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authorNeilBrown <neilb@suse.de>2014-12-15 12:56:56 +1100
committerNeilBrown <neilb@suse.de>2015-02-04 08:35:52 +1100
commit5c675f83c68fbdf9c0e103c1090b06be747fa62c (patch)
tree9a03f84c7a3bcef7d5e757dc28ce7bd5d205b26a /drivers/md/multipath.c
parent85572d7c75fd5b9fa3fc911e1c99c68ec74903a0 (diff)
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/multipath.c')
-rw-r--r--drivers/md/multipath.c10
1 files changed, 2 insertions, 8 deletions
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index 399272f9c042..fedb1b31877d 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -153,15 +153,11 @@ static void multipath_status (struct seq_file *seq, struct mddev *mddev)
seq_printf (seq, "]");
}
-static int multipath_congested(void *data, int bits)
+static int multipath_congested(struct mddev *mddev, int bits)
{
- struct mddev *mddev = data;
struct mpconf *conf = mddev->private;
int i, ret = 0;
- if (mddev_congested(mddev, bits))
- return 1;
-
rcu_read_lock();
for (i = 0; i < mddev->raid_disks ; i++) {
struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
@@ -489,9 +485,6 @@ static int multipath_run (struct mddev *mddev)
*/
md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
- mddev->queue->backing_dev_info.congested_fn = multipath_congested;
- mddev->queue->backing_dev_info.congested_data = mddev;
-
if (md_integrity_register(mddev))
goto out_free_conf;
@@ -533,6 +526,7 @@ static struct md_personality multipath_personality =
.hot_add_disk = multipath_add_disk,
.hot_remove_disk= multipath_remove_disk,
.size = multipath_size,
+ .congested = multipath_congested,
};
static int __init multipath_init (void)