[tip:x86/mm] x86/mm/cpa: Make cpa_data::numpages invariant

tip-bot for Peter Zijlstra
2018-12-17T18:24:37Z

Commit-ID: 83b4e39146aa70913580966e0f2b78b7c3492760
Gitweb: https://git.kernel.org/tip/83b4e39146aa70913580966e0f2b78b7c3492760
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Mon, 3 Dec 2018 18:03:50 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 17 Dec 2018 18:54:27 +0100

x86/mm/cpa: Make cpa_data::numpages invariant

Make sure __change_page_attr_set_clr() doesn't modify cpa->numpages.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom.StDenis@amd.com
Cc: dave.hansen@intel.com
Link: http://lkml.kernel.org/r/20181203171043.493000228@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/mm/pageattr.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 351874259a71..12b69263e501 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1625,14 +1625,15 @@ static int cpa_process_alias(struct cpa_data *cpa)
static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias)
{
unsigned long numpages = cpa->numpages;
- int ret;
+ unsigned long rempages = numpages;
+ int ret = 0;

- while (numpages) {
+ while (rempages) {
/*
* Store the remaining nr of pages for the large page
* preservation check.
*/
- cpa->numpages = numpages;
+ cpa->numpages = rempages;
/* for array changes, we can't use large page */
if (cpa->flags & (CPA_ARRAY | CPA_PAGES_ARRAY))
cpa->numpages = 1;
@@ -1643,12 +1644,12 @@ static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias)
if (!debug_pagealloc_enabled())
spin_unlock(&cpa_lock);
if (ret)
- return ret;
+ goto out;

if (checkalias) {
ret = cpa_process_alias(cpa);
if (ret)
- return ret;
+ goto out;
}

/*
@@ -1656,11 +1657,15 @@ static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias)
* CPA operation. Either a large page has been
* preserved or a single page update happened.
*/
- BUG_ON(cpa->numpages > numpages || !cpa->numpages);
- numpages -= cpa->numpages;
+ BUG_ON(cpa->numpages > rempages || !cpa->numpages);
+ rempages -= cpa->numpages;
cpa->curpage += cpa->numpages;
}
- return 0;
+
+out:
+ /* Restore the original numpages */
+ cpa->numpages = numpages;
+ return ret;
}

/*