Commit dbbee9d5 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm/page_alloc: convert per-cpu list protection to local_lock

There is a lack of clarity of what exactly
local_irq_save/local_irq_restore protects in page_alloc.c .  It conflates
the protection of per-cpu page allocation structures with per-cpu vmstat
deltas.

This patch protects the PCP structure using local_lock which for most
configurations is identical to IRQ enabling/disabling.  The scope of the
lock is still wider than it should be but this is decreased later.

It is possible for the local_lock to be embedded safely within struct
per_cpu_pages but it adds complexity to free_unref_page_list.

[akpm@linux-foundation.org: coding style fixes]
[mgorman@techsingularity.net: work around a pahole limitation with zero-sized struct pagesets]
  Link: https://lkml.kernel.org/r/20210526080741.GW30378@techsingularity.net
[lkp@intel.com: Make pagesets static]

Link: https://lkml.kernel.org/r/20210512095458.30632-3-mgorman@techsingularity.net

Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 28f836b6
......@@ -20,6 +20,7 @@
#include <linux/atomic.h>
#include <linux/mm_types.h>
#include <linux/page-flags.h>
#include <linux/local_lock.h>
#include <asm/page.h>
/* Free memory management - zoned buddy allocator. */
......@@ -337,6 +338,7 @@ enum zone_watermarks {
#define high_wmark_pages(z) (z->_watermark[WMARK_HIGH] + z->watermark_boost)
#define wmark_pages(z, i) (z->_watermark[i] + z->watermark_boost)
/* Fields and list protected by pagesets local_lock in page_alloc.c */
struct per_cpu_pages {
int count; /* number of pages in the list */
int high; /* high watermark, emptying needed */
......
......@@ -313,6 +313,9 @@ config DEBUG_INFO_BTF
config PAHOLE_HAS_SPLIT_BTF
def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119")
config PAHOLE_HAS_ZEROSIZE_PERCPU_SUPPORT
def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "122")
config DEBUG_INFO_BTF_MODULES
def_bool y
depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF
......
......@@ -122,6 +122,24 @@ typedef int __bitwise fpi_t;
static DEFINE_MUTEX(pcp_batch_high_lock);
#define MIN_PERCPU_PAGELIST_FRACTION (8)
struct pagesets {
local_lock_t lock;
#if defined(CONFIG_DEBUG_INFO_BTF) && \
!defined(CONFIG_DEBUG_LOCK_ALLOC) && \
!defined(CONFIG_PAHOLE_HAS_ZEROSIZE_PERCPU_SUPPORT)
/*
* pahole 1.21 and earlier gets confused by zero-sized per-CPU
* variables and produces invalid BTF. Ensure that
* sizeof(struct pagesets) != 0 for older versions of pahole.
*/
char __pahole_hack;
#warning "pahole too old to support zero-sized struct pagesets"
#endif
};
static DEFINE_PER_CPU(struct pagesets, pagesets) = {
.lock = INIT_LOCAL_LOCK(lock),
};
#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
DEFINE_PER_CPU(int, numa_node);
EXPORT_PER_CPU_SYMBOL(numa_node);
......@@ -1453,6 +1471,10 @@ static void free_pcppages_bulk(struct zone *zone, int count,
} while (--count && --batch_free && !list_empty(list));
}
/*
* local_lock_irq held so equivalent to spin_lock_irqsave for
* both PREEMPT_RT and non-PREEMPT_RT configurations.
*/
spin_lock(&zone->lock);
isolated_pageblocks = has_isolate_pageblock(zone);
......@@ -1573,6 +1595,11 @@ static void __free_pages_ok(struct page *page, unsigned int order,
return;
migratetype = get_pfnblock_migratetype(page, pfn);
/*
* TODO FIX: Disable IRQs before acquiring IRQ-safe zone->lock
* and protect vmstat updates.
*/
local_irq_save(flags);
