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mm/page_alloc: replace local_lock with normal spinlock

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struct per_cpu_pages is no longer strictly local as PCP lists can be
drained remotely using a lock for protection.  While the use of local_lock
works, it goes against the intent of local_lock which is for "pure CPU
local concurrency control mechanisms and not suited for inter-CPU
concurrency control" (Documentation/locking/locktypes.rst)

local_lock protects against migration between when the percpu pointer is
accessed and the pcp->lock acquired.  The lock acquisition is a preemption
point so in the worst case, a task could migrate to another NUMA node and
accidentally allocate remote memory.  The main requirement is to pin the
task to a CPU that is suitable for PREEMPT_RT and !PREEMPT_RT.

Replace local_lock with helpers that pin a task to a CPU, lookup the
per-cpu structure and acquire the embedded lock.  It's similar to
local_lock without breaking the intent behind the API.  It is not a
complete API as only the parts needed for PCP-alloc are implemented but in
theory, the generic helpers could be promoted to a general API if there
was demand for an embedded lock within a per-cpu struct with a guarantee
that the per-cpu structure locked matches the running CPU and cannot use
get_cpu_var due to RT concerns.  PCP requires these semantics to avoid
accidentally allocating remote memory.

[mgorman@techsingularity.net: use pcp_spin_trylock_irqsave instead of pcpu_spin_trylock_irqsave]
  Link: https://lkml.kernel.org/r/20220627084645.GA27531@techsingularity.net
Link: https://lkml.kernel.org/r/20220624125423.6126-8-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Tested-by: Yu Zhao <yuzhao@google.com>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Mel Gorman 2022-06-24 13:54:23 +01:00 committed by akpm
parent 443c2accd1
commit 01b44456a7
1 changed files with 95 additions and 45 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

