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author | 2008-07-21 17:05:25 +1000 | |
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committer | 2008-07-21 17:05:25 +1000 | |
commit | 4b80991c6cb9efa607bc4fd6f3ecdf5511c31bb0 (patch) | |
tree | 5e2ba7d509af245c29bdf04b00960cc367972c44 /include/linux/raid | |
parent | md: only count actual openers as access which prevent a 'stop' (diff) | |
download | linux-4b80991c6cb9efa607bc4fd6f3ecdf5511c31bb0.tar.gz linux-4b80991c6cb9efa607bc4fd6f3ecdf5511c31bb0.tar.bz2 linux-4b80991c6cb9efa607bc4fd6f3ecdf5511c31bb0.zip |
md: Protect access to mddev->disks list using RCU
All modifications and most access to the mddev->disks list are made
under the reconfig_mutex lock. However there are three places where
the list is walked without any locking. If a reconfig happens at this
time, havoc (and oops) can ensue.
So use RCU to protect these accesses:
- wrap them in rcu_read_{,un}lock()
- use list_for_each_entry_rcu
- add to the list with list_add_rcu
- delete from the list with list_del_rcu
- delay the 'free' with call_rcu rather than schedule_work
Note that export_rdev did a list_del_init on this list. In almost all
cases the entry was not in the list anymore so it was a no-op and so
safe. It is no longer safe as after list_del_rcu we may not touch
the list_head.
An audit shows that export_rdev is called:
- after unbind_rdev_from_array, in which case the delete has
already been done,
- after bind_rdev_to_array fails, in which case the delete isn't needed.
- before the device has been put on a list at all (e.g. in
add_new_disk where reading the superblock fails).
- and in autorun devices after a failure when the device is on a
different list.
So remove the list_del_init call from export_rdev, and add it back
immediately before the called to export_rdev for that last case.
Note also that ->same_set is sometimes used for lists other than
mddev->list (e.g. candidates). In these cases rcu is not needed.
Signed-off-by: NeilBrown <neilb@suse.de>
Diffstat (limited to 'include/linux/raid')
-rw-r--r-- | include/linux/raid/md_k.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h index 4bef4791d80d..9f2549ac0e2d 100644 --- a/include/linux/raid/md_k.h +++ b/include/linux/raid/md_k.h @@ -339,6 +339,9 @@ static inline char * mdname (mddev_t * mddev) #define rdev_for_each(rdev, tmp, mddev) \ rdev_for_each_list(rdev, tmp, (mddev)->disks) +#define rdev_for_each_rcu(rdev, mddev) \ + list_for_each_entry_rcu(rdev, &((mddev)->disks), same_set) + typedef struct mdk_thread_s { void (*run) (mddev_t *mddev); mddev_t *mddev; |