Commit 26723911 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds

mm, powerpc: move the RCU page-table freeing into generic code

In case other architectures require RCU freed page-tables to implement
gup_fast() and software filled hashes and similar things, provide the
means to do so by moving the logic into generic code.
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Requested-by: default avatarDavid Miller <davem@davemloft.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Tony Luck <tony.luck@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1c395176
......@@ -175,4 +175,7 @@ config HAVE_ARCH_JUMP_LABEL
config HAVE_ARCH_MUTEX_CPU_RELAX
bool
config HAVE_RCU_TABLE_FREE
bool
source "kernel/gcov/Kconfig"
......@@ -140,6 +140,7 @@ config PPC
select IRQ_PER_CPU
select GENERIC_IRQ_SHOW
select GENERIC_IRQ_SHOW_LEVEL
select HAVE_RCU_TABLE_FREE if SMP
config EARLY_PRINTK
bool
......
......@@ -31,14 +31,29 @@ static inline void pte_free(struct mm_struct *mm, pgtable_t ptepage)
#endif
#ifdef CONFIG_SMP
extern void pgtable_free_tlb(struct mmu_gather *tlb, void *table, unsigned shift);
extern void pte_free_finish(struct mmu_gather *tlb);
struct mmu_gather;
extern void tlb_remove_table(struct mmu_gather *, void *);
static inline void pgtable_free_tlb(struct mmu_gather *tlb, void *table, int shift)
{
unsigned long pgf = (unsigned long)table;
BUG_ON(shift > MAX_PGTABLE_INDEX_SIZE);
pgf |= shift;
tlb_remove_table(tlb, (void *)pgf);
}
static inline void __tlb_remove_table(void *_table)
{
void *table = (void *)((unsigned long)_table & ~MAX_PGTABLE_INDEX_SIZE);
unsigned shift = (unsigned long)_table & MAX_PGTABLE_INDEX_SIZE;
pgtable_free(table, shift);
}
#else /* CONFIG_SMP */
static inline void pgtable_free_tlb(struct mmu_gather *tlb, void *table, unsigned shift)
{
pgtable_free(table, shift);
}
static inline void pte_free_finish(struct mmu_gather *tlb) { }
#endif /* !CONFIG_SMP */
static inline void __pte_free_tlb(struct mmu_gather *tlb, struct page *ptepage,
......
......@@ -28,16 +28,6 @@
#define tlb_start_vma(tlb, vma) do { } while (0)
#define tlb_end_vma(tlb, vma) do { } while (0)
#define HAVE_ARCH_MMU_GATHER 1
struct pte_freelist_batch;
struct arch_mmu_gather {
struct pte_freelist_batch *batch;
};
#define ARCH_MMU_GATHER_INIT (struct arch_mmu_gather){ .batch = NULL, }
extern void tlb_flush(struct mmu_gather *tlb);
/* Get the generic bits... */
......
......@@ -33,104 +33,6 @@
#include "mmu_decl.h"
#ifdef CONFIG_SMP
/*
* Handle batching of page table freeing on SMP. Page tables are
* queued up and send to be freed later by RCU in order to avoid
* freeing a page table page that is being walked without locks
*/
static unsigned long pte_freelist_forced_free;
struct pte_freelist_batch
{
struct rcu_head rcu;
unsigned int index;
unsigned long tables[0];
};
#define PTE_FREELIST_SIZE \
((PAGE_SIZE - sizeof(struct pte_freelist_batch)) \
/ sizeof(unsigned long))
static void pte_free_smp_sync(void *arg)
{
/* Do nothing, just ensure we sync with all CPUs */
}
/* This is only called when we are critically out of memory
* (and fail to get a page in pte_free_tlb).
*/
static void pgtable_free_now(void *table, unsigned shift)
{
pte_freelist_forced_free++;
smp_call_function(pte_free_smp_sync, NULL, 1);
pgtable_free(table, shift);
}
static void pte_free_rcu_callback(struct rcu_head *head)
{
struct pte_freelist_batch *batch =
container_of(head, struct pte_freelist_batch, rcu);
unsigned int i;
for (i = 0; i < batch->index; i++) {
void *table = (void *)(batch->tables[i] & ~MAX_PGTABLE_INDEX_SIZE);
unsigned shift = batch->tables[i] & MAX_PGTABLE_INDEX_SIZE;
pgtable_free(table, shift);
}
free_page((unsigned long)batch);
}
static void pte_free_submit(struct pte_freelist_batch *batch)
{
call_rcu_sched(&batch->rcu, pte_free_rcu_callback);
}
void pgtable_free_tlb(struct mmu_gather *tlb, void *table, unsigned shift)
{
struct pte_freelist_batch **batchp = &tlb->arch.batch;
unsigned long pgf;
if (atomic_read(&tlb->mm->mm_users) < 2) {
pgtable_free(table, shift);
return;
}
if (*batchp == NULL) {
*batchp = (struct pte_freelist_batch *)__get_free_page(GFP_ATOMIC);
if (*batchp == NULL) {
pgtable_free_now(table, shift);
return;
}
(*batchp)->index = 0;
}
BUG_ON(shift > MAX_PGTABLE_INDEX_SIZE);
pgf = (unsigned long)table | shift;
(*batchp)->tables[(*batchp)->index++] = pgf;
if ((*batchp)->index == PTE_FREELIST_SIZE) {
pte_free_submit(*batchp);
*batchp = NULL;
}
}
void pte_free_finish(struct mmu_gather *tlb)
{
struct pte_freelist_batch **batchp = &tlb->arch.batch;
if (*batchp == NULL)
return;
pte_free_submit(*batchp);
*batchp = NULL;
}
#endif /* CONFIG_SMP */
static inline int is_exec_fault(void)
{
return current->thread.regs && TRAP(current->thread.regs) == 0x400;
......
