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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <20221117115023.1350181-2-dwysocha@redhat.com>
References: <20221117115023.1350181-2-dwysocha@redhat.com> <20221117115023.1350181-1-dwysocha@redhat.com>
To:     Dave Wysochanski <dwysocha@redhat.com>
Cc:     dhowells@redhat.com, Daire Byrne <daire.byrne@gmail.com>,
        Benjamin Maynard <benmaynard@google.com>,
        linux-cachefs@redhat.com, linux-nfs@vger.kernel.org
Subject: Re: [PATCH 1/1] fscache: Fix oops due to race with cookie_lru and use_cookie
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Content-ID: <3716090.1668692187.1@warthog.procyon.org.uk>
Date:   Thu, 17 Nov 2022 13:36:27 +0000
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You can probably make this easier to trigger by putting a delay in the state
machine if the flag is set:

[fs/fscache/cookie.c]
+#include <linux/delay.h>
...
 static void fscache_cookie_state_machine(struct fscache_cookie *cookie)
 {
 	enum fscache_cookie_state state;
 	bool wake = false;

 	_enter("c=%x", cookie->debug_id);

 again:
+	if (test_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &cookie->flags))
+		msleep(100);
 again_locked:
 	state = cookie->state;
 	switch (state) {

David