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[dm-devel] [PATCH v4 2/2] block: Convert integrity to bvec_alloc_bs()



This adds a pointer to the bvec array to struct bio_integrity_payload,
instead of the bvecs always being inline; then the bvecs are allocated
with bvec_alloc_bs().

Changed bvec_alloc_bs() and bvec_free_bs() to take a pointer to a
mempool instead of the bioset, so that bio integrity can use a different
mempool for its bvecs, and thus avoid a potential deadlock.

This is eventually for immutable bio vecs - immutable bvecs aren't
useful if we still have to copy them, hence the need for the pointer.
Less code is always nice too, though.

Also, bio_integrity_alloc() was using fs_bio_set if no bio_set was
specified. This was wrong - using the bio_set doesn't protect us from
memory allocation failures, because we just used kmalloc for the
bio_integrity_payload. But it does introduce the possibility of
deadlock, if for some reason we weren't supposed to be using fs_bio_set.

Signed-off-by: Kent Overstreet <koverstreet google com>
CC: Jens Axboe <axboe kernel dk>
CC: Martin K. Petersen <martin petersen oracle com>
---
 fs/bio-integrity.c  | 132 +++++++++++++++++++---------------------------------
 fs/bio.c            |  36 ++++++--------
 include/linux/bio.h |   8 ++--
 3 files changed, 68 insertions(+), 108 deletions(-)

diff --git a/fs/bio-integrity.c b/fs/bio-integrity.c
index 94fa1c5..8c4c604 100644
--- a/fs/bio-integrity.c
+++ b/fs/bio-integrity.c
@@ -27,48 +27,11 @@
 #include <linux/workqueue.h>
 #include <linux/slab.h>
 
-struct integrity_slab {
-	struct kmem_cache *slab;
-	unsigned short nr_vecs;
-	char name[8];
-};
-
-#define IS(x) { .nr_vecs = x, .name = "bip-"__stringify(x) }
-struct integrity_slab bip_slab[BIOVEC_NR_POOLS] __read_mostly = {
-	IS(1), IS(4), IS(16), IS(64), IS(128), IS(BIO_MAX_PAGES),
-};
-#undef IS
+#define BIP_INLINE_VECS	4
 
+static struct kmem_cache *bip_slab;
 static struct workqueue_struct *kintegrityd_wq;
 
-static inline unsigned int vecs_to_idx(unsigned int nr)
-{
-	switch (nr) {
-	case 1:
-		return 0;
-	case 2 ... 4:
-		return 1;
-	case 5 ... 16:
-		return 2;
-	case 17 ... 64:
-		return 3;
-	case 65 ... 128:
-		return 4;
-	case 129 ... BIO_MAX_PAGES:
-		return 5;
-	default:
-		BUG();
-	}
-}
-
-static inline int use_bip_pool(unsigned int idx)
-{
-	if (idx == BIOVEC_MAX_IDX)
-		return 1;
-
-	return 0;
-}
-
 /**
  * bio_integrity_alloc - Allocate integrity payload and attach it to bio
  * @bio:	bio to attach integrity metadata to
@@ -84,38 +47,41 @@ struct bio_integrity_payload *bio_integrity_alloc(struct bio *bio,
 						  unsigned int nr_vecs)
 {
 	struct bio_integrity_payload *bip;
-	unsigned int idx = vecs_to_idx(nr_vecs);
 	struct bio_set *bs = bio->bi_pool;
-
-	if (!bs)
-		bs = fs_bio_set;
-
-	BUG_ON(bio == NULL);
-	bip = NULL;
-
-	/* Lower order allocations come straight from slab */
-	if (!use_bip_pool(idx))
-		bip = kmem_cache_alloc(bip_slab[idx].slab, gfp_mask);
-
-	/* Use mempool if lower order alloc failed or max vecs were requested */
-	if (bip == NULL) {
-		idx = BIOVEC_MAX_IDX;  /* so we free the payload properly later */
+	unsigned long idx = BIO_POOL_NONE;
+	unsigned inline_vecs;
+
+	if (!bs) {
+		bip = kmalloc(sizeof(struct bio_integrity_payload) +
+			      sizeof(struct bio_vec) * nr_vecs, gfp_mask);
+		inline_vecs = nr_vecs;
+	} else {
 		bip = mempool_alloc(bs->bio_integrity_pool, gfp_mask);
-
-		if (unlikely(bip == NULL)) {
-			printk(KERN_ERR "%s: could not alloc bip\n", __func__);
-			return NULL;
-		}
+		inline_vecs = BIP_INLINE_VECS;
 	}
 
+	if (unlikely(!bip))
+		return NULL;
+
 	memset(bip, 0, sizeof(*bip));
 
+	if (nr_vecs > inline_vecs) {
+		bip->bip_vec = bvec_alloc(gfp_mask, nr_vecs, &idx,
+					  bs->bvec_integrity_pool);
+		if (!bip->bip_vec)
+			goto err;
+	} else {
+		bip->bip_vec = bip->bip_inline_vecs;
+	}
+
 	bip->bip_slab = idx;
 	bip->bip_bio = bio;
-	bip->bip_vec = bip->bip_inline_vecs;
 	bio->bi_integrity = bip;
 
 	return bip;
+err:
+	mempool_free(bip, bs->bio_integrity_pool);
+	return NULL;
 }
 EXPORT_SYMBOL(bio_integrity_alloc);
 
