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authorNeilBrown <neilb@suse.de>2014-12-15 04:56:56 +0300
committerNeilBrown <neilb@suse.de>2015-02-04 00:35:52 +0300
commit5c675f83c68fbdf9c0e103c1090b06be747fa62c (patch)
tree9a03f84c7a3bcef7d5e757dc28ce7bd5d205b26a /drivers/md/md.h
parent85572d7c75fd5b9fa3fc911e1c99c68ec74903a0 (diff)
downloadlinux-5c675f83c68fbdf9c0e103c1090b06be747fa62c.tar.xz
md: make ->congested robust against personality changes.
There is currently no locking around calls to the 'congested' bdi function. If called at an awkward time while an array is being converted from one level (or personality) to another, there is a tiny chance of running code in an unreferenced module etc. So add a 'congested' function to the md_personality operations structure, and call it with appropriate locking from a central 'mddev_congested'. When the array personality is changing the array will be 'suspended' so no IO is processed. If mddev_congested detects this, it simply reports that the array is congested, which is a safe guess. As mddev_suspend calls synchronize_rcu(), mddev_congested can avoid races by included the whole call inside an rcu_read_lock() region. This require that the congested functions for all subordinate devices can be run under rcu_lock. Fortunately this is the case. Signed-off-by: NeilBrown <neilb@suse.de>
Diffstat (limited to 'drivers/md/md.h')
-rw-r--r--drivers/md/md.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/md/md.h b/drivers/md/md.h
index f0d15bdd96d4..f2602280fac1 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -496,6 +496,9 @@ struct md_personality
* array.
*/
void *(*takeover) (struct mddev *mddev);
+ /* congested implements bdi.congested_fn().
+ * Will not be called while array is 'suspended' */
+ int (*congested)(struct mddev *mddev, int bits);
};
struct md_sysfs_entry {