[PATCH v4 0/5] Introduce sgl_alloc() and sgl_free()

[PATCH v4 0/5] Introduce sgl_alloc() and sgl_free()

[Bart Van Assche]

Hello Jens,

As you know there are multiple drivers that both allocate a scatter/gather
list and populate that list with pages. This patch series moves the code for
allocating and freeing such scatterlists from several drivers into
lib/scatterlist.c. Please consider this patch series for kernel v4.16.

Changes between v3 and v4:
- Left out patches 6..8 as requested by Martin Petersen. These patches will be
  sent to Martin after this series has been merged.

Changes between v2 and v3:
- Added Reviewed-by tags that had been posted as replies on v2.
- Cc'ed the crypto maintainers for the entire patch series.

Changes between v1 and v2:
- Moved the sgl_alloc*() and sgl_free() functions from a new source file into
  lib/scatterlist.c.
- Changed the argument order for the sgl_alloc*() functions such that the
  (pointer to) the output argument comes last.

Bart Van Assche (5):
  lib/scatterlist: Introduce sgl_alloc() and sgl_free()
  crypto: scompress - use sgl_alloc() and sgl_free()
  nvmet/fc: Use sgl_alloc() and sgl_free()
  nvmet/rdma: Use sgl_alloc() and sgl_free()
  target: Use sgl_alloc_order() and sgl_free()

 crypto/Kconfig                         |   1 +
 crypto/scompress.c                     |  51 +---------------
 drivers/nvme/target/Kconfig            |   2 +
 drivers/nvme/target/fc.c               |  36 +----------
 drivers/nvme/target/rdma.c             |  63 ++------------------
 drivers/target/Kconfig                 |   1 +
 drivers/target/target_core_transport.c |  46 ++-------------
 include/linux/scatterlist.h            |  10 ++++
 lib/Kconfig                            |   4 ++
 lib/scatterlist.c                      | 105 +++++++++++++++++++++++++++++++++
 10 files changed, 135 insertions(+), 184 deletions(-)

-- 
2.15.1

[PATCH v4 1/5] lib/scatterlist: Introduce sgl_alloc() and sgl_free()

[Bart Van Assche]

Many kernel drivers contain code that allocates and frees both a
scatterlist and the pages that populate that scatterlist.
Introduce functions in lib/scatterlist.c that perform these tasks
instead of duplicating this functionality in multiple drivers.
Only include these functions in the build if CONFIG_SGL_ALLOC=y
to avoid that the kernel size increases if this functionality is
not used.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 include/linux/scatterlist.h |  10 +++++
 lib/Kconfig                 |   4 ++
 lib/scatterlist.c           | 105 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 119 insertions(+)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index b7c83254c566..b8a7c1d1dbe3 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -276,6 +276,16 @@ int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
 			      unsigned int n_pages, unsigned int offset,
 			      unsigned long size, gfp_t gfp_mask);
 
+#ifdef CONFIG_SGL_ALLOC
+struct scatterlist *sgl_alloc_order(unsigned long long length,
+				    unsigned int order, bool chainable,
+				    gfp_t gfp, unsigned int *nent_p);
+struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
+			      unsigned int *nent_p);
+void sgl_free_order(struct scatterlist *sgl, int order);
+void sgl_free(struct scatterlist *sgl);
+#endif /* CONFIG_SGL_ALLOC */
+
 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 		      size_t buflen, off_t skip, bool to_buffer);
 
diff --git a/lib/Kconfig b/lib/Kconfig
index c5e84fbcb30b..4dd5c11366f9 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -409,6 +409,10 @@ config HAS_DMA
 	depends on !NO_DMA
 	default y
 
+config SGL_ALLOC
+	bool
+	default n
+
 config DMA_NOOP_OPS
 	bool
 	depends on HAS_DMA && (!64BIT || ARCH_DMA_ADDR_T_64BIT)
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 7c1c55f7daaa..9afc9b432083 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -474,6 +474,111 @@ int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
 }
 EXPORT_SYMBOL(sg_alloc_table_from_pages);
 
