diff options
author | Kiyoshi Ueda <k-ueda@ct.jp.nec.com> | 2010-08-03 11:30:32 +1000 |
---|---|---|
committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2010-08-03 11:30:32 +1000 |
commit | 27b97f99a74952db6bb87dcf19e0ce6eaa67d597 (patch) | |
tree | 733790cce5513b4d72616a0700c9fa7d5bac5842 /drivers/md | |
parent | 024b154ad724dd08d8f701cbed298f1de79c62fb (diff) |
dm-ioctl-release-_hash_lock-between-devices-in-remove_all
This patch changes dm_hash_remove_all() to release _hash_lock when
removing a device. After removing the device, dm_hash_remove_all()
takes _hash_lock and searches the hash from scratch again.
This patch is a preparation for the next patch, which changes device
deletion code to wait for md reference to be 0. Without this patch,
the wait in the next patch may cause AB-BA deadlock:
CPU0 CPU1
-----------------------------------------------------------------------
dm_hash_remove_all()
down_write(_hash_lock)
table_status()
md = find_device()
dm_get(md)
<increment md->holders>
dm_get_live_or_inactive_table()
dm_get_inactive_table()
down_write(_hash_lock)
<in the md deletion code>
<wait for md->holders to be 0>
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: stable@kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r-- | drivers/md/dm-ioctl.c | 44 |
1 files changed, 25 insertions, 19 deletions
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 79ee5ba217f2..6a6d475f8e80 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -249,40 +249,46 @@ static void __hash_remove(struct hash_cell *hc) static void dm_hash_remove_all(int keep_open_devices) { - int i, dev_skipped, dev_removed; + int i, dev_skipped; struct hash_cell *hc; - struct list_head *tmp, *n; + struct mapped_device *md; + +retry: + dev_skipped = 0; down_write(&_hash_lock); -retry: - dev_skipped = dev_removed = 0; for (i = 0; i < NUM_BUCKETS; i++) { - list_for_each_safe (tmp, n, _name_buckets + i) { - hc = list_entry(tmp, struct hash_cell, name_list); + list_for_each_entry(hc, _name_buckets + i, name_list) { + md = hc->md; + dm_get(md); - if (keep_open_devices && - dm_lock_for_deletion(hc->md)) { + if (keep_open_devices && dm_lock_for_deletion(md)) { + dm_put(md); dev_skipped++; continue; } + __hash_remove(hc); - dev_removed = 1; - } - } - /* - * Some mapped devices may be using other mapped devices, so if any - * still exist, repeat until we make no further progress. - */ - if (dev_skipped) { - if (dev_removed) - goto retry; + up_write(&_hash_lock); - DMWARN("remove_all left %d open device(s)", dev_skipped); + dm_put(md); + + /* + * Some mapped devices may be using other mapped + * devices, so repeat until we make no further + * progress. If a new mapped device is created + * here it will also get removed. + */ + goto retry; + } } up_write(&_hash_lock); + + if (dev_skipped) + DMWARN("remove_all left %d open device(s)", dev_skipped); } static struct mapped_device *dm_hash_rename(struct dm_ioctl *param, |