mm: zbud: prevent softirq during zbud alloc, free and reclaim

The following deadlock is observed.

Core 2 waiting on mapping->tree_lock which is taken by core 6

do_raw_spin_lock
raw_spin_lock_irq
atomic_cmpxchg
page_freeze_refs
__remove_mapping
shrink_page_list
shrink_inactive_list
shrink_list
shrink_lruvec
shrink_zone
shrink_zones
do_try_to_free_pages
try_to_free_pages(?, ?, ?, ?)
__perform_reclaim
__alloc_pages_direct_reclaim
__alloc_pages_slowpath
__alloc_pages_nodemask
alloc_kmem_pages_node
alloc_thread_info_node
dup_task_struct
copy_process.part.56
do_fork
sys_clone
el0_svc_naked

Core 6 after taking mapping->tree_lock is waiting on zbud pool lock
which is held by core 5

zbud_alloc
zcache_store_page
__cleancache_put_page
cleancache_put_page
__delete_from_page_cache
spin_unlock_irq
__remove_mapping
shrink_page_list
shrink_inactive_list
shrink_list
shrink_lruvec
shrink_zone
bitmap_zero
__nodes_clear
kswapd_shrink_zone.constprop.58
balance_pgdat
kswapd_try_to_sleep
kswapd
kthread
ret_from_fork

Core 5 after taking zbud pool lock from zbud_free received an IRQ, and
after IRQ exit, softirqs were scheduled and end_page_writeback tried to
lock on mapping->tree_lock which is already held by Core 6. Deadlock.

do_raw_spin_lock
raw_spin_lock_irqsave
test_clear_page_writeba
end_page_writeback
ext4_finish_bio
ext4_end_bio
bio_endio
blk_update_request
end_clone_bio
bio_endio
blk_update_request
blk_update_bidi_request
blk_end_bidi_request
blk_end_request
mmc_blk_cmdq_complete_r
mmc_cmdq_softirq_done
blk_done_softirq
static_key_count
static_key_false
trace_softirq_exit
__do_softirq()
tick_irq_exit
irq_exit()
set_irq_regs
__handle_domain_irq
gic_handle_irq
el1_irq
exception
__list_del_entry
list_del
zbud_free
zcache_load_page
__cleancache_get_page(?

So protect zbud_alloc/free/reclaim with spink_lock_bh

CRs-Fixed: 986783
Change-Id: Ib0605b38e7371c29316ed81e43549a0b9503d531
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>

1 files changed, 13 insertions, 13 deletions

diff --git a/mm/zbud.c b/mm/zbud.c
index 011e42bbf056..04359b845ead 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -364,7 +364,7 @@ int zbud_alloc(struct zbud_pool *pool, size_t size, gfp_t gfp,
 	if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
 		return -ENOSPC;
 	chunks = size_to_chunks(size);
-	spin_lock(&pool->lock);
+	spin_lock_bh(&pool->lock);
 
 	/* First, try to find an unbuddied zbud page. */
 	zhdr = NULL;
@@ -383,11 +383,11 @@ int zbud_alloc(struct zbud_pool *pool, size_t size, gfp_t gfp,
 	}
 
 	/* Couldn't find unbuddied zbud page, create new one */
-	spin_unlock(&pool->lock);
+	spin_unlock_bh(&pool->lock);
 	page = alloc_page(gfp);
 	if (!page)
 		return -ENOMEM;
-	spin_lock(&pool->lock);
+	spin_lock_bh(&pool->lock);
 	pool->pages_nr++;
 	zhdr = init_zbud_page(page);
 	bud = FIRST;
@@ -415,7 +415,7 @@ found:
 	*handle = encode_handle(zhdr, bud);
 	if ((gfp & __GFP_ZERO) && found)
 		memset((void *)*handle, 0, size);
-	spin_unlock(&pool->lock);
+	spin_unlock_bh(&pool->lock);
 
 	return 0;
 }
@@ -435,7 +435,7 @@ void zbud_free(struct zbud_pool *pool, unsigned long handle)
 	struct zbud_header *zhdr;
 	int freechunks;
 
-	spin_lock(&pool->lock);
+	spin_lock_bh(&pool->lock);
 	zhdr = handle_to_zbud_header(handle);
 
 	/* If first buddy, handle will be page aligned */
@@ -446,7 +446,7 @@ void zbud_free(struct zbud_pool *pool, unsigned long handle)
 
 	if (zhdr->under_reclaim) {
 		/* zbud page is under reclaim, reclaim will free */
-		spin_unlock(&pool->lock);
+		spin_unlock_bh(&pool->lock);
 		return;
 	}
 
@@ -464,7 +464,7 @@ void zbud_free(struct zbud_pool *pool, unsigned long handle)
 		list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
 	}
 
-	spin_unlock(&pool->lock);
+	spin_unlock_bh(&pool->lock);
 }
 
 #define list_tail_entry(ptr, type, member) \
@@ -511,10 +511,10 @@ int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries)
 	struct zbud_header *zhdr;
 	unsigned long first_handle = 0, last_handle = 0;
 
-	spin_lock(&pool->lock);
+	spin_lock_bh(&pool->lock);
 	if (!pool->ops || !pool->ops->evict || list_empty(&pool->lru) ||
 			retries == 0) {
-		spin_unlock(&pool->lock);
+		spin_unlock_bh(&pool->lock);
 		return -EINVAL;
 	}
 	for (i = 0; i < retries; i++) {
@@ -533,7 +533,7 @@ int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries)
 			first_handle = encode_handle(zhdr, FIRST);
 		if (zhdr->last_chunks)
 			last_handle = encode_handle(zhdr, LAST);
-		spin_unlock(&pool->lock);
+		spin_unlock_bh(&pool->lock);
 
 		/* Issue the eviction callback(s) */
 		if (first_handle) {
@@ -547,7 +547,7 @@ int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries)
 				goto next;
 		}
 next:
-		spin_lock(&pool->lock);
+		spin_lock_bh(&pool->lock);
 		zhdr->under_reclaim = false;
 		if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
 			/*
@@ -556,7 +556,7 @@ next:
 			 */
 			free_zbud_page(zhdr);
 			pool->pages_nr--;
-			spin_unlock(&pool->lock);
+			spin_unlock_bh(&pool->lock);
 			return 0;
 		} else if (zhdr->first_chunks == 0 ||
 				zhdr->last_chunks == 0) {
@@ -571,7 +571,7 @@ next:
 		/* add to beginning of LRU */
 		list_add(&zhdr->lru, &pool->lru);
 	}
-	spin_unlock(&pool->lock);
+	spin_unlock_bh(&pool->lock);
 	return -EAGAIN;
 }