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authorKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2013-06-07 15:26:03 -0400
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2013-06-10 10:14:33 -0400
commitb2c75c446ae72387916e2caf6e6dca815b6e5e6e (patch)
tree5b97f2908fec2b03b6dfef5f52d5e79f2597f750 /drivers/xen
parent466318a87f28cb3ba0d08a3b7ef1a37ae73d5aa7 (diff)
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xen/tmem: Don't over-write tmem_frontswap_poolid after tmem_frontswap_init set it.
Commit 10a7a0771399a57a297fca9615450dbb3f88081a ("xen: tmem: enable Xen tmem shim to be built/loaded as a module") allows the tmem module to be loaded any time. For this work the frontswap API had to be able to asynchronously to call tmem_frontswap_init before or after the swap image had been set. That was added in git commit 905cd0e1bf9ffe82d6906a01fd974ea0f70be97a ("mm: frontswap: lazy initialization to allow tmem backends to build/run as modules"). Which means we could do this (The common case): modprobe tmem [so calls frontswap_register_ops, no ->init] modifies tmem_frontswap_poolid = -1 swapon /dev/xvda1 [__frontswap_init, calls -> init, tmem_frontswap_poolid is < 0 so tmem hypercall done] Or the failing one: swapon /dev/xvda1 [calls __frontswap_init, sets the need_init bitmap] modprobe tmem [calls frontswap_register_ops, -->init calls, finds out tmem_frontswap_poolid is 0, does not make a hypercall. Later in the module_init, sets tmem_frontswap_poolid=-1] Which meant that in the failing case we would not call the hypercall to initialize the pool and never be able to make any frontswap backend calls. Moving the frontswap_register_ops after setting the tmem_frontswap_poolid fixes it. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Reviewed-by: Bob Liu <bob.liu@oracle.com>
Diffstat (limited to 'drivers/xen')
-rw-r--r--drivers/xen/tmem.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
index cc072c6..0f0493c 100644
--- a/drivers/xen/tmem.c
+++ b/drivers/xen/tmem.c
@@ -379,10 +379,10 @@ static int xen_tmem_init(void)
#ifdef CONFIG_FRONTSWAP
if (tmem_enabled && frontswap) {
char *s = "";
- struct frontswap_ops *old_ops =
- frontswap_register_ops(&tmem_frontswap_ops);
+ 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);