@@ -131,20 +97,20 @@ void bio_integrity_free(struct bio *bio)
 	struct bio_integrity_payload *bip = bio->bi_integrity;
 	struct bio_set *bs = bio->bi_pool;
 
-	if (!bs)
-		bs = fs_bio_set;
-
-	BUG_ON(bip == NULL);
-
 	/* A cloned bio doesn't own the integrity metadata */
 	if (!bio_flagged(bio, BIO_CLONED) && !bio_flagged(bio, BIO_FS_INTEGRITY)
 	    && bip->bip_buf != NULL)
 		kfree(bip->bip_buf);
 
-	if (use_bip_pool(bip->bip_slab))
+	if (bs) {
+		if (bip->bip_slab != BIO_POOL_NONE)
+			bvec_free(bs->bvec_integrity_pool, bip->bip_vec,
+				  bip->bip_slab);
+
 		mempool_free(bip, bs->bio_integrity_pool);
-	else
-		kmem_cache_free(bip_slab[bip->bip_slab].slab, bip);
+	} else {
+		kfree(bip);
+	}
 
 	bio->bi_integrity = NULL;
 }
@@ -747,13 +713,14 @@ EXPORT_SYMBOL(bio_integrity_clone);
 
 int bioset_integrity_create(struct bio_set *bs, int pool_size)
 {
-	unsigned int max_slab = vecs_to_idx(BIO_MAX_PAGES);
-
 	if (bs->bio_integrity_pool)
 		return 0;
 
-	bs->bio_integrity_pool =
-		mempool_create_slab_pool(pool_size, bip_slab[max_slab].slab);
+	bs->bio_integrity_pool = mempool_create_slab_pool(pool_size, bip_slab);
+
+	bs->bvec_integrity_pool = biovec_create_pool(bs, pool_size);
+	if (!bs->bvec_integrity_pool)
+		return -1;
 
 	if (!bs->bio_integrity_pool)
 		return -1;
@@ -766,13 +733,14 @@ void bioset_integrity_free(struct bio_set *bs)
 {
 	if (bs->bio_integrity_pool)
 		mempool_destroy(bs->bio_integrity_pool);
+
+	if (bs->bvec_integrity_pool)
+		mempool_destroy(bs->bio_integrity_pool);
 }
 EXPORT_SYMBOL(bioset_integrity_free);
 
 void __init bio_integrity_init(void)
 {
-	unsigned int i;
-
 	/*
 	 * kintegrityd won't block much but may burn a lot of CPU cycles.
 	 * Make it highpri CPU intensive wq with max concurrency of 1.
@@ -782,14 +750,10 @@ void __init bio_integrity_init(void)
 	if (!kintegrityd_wq)
 		panic("Failed to create kintegrityd\n");
 
-	for (i = 0 ; i < BIOVEC_NR_POOLS ; i++) {
-		unsigned int size;
-
-		size = sizeof(struct bio_integrity_payload)
-			+ bip_slab[i].nr_vecs * sizeof(struct bio_vec);
-
-		bip_slab[i].slab =
-			kmem_cache_create(bip_slab[i].name, size, 0,
-					  SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
-	}
+	bip_slab = kmem_cache_create("bio_integrity_payload",
+				     sizeof(struct bio_integrity_payload) +
+				     sizeof(struct bio_vec) * BIP_INLINE_VECS,
+				     0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+	if (!bip_slab)
+		panic("Failed to create slab\n");
 }
diff --git a/fs/bio.c b/fs/bio.c
index 9aa1938..f16aa6b 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -158,12 +158,12 @@ unsigned int bvec_nr_vecs(unsigned short idx)
 	return bvec_slabs[idx].nr_vecs;
 }
 
-void bvec_free_bs(struct bio_set *bs, struct bio_vec *bv, unsigned int idx)
+void bvec_free(mempool_t *pool, struct bio_vec *bv, unsigned int idx)
 {
 	BIO_BUG_ON(idx >= BIOVEC_NR_POOLS);
 
 	if (idx == BIOVEC_MAX_IDX)
-		mempool_free(bv, bs->bvec_pool);
+		mempool_free(bv, pool);
 	else {
 		struct biovec_slab *bvs = bvec_slabs + idx;
 
@@ -171,8 +171,8 @@ void bvec_free_bs(struct bio_set *bs, struct bio_vec *bv, unsigned int idx)
 	}
 }
 
-struct bio_vec *bvec_alloc_bs(gfp_t gfp_mask, int nr, unsigned long *idx,
-			      struct bio_set *bs)
+struct bio_vec *bvec_alloc(gfp_t gfp_mask, int nr, unsigned long *idx,
+			   mempool_t *pool)
 {
 	struct bio_vec *bvl;
 
