[PATCH 1/2] block: increase bio_slab_nr only for necessary case

[PATCH 1/2] block: increase bio_slab_nr only for necessary case

[Chengguang Xu]

When fail to create new cache in bio_find_or_create_slab(),
we should not increase bio_slab_nr because it will cause
referring uninitilized data in subsequent search.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
---
 block/bio.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index 4db1008309ed..8081906f5d01 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -109,7 +109,7 @@ static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
 		bio_slabs = new_bio_slabs;
 	}
 	if (entry == -1)
-		entry = bio_slab_nr++;
+		entry = bio_slab_nr;
 
 	bslab = &bio_slabs[entry];
 
@@ -122,6 +122,10 @@ static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
 	bslab->slab = slab;
 	bslab->slab_ref = 1;
 	bslab->slab_size = sz;
+
+	if (entry == bio_slab_nr)
+		bio_slab_nr++;
+
 out_unlock:
 	mutex_unlock(&bio_slab_lock);
 	return slab;
-- 
2.20.1

[PATCH 2/2] block: code cleanup for bio_find_or_create_slab()

[Chengguang Xu]

It's just a simple code cleanup, not functional change.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
---
 block/bio.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 8081906f5d01..fefd49a561ab 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -90,29 +90,27 @@ static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
 		else if (bslab->slab_size == sz) {
 			slab = bslab->slab;
 			bslab->slab_ref++;
-			break;
+			goto out_unlock;
 		}
 		i++;
 	}
 
-	if (slab)
-		goto out_unlock;
-
-	if (bio_slab_nr == bio_slab_max && entry == -1) {
-		new_bio_slab_max = bio_slab_max << 1;
-		new_bio_slabs = krealloc(bio_slabs,
+	if (entry == -1) {
+		if (bio_slab_nr == bio_slab_max) {
+			new_bio_slab_max = bio_slab_max << 1;
+			new_bio_slabs = krealloc(bio_slabs,
 					 new_bio_slab_max * sizeof(struct bio_slab),
 					 GFP_KERNEL);
-		if (!new_bio_slabs)
-			goto out_unlock;
-		bio_slab_max = new_bio_slab_max;
-		bio_slabs = new_bio_slabs;
-	}
-	if (entry == -1)
+			if (!new_bio_slabs)
+				goto out_unlock;
+			bio_slab_max = new_bio_slab_max;
+			bio_slabs = new_bio_slabs;
+		}
+
 		entry = bio_slab_nr;
+	}
 
 	bslab = &bio_slabs[entry];
-
 	snprintf(bslab->name, sizeof(bslab->name), "bio-%d", entry);
 	slab = kmem_cache_create(bslab->name, sz, ARCH_KMALLOC_MINALIGN,
 				 SLAB_HWCACHE_ALIGN, NULL);
-- 
2.20.1

Re: [PATCH 1/2] block: increase bio_slab_nr only for necessary case

[cgxu519]

On 3/8/19 6:15 PM, Chengguang Xu wrote:
> When fail to create new cache in bio_find_or_create_slab(),
> we should not increase bio_slab_nr because it will cause
> referring uninitilized data in subsequent search.
>
> Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
> ---
>   block/bio.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 4db1008309ed..8081906f5d01 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -109,7 +109,7 @@ static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
>   		bio_slabs = new_bio_slabs;
>   	}
>   	if (entry == -1)
> -		entry = bio_slab_nr++;
> +		entry = bio_slab_nr;
>
>   	bslab = &bio_slabs[entry];
>
> @@ -122,6 +122,10 @@ static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
>   	bslab->slab = slab;
>   	bslab->slab_ref = 1;
>   	bslab->slab_size = sz;
> +
> +	if (entry == bio_slab_nr)
> +		bio_slab_nr++;
> +
>   out_unlock:
>   	mutex_unlock(&bio_slab_lock);
>   	return slab;

Any suggestion?

Thanks.