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-rw-r--r--mm/mmu_gather.c332
1 files changed, 332 insertions, 0 deletions
diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c
new file mode 100644
index 000000000..205fdbb57
--- /dev/null
+++ b/mm/mmu_gather.c
@@ -0,0 +1,332 @@
+#include <linux/gfp.h>
+#include <linux/highmem.h>
+#include <linux/kernel.h>
+#include <linux/mmdebug.h>
+#include <linux/mm_types.h>
+#include <linux/pagemap.h>
+#include <linux/rcupdate.h>
+#include <linux/smp.h>
+#include <linux/swap.h>
+
+#include <asm/pgalloc.h>
+#include <asm/tlb.h>
+
+#ifndef CONFIG_MMU_GATHER_NO_GATHER
+
+static bool tlb_next_batch(struct mmu_gather *tlb)
+{
+ struct mmu_gather_batch *batch;
+
+ batch = tlb->active;
+ if (batch->next) {
+ tlb->active = batch->next;
+ return true;
+ }
+
+ if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
+ return false;
+
+ batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
+ if (!batch)
+ return false;
+
+ tlb->batch_count++;
+ batch->next = NULL;
+ batch->nr = 0;
+ batch->max = MAX_GATHER_BATCH;
+
+ tlb->active->next = batch;
+ tlb->active = batch;
+
+ 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_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 /* MMU_GATHER_NO_GATHER */
+
+#ifdef CONFIG_MMU_GATHER_TABLE_FREE
+
+static void __tlb_remove_table_free(struct mmu_table_batch *batch)
+{
+ int i;
+
+ for (i = 0; i < batch->nr; i++)
+ __tlb_remove_table(batch->tables[i]);
+
+ free_page((unsigned long)batch);
+}
+
+#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE
+
+/*
+ * Semi RCU freeing of the page directories.
+ *
+ * This is needed by some architectures to implement software pagetable walkers.
+ *
+ * gup_fast() and other software pagetable walkers do a lockless page-table
+ * walk and therefore needs some synchronization with the freeing of the page
+ * directories. The chosen means to accomplish that is by disabling IRQs over
+ * the walk.
+ *
+ * Architectures that use IPIs to flush TLBs will then automagically DTRT,
+ * since we unlink the page, flush TLBs, free the page. Since the disabling of
+ * IRQs delays the completion of the TLB flush we can never observe an already
+ * freed page.
+ *
+ * Architectures that do not have this (PPC) need to delay the freeing by some
+ * other means, this is that means.
+ *
+ * What we do is batch the freed directory pages (tables) and RCU free them.
+ * We use the sched RCU variant, as that guarantees that IRQ/preempt disabling
+ * holds off grace periods.
+ *
+ * However, in order to batch these pages we need to allocate storage, this
+ * allocation is deep inside the MM code and can thus easily fail on memory
+ * pressure. To guarantee progress we fall back to single table freeing, see
+ * the implementation of tlb_remove_table_one().
+ *
+ */
+
+static void tlb_remove_table_smp_sync(void *arg)
+{
+ /* Simply deliver the interrupt */
+}
+
+void tlb_remove_table_sync_one(void)
+{
+ /*
+ * This isn't an RCU grace period and hence the page-tables cannot be
+ * assumed to be actually RCU-freed.
+ *
+ * It is however sufficient for software page-table walkers that rely on
+ * IRQ disabling.
+ */
+ smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
+}
+
+static void tlb_remove_table_rcu(struct rcu_head *head)
+{
+ __tlb_remove_table_free(container_of(head, struct mmu_table_batch, rcu));
+}
+
+static void tlb_remove_table_free(struct mmu_table_batch *batch)
+{
+ call_rcu(&batch->rcu, tlb_remove_table_rcu);
+}
+
+#else /* !CONFIG_MMU_GATHER_RCU_TABLE_FREE */
+
+static void tlb_remove_table_free(struct mmu_table_batch *batch)
+{
+ __tlb_remove_table_free(batch);
+}
+
+#endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */
+
+/*
+ * If we want tlb_remove_table() to imply TLB invalidates.
+ */
+static inline void tlb_table_invalidate(struct mmu_gather *tlb)
+{
+ if (tlb_needs_table_invalidate()) {
+ /*
+ * Invalidate page-table caches used by hardware walkers. Then
+ * we still need to RCU-sched wait while freeing the pages
+ * because software walkers can still be in-flight.
