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Subject[PATCH v6 13/18] asm-generic/tlb: Introduce HAVE_MMU_GATHER_NO_GATHER
Add the Kconfig option HAVE_MMU_GATHER_NO_GATHER to the generic
mmu_gather code. If the option is set the mmu_gather will not
track individual pages for delayed page free anymore. A platform
that enables the option needs to provide its own implementation
of the __tlb_remove_page_size function to free pages.

Cc: npiggin@gmail.com
Cc: heiko.carstens@de.ibm.com
Cc: will.deacon@arm.com
Cc: aneesh.kumar@linux.vnet.ibm.com
Cc: akpm@linux-foundation.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux@armlinux.org.uk
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180918125151.31744-2-schwidefsky@de.ibm.com
---
arch/Kconfig | 3 +
include/asm-generic/tlb.h | 9 +++
mm/mmu_gather.c | 107 +++++++++++++++++++++++++---------------------
3 files changed, 70 insertions(+), 49 deletions(-)

--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -368,6 +368,9 @@ config HAVE_RCU_TABLE_NO_INVALIDATE
config HAVE_MMU_GATHER_PAGE_SIZE
bool

+config HAVE_MMU_GATHER_NO_GATHER
+ bool
+
config ARCH_HAVE_NMI_SAFE_CMPXCHG
bool

--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -184,6 +184,7 @@ extern void tlb_remove_table(struct mmu_

#endif

+#ifndef CONFIG_HAVE_MMU_GATHER_NO_GATHER
/*
* If we can't allocate a page to make a big batch of page pointers
* to work on, then just handle a few from the on-stack structure.
@@ -208,6 +209,10 @@ struct mmu_gather_batch {
*/
#define MAX_GATHER_BATCH_COUNT (10000UL/MAX_GATHER_BATCH)

+extern bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page,
+ int page_size);
+#endif
+
/*
* struct mmu_gather is an opaque type used by the mm code for passing around
* any data needed by arch specific code for tlb_remove_page.
@@ -254,6 +259,7 @@ struct mmu_gather {

unsigned int batch_count;

+#ifndef CONFIG_HAVE_MMU_GATHER_NO_GATHER
struct mmu_gather_batch *active;
struct mmu_gather_batch local;
struct page *__pages[MMU_GATHER_BUNDLE];
@@ -261,6 +267,7 @@ struct mmu_gather {
#ifdef CONFIG_HAVE_MMU_GATHER_PAGE_SIZE
unsigned int page_size;
#endif
+#endif
};

void arch_tlb_gather_mmu(struct mmu_gather *tlb,
@@ -269,8 +276,6 @@ void tlb_flush_mmu(struct mmu_gather *tl
void arch_tlb_finish_mmu(struct mmu_gather *tlb,
unsigned long start, unsigned long end, bool force);
void tlb_flush_mmu_free(struct mmu_gather *tlb);
-extern bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page,
- int page_size);

static inline void __tlb_adjust_range(struct mmu_gather *tlb,
unsigned long address,
--- a/mm/mmu_gather.c
+++ b/mm/mmu_gather.c
@@ -13,6 +13,8 @@

#ifdef HAVE_GENERIC_MMU_GATHER

+#ifndef CONFIG_HAVE_MMU_GATHER_NO_GATHER
+
static bool tlb_next_batch(struct mmu_gather *tlb)
{
struct mmu_gather_batch *batch;
@@ -41,6 +43,56 @@ static bool tlb_next_batch(struct mmu_ga
return true;
}

