kernel: backport pgalloc memory leak fix

Backport a fix for the massive memory leak observed in Octeon after
switching to kernel 5.10.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
(cherry picked from commit 9283359bd53a889a270da4a7d5bbe3eaaa771e70)

1 files changed, 48 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.10/350-v5.18-MIPS-pgalloc-fix-memory-leak-caused-by-pgd_free.patch b/target/linux/generic/backport-5.10/350-v5.18-MIPS-pgalloc-fix-memory-leak-caused-by-pgd_free.patch
new file mode 100644
index 0000000000..28ddbc2fbc
--- /dev/null
+++ b/target/linux/generic/backport-5.10/350-v5.18-MIPS-pgalloc-fix-memory-leak-caused-by-pgd_free.patch
@@ -0,0 +1,48 @@
+From e852442da56f43795cb6255d90b9fd0c84b209bb Mon Sep 17 00:00:00 2001
+From: Yaliang Wang <Yaliang.Wang@windriver.com>
+Date: Thu, 10 Mar 2022 19:31:16 +0800
+Subject: [PATCH] MIPS: pgalloc: fix memory leak caused by pgd_free()
+
+pgd page is freed by generic implementation pgd_free() since commit
+f9cb654cb550 ("asm-generic: pgalloc: provide generic pgd_free()"),
+however, there are scenarios that the system uses more than one page as
+the pgd table, in such cases the generic implementation pgd_free() won't
+be applicable anymore. For example, when PAGE_SIZE_4KB is enabled and
+MIPS_VA_BITS_48 is not enabled in a 64bit system, the macro "PGD_ORDER"
+will be set as "1", which will cause allocating two pages as the pgd
+table. Well, at the same time, the generic implementation pgd_free()
+just free one pgd page, which will result in the memory leak.
+
+The memory leak can be easily detected by executing shell command:
+"while true; do ls > /dev/null; grep MemFree /proc/meminfo; done"
+
+Fixes: f9cb654cb550 ("asm-generic: pgalloc: provide generic pgd_free()")
+Signed-off-by: Yaliang Wang <Yaliang.Wang@windriver.com>
+Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
+(cherry picked from commit 2bc5bab9a763d520937e4f3fe8df51c6a1eceb97)
+---
+ arch/mips/include/asm/pgalloc.h | 6 ++++++
+ 1 file changed, 6 insertions(+)
+
+--- a/arch/mips/include/asm/pgalloc.h
++++ b/arch/mips/include/asm/pgalloc.h
+@@ -15,6 +15,7 @@
+ 
+ #define __HAVE_ARCH_PMD_ALLOC_ONE
+ #define __HAVE_ARCH_PUD_ALLOC_ONE
++#define __HAVE_ARCH_PGD_FREE
+ #include <asm-generic/pgalloc.h>
+ 
+ static inline void pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd,
+@@ -49,6 +50,11 @@ static inline void pud_populate(struct m
+ extern void pgd_init(unsigned long page);
+ extern pgd_t *pgd_alloc(struct mm_struct *mm);
+ 
++static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
++{
++	free_pages((unsigned long)pgd, PGD_ORDER);
++}
++
+ #define __pte_free_tlb(tlb,pte,address)			\
+ do {							\
+ 	pgtable_pte_page_dtor(pte);			\