+#ifdef CONFIG_SGL_ALLOC
+
+/**
+ * sgl_alloc_order - allocate a scatterlist and its pages
+ * @length: Length in bytes of the scatterlist. Must be at least one
+ * @order: Second argument for alloc_pages()
+ * @chainable: Whether or not to allocate an extra element in the scatterlist
+ *	for scatterlist chaining purposes
+ * @gfp: Memory allocation flags
+ * @nent_p: [out] Number of entries in the scatterlist that have pages
+ *
+ * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
+ */
+struct scatterlist *sgl_alloc_order(unsigned long long length,
+				    unsigned int order, bool chainable,
+				    gfp_t gfp, unsigned int *nent_p)
+{
+	struct scatterlist *sgl, *sg;
+	struct page *page;
+	unsigned int nent, nalloc;
+	u32 elem_len;
+
+	nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order);
+	/* Check for integer overflow */
+	if (length > (nent << (PAGE_SHIFT + order)))
+		return NULL;
+	nalloc = nent;
+	if (chainable) {
+		/* Check for integer overflow */
+		if (nalloc + 1 < nalloc)
+			return NULL;
+		nalloc++;
+	}
+	sgl = kmalloc_array(nalloc, sizeof(struct scatterlist),
+			    (gfp & ~GFP_DMA) | __GFP_ZERO);
+	if (!sgl)
+		return NULL;
+
+	sg_init_table(sgl, nent);
+	sg = sgl;
+	while (length) {
+		elem_len = min_t(u64, length, PAGE_SIZE << order);
+		page = alloc_pages(gfp, order);
+		if (!page) {
+			sgl_free(sgl);
+			return NULL;
+		}
+
+		sg_set_page(sg, page, elem_len, 0);
+		length -= elem_len;
+		sg = sg_next(sg);
+	}
+	WARN_ON_ONCE(sg);
+	if (nent_p)
+		*nent_p = nent;
+	return sgl;
+}
+EXPORT_SYMBOL(sgl_alloc_order);
+
+/**
+ * sgl_alloc - allocate a scatterlist and its pages
+ * @length: Length in bytes of the scatterlist
+ * @gfp: Memory allocation flags
+ * @nent_p: [out] Number of entries in the scatterlist
+ *
+ * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
+ */
+struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
+			      unsigned int *nent_p)
+{
+	return sgl_alloc_order(length, 0, false, gfp, nent_p);
+}
+EXPORT_SYMBOL(sgl_alloc);
+
+/**
+ * sgl_free_order - free a scatterlist and its pages
+ * @sgl: Scatterlist with one or more elements
+ * @order: Second argument for __free_pages()
+ */
+void sgl_free_order(struct scatterlist *sgl, int order)
+{
+	struct scatterlist *sg;
+	struct page *page;
+
+	for (sg = sgl; sg; sg = sg_next(sg)) {
+		page = sg_page(sg);
+		if (page)
+			__free_pages(page, order);
+	}
+	kfree(sgl);
+}
+EXPORT_SYMBOL(sgl_free_order);
+
+/**
+ * sgl_free - free a scatterlist and its pages
+ * @sgl: Scatterlist with one or more elements
+ */
+void sgl_free(struct scatterlist *sgl)
+{
+	sgl_free_order(sgl, 0);
+}
+EXPORT_SYMBOL(sgl_free);
+
+#endif /* CONFIG_SGL_ALLOC */
+
 void __sg_page_iter_start(struct sg_page_iter *piter,
 			  struct scatterlist *sglist, unsigned int nents,
 			  unsigned long pgoffset)
-- 
2.15.1

[PATCH v4 2/5] crypto: scompress - use sgl_alloc() and sgl_free()

[Bart Van Assche]

