linux-kernel - [PATCH 3.16 292/366] cachefiles: Wait rather than BUG'ing on "Unexpected object collision"

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Date:   Sun, 11 Nov 2018 19:49:05 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Kiran Kumar Modukuri" <kiran.modukuri@...il.com>,
        "David Howells" <dhowells@...hat.com>
Subject: [PATCH 3.16 292/366] cachefiles: Wait rather than BUG'ing on
 "Unexpected object collision"

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Kiran Kumar Modukuri <kiran.modukuri@...il.com>

commit c2412ac45a8f8f1cd582723c1a139608694d410d upstream.

If we meet a conflicting object that is marked FSCACHE_OBJECT_IS_LIVE in
the active object tree, we have been emitting a BUG after logging
information about it and the new object.

Instead, we should wait for the CACHEFILES_OBJECT_ACTIVE flag to be cleared
on the old object (or return an error).  The ACTIVE flag should be cleared
after it has been removed from the active object tree.  A timeout of 60s is
used in the wait, so we shouldn't be able to get stuck there.

Fixes: 9ae326a69004 ("CacheFiles: A cache that backs onto a mounted filesystem")
Signed-off-by: Kiran Kumar Modukuri <kiran.modukuri@...il.com>
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/cachefiles/namei.c | 1 -
 1 file changed, 1 deletion(-)

--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -194,7 +194,6 @@ wait_for_old_object:
 		pr_err("\n");
 		pr_err("Error: Unexpected object collision\n");
 		cachefiles_printk_object(object, xobject);
-		BUG();
 	}
 	atomic_inc(&xobject->usage);
 	write_unlock(&cache->active_lock);