From f52afc93cd018fe6910133a05d44671192d1aeb0 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 27 Sep 2018 13:23:32 +0200
Subject: [PATCH] dax: Fix deadlock in dax_lock_mapping_entry()
Git-commit: f52afc93cd018fe6910133a05d44671192d1aeb0
Patch-mainline: v4.19-rc6
References: bsc#1109951

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: c2a7d2a11552 ("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>
Acked-by: Jan Kara <jack@suse.cz>

---
 fs/dax.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/dax.c
+++ b/fs/dax.c
@@ -405,6 +405,7 @@ bool dax_lock_mapping_entry(struct page
 			spin_unlock_irq(&mapping->tree_lock);
 			break;
 		} else if (IS_ERR(entry)) {
+			spin_unlock_irq(&mapping->tree_lock);
 			WARN_ON_ONCE(PTR_ERR(entry) != -EAGAIN);
 			continue;
 		}