Use the sgl_alloc() and sgl_free() functions instead of open coding
these functions.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
---
 crypto/Kconfig     |  1 +
 crypto/scompress.c | 51 ++-------------------------------------------------
 2 files changed, 3 insertions(+), 49 deletions(-)

diff --git a/crypto/Kconfig b/crypto/Kconfig
index f7911963bb79..20360e040425 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -106,6 +106,7 @@ config CRYPTO_KPP
 config CRYPTO_ACOMP2
 	tristate
 	select CRYPTO_ALGAPI2
+	select SGL_ALLOC
 
 config CRYPTO_ACOMP
 	tristate
diff --git a/crypto/scompress.c b/crypto/scompress.c
index 2075e2c4e7df..968bbcf65c94 100644
--- a/crypto/scompress.c
+++ b/crypto/scompress.c
@@ -140,53 +140,6 @@ static int crypto_scomp_init_tfm(struct crypto_tfm *tfm)
 	return ret;
 }
 
-static void crypto_scomp_sg_free(struct scatterlist *sgl)
-{
-	int i, n;
-	struct page *page;
-
-	if (!sgl)
-		return;
-
-	n = sg_nents(sgl);
-	for_each_sg(sgl, sgl, n, i) {
-		page = sg_page(sgl);
-		if (page)
-			__free_page(page);
-	}
-
-	kfree(sgl);
-}
-
-static struct scatterlist *crypto_scomp_sg_alloc(size_t size, gfp_t gfp)
-{
-	struct scatterlist *sgl;
-	struct page *page;
-	int i, n;
-
-	n = ((size - 1) >> PAGE_SHIFT) + 1;
-
-	sgl = kmalloc_array(n, sizeof(struct scatterlist), gfp);
-	if (!sgl)
-		return NULL;
-
-	sg_init_table(sgl, n);
-
-	for (i = 0; i < n; i++) {
-		page = alloc_page(gfp);
-		if (!page)
-			goto err;
-		sg_set_page(sgl + i, page, PAGE_SIZE, 0);
-	}
-
-	return sgl;
-
-err:
-	sg_mark_end(sgl + i);
-	crypto_scomp_sg_free(sgl);
-	return NULL;
-}
-
 static int scomp_acomp_comp_decomp(struct acomp_req *req, int dir)
 {
 	struct crypto_acomp *tfm = crypto_acomp_reqtfm(req);
@@ -220,7 +173,7 @@ static int scomp_acomp_comp_decomp(struct acomp_req *req, int dir)
 					      scratch_dst, &req->dlen, *ctx);
 	if (!ret) {
 		if (!req->dst) {
-			req->dst = crypto_scomp_sg_alloc(req->dlen, GFP_ATOMIC);
+			req->dst = sgl_alloc(req->dlen, GFP_ATOMIC, NULL);
 			if (!req->dst)
 				goto out;
 		}
@@ -274,7 +227,7 @@ int crypto_init_scomp_ops_async(struct crypto_tfm *tfm)
 
 	crt->compress = scomp_acomp_compress;
 	crt->decompress = scomp_acomp_decompress;
-	crt->dst_free = crypto_scomp_sg_free;
+	crt->dst_free = sgl_free;
 	crt->reqsize = sizeof(void *);
 
 	return 0;
-- 
2.15.1

[PATCH v4 3/5] nvmet/fc: Use sgl_alloc() and sgl_free()

[Bart Van Assche]

Use the sgl_alloc() and sgl_free() functions instead of open coding
these functions.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: James Smart <james.smart@broadcom.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/target/Kconfig |  1 +
 drivers/nvme/target/fc.c    | 36 ++----------------------------------
 2 files changed, 3 insertions(+), 34 deletions(-)