@@ -208,7 +208,7 @@ struct bio_vec *bvec_alloc_bs(gfp_t gfp_mask, int nr, unsigned long *idx,
 	 */
 	if (*idx == BIOVEC_MAX_IDX) {
 fallback:
-		bvl = mempool_alloc(bs->bvec_pool, gfp_mask);
+		bvl = mempool_alloc(pool, gfp_mask);
 	} else {
 		struct biovec_slab *bvs = bvec_slabs + *idx;
 		gfp_t __gfp_mask = gfp_mask & ~(__GFP_WAIT | __GFP_IO);
@@ -251,7 +251,7 @@ static void bio_free(struct bio *bio)
 
 	if (bs) {
 		if (bio_has_allocated_vec(bio))
-			bvec_free_bs(bs, bio->bi_io_vec, BIO_POOL_IDX(bio));
+			bvec_free(bs->bvec_pool, bio->bi_io_vec, BIO_POOL_IDX(bio));
 
 		/*
 		 * If we have front padding, adjust the bio pointer before freeing
@@ -440,11 +440,11 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
 	bio_init(bio);
 
 	if (nr_iovecs > inline_vecs) {
-		bvl = bvec_alloc_bs(gfp_mask, nr_iovecs, &idx, bs);
+		bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
 		if (!bvl && gfp_mask != saved_gfp) {
 			punt_bios_to_rescuer(bs);
 			gfp_mask = saved_gfp;
-			bvl = bvec_alloc_bs(gfp_mask, nr_iovecs, &idx, bs);
+			bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, bs->bvec_pool);
 		}
 
 		if (unlikely(!bvl))
@@ -1657,20 +1657,11 @@ EXPORT_SYMBOL(bio_sector_offset);
  * create memory pools for biovec's in a bio_set.
  * use the global biovec slabs created for general use.
  */
-static int biovec_create_pools(struct bio_set *bs, int pool_entries)
+mempool_t *biovec_create_pool(struct bio_set *bs, int pool_entries)
 {
 	struct biovec_slab *bp = bvec_slabs + BIOVEC_MAX_IDX;
 
-	bs->bvec_pool = mempool_create_slab_pool(pool_entries, bp->slab);
-	if (!bs->bvec_pool)
-		return -ENOMEM;
-
-	return 0;
-}
-
-static void biovec_free_pools(struct bio_set *bs)
-{
-	mempool_destroy(bs->bvec_pool);
+	return mempool_create_slab_pool(pool_entries, bp->slab);
 }
 
 void bioset_free(struct bio_set *bs)
@@ -1681,8 +1672,10 @@ void bioset_free(struct bio_set *bs)
 	if (bs->bio_pool)
 		mempool_destroy(bs->bio_pool);
 
+	if (bs->bvec_pool)
+		mempool_destroy(bs->bvec_pool);
+
 	bioset_integrity_free(bs);
-	biovec_free_pools(bs);
 	bio_put_slab(bs);
 
 	kfree(bs);
@@ -1727,7 +1720,8 @@ struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad)
 	if (!bs->bio_pool)
 		goto bad;
 
-	if (biovec_create_pools(bs, pool_size))
+	bs->bvec_pool = biovec_create_pool(bs, pool_size);
+	if (!bs->bvec_pool)
 		goto bad;
 
 	bs->rescue_workqueue = alloc_workqueue("bioset", WQ_MEM_RECLAIM, 0);
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 81004fd..669b1cb 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -213,6 +213,7 @@ extern void bio_pair_release(struct bio_pair *dbio);
 
 extern struct bio_set *bioset_create(unsigned int, unsigned int);
 extern void bioset_free(struct bio_set *);
+extern mempool_t *biovec_create_pool(struct bio_set *bs, int pool_entries);
 
 extern struct bio *bio_alloc_bioset(gfp_t, int, struct bio_set *);
 extern void bio_put(struct bio *);
@@ -288,8 +289,8 @@ extern struct bio *bio_copy_user_iov(struct request_queue *,
 				     int, int, gfp_t);
 extern int bio_uncopy_user(struct bio *);
 void zero_fill_bio(struct bio *bio);
-extern struct bio_vec *bvec_alloc_bs(gfp_t, int, unsigned long *, struct bio_set *);
-extern void bvec_free_bs(struct bio_set *, struct bio_vec *, unsigned int);
+extern struct bio_vec *bvec_alloc(gfp_t, int, unsigned long *, mempool_t *);
+extern void bvec_free(mempool_t *, struct bio_vec *, unsigned int);
 extern unsigned int bvec_nr_vecs(unsigned short idx);
 
 #ifdef CONFIG_BLK_CGROUP
@@ -511,10 +512,11 @@ struct bio_set {
 	unsigned int front_pad;
 
 	mempool_t *bio_pool;
+	mempool_t *bvec_pool;
 #if defined(CONFIG_BLK_DEV_INTEGRITY)
 	mempool_t *bio_integrity_pool;
+	mempool_t *bvec_integrity_pool;
 #endif
-	mempool_t *bvec_pool;
 
 	/*
 	 * Deadlock avoidance for stacking block drivers: see comments in
-- 
1.7.12


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