[PATCH 0/8] Introduce sgl_alloc() and sgl_free()

[PATCH 0/8] Introduce sgl_alloc() and sgl_free()

[Bart Van Assche]

Hello Jens,

As you probably 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 these drivers into
a new source file, namely lib/sgl_alloc. Please consider this patch series for
kernel v4.15.

Notes:
- Only the ib_srpt driver changes have been tested but none of the other
  drivers have been retested.
- The next step is to introduce a caching mechanism for these scatterlists
  and make the nvmet/rdma and SCSI target drivers use that caching mechanism
  since for these drivers sgl allocation occurs in the hot path.

Thanks,

Bart.

Bart Van Assche (8):
  lib: 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()
  scsi/ipr: Use sgl_alloc_order() and sgl_free_order()
  scsi/pmcraid: Remove an unused structure member
  scsi/pmcraid: Use sgl_alloc_order() and sgl_free_order()

 crypto/Kconfig                         |   1 +
 crypto/scompress.c                     |  52 +----------------
 drivers/nvme/target/Kconfig            |   2 +
 drivers/nvme/target/fc.c               |  37 +-----------
 drivers/nvme/target/rdma.c             |  64 ++-------------------
 drivers/scsi/Kconfig                   |   2 +
 drivers/scsi/ipr.c                     |  50 +++-------------
 drivers/scsi/ipr.h                     |   2 +-
 drivers/scsi/pmcraid.c                 |  44 ++------------
 drivers/scsi/pmcraid.h                 |   3 +-
 drivers/target/Kconfig                 |   1 +
 drivers/target/target_core_transport.c |  47 ++-------------
 include/linux/sgl_alloc.h              |  16 ++++++
 lib/Kconfig                            |   4 ++
 lib/Makefile                           |   1 +
 lib/sgl_alloc.c                        | 102 +++++++++++++++++++++++++++++++++
 16 files changed, 161 insertions(+), 267 deletions(-)
 create mode 100644 include/linux/sgl_alloc.h
 create mode 100644 lib/sgl_alloc.c

-- 
2.14.2

[PATCH 1/8] lib: Introduce sgl_alloc() and sgl_free()

[Bart Van Assche]

Many kernel drivers contain code that allocate and free both a
scatterlist and the pages that populate that scatterlist.
Introduce functions under lib/ that perform these tasks instead
of duplicating this functionality in multiple drivers.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
---
 include/linux/sgl_alloc.h |  16 ++++++++
 lib/Kconfig               |   4 ++
 lib/Makefile              |   1 +
 lib/sgl_alloc.c           | 102 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 123 insertions(+)
 create mode 100644 include/linux/sgl_alloc.h
 create mode 100644 lib/sgl_alloc.c

diff --git a/include/linux/sgl_alloc.h b/include/linux/sgl_alloc.h
new file mode 100644
index 000000000000..a0f719690c9e
--- /dev/null
+++ b/include/linux/sgl_alloc.h
@@ -0,0 +1,16 @@
+#ifndef _SGL_ALLOC_H_
+#define _SGL_ALLOC_H_
+
+#include <linux/types.h> /* bool, gfp_t */
+
+struct scatterlist;
+
+struct scatterlist *sgl_alloc_order(unsigned long long length,
+				    unsigned int order, unsigned int *nent_p,
+				    gfp_t gfp, bool chainable);
+struct scatterlist *sgl_alloc(unsigned long long length, unsigned int *nent_p,
+			      gfp_t gfp);
+void sgl_free_order(struct scatterlist *sgl, int order);
+void sgl_free(struct scatterlist *sgl);
+
+#endif /* _SGL_ALLOC_H_ */
diff --git a/lib/Kconfig b/lib/Kconfig
index b1445b22a6de..8396c4cfa1ab 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -413,6 +413,10 @@ 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/Makefile b/lib/Makefile
index dafa79613fb4..4a0e9caf3c0e 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -27,6 +27,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
+lib-$(CONFIG_SGL_ALLOC) += sgl_alloc.o
 lib-$(CONFIG_DMA_NOOP_OPS) += dma-noop.o
 lib-$(CONFIG_DMA_VIRT_OPS) += dma-virt.o
 