+ */
+ tlb_flush_mmu_tlbonly(tlb);
+ }
+}
+
+static void tlb_remove_table_one(void *table)
+{
+ tlb_remove_table_sync_one();
+ __tlb_remove_table(table);
+}
+
+static void tlb_table_flush(struct mmu_gather *tlb)
+{
+ struct mmu_table_batch **batch = &tlb->batch;
+
+ if (*batch) {
+ tlb_table_invalidate(tlb);
+ tlb_remove_table_free(*batch);
+ *batch = NULL;
+ }
+}
+
+void tlb_remove_table(struct mmu_gather *tlb, void *table)
+{
+ struct mmu_table_batch **batch = &tlb->batch;
+
+ if (*batch == NULL) {
+ *batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
+ if (*batch == NULL) {
+ tlb_table_invalidate(tlb);
+ tlb_remove_table_one(table);
+ return;
+ }
+ (*batch)->nr = 0;
+ }
+
+ (*batch)->tables[(*batch)->nr++] = table;
+ if ((*batch)->nr == MAX_TABLE_BATCH)
+ tlb_table_flush(tlb);
+}
+
+static inline void tlb_table_init(struct mmu_gather *tlb)
+{
+ tlb->batch = NULL;
+}
+
+#else /* !CONFIG_MMU_GATHER_TABLE_FREE */
+
+static inline void tlb_table_flush(struct mmu_gather *tlb) { }
+static inline void tlb_table_init(struct mmu_gather *tlb) { }
+
+#endif /* CONFIG_MMU_GATHER_TABLE_FREE */
+
+static void tlb_flush_mmu_free(struct mmu_gather *tlb)
+{
+ tlb_table_flush(tlb);
+#ifndef CONFIG_MMU_GATHER_NO_GATHER
+ tlb_batch_pages_flush(tlb);
+#endif
+}
+
+void tlb_flush_mmu(struct mmu_gather *tlb)
+{
+ tlb_flush_mmu_tlbonly(tlb);
+ tlb_flush_mmu_free(tlb);
+}
+
+/**
+ * tlb_gather_mmu - initialize an mmu_gather structure for page-table tear-down
+ * @tlb: the mmu_gather structure to initialize
+ * @mm: the mm_struct of the target address space
+ * @start: start of the region that will be removed from the page-table
+ * @end: end of the region that will be removed from the page-table
+ *
+ * Called to initialize an (on-stack) mmu_gather structure for page-table
+ * tear-down from @mm. The @start and @end are set to 0 and -1
+ * respectively when @mm is without users and we're going to destroy
+ * the full address space (exit/execve).
+ */
+void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+ tlb->mm = mm;
+
+ /* Is it from 0 to ~0? */
+ tlb->fullmm = !(start | (end+1));
+
+#ifndef CONFIG_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
+
+ tlb_table_init(tlb);
+#ifdef CONFIG_MMU_GATHER_PAGE_SIZE
+ tlb->page_size = 0;
+#endif
+
+ __tlb_reset_range(tlb);
+ inc_tlb_flush_pending(tlb->mm);
+}
+
+/**
+ * tlb_finish_mmu - finish an mmu_gather structure
+ * @tlb: the mmu_gather structure to finish
+ * @start: start of the region that will be removed from the page-table
+ * @end: end of the region that will be removed from the page-table
+ *
+ * Called at the end of the shootdown operation to free up any resources that
+ * were required.
+ */
+void tlb_finish_mmu(struct mmu_gather *tlb,
+ unsigned long start, unsigned long end)
+{
+ /*
+ * If there are parallel threads are doing PTE changes on same range
+ * under non-exclusive lock (e.g., mmap_lock read-side) but defer TLB
+ * flush by batching, one thread may end up seeing inconsistent PTEs
+ * and result in having stale TLB entries. So flush TLB forcefully
+ * if we detect parallel PTE batching threads.
+ *
+ * However, some syscalls, e.g. munmap(), may free page tables, this
+ * needs force flush everything in the given range. Otherwise this
+ * may result in having stale TLB entries for some architectures,
+ * e.g. aarch64, that could specify flush what level TLB.
+ */
+ if (mm_tlb_flush_nested(tlb->mm)) {
+ /*
+ * The aarch64 yields better performance with fullmm by
+ * avoiding multiple CPUs spamming TLBI messages at the
+ * same time.
+ *
+ * On x86 non-fullmm doesn't yield significant difference
+ * against fullmm.
+ */
+ tlb->fullmm = 1;
+ __tlb_reset_range(tlb);
+ tlb->freed_tables = 1;
+ }
+
+ tlb_flush_mmu(tlb);
+
+#ifndef CONFIG_MMU_GATHER_NO_GATHER
+ tlb_batch_list_free(tlb);
+#endif
+ dec_tlb_flush_pending(tlb->mm);
+}