From d1dc6f1bcf1e998e7ce65fc120da371ab047a999 Mon Sep 17 00:00:00 2001 From: Dan Streetman Date: Wed, 24 Jun 2015 16:58:18 -0700 Subject: frontswap: allow multiple backends Change frontswap single pointer to a singly linked list of frontswap implementations. Update Xen tmem implementation as register no longer returns anything. Frontswap only keeps track of a single implementation; any implementation that registers second (or later) will replace the previously registered implementation, and gets a pointer to the previous implementation that the new implementation is expected to pass all frontswap functions to if it can't handle the function itself. However that method doesn't really make much sense, as passing that work on to every implementation adds unnecessary work to implementations; instead, frontswap should simply keep a list of all registered implementations and try each implementation for any function. Most importantly, neither of the two currently existing frontswap implementations in the kernel actually do anything with any previous frontswap implementation that they replace when registering. This allows frontswap to successfully manage multiple implementations by keeping a list of them all. Signed-off-by: Dan Streetman Cc: Konrad Rzeszutek Wilk Cc: Boris Ostrovsky Cc: David Vrabel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/xen/tmem.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) (limited to 'drivers/xen') diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c index c4211a31612d..d88f36754bf7 100644 --- a/drivers/xen/tmem.c +++ b/drivers/xen/tmem.c @@ -381,15 +381,9 @@ static int __init xen_tmem_init(void) #ifdef CONFIG_FRONTSWAP if (tmem_enabled && frontswap) { char *s = ""; - struct frontswap_ops *old_ops; tmem_frontswap_poolid = -1; - old_ops = frontswap_register_ops(&tmem_frontswap_ops); - if (IS_ERR(old_ops) || old_ops) { - if (IS_ERR(old_ops)) - return PTR_ERR(old_ops); - s = " (WARNING: frontswap_ops overridden)"; - } + frontswap_register_ops(&tmem_frontswap_ops); pr_info("frontswap enabled, RAM provided by Xen Transcendent Memory%s\n", s); } -- cgit v1.2.3-58-ga151