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mm/page_alloc: avoid conflating IRQs disabled with zone->lock 

Historically when freeing pages, free_one_page() assumed that callers had
IRQs disabled and the zone->lock could be acquired with spin_lock().  This
confuses the scope of what local_lock_irq is protecting and what
zone->lock is protecting in free_unref_page_list in particular.

This patch uses spin_lock_irqsave() for the zone->lock in free_one_page()
instead of relying on callers to have disabled IRQs.
free_unref_page_commit() is changed to only deal with PCP pages protected
by the local lock.  free_unref_page_list() then first frees isolated pages
to the buddy lists with free_one_page() and frees the rest of the pages to
the PCP via free_unref_page_commit().  The end result is that
free_one_page() is no longer depending on side-effects of local_lock to be
correct.

Note that this may incur a performance penalty while memory hot-remove is
running but that is not a common operation.

[lkp@intel.com: Ensure CMA pages get addded to correct pcp list]

Link: https://lkml.kernel.org/r/20210512095458.30632-9-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Peter 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mel Gorman 2021-06-28 19:42:00 -07:00 committed by Linus Torvalds
parent 56f0e661ea
commit df1acc8569
1 changed files with 49 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

75
mm/page_alloc.c
View File

@ -1501,13 +1501,15 @@ static void free_one_page(struct zone *zone,
unsigned int order,
int migratetype, fpi_t fpi_flags)
{
spin_lock(&zone->lock);
unsigned long flags;
spin_lock_irqsave(&zone->lock, flags);
if (unlikely(has_isolate_pageblock(zone) ||
is_migrate_isolate(migratetype))) {
migratetype = get_pfnblock_migratetype(page, pfn);
}
__free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
spin_unlock(&zone->lock);
spin_unlock_irqrestore(&zone->lock, flags);
}
static void __meminit __init_single_page(struct page *page, unsigned long pfn,
@ -3285,31 +3287,13 @@ static bool free_unref_page_prepare(struct page *page, unsigned long pfn)
return true;
}
static void free_unref_page_commit(struct page *page, unsigned long pfn)
static void free_unref_page_commit(struct page *page, unsigned long pfn,
int migratetype)
{
struct zone *zone = page_zone(page);
struct per_cpu_pages *pcp;
int migratetype;
migratetype = get_pcppage_migratetype(page);
__count_vm_event(PGFREE);
/*
* We only track unmovable, reclaimable and movable on pcp lists.
* Free ISOLATE pages back to the allocator because they are being
* offlined but treat HIGHATOMIC as movable pages so we can get those
* areas back if necessary. Otherwise, we may have to free
* excessively into the page allocator
*/
if (migratetype >= MIGRATE_PCPTYPES) {
if (unlikely(is_migrate_isolate(migratetype))) {
free_one_page(zone, page, pfn, 0, migratetype,
FPI_NONE);
return;
}
migratetype = MIGRATE_MOVABLE;
}
pcp = this_cpu_ptr(zone->per_cpu_pageset);
list_add(&page->lru, &pcp->lists[migratetype]);
pcp->count++;
@ -3324,12 +3308,29 @@ void free_unref_page(struct page *page)
{
unsigned long flags;
unsigned long pfn = page_to_pfn(page);
int migratetype;
if (!free_unref_page_prepare(page, pfn))
return;
/*
* We only track unmovable, reclaimable and movable on pcp lists.
* Place ISOLATE pages on the isolated list because they are being
* offlined but treat HIGHATOMIC as movable pages so we can get those
* areas back if necessary. Otherwise, we may have to free
* excessively into the page allocator
*/
migratetype = get_pcppage_migratetype(page);
if (unlikely(migratetype >= MIGRATE_PCPTYPES)) {
if (unlikely(is_migrate_isolate(migratetype))) {
free_one_page(page_zone(page), page, pfn, 0, migratetype, FPI_NONE);
return;
}
migratetype = MIGRATE_MOVABLE;
}
local_lock_irqsave(&pagesets.lock, flags);
free_unref_page_commit(page, pfn);
free_unref_page_commit(page, pfn, migratetype);
local_unlock_irqrestore(&pagesets.lock, flags);
}
@ -3341,22 +3342,44 @@ void free_unref_page_list(struct list_head *list)
struct page *page, *next;
unsigned long flags, pfn;
int batch_count = 0;
int migratetype;
/* Prepare pages for freeing */
list_for_each_entry_safe(page, next, list, lru) {
pfn = page_to_pfn(page);
if (!free_unref_page_prepare(page, pfn))
list_del(&page->lru);
/*
* Free isolated pages directly to the allocator, see
* comment in free_unref_page.
*/
migratetype = get_pcppage_migratetype(page);
if (unlikely(migratetype >= MIGRATE_PCPTYPES)) {
if (unlikely(is_migrate_isolate(migratetype))) {
list_del(&page->lru);
free_one_page(page_zone(page), page, pfn, 0,
migratetype, FPI_NONE);
continue;
}
/*
* Non-isolated types over MIGRATE_PCPTYPES get added
* to the MIGRATE_MOVABLE pcp list.
*/
set_pcppage_migratetype(page, MIGRATE_MOVABLE);
}
set_page_private(page, pfn);
}
local_lock_irqsave(&pagesets.lock, flags);
list_for_each_entry_safe(page, next, list, lru) {
unsigned long pfn = page_private(page);
pfn = page_private(page);
set_page_private(page, 0);
migratetype = get_pcppage_migratetype(page);
trace_mm_page_free_batched(page);
free_unref_page_commit(page, pfn);
free_unref_page_commit(page, pfn, migratetype);
/*
* Guard against excessive IRQ disabled times when we get