140
mm/page_alloc.c
View file

@ -126,13 +126,6 @@ typedef int __bitwise fpi_t;
static DEFINE_MUTEX(pcp_batch_high_lock);
#define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)
struct pagesets {
local_lock_t lock;
};
static DEFINE_PER_CPU(struct pagesets, pagesets) = {
.lock = INIT_LOCAL_LOCK(lock),
};
#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
/*
* On SMP, spin_trylock is sufficient protection.
@ -147,6 +140,83 @@ static DEFINE_PER_CPU(struct pagesets, pagesets) = {
#define pcp_trylock_finish(flags) local_irq_restore(flags)
#endif
/*
* Locking a pcp requires a PCP lookup followed by a spinlock. To avoid
* a migration causing the wrong PCP to be locked and remote memory being
* potentially allocated, pin the task to the CPU for the lookup+lock.
* preempt_disable is used on !RT because it is faster than migrate_disable.
* migrate_disable is used on RT because otherwise RT spinlock usage is
* interfered with and a high priority task cannot preempt the allocator.
*/
#ifndef CONFIG_PREEMPT_RT
#define pcpu_task_pin() preempt_disable()
#define pcpu_task_unpin() preempt_enable()
#else
#define pcpu_task_pin() migrate_disable()
#define pcpu_task_unpin() migrate_enable()
#endif
/*
* Generic helper to lookup and a per-cpu variable with an embedded spinlock.
* Return value should be used with equivalent unlock helper.
*/
#define pcpu_spin_lock(type, member, ptr) \
({ \
type *_ret; \
pcpu_task_pin(); \
_ret = this_cpu_ptr(ptr); \
spin_lock(&_ret->member); \
_ret; \
})
#define pcpu_spin_lock_irqsave(type, member, ptr, flags) \
({ \
type *_ret; \
pcpu_task_pin(); \
_ret = this_cpu_ptr(ptr); \
spin_lock_irqsave(&_ret->member, flags); \
_ret; \
})
#define pcpu_spin_trylock_irqsave(type, member, ptr, flags) \
({ \
type *_ret; \
pcpu_task_pin(); \
_ret = this_cpu_ptr(ptr); \
if (!spin_trylock_irqsave(&_ret->member, flags)) { \
pcpu_task_unpin(); \
_ret = NULL; \
} \
_ret; \
})
#define pcpu_spin_unlock(member, ptr) \
({ \
spin_unlock(&ptr->member); \
pcpu_task_unpin(); \
})
#define pcpu_spin_unlock_irqrestore(member, ptr, flags) \
({ \
spin_unlock_irqrestore(&ptr->member, flags); \
pcpu_task_unpin(); \
})
/* struct per_cpu_pages specific helpers. */
#define pcp_spin_lock(ptr) \
pcpu_spin_lock(struct per_cpu_pages, lock, ptr)
#define pcp_spin_lock_irqsave(ptr, flags) \
pcpu_spin_lock_irqsave(struct per_cpu_pages, lock, ptr, flags)
#define pcp_spin_trylock_irqsave(ptr, flags) \
pcpu_spin_trylock_irqsave(struct per_cpu_pages, lock, ptr, flags)
#define pcp_spin_unlock(ptr) \
pcpu_spin_unlock(lock, ptr)
#define pcp_spin_unlock_irqrestore(ptr, flags) \
pcpu_spin_unlock_irqrestore(lock, ptr, flags)
#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
DEFINE_PER_CPU(int, numa_node);
EXPORT_PER_CPU_SYMBOL(numa_node);
@ -1485,10 +1555,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
/* Ensure requested pindex is drained first. */
pindex = pindex - 1;
/*
* local_lock_irq held so equivalent to spin_lock_irqsave for
* both PREEMPT_RT and non-PREEMPT_RT configurations.
*/
/* Caller must hold IRQ-safe pcp->lock so IRQs are disabled. */
spin_lock(&zone->lock);
isolated_pageblocks = has_isolate_pageblock(zone);
@ -3056,10 +3123,7 @@ 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.
*/
/* Caller must hold IRQ-safe pcp->lock so IRQs are disabled. */
spin_lock(&zone->lock);
for (i = 0; i < count; ++i) {
struct page *page = __rmqueue(zone, order, migratetype,
@ -3431,18 +3495,16 @@ void free_unref_page(struct page *page, unsigned int order)
migratetype = MIGRATE_MOVABLE;
}
local_lock_irqsave(&pagesets.lock, flags);
zone = page_zone(page);
pcp_trylock_prepare(UP_flags);
pcp = this_cpu_ptr(zone->per_cpu_pageset);
if (spin_trylock(&pcp->lock)) {
pcp = pcp_spin_trylock_irqsave(zone->per_cpu_pageset, flags);
if (pcp) {
free_unref_page_commit(zone, pcp, page, migratetype, order);
spin_unlock(&pcp->lock);
pcp_spin_unlock_irqrestore(pcp, flags);
} else {
free_one_page(zone, page, pfn, order, migratetype, FPI_NONE);
}
pcp_trylock_finish(UP_flags);
local_unlock_irqrestore(&pagesets.lock, flags);
}
/*
@ -3477,17 +3539,16 @@ void free_unref_page_list(struct list_head *list)
}
}
local_lock_irqsave(&pagesets.lock, flags);
list_for_each_entry_safe(page, next, list, lru) {
struct zone *zone = page_zone(page);
/* Different zone, different pcp lock. */
if (zone != locked_zone) {
if (pcp)
spin_unlock(&pcp->lock);
pcp_spin_unlock_irqrestore(pcp, flags);
locked_zone = zone;
pcp = this_cpu_ptr(zone->per_cpu_pageset);
spin_lock(&pcp->lock);
pcp = pcp_spin_lock_irqsave(locked_zone->per_cpu_pageset, flags);
}
/*
@ -3506,18 +3567,14 @@ void free_unref_page_list(struct list_head *list)
* a large list of pages to free.
*/
if (++batch_count == SWAP_CLUSTER_MAX) {
spin_unlock(&pcp->lock);
local_unlock_irqrestore(&pagesets.lock, flags);
pcp_spin_unlock_irqrestore(pcp, flags);
batch_count = 0;
local_lock_irqsave(&pagesets.lock, flags);
pcp = this_cpu_ptr(locked_zone->per_cpu_pageset);
spin_lock(&pcp->lock);
pcp = pcp_spin_lock_irqsave(locked_zone->per_cpu_pageset, flags);
}
}
if (pcp)
spin_unlock(&pcp->lock);
local_unlock_irqrestore(&pagesets.lock, flags);
pcp_spin_unlock_irqrestore(pcp, flags);
}
/*
@ -3732,17 +3789,14 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
unsigned long flags;
unsigned long __maybe_unused UP_flags;
local_lock_irqsave(&pagesets.lock, flags);
/*
* spin_trylock may fail due to a parallel drain. In the future, the
* trylock will also protect against IRQ reentrancy.
*/
pcp = this_cpu_ptr(zone->per_cpu_pageset);
pcp_trylock_prepare(UP_flags);
if (!spin_trylock(&pcp->lock)) {
pcp = pcp_spin_trylock_irqsave(zone->per_cpu_pageset, flags);
if (!pcp) {
pcp_trylock_finish(UP_flags);
local_unlock_irqrestore(&pagesets.lock, flags);
return NULL;
}
@ -3754,9 +3808,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
pcp->free_factor >>= 1;
list = &pcp->lists[order_to_pindex(migratetype, order)];
page = __rmqueue_pcplist(zone, order, migratetype, alloc_flags, pcp, list);
spin_unlock(&pcp->lock);
pcp_spin_unlock_irqrestore(pcp, flags);
pcp_trylock_finish(UP_flags);
local_unlock_irqrestore(&pagesets.lock, flags);
if (page) {
__count_zid_vm_events(PGALLOC, page_zonenum(page), 1);
zone_statistics(preferred_zone, zone, 1);
@ -5358,10 +5411,9 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
goto failed;
/* Is a parallel drain in progress? */
local_lock_irqsave(&pagesets.lock, flags);
pcp_trylock_prepare(UP_flags);
pcp = this_cpu_ptr(zone->per_cpu_pageset);
if (!spin_trylock(&pcp->lock))
pcp = pcp_spin_trylock_irqsave(zone->per_cpu_pageset, flags);
if (!pcp)
goto failed_irq;
/* Attempt the batch allocation */
@ -5379,7 +5431,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
if (unlikely(!page)) {
/* Try and allocate at least one page */
if (!nr_account) {
spin_unlock(&pcp->lock);
pcp_spin_unlock_irqrestore(pcp, flags);
goto failed_irq;
}
break;
@ -5394,9 +5446,8 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
nr_populated++;
}
spin_unlock(&pcp->lock);
pcp_spin_unlock_irqrestore(pcp, flags);
pcp_trylock_finish(UP_flags);
local_unlock_irqrestore(&pagesets.lock, flags);
__count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account);
zone_statistics(ac.preferred_zoneref->zone, zone, nr_account);
@ -5406,7 +5457,6 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
failed_irq:
pcp_trylock_finish(UP_flags);
local_unlock_irqrestore(&pagesets.lock, flags);
failed:
page = __alloc_pages(gfp, 0, preferred_nid, nodemask);