......@@ -71,9 +71,6 @@ void tlb_flush(struct mmu_gather *tlb)
*/
_tlbia();
}
/* Push out batch of freed page tables */
pte_free_finish(tlb);
}
/*
......
......@@ -165,9 +165,6 @@ void tlb_flush(struct mmu_gather *tlb)
__flush_tlb_pending(tlbbatch);
put_cpu_var(ppc64_tlb_batch);
/* Push out batch of freed page tables */
pte_free_finish(tlb);
}
/**
......
......@@ -299,9 +299,6 @@ EXPORT_SYMBOL(flush_tlb_range);
void tlb_flush(struct mmu_gather *tlb)
{
flush_tlb_mm(tlb->mm);
/* Push out batch of freed page tables */
pte_free_finish(tlb);
}
/*
......
......@@ -29,6 +29,49 @@
#define tlb_fast_mode(tlb) 1
#endif
#ifdef CONFIG_HAVE_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().
*
*/
struct mmu_table_batch {
struct rcu_head rcu;
unsigned int nr;
void *tables[0];
};
#define MAX_TABLE_BATCH \
((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))
extern void tlb_table_flush(struct mmu_gather *tlb);
extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
#endif
/*
* 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.
......@@ -40,13 +83,13 @@
*/
struct mmu_gather {
struct mm_struct *mm;
#ifdef CONFIG_HAVE_RCU_TABLE_FREE
struct mmu_table_batch *batch;
#endif
unsigned int nr; /* set to ~0U means fast mode */
unsigned int max; /* nr < max */
unsigned int need_flush;/* Really unmapped some ptes? */
unsigned int fullmm; /* non-zero means full mm flush */
#ifdef HAVE_ARCH_MMU_GATHER
struct arch_mmu_gather arch;
#endif
struct page **pages;
struct page *local[MMU_GATHER_BUNDLE];
};
......@@ -82,8 +125,8 @@ tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm)
tlb->fullmm = fullmm;
#ifdef HAVE_ARCH_MMU_GATHER
tlb->arch = ARCH_MMU_GATHER_INIT;
#ifdef CONFIG_HAVE_RCU_TABLE_FREE
tlb->batch = NULL;
#endif
}
......@@ -94,6 +137,9 @@ tlb_flush_mmu(struct mmu_gather *tlb)
return;
tlb->need_flush = 0;
tlb_flush(tlb);
#ifdef CONFIG_HAVE_RCU_TABLE_FREE
tlb_table_flush(tlb);
#endif
if (!tlb_fast_mode(tlb)) {
free_pages_and_swap_cache(tlb->pages, tlb->nr);
tlb->nr = 0;
......
......@@ -193,6 +193,83 @@ static void check_sync_rss_stat(struct task_struct *task)
#endif
#ifdef CONFIG_HAVE_RCU_TABLE_FREE
/*
* See the comment near struct mmu_table_batch.
*/
static void tlb_remove_table_smp_sync(void *arg)
{
/* Simply deliver the interrupt */
}
static void tlb_remove_table_one(void *table)
{
/*
* 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. See the comment near struct mmu_table_batch.
*/
smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
__tlb_remove_table(table);
}
static void tlb_remove_table_rcu(struct rcu_head *head)
{
struct mmu_table_batch *batch;
int i;
batch = container_of(head, struct mmu_table_batch, rcu);
for (i = 0; i < batch->nr; i++)
__tlb_remove_table(batch->tables[i]);
free_page((unsigned long)batch);
}
void tlb_table_flush(struct mmu_gather *tlb)
{
struct mmu_table_batch **batch = &tlb->batch;
if (*batch) {
call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
*batch = NULL;
}
}
void tlb_remove_table(struct mmu_gather *tlb, void *table)
{
struct mmu_table_batch **batch = &tlb->batch;
tlb->need_flush = 1;
/*
* When there's less then two users of this mm there cannot be a
* concurrent page-table walk.
*/
if (atomic_read(&tlb->mm->mm_users) < 2) {
__tlb_remove_table(table);
return;
}
if (*batch == NULL) {
*batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
if (*batch == NULL) {
tlb_remove_table_one(table);
return;
}
(*batch)->nr = 0;
}
(*batch)->tables[(*batch)->nr++] = table;
if ((*batch)->nr == MAX_TABLE_BATCH)
tlb_table_flush(tlb);
}
#endif
/*
* If a p?d_bad entry is found while walking page tables, report
* the error, before resetting entry to p?d_none. Usually (but
......
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