Commit a12f5d48 authored by Eric Dumazet's avatar Eric Dumazet Committed by Mike Snitzer
Browse files

dm: use rcu_dereference_protected instead of rcu_dereference 



rcu_dereference() should be used in sections protected by rcu_read_lock.

For writers, holding some kind of mutex or lock,
rcu_dereference_protected() is the way to go, adding explicit lockdep
bits.

In __unbind(), we are the last user of this mapped device, so can use
the constant '1' instead of a lockdep_is_held(), not consistent with
other uses of rcu_dereference_protected() which use md->suspend_lock
mutex.

Reported-by: default avatarKirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Fixes: 33423974 ("dm: Use rcu_dereference() for accessing rcu pointer")
Cc: Pranith Kumar <bobby.prani@gmail.com>
[snitzer: allow lines longer than 80 columns, refine subject]
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent d200c30e

drivers/md/dm.c

+5 −5
Original line number Diff line number Diff line
@@ -2335,7 +2335,7 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t, 


	merge_is_optional = dm_table_merge_is_optional(t);



	old_map = rcu_dereference(md->map);

	old_map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));

	rcu_assign_pointer(md->map, t);

	md->immutable_target_type = dm_table_get_immutable_target_type(t);
@@ -2355,7 +2355,7 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t, 
 */

static struct dm_table *__unbind(struct mapped_device *md)

{

	struct dm_table *map = rcu_dereference(md->map);

	struct dm_table *map = rcu_dereference_protected(md->map, 1);



	if (!map)

		return NULL;
@@ -2850,7 +2850,7 @@ retry: 
		goto retry;

	}



	map = rcu_dereference(md->map);

	map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));



	r = __dm_suspend(md, map, suspend_flags, TASK_INTERRUPTIBLE);

	if (r)
@@ -2908,7 +2908,7 @@ retry: 
		goto retry;

	}



	map = rcu_dereference(md->map);

	map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));

	if (!map || !dm_table_get_size(map))

		goto out;
@@ -2943,7 +2943,7 @@ static void __dm_internal_suspend(struct mapped_device *md, unsigned suspend_fla 
		return; /* nest suspend */

	}



	map = rcu_dereference(md->map);

	map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));



	/*

	 * Using TASK_UNINTERRUPTIBLE because only NOFLUSH internal suspend is

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