diff --git a/drivers/nvme/target/Kconfig b/drivers/nvme/target/Kconfig
index 03e4ab65fe77..4d9715630e21 100644
--- a/drivers/nvme/target/Kconfig
+++ b/drivers/nvme/target/Kconfig
@@ -39,6 +39,7 @@ config NVME_TARGET_FC
 	tristate "NVMe over Fabrics FC target driver"
 	depends on NVME_TARGET
 	depends on HAS_DMA
+	select SGL_ALLOC
 	help
 	  This enables the NVMe FC target support, which allows exporting NVMe
 	  devices over FC.
diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c
index 5fd86039e353..840d1a39de33 100644
--- a/drivers/nvme/target/fc.c
+++ b/drivers/nvme/target/fc.c
@@ -1697,31 +1697,12 @@ static int
 nvmet_fc_alloc_tgt_pgs(struct nvmet_fc_fcp_iod *fod)
 {
 	struct scatterlist *sg;
-	struct page *page;
 	unsigned int nent;
-	u32 page_len, length;
-	int i = 0;
 
-	length = fod->req.transfer_len;
-	nent = DIV_ROUND_UP(length, PAGE_SIZE);
-	sg = kmalloc_array(nent, sizeof(struct scatterlist), GFP_KERNEL);
+	sg = sgl_alloc(fod->req.transfer_len, GFP_KERNEL, &nent);
 	if (!sg)
 		goto out;
 
-	sg_init_table(sg, nent);
-
-	while (length) {
-		page_len = min_t(u32, length, PAGE_SIZE);
-
-		page = alloc_page(GFP_KERNEL);
-		if (!page)
-			goto out_free_pages;
-
-		sg_set_page(&sg[i], page, page_len, 0);
-		length -= page_len;
-		i++;
-	}
-
 	fod->data_sg = sg;
 	fod->data_sg_cnt = nent;
 	fod->data_sg_cnt = fc_dma_map_sg(fod->tgtport->dev, sg, nent,
@@ -1731,14 +1712,6 @@ nvmet_fc_alloc_tgt_pgs(struct nvmet_fc_fcp_iod *fod)
 
 	return 0;
 
-out_free_pages:
-	while (i > 0) {
-		i--;
-		__free_page(sg_page(&sg[i]));
-	}
-	kfree(sg);
-	fod->data_sg = NULL;
-	fod->data_sg_cnt = 0;
 out:
 	return NVME_SC_INTERNAL;
 }
@@ -1746,18 +1719,13 @@ nvmet_fc_alloc_tgt_pgs(struct nvmet_fc_fcp_iod *fod)
 static void
 nvmet_fc_free_tgt_pgs(struct nvmet_fc_fcp_iod *fod)
 {
-	struct scatterlist *sg;
-	int count;
-
 	if (!fod->data_sg || !fod->data_sg_cnt)
 		return;
 
 	fc_dma_unmap_sg(fod->tgtport->dev, fod->data_sg, fod->data_sg_cnt,
 				((fod->io_dir == NVMET_FCP_WRITE) ?
 					DMA_FROM_DEVICE : DMA_TO_DEVICE));
-	for_each_sg(fod->data_sg, sg, fod->data_sg_cnt, count)
-		__free_page(sg_page(sg));
-	kfree(fod->data_sg);
+	sgl_free(fod->data_sg);
 	fod->data_sg = NULL;
 	fod->data_sg_cnt = 0;
 }
-- 
2.15.1

Re: [PATCH v4 3/5] nvmet/fc: Use sgl_alloc() and sgl_free()

[James Smart]

On 1/5/2018 8:26 AM, Bart Van Assche wrote:
> Use the sgl_alloc() and sgl_free() functions instead of open coding
> these functions.
>
> Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
> Reviewed-by: Hannes Reinecke <hare@suse.com>
> Cc: Keith Busch <keith.busch@intel.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: James Smart <james.smart@broadcom.com>
> Cc: Sagi Grimberg <sagi@grimberg.me>
> ---
>   drivers/nvme/target/Kconfig |  1 +
>   drivers/nvme/target/fc.c    | 36 ++----------------------------------
>   2 files changed, 3 insertions(+), 34 deletions(-)

Reviewed-by:  James Smart <james.smart@broadcom.com>

-- james

[PATCH v4 4/5] nvmet/rdma: Use sgl_alloc() and sgl_free()

[Bart Van Assche]

