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Commit 0e28e01f authored by Oleg Nesterov's avatar Oleg Nesterov
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document rwsem_release() in sb_wait_write() 



Not only we need to avoid the warning from lockdep_sys_exit(), the
caller of freeze_super() can never release this lock. Another thread
can do this, so there is another reason for rwsem_release().

Plus the comment should explain why we have to fool lockdep.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarJan Kara <jack@suse.com>
parent f4b554af

fs/super.c

+9 −3
Original line number Diff line number Diff line
@@ -1236,11 +1236,17 @@ static void sb_wait_write(struct super_block *sb, int level) 
{

	s64 writers;



	rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_);

	/*

	 * We just cycle-through lockdep here so that it does not complain

	 * about returning with lock to userspace

	 * We are going to return to userspace and forget about this lock, the

	 * ownership goes to the caller of thaw_super() which does unlock.

	 *

	 * FIXME: we should do this before return from freeze_super() after we

	 * called sync_filesystem(sb) and s_op->freeze_fs(sb), and thaw_super()

	 * should re-acquire these locks before s_op->unfreeze_fs(sb). However

	 * this leads to lockdep false-positives, so currently we do the early

	 * release right after acquire.

	 */

	rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_);

	rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_);



	do {