dm ioctl: release _hash_lock between devices in remove_all (98f33285) · Commits · 戴 / test

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>

drivers/md/dm-ioctl.c

+25 −19

Original line number	Diff line number	Diff line
		@@ -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;
		}
		}

		up_write(&_hash_lock);

		dm_put(md);

		/*
		* Some mapped devices may be using other mapped devices, so if any
		* still exist, repeat until we make no further progress.
		* 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.
		*/
		if (dev_skipped) {
		if (dev_removed)
		goto retry;

		DMWARN("remove_all left %d open device(s)", dev_skipped);
		}
		}

		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,

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