diff --git a/lib/sgl_alloc.c b/lib/sgl_alloc.c
new file mode 100644
index 000000000000..d96b395dd5c8
--- /dev/null
+++ b/lib/sgl_alloc.c
@@ -0,0 +1,102 @@
+#include <linux/kernel.h>
+#include <linux/scatterlist.h>
+#include <linux/sgl_alloc.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <asm/page.h>
+
+/**
+ * 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()
+ * @nent_p: [out] Number of entries in the scatterlist that have pages
+ * @gfp: Memory allocation flags
+ * @chainable: Whether or not to allocate an extra element in the scatterlist
+ *	for scatterlist chaining purposes
+ *
+ * Returns: %NULL upon failure or a pointer to an initialized scatterlist.
+ */
+struct scatterlist *sgl_alloc_order(unsigned long long length,
+				    unsigned int order, unsigned int *nent_p,
+				    gfp_t gfp, bool chainable)
+{
+	struct scatterlist *sgl, *sg;
+	struct page *page;
+	unsigned int nent, nalloc;
+	u32 elem_len;
+
+	nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order);
+	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
+ * @nent_p: [out] Number of entries in the scatterlist
+ * @gfp: Memory allocation flags
+ */
+struct scatterlist *sgl_alloc(unsigned long long length, unsigned int *nent_p,
+			      gfp_t gfp)
+{
+	return sgl_alloc_order(length, 0, nent_p, gfp, false);
+}
+EXPORT_SYMBOL(sgl_alloc);
+
+/**
+ * sgl_free_order - free a scatterlist and its pages
+ * @sg: 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
+ * @sg: Scatterlist with one or more elements
+ */
+void sgl_free(struct scatterlist *sgl)
+{
+	sgl_free_order(sgl, 0);
+}
+EXPORT_SYMBOL(sgl_free);
-- 
2.14.2

[PATCH 2/8] 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>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
---
 crypto/Kconfig     |  1 +
 crypto/scompress.c | 52 +++-------------------------------------------------
 2 files changed, 4 insertions(+), 49 deletions(-)

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 0a121f9ddf8e..a0667dd284ff 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -105,6 +105,7 @@ 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..ea4d5a3e01d1 100644
--- a/crypto/scompress.c
+++ b/crypto/scompress.c
@@ -24,6 +24,7 @@
 #include <linux/cryptouser.h>
 #include <net/netlink.h>
 #include <linux/scatterlist.h>
+#include <linux/sgl_alloc.h>
 #include <crypto/scatterwalk.h>
 #include <crypto/internal/acompress.h>
 #include <crypto/internal/scompress.h>
@@ -140,53 +141,6 @@ 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 +174,7 @@ 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, NULL, GFP_ATOMIC);
 			if (!req->dst)
 				goto out;
 		}
@@ -274,7 +228,7 @@ 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;
-- 
2.14.2

[PATCH 3/8] 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>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: James Smart <james.smart@broadcom.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/target/Kconfig |  1 +
 drivers/nvme/target/fc.c    | 37 +++----------------------------------
 2 files changed, 4 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 58e010bdda3e..02084539de5b 100644
--- a/drivers/nvme/target/fc.c
+++ b/drivers/nvme/target/fc.c
@@ -16,6 +16,7 @@
  */
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 #include <linux/module.h>
+#include <linux/sgl_alloc.h>
 #include <linux/slab.h>
 #include <linux/blk-mq.h>
 #include <linux/parser.h>
@@ -1683,31 +1684,12 @@ 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->total_length;
-	nent = DIV_ROUND_UP(length, PAGE_SIZE);
-	sg = kmalloc_array(nent, sizeof(struct scatterlist), GFP_KERNEL);
+	sg = sgl_alloc(fod->total_length, &nent, GFP_KERNEL);
 	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,
@@ -1717,14 +1699,6 @@ 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;
 }
@@ -1732,18 +1706,13 @@ 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;
 }
-- 
2.14.2