Use the sgl_alloc() and sgl_free() functions instead of open coding
these functions.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/target/Kconfig |  1 +
 drivers/nvme/target/rdma.c  | 63 +++------------------------------------------
 2 files changed, 5 insertions(+), 59 deletions(-)

diff --git a/drivers/nvme/target/Kconfig b/drivers/nvme/target/Kconfig
index 4d9715630e21..5f4f8b16685f 100644
--- a/drivers/nvme/target/Kconfig
+++ b/drivers/nvme/target/Kconfig
@@ -29,6 +29,7 @@ config NVME_TARGET_RDMA
 	tristate "NVMe over Fabrics RDMA target support"
 	depends on INFINIBAND
 	depends on NVME_TARGET
+	select SGL_ALLOC
 	help
 	  This enables the NVMe RDMA target support, which allows exporting NVMe
 	  devices over RDMA.
diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
index 49912909c298..0e4c15754c58 100644
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -185,59 +185,6 @@ nvmet_rdma_put_rsp(struct nvmet_rdma_rsp *rsp)
 	spin_unlock_irqrestore(&rsp->queue->rsps_lock, flags);
 }
 
-static void nvmet_rdma_free_sgl(struct scatterlist *sgl, unsigned int nents)
-{
-	struct scatterlist *sg;
-	int count;
-
-	if (!sgl || !nents)
-		return;
-
-	for_each_sg(sgl, sg, nents, count)
-		__free_page(sg_page(sg));
-	kfree(sgl);
-}
-
-static int nvmet_rdma_alloc_sgl(struct scatterlist **sgl, unsigned int *nents,
-		u32 length)
-{
-	struct scatterlist *sg;
-	struct page *page;
-	unsigned int nent;
-	int i = 0;
-
-	nent = DIV_ROUND_UP(length, PAGE_SIZE);
-	sg = kmalloc_array(nent, sizeof(struct scatterlist), GFP_KERNEL);
-	if (!sg)
-		goto out;
-
-	sg_init_table(sg, nent);
-
-	while (length) {
-		u32 page_len = min_t(u32, length, PAGE_SIZE);
-
-		page = alloc_page(GFP_KERNEL);
-		if (!page)
-			goto out_free_pages;
-
-		sg_set_page(&sg[i], page, page_len, 0);
-		length -= page_len;
-		i++;
-	}
-	*sgl = sg;
-	*nents = nent;
-	return 0;
-
-out_free_pages:
-	while (i > 0) {
-		i--;
-		__free_page(sg_page(&sg[i]));
-	}
-	kfree(sg);
-out:
-	return NVME_SC_INTERNAL;
-}
-
 static int nvmet_rdma_alloc_cmd(struct nvmet_rdma_device *ndev,
 			struct nvmet_rdma_cmd *c, bool admin)
 {
@@ -484,7 +431,7 @@ static void nvmet_rdma_release_rsp(struct nvmet_rdma_rsp *rsp)
 	}
 
 	if (rsp->req.sg != &rsp->cmd->inline_sg)
-		nvmet_rdma_free_sgl(rsp->req.sg, rsp->req.sg_cnt);
+		sgl_free(rsp->req.sg);
 
 	if (unlikely(!list_empty_careful(&queue->rsp_wr_wait_list)))
 		nvmet_rdma_process_wr_wait_list(queue);
@@ -621,16 +568,14 @@ static u16 nvmet_rdma_map_sgl_keyed(struct nvmet_rdma_rsp *rsp,
 	u32 len = get_unaligned_le24(sgl->length);
 	u32 key = get_unaligned_le32(sgl->key);
 	int ret;
-	u16 status;
 
 	/* no data command? */
 	if (!len)
 		return 0;
 
