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dax: Fix deadlock in dax_lock_mapping_entry() 

When dax_lock_mapping_entry() has to sleep to obtain entry lock, it will
fail to unlock mapping->i_pages spinlock and thus immediately deadlock
against itself when retrying to grab the entry lock again. Fix the
problem by unlocking mapping->i_pages before retrying.

Fixes: c2a7d2a115 ("filesystem-dax: Introduce dax_lock_mapping_entry()")
Reported-by: Barret Rhoden <brho@google.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Jan Kara 2018-09-27 13:23:32 +02:00 committed by Dan Williams
parent 6bf4ca7fbc
commit f52afc93cd
1 changed files with 1 additions and 0 deletions
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fs/dax.c
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@ -447,6 +447,7 @@ bool dax_lock_mapping_entry(struct page *page)
xa_unlock_irq(&mapping->i_pages);
break;
} else if (IS_ERR(entry)) {
xa_unlock_irq(&mapping->i_pages);
WARN_ON_ONCE(PTR_ERR(entry) != -EAGAIN);
continue;
}