+static void tlb_batch_pages_flush(struct mmu_gather *tlb)
+{
+ struct mmu_gather_batch *batch;
+
+ for (batch = &tlb->local; batch && batch->nr; batch = batch->next) {
+ free_pages_and_swap_cache(batch->pages, batch->nr);
+ batch->nr = 0;
+ }
+ tlb->active = &tlb->local;
+}
+
+static void tlb_batch_list_free(struct mmu_gather *tlb)
+{
+ struct mmu_gather_batch *batch, *next;
+
+ for (batch = tlb->local.next; batch; batch = next) {
+ next = batch->next;
+ free_pages((unsigned long)batch, 0);
+ }
+ tlb->local.next = NULL;
+}
+
+bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, int page_size)
+{
+ struct mmu_gather_batch *batch;
+
+ VM_BUG_ON(!tlb->end);
+
+#ifdef CONFIG_HAVE_MMU_GATHER_PAGE_SIZE
+ VM_WARN_ON(tlb->page_size != page_size);
+#endif
+
+ batch = tlb->active;
+ /*
+ * Add the page and check if we are full. If so
+ * force a flush.
+ */
+ batch->pages[batch->nr++] = page;
+ if (batch->nr == batch->max) {
+ if (!tlb_next_batch(tlb))
+ return true;
+ batch = tlb->active;
+ }
+ VM_BUG_ON_PAGE(batch->nr > batch->max, page);
+
+ return false;
+}
+
+#endif /* HAVE_MMU_GATHER_NO_GATHER */
+
void arch_tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
unsigned long start, unsigned long end)
{
@@ -48,12 +100,15 @@ void arch_tlb_gather_mmu(struct mmu_gath

/* Is it from 0 to ~0? */
tlb->fullmm = !(start | (end+1));
+
+#ifndef CONFIG_HAVE_MMU_GATHER_NO_GATHER
tlb->need_flush_all = 0;
tlb->local.next = NULL;
tlb->local.nr = 0;
tlb->local.max = ARRAY_SIZE(tlb->__pages);
tlb->active = &tlb->local;
tlb->batch_count = 0;
+#endif

#ifdef CONFIG_HAVE_RCU_TABLE_FREE
tlb->batch = NULL;
@@ -67,16 +122,12 @@ void arch_tlb_gather_mmu(struct mmu_gath

void tlb_flush_mmu_free(struct mmu_gather *tlb)
{
- struct mmu_gather_batch *batch;
-
#ifdef CONFIG_HAVE_RCU_TABLE_FREE
tlb_table_flush(tlb);
#endif
- for (batch = &tlb->local; batch && batch->nr; batch = batch->next) {
- free_pages_and_swap_cache(batch->pages, batch->nr);
- batch->nr = 0;
- }
- tlb->active = &tlb->local;
+#ifndef CONFIG_HAVE_MMU_GATHER_NO_GATHER
+ tlb_batch_pages_flush(tlb);
+#endif
}

void tlb_flush_mmu(struct mmu_gather *tlb)
@@ -92,8 +143,6 @@ void tlb_flush_mmu(struct mmu_gather *tl
void arch_tlb_finish_mmu(struct mmu_gather *tlb,
unsigned long start, unsigned long end, bool force)
{
- struct mmu_gather_batch *batch, *next;
-
if (force) {
__tlb_reset_range(tlb);
__tlb_adjust_range(tlb, start, end - start);
@@ -103,45 +152,9 @@ void arch_tlb_finish_mmu(struct mmu_gath

/* keep the page table cache within bounds */
check_pgt_cache();
-
- for (batch = tlb->local.next; batch; batch = next) {
- next = batch->next;
- free_pages((unsigned long)batch, 0);
- }
- tlb->local.next = NULL;
-}
-
-/* __tlb_remove_page
- * Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
- * handling the additional races in SMP caused by other CPUs caching valid
- * mappings in their TLBs. Returns the number of free page slots left.
- * When out of page slots we must call tlb_flush_mmu().
- *returns true if the caller should flush.
- */
-bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, int page_size)
-{
- struct mmu_gather_batch *batch;
-
- VM_BUG_ON(!tlb->end);
-
-#ifdef CONFIG_HAVE_MMU_GATHER_PAGE_SIZE
- VM_WARN_ON(tlb->page_size != page_size);
+#ifndef CONFIG_HAVE_MMU_GATHER_NO_GATHER
+ tlb_batch_list_free(tlb);
#endif
-
- batch = tlb->active;
- /*
- * Add the page and check if we are full. If so
- * force a flush.
- */
- batch->pages[batch->nr++] = page;
- if (batch->nr == batch->max) {
- if (!tlb_next_batch(tlb))
- return true;
- batch = tlb->active;
- }
- VM_BUG_ON_PAGE(batch->nr > batch->max, page);
-
- return false;
}

#endif /* HAVE_GENERIC_MMU_GATHER */

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