[PATCH 4/8] 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>
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  | 64 ++++-----------------------------------------
 2 files changed, 6 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 76d2bb793afe..bec0c8421b69 100644
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -23,6 +23,7 @@
 #include <linux/string.h>
 #include <linux/wait.h>
 #include <linux/inet.h>
+#include <linux/sgl_alloc.h>
 #include <asm/unaligned.h>
 
 #include <rdma/ib_verbs.h>
@@ -185,59 +186,6 @@ 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 +432,7 @@ 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);
@@ -620,16 +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, &rsp->req.sg_cnt, GFP_KERNEL);
+	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,
-- 
2.14.2

[PATCH 5/8] 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>
Cc: Nicholas A. Bellinger <nab@linux-iscsi.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/target/Kconfig                 |  1 +
 drivers/target/target_core_transport.c | 47 ++++------------------------------
 2 files changed, 6 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 836d552b0385..e8f0eabd25ab 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -34,6 +34,7 @@
 #include <linux/cdrom.h>
 #include <linux/module.h>
 #include <linux/ratelimit.h>
+#include <linux/sgl_alloc.h>
 #include <linux/vmalloc.h>
 #include <asm/unaligned.h>
 #include <net/sock.h>
@@ -2293,13 +2294,7 @@ 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);
 
@@ -2423,42 +2418,10 @@ 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, nents, gfp, chainable);
+	return *sgl ? 0 : -ENOMEM;
 }
 EXPORT_SYMBOL(target_alloc_sgl);
 
-- 
2.14.2

[PATCH 6/8] scsi/ipr: Use sgl_alloc_order() and sgl_free_order()

[Bart Van Assche]

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

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: linux-scsi@vger.kernel.org
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Brian King <brking@linux.vnet.ibm.com>
---
 drivers/scsi/Kconfig |  1 +
 drivers/scsi/ipr.c   | 50 +++++++++-----------------------------------------
 drivers/scsi/ipr.h   |  2 +-
 3 files changed, 11 insertions(+), 42 deletions(-)

diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index 41366339b950..d11e75e76195 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -1058,6 +1058,7 @@ config SCSI_IPR
 	depends on PCI && SCSI && ATA
 	select FW_LOADER
 	select IRQ_POLL
+	select SGL_ALLOC
 	---help---
 	  This driver supports the IBM Power Linux family RAID adapters.
 	  This includes IBM pSeries 5712, 5703, 5709, and 570A, as well
diff --git a/drivers/scsi/ipr.c b/drivers/scsi/ipr.c
index f838bd73befa..b197995a6f34 100644
--- a/drivers/scsi/ipr.c
+++ b/drivers/scsi/ipr.c
@@ -76,6 +76,7 @@
 #include <linux/hdreg.h>
 #include <linux/reboot.h>
 #include <linux/stringify.h>
+#include <linux/sgl_alloc.h>
 #include <asm/io.h>
 #include <asm/irq.h>
 #include <asm/processor.h>
@@ -3815,10 +3816,8 @@ static struct device_attribute ipr_iopoll_weight_attr = {
  **/
 static struct ipr_sglist *ipr_alloc_ucode_buffer(int buf_len)
 {
-	int sg_size, order, bsize_elem, num_elem, i, j;
+	int sg_size, order;
 	struct ipr_sglist *sglist;
-	struct scatterlist *scatterlist;
-	struct page *page;
 
 	/* Get the minimum size per scatter/gather element */
 	sg_size = buf_len / (IPR_MAX_SGLIST - 1);
@@ -3826,45 +3825,18 @@ static struct ipr_sglist *ipr_alloc_ucode_buffer(int buf_len)
 	/* Get the actual size per element */
 	order = get_order(sg_size);
 