-	status = nvmet_rdma_alloc_sgl(&rsp->req.sg, &rsp->req.sg_cnt,
-			len);
-	if (status)
-		return status;
+	rsp->req.sg = sgl_alloc(len, GFP_KERNEL, &rsp->req.sg_cnt);
+	if (!rsp->req.sg)
+		return NVME_SC_INTERNAL;
 
 	ret = rdma_rw_ctx_init(&rsp->rw, cm_id->qp, cm_id->port_num,
 			rsp->req.sg, rsp->req.sg_cnt, 0, addr, key,
-- 
2.15.1

[PATCH v4 5/5] target: Use sgl_alloc_order() and sgl_free()

[Bart Van Assche]

Use the sgl_alloc_order() and sgl_free() functions instead of open
coding these functions.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Acked-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/target/Kconfig                 |  1 +
 drivers/target/target_core_transport.c | 46 +++-------------------------------
 2 files changed, 5 insertions(+), 42 deletions(-)

diff --git a/drivers/target/Kconfig b/drivers/target/Kconfig
index e2bc99980f75..4c44d7bed01a 100644
--- a/drivers/target/Kconfig
+++ b/drivers/target/Kconfig
@@ -5,6 +5,7 @@ menuconfig TARGET_CORE
 	select CONFIGFS_FS
 	select CRC_T10DIF
 	select BLK_SCSI_REQUEST # only for scsi_command_size_tbl..
+	select SGL_ALLOC
 	default n
 	help
 	Say Y or M here to enable the TCM Storage Engine and ConfigFS enabled
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 58caacd54a3b..a001ba711cca 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2300,13 +2300,7 @@ static void target_complete_ok_work(struct work_struct *work)
 
 void target_free_sgl(struct scatterlist *sgl, int nents)
 {
-	struct scatterlist *sg;
-	int count;
-
-	for_each_sg(sgl, sg, nents, count)
-		__free_page(sg_page(sg));
-
-	kfree(sgl);
+	sgl_free(sgl);
 }
 EXPORT_SYMBOL(target_free_sgl);
 
@@ -2414,42 +2408,10 @@ int
 target_alloc_sgl(struct scatterlist **sgl, unsigned int *nents, u32 length,
 		 bool zero_page, bool chainable)
 {
-	struct scatterlist *sg;
-	struct page *page;
-	gfp_t zero_flag = (zero_page) ? __GFP_ZERO : 0;
-	unsigned int nalloc, nent;
-	int i = 0;
-
-	nalloc = nent = DIV_ROUND_UP(length, PAGE_SIZE);
-	if (chainable)
-		nalloc++;
-	sg = kmalloc_array(nalloc, sizeof(struct scatterlist), GFP_KERNEL);
-	if (!sg)
-		return -ENOMEM;
+	gfp_t gfp = GFP_KERNEL | (zero_page ? __GFP_ZERO : 0);
 
-	sg_init_table(sg, nalloc);
-
-	while (length) {
-		u32 page_len = min_t(u32, length, PAGE_SIZE);
-		page = alloc_page(GFP_KERNEL | zero_flag);
-		if (!page)
-			goto out;
-
-		sg_set_page(&sg[i], page, page_len, 0);
-		length -= page_len;
-		i++;
-	}
-	*sgl = sg;
-	*nents = nent;
-	return 0;
-
-out:
-	while (i > 0) {
-		i--;
-		__free_page(sg_page(&sg[i]));
-	}
-	kfree(sg);
-	return -ENOMEM;
+	*sgl = sgl_alloc_order(length, 0, chainable, gfp, nents);
+	return *sgl ? 0 : -ENOMEM;
 }
 EXPORT_SYMBOL(target_alloc_sgl);
 
-- 
2.15.1

Re: [PATCH v4 0/5] Introduce sgl_alloc() and sgl_free()

[Jens Axboe]

On 1/5/18 9:26 AM, Bart Van Assche wrote:
> Hello Jens,
> 
> As you know there are multiple drivers that both allocate a scatter/gather
> list and populate that list with pages. This patch series moves the code for
> allocating and freeing such scatterlists from several drivers into
> lib/scatterlist.c. Please consider this patch series for kernel v4.16.

Thanks Bart, applied for 4.16.

-- 
Jens Axboe