> -----Original Message----- > From: Mike Kravetz [mailto:mike.kravetz@xxxxxxxxxx] > Sent: Tuesday, March 30, 2021 12:24 PM > To: linux-mm@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > Cc: Roman Gushchin <guro@xxxxxx>; Michal Hocko <mhocko@xxxxxxxx>; Shakeel Butt > <shakeelb@xxxxxxxxxx>; Oscar Salvador <osalvador@xxxxxxx>; David Hildenbrand > <david@xxxxxxxxxx>; Muchun Song <songmuchun@xxxxxxxxxxxxx>; David Rientjes > <rientjes@xxxxxxxxxx>; linmiaohe <linmiaohe@xxxxxxxxxx>; Peter Zijlstra > <peterz@xxxxxxxxxxxxx>; Matthew Wilcox <willy@xxxxxxxxxxxxx>; HORIGUCHI NAOYA > <naoya.horiguchi@xxxxxxx>; Aneesh Kumar K . V <aneesh.kumar@xxxxxxxxxxxxx>; > Waiman Long <longman@xxxxxxxxxx>; Peter Xu <peterx@xxxxxxxxxx>; Mina Almasry > <almasrymina@xxxxxxxxxx>; Hillf Danton <hdanton@xxxxxxxx>; Joonsoo Kim > <iamjoonsoo.kim@xxxxxxx>; Song Bao Hua (Barry Song) > <song.bao.hua@xxxxxxxxxxxxx>; Will Deacon <will@xxxxxxxxxx>; Andrew Morton > <akpm@xxxxxxxxxxxxxxxxxxxx>; Mike Kravetz <mike.kravetz@xxxxxxxxxx> > Subject: [PATCH v2 1/8] mm/cma: change cma mutex to irq safe spinlock > > Ideally, cma_release could be called from any context. However, that is > not possible because a mutex is used to protect the per-area bitmap. > Change the bitmap to an irq safe spinlock. > > Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> It seems mutex_lock is locking some areas with bitmap operations which should be safe to atomic context. Reviewed-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx> > --- > mm/cma.c | 20 +++++++++++--------- > mm/cma.h | 2 +- > mm/cma_debug.c | 10 ++++++---- > 3 files changed, 18 insertions(+), 14 deletions(-) > > diff --git a/mm/cma.c b/mm/cma.c > index b2393b892d3b..80875fd4487b 100644 > --- a/mm/cma.c > +++ b/mm/cma.c > @@ -24,7 +24,6 @@ > #include <linux/memblock.h> > #include <linux/err.h> > #include <linux/mm.h> > -#include <linux/mutex.h> > #include <linux/sizes.h> > #include <linux/slab.h> > #include <linux/log2.h> > @@ -83,13 +82,14 @@ static void cma_clear_bitmap(struct cma *cma, unsigned long > pfn, > unsigned int count) > { > unsigned long bitmap_no, bitmap_count; > + unsigned long flags; > > bitmap_no = (pfn - cma->base_pfn) >> cma->order_per_bit; > bitmap_count = cma_bitmap_pages_to_bits(cma, count); > > - mutex_lock(&cma->lock); > + spin_lock_irqsave(&cma->lock, flags); > bitmap_clear(cma->bitmap, bitmap_no, bitmap_count); > - mutex_unlock(&cma->lock); > + spin_unlock_irqrestore(&cma->lock, flags); > } > > static void __init cma_activate_area(struct cma *cma) > @@ -118,7 +118,7 @@ static void __init cma_activate_area(struct cma *cma) > pfn += pageblock_nr_pages) > init_cma_reserved_pageblock(pfn_to_page(pfn)); > > - mutex_init(&cma->lock); > + spin_lock_init(&cma->lock); > > #ifdef CONFIG_CMA_DEBUGFS > INIT_HLIST_HEAD(&cma->mem_head); > @@ -391,8 +391,9 @@ static void cma_debug_show_areas(struct cma *cma) > unsigned long start = 0; > unsigned long nr_part, nr_total = 0; > unsigned long nbits = cma_bitmap_maxno(cma); > + unsigned long flags; > > - mutex_lock(&cma->lock); > + spin_lock_irqsave(&cma->lock, flags); > pr_info("number of available pages: "); > for (;;) { > next_zero_bit = find_next_zero_bit(cma->bitmap, nbits, start); > @@ -407,7 +408,7 @@ static void cma_debug_show_areas(struct cma *cma) > start = next_zero_bit + nr_zero; > } > pr_cont("=> %lu free of %lu total pages\n", nr_total, cma->count); > - mutex_unlock(&cma->lock); > + spin_unlock_irqrestore(&cma->lock, flags); > } > #else > static inline void cma_debug_show_areas(struct cma *cma) { } > @@ -430,6 +431,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, > unsigned int align, > unsigned long pfn = -1; > unsigned long start = 0; > unsigned long bitmap_maxno, bitmap_no, bitmap_count; > + unsigned long flags; > size_t i; > struct page *page = NULL; > int ret = -ENOMEM; > @@ -454,12 +456,12 @@ struct page *cma_alloc(struct cma *cma, size_t count, > unsigned int align, > goto out; > > for (;;) { > - mutex_lock(&cma->lock); > + spin_lock_irqsave(&cma->lock, flags); > bitmap_no = bitmap_find_next_zero_area_off(cma->bitmap, > bitmap_maxno, start, bitmap_count, mask, > offset); > if (bitmap_no >= bitmap_maxno) { > - mutex_unlock(&cma->lock); > + spin_unlock_irqrestore(&cma->lock, flags); > break; > } > bitmap_set(cma->bitmap, bitmap_no, bitmap_count); > @@ -468,7 +470,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, > unsigned int align, > * our exclusive use. If the migration fails we will take the > * lock again and unmark it. > */ > - mutex_unlock(&cma->lock); > + spin_unlock_irqrestore(&cma->lock, flags); > > pfn = cma->base_pfn + (bitmap_no << cma->order_per_bit); > ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA, > diff --git a/mm/cma.h b/mm/cma.h > index 68ffad4e430d..2c775877eae2 100644 > --- a/mm/cma.h > +++ b/mm/cma.h > @@ -15,7 +15,7 @@ struct cma { > unsigned long count; > unsigned long *bitmap; > unsigned int order_per_bit; /* Order of pages represented by one bit */ > - struct mutex lock; > + spinlock_t lock; > #ifdef CONFIG_CMA_DEBUGFS > struct hlist_head mem_head; > spinlock_t mem_head_lock; > diff --git a/mm/cma_debug.c b/mm/cma_debug.c > index d5bf8aa34fdc..6379cfbfd568 100644 > --- a/mm/cma_debug.c > +++ b/mm/cma_debug.c > @@ -35,11 +35,12 @@ static int cma_used_get(void *data, u64 *val) > { > struct cma *cma = data; > unsigned long used; > + unsigned long flags; > > - mutex_lock(&cma->lock); > + spin_lock_irqsave(&cma->lock, flags); > /* pages counter is smaller than sizeof(int) */ > used = bitmap_weight(cma->bitmap, (int)cma_bitmap_maxno(cma)); > - mutex_unlock(&cma->lock); > + spin_unlock_irqrestore(&cma->lock, flags); > *val = (u64)used << cma->order_per_bit; > > return 0; > @@ -52,8 +53,9 @@ static int cma_maxchunk_get(void *data, u64 *val) > unsigned long maxchunk = 0; > unsigned long start, end = 0; > unsigned long bitmap_maxno = cma_bitmap_maxno(cma); > + unsigned long flags; > > - mutex_lock(&cma->lock); > + spin_lock_irqsave(&cma->lock, flags); > for (;;) { > start = find_next_zero_bit(cma->bitmap, bitmap_maxno, end); > if (start >= bitmap_maxno) > @@ -61,7 +63,7 @@ static int cma_maxchunk_get(void *data, u64 *val) > end = find_next_bit(cma->bitmap, bitmap_maxno, start); > maxchunk = max(end - start, maxchunk); > } > - mutex_unlock(&cma->lock); > + spin_unlock_irqrestore(&cma->lock, flags); > *val = (u64)maxchunk << cma->order_per_bit; > > return 0; > -- > 2.30.2
