Re: [PATCH] block: setup bounce bio_sets properly

[Jens Axboe <axboe@kernel.dk>]

On 10/19/18 3:10 AM, Ming Lei wrote:
> On Thu, Oct 18, 2018 at 03:24:47PM -0600, Jens Axboe wrote:
>> We're only setting up the bounce bio sets if we happen
>> to need bouncing for regular HIGHMEM, not if we only need
>> it for ISA devices.
>>
>> Reported-by: Ondrej Zary <linux@rainbow-software.org>
>> Tested-by: Ondrej Zary <linux@rainbow-software.org>
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>>
>> diff --git a/block/bounce.c b/block/bounce.c
>> index b30071ac4ec6..1356a2f4aae2 100644
>> --- a/block/bounce.c
>> +++ b/block/bounce.c
>> @@ -31,6 +31,24 @@
>>  static struct bio_set bounce_bio_set, bounce_bio_split;
>>  static mempool_t page_pool, isa_page_pool;
>>  
>> +static void init_bounce_bioset(void)
>> +{
>> +	static bool bounce_bs_setup;
>> +	int ret;
>> +
>> +	if (bounce_bs_setup)
>> +		return;
>> +
>> +	ret = bioset_init(&bounce_bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
>> +	BUG_ON(ret);
>> +	if (bioset_integrity_create(&bounce_bio_set, BIO_POOL_SIZE))
>> +		BUG_ON(1);
>> +
>> +	ret = bioset_init(&bounce_bio_split, BIO_POOL_SIZE, 0, 0);
>> +	BUG_ON(ret);
>> +	bounce_bs_setup = true;
> 
> When initcall is run from do_basic_setup(), all CPUs and scheduler have been up,
> it is likely that init_emergency_pool() is run when one driver is calling
> blk_queue_bounce_limit() to start init_emergency_isa_pool().
> 
> So the above code might be run twice.

Good point, it's actually not even safe right now with the mempool
setup. How about the below?


diff --git a/block/bounce.c b/block/bounce.c
index b30071ac4ec6..ec0d99995f5f 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -31,6 +31,24 @@
 static struct bio_set bounce_bio_set, bounce_bio_split;
 static mempool_t page_pool, isa_page_pool;
 
+static void init_bounce_bioset(void)
+{
+	static bool bounce_bs_setup;
+	int ret;
+
+	if (bounce_bs_setup)
+		return;
+
+	ret = bioset_init(&bounce_bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
+	BUG_ON(ret);
+	if (bioset_integrity_create(&bounce_bio_set, BIO_POOL_SIZE))
+		BUG_ON(1);
+
+	ret = bioset_init(&bounce_bio_split, BIO_POOL_SIZE, 0, 0);
+	BUG_ON(ret);
+	bounce_bs_setup = true;
+}
+
 #if defined(CONFIG_HIGHMEM)
 static __init int init_emergency_pool(void)
 {
@@ -44,14 +62,7 @@ static __init int init_emergency_pool(void)
 	BUG_ON(ret);
 	pr_info("pool size: %d pages\n", POOL_SIZE);
 
-	ret = bioset_init(&bounce_bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
-	BUG_ON(ret);
-	if (bioset_integrity_create(&bounce_bio_set, BIO_POOL_SIZE))
-		BUG_ON(1);
-
-	ret = bioset_init(&bounce_bio_split, BIO_POOL_SIZE, 0, 0);
-	BUG_ON(ret);
-
+	init_bounce_bioset();
 	return 0;
 }
 
@@ -86,6 +97,8 @@ static void *mempool_alloc_pages_isa(gfp_t gfp_mask, void *data)
 	return mempool_alloc_pages(gfp_mask | GFP_DMA, data);
 }
 
+static DEFINE_MUTEX(isa_mutex);
+
 /*
  * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
  * as the max address, so check if the pool has already been created.
@@ -94,14 +107,20 @@ int init_emergency_isa_pool(void)
 {
 	int ret;
 
-	if (mempool_initialized(&isa_page_pool))
+	mutex_lock(&isa_mutex);
+
+	if (mempool_initialized(&isa_page_pool)) {
+		mutex_unlock(&isa_mutex);
 		return 0;
+	}
 
 	ret = mempool_init(&isa_page_pool, ISA_POOL_SIZE, mempool_alloc_pages_isa,
 			   mempool_free_pages, (void *) 0);
 	BUG_ON(ret);
 
 	pr_info("isa pool size: %d pages\n", ISA_POOL_SIZE);
+	init_bounce_bioset();
+	mutex_unlock(&isa_mutex);
 	return 0;
 }
 

-- 
Jens Axboe