct kobject *kobj, struct attribute *attr,
{
struct rdev_sysfs_entry *entry = container_of(attr, struct rdev_sysfs_entry, attr);
mdk_rdev_t *rdev = container_of(kobj, mdk_rdev_t, kobj);
- int rv;
+ ssize_t rv;
+ mddev_t *mddev = rdev->mddev;
if (!entry->store)
return -EIO;
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
- rv = mddev_lock(rdev->mddev);
+ rv = mddev ? mddev_lock(mddev): -EBUSY;
if (!rv) {
- rv = entry->store(rdev, page, length);
+ if (rdev->mddev == NULL)
+ rv = -EBUSY;
+ else
+ rv = entry->store(rdev, page, length);
mddev_unlock(rdev->mddev);
}
return rv;