From 98f332855effef02aeb738e4d62e9a5b903c52fd Mon Sep 17 00:00:00 2001 From: Kiyoshi Ueda Date: Thu, 12 Aug 2010 04:13:55 +0100 Subject: [PATCH] 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) holders> dm_get_live_or_inactive_table() dm_get_inactive_table() down_write(_hash_lock) holders to be 0> Signed-off-by: Kiyoshi Ueda Signed-off-by: Jun'ichi Nomura Cc: stable@kernel.org Signed-off-by: Alasdair G Kergon --- drivers/md/dm-ioctl.c | 44 ++++++++++++++++++++++++------------------- 1 file changed, 25 insertions(+), 19 deletions(-) diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 79ee5ba217f..6a6d475f8e8 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, -- 2.20.1