-	/* Determine the actual number of bytes per element */
-	bsize_elem = PAGE_SIZE * (1 << order);
-
-	/* Determine the actual number of sg entries needed */
-	if (buf_len % bsize_elem)
-		num_elem = (buf_len / bsize_elem) + 1;
-	else
-		num_elem = buf_len / bsize_elem;
-
 	/* Allocate a scatter/gather list for the DMA */
-	sglist = kzalloc(sizeof(struct ipr_sglist) +
-			 (sizeof(struct scatterlist) * (num_elem - 1)),
-			 GFP_KERNEL);
-
+	sglist = kzalloc(sizeof(struct ipr_sglist), GFP_KERNEL);
 	if (sglist == NULL) {
 		ipr_trace;
 		return NULL;
 	}
-
-	scatterlist = sglist->scatterlist;
-	sg_init_table(scatterlist, num_elem);
-
 	sglist->order = order;
-	sglist->num_sg = num_elem;
-
-	/* Allocate a bunch of sg elements */
-	for (i = 0; i < num_elem; i++) {
-		page = alloc_pages(GFP_KERNEL, order);
-		if (!page) {
-			ipr_trace;
-
-			/* Free up what we already allocated */
-			for (j = i - 1; j >= 0; j--)
-				__free_pages(sg_page(&scatterlist[j]), order);
-			kfree(sglist);
-			return NULL;
-		}
-
-		sg_set_page(&scatterlist[i], page, 0, 0);
+	sglist->scatterlist = sgl_alloc_order(buf_len, order, &sglist->num_sg,
+					      GFP_KERNEL, false);
+	if (!sglist->scatterlist) {
+		kfree(sglist);
+		return NULL;
 	}
 
 	return sglist;
@@ -3882,11 +3854,7 @@ static struct ipr_sglist *ipr_alloc_ucode_buffer(int buf_len)
  **/
 static void ipr_free_ucode_buffer(struct ipr_sglist *sglist)
 {
-	int i;
-
-	for (i = 0; i < sglist->num_sg; i++)
-		__free_pages(sg_page(&sglist->scatterlist[i]), sglist->order);
-
+	sgl_free_order(sglist->scatterlist, sglist->order);
 	kfree(sglist);
 }
 
diff --git a/drivers/scsi/ipr.h b/drivers/scsi/ipr.h
index c7f0e9e3cd7d..93570734cbfb 100644
--- a/drivers/scsi/ipr.h
+++ b/drivers/scsi/ipr.h
@@ -1454,7 +1454,7 @@ struct ipr_sglist {
 	u32 num_sg;
 	u32 num_dma_sg;
 	u32 buffer_len;
-	struct scatterlist scatterlist[1];
+	struct scatterlist *scatterlist;
 };
 
 enum ipr_sdt_state {
-- 
2.14.2

[PATCH 7/8] scsi/pmcraid: Remove an unused structure member

[Bart Van Assche]

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: linux-scsi@vger.kernel.org
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Anil Ravindranath <anil_ravindranath@pmc-sierra.com>
---
 drivers/scsi/pmcraid.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/scsi/pmcraid.h b/drivers/scsi/pmcraid.h
index 8bfac72a242b..44da91712115 100644
--- a/drivers/scsi/pmcraid.h
+++ b/drivers/scsi/pmcraid.h
@@ -542,7 +542,6 @@ struct pmcraid_sglist {
 	u32 order;
 	u32 num_sg;
 	u32 num_dma_sg;
-	u32 buffer_len;
 	struct scatterlist scatterlist[1];
 };
 
-- 
2.14.2

[PATCH 8/8] scsi/pmcraid: Use sgl_alloc_order() and sgl_free_order()

[Bart Van Assche]