__count_vm_events(PGFREE, 1 << order);
free_one_page(page_zone(page), page, pfn, order, migratetype,
......@@ -2955,6 +2982,10 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
{
int i, allocated = 0;
/*
* local_lock_irq held so equivalent to spin_lock_irqsave for
* both PREEMPT_RT and non-PREEMPT_RT configurations.
*/
spin_lock(&zone->lock);
for (i = 0; i < count; ++i) {
struct page *page = __rmqueue(zone, order, migratetype,
......@@ -3007,12 +3038,12 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
unsigned long flags;
int to_drain, batch;
local_irq_save(flags);
local_lock_irqsave(&pagesets.lock, flags);
batch = READ_ONCE(pcp->batch);
to_drain = min(pcp->count, batch);
if (to_drain > 0)
free_pcppages_bulk(zone, to_drain, pcp);
local_irq_restore(flags);
local_unlock_irqrestore(&pagesets.lock, flags);
}
#endif
......@@ -3028,13 +3059,13 @@ static void drain_pages_zone(unsigned int cpu, struct zone *zone)
unsigned long flags;
struct per_cpu_pages *pcp;
local_irq_save(flags);
local_lock_irqsave(&pagesets.lock, flags);
pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
if (pcp->count)
free_pcppages_bulk(zone, pcp->count, pcp);
local_irq_restore(flags);
local_unlock_irqrestore(&pagesets.lock, flags);
}
/*
......@@ -3297,9 +3328,9 @@ void free_unref_page(struct page *page)
if (!free_unref_page_prepare(page, pfn))
return;
local_irq_save(flags);
local_lock_irqsave(&pagesets.lock, flags);
free_unref_page_commit(page, pfn);
local_irq_restore(flags);
local_unlock_irqrestore(&pagesets.lock, flags);
}
/*
......@@ -3319,7 +3350,7 @@ void free_unref_page_list(struct list_head *list)
set_page_private(page, pfn);
}
local_irq_save(flags);
local_lock_irqsave(&pagesets.lock, flags);
list_for_each_entry_safe(page, next, list, lru) {
unsigned long pfn = page_private(page);
......@@ -3332,12 +3363,12 @@ void free_unref_page_list(struct list_head *list)
* a large list of pages to free.
*/
if (++batch_count == SWAP_CLUSTER_MAX) {
local_irq_restore(flags);
local_unlock_irqrestore(&pagesets.lock, flags);
batch_count = 0;
local_irq_save(flags);
local_lock_irqsave(&pagesets.lock, flags);
}
}
local_irq_restore(flags);
local_unlock_irqrestore(&pagesets.lock, flags);
}
/*
......@@ -3494,7 +3525,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
struct page *page;
unsigned long flags;
local_irq_save(flags);
local_lock_irqsave(&pagesets.lock, flags);
pcp = this_cpu_ptr(zone->per_cpu_pageset);
list = &pcp->lists[migratetype];
page = __rmqueue_pcplist(zone, migratetype, alloc_flags, pcp, list);
......@@ -3502,7 +3533,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
__count_zid_vm_events(PGALLOC, page_zonenum(page), 1);
zone_statistics(preferred_zone, zone);
}
local_irq_restore(flags);
local_unlock_irqrestore(&pagesets.lock, flags);
return page;
}
......@@ -5103,7 +5134,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
goto failed;
/* Attempt the batch allocation */
local_irq_save(flags);
local_lock_irqsave(&pagesets.lock, flags);
pcp = this_cpu_ptr(zone->per_cpu_pageset);
pcp_list = &pcp->lists[ac.migratetype];
......@@ -5141,12 +5172,12 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
nr_populated++;
}
local_irq_restore(flags);
local_unlock_irqrestore(&pagesets.lock, flags);
return nr_populated;
failed_irq:
local_irq_restore(flags);
local_unlock_irqrestore(&pagesets.lock, flags);
failed:
page = __alloc_pages(gfp, 0, preferred_nid, nodemask);
......
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