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Commit 98f33285 authored by Kiyoshi Ueda's avatar Kiyoshi Ueda Committed by Alasdair G Kergon
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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: default avatarKiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: default avatarJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: stable@kernel.org
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent abdc568b

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,