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

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: linux-scsi@vger.kernel.org
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Anil Ravindranath <anil_ravindranath@pmc-sierra.com>
---
 drivers/scsi/Kconfig   |  1 +
 drivers/scsi/pmcraid.c | 44 +++++---------------------------------------
 drivers/scsi/pmcraid.h |  2 +-
 3 files changed, 7 insertions(+), 40 deletions(-)

diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index d11e75e76195..632200ec36a6 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -1576,6 +1576,7 @@ config ZFCP
 config SCSI_PMCRAID
 	tristate "PMC SIERRA Linux MaxRAID adapter support"
 	depends on PCI && SCSI && NET
+	select SGL_ALLOC
 	---help---
 	  This driver supports the PMC SIERRA MaxRAID adapters.
 
diff --git a/drivers/scsi/pmcraid.c b/drivers/scsi/pmcraid.c
index b4d6cd8cd1ad..5f3ea3f3dc64 100644
--- a/drivers/scsi/pmcraid.c
+++ b/drivers/scsi/pmcraid.c
@@ -46,6 +46,7 @@
 #include <linux/libata.h>
 #include <linux/mutex.h>
 #include <linux/ktime.h>
+#include <linux/sgl_alloc.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_device.h>
@@ -3232,12 +3233,7 @@ static int pmcraid_build_ioadl(
  */
 static void pmcraid_free_sglist(struct pmcraid_sglist *sglist)
 {
-	int i;
-
-	for (i = 0; i < sglist->num_sg; i++)
-		__free_pages(sg_page(&(sglist->scatterlist[i])),
-			     sglist->order);
-
+	sgl_free_order(sglist->scatterlist, sglist->order);
 	kfree(sglist);
 }
 
@@ -3254,50 +3250,20 @@ static void pmcraid_free_sglist(struct pmcraid_sglist *sglist)
 static struct pmcraid_sglist *pmcraid_alloc_sglist(int buflen)
 {
 	struct pmcraid_sglist *sglist;
-	struct scatterlist *scatterlist;
-	struct page *page;
-	int num_elem, i, j;
 	int sg_size;
 	int order;
-	int bsize_elem;
 
 	sg_size = buflen / (PMCRAID_MAX_IOADLS - 1);
 	order = (sg_size > 0) ? get_order(sg_size) : 0;
-	bsize_elem = PAGE_SIZE * (1 << order);
-
-	/* Determine the actual number of sg entries needed */
-	if (buflen % bsize_elem)
-		num_elem = (buflen / bsize_elem) + 1;
-	else
-		num_elem = buflen / bsize_elem;
 
 	/* Allocate a scatter/gather list for the DMA */
-	sglist = kzalloc(sizeof(struct pmcraid_sglist) +
-			 (sizeof(struct scatterlist) * (num_elem - 1)),
-			 GFP_KERNEL);
-
+	sglist = kzalloc(sizeof(struct pmcraid_sglist), GFP_KERNEL);
 	if (sglist == NULL)
 		return NULL;
 
-	scatterlist = sglist->scatterlist;
-	sg_init_table(scatterlist, num_elem);
 	sglist->order = order;
-	sglist->num_sg = num_elem;
-	sg_size = buflen;
-
-	for (i = 0; i < num_elem; i++) {
-		page = alloc_pages(GFP_KERNEL|GFP_DMA|__GFP_ZERO, order);
-		if (!page) {
-			for (j = i - 1; j >= 0; j--)
-				__free_pages(sg_page(&scatterlist[j]), order);
-			kfree(sglist);
-			return NULL;
-		}
-
-		sg_set_page(&scatterlist[i], page,
-			sg_size < bsize_elem ? sg_size : bsize_elem, 0);
-		sg_size -= bsize_elem;
-	}
+	sgl_alloc_order(buflen, order, &sglist->num_sg,
+			GFP_KERNEL | GFP_DMA | __GFP_ZERO, false);
 
 	return sglist;
 }
diff --git a/drivers/scsi/pmcraid.h b/drivers/scsi/pmcraid.h
index 44da91712115..754ef30927e2 100644
--- a/drivers/scsi/pmcraid.h
+++ b/drivers/scsi/pmcraid.h
@@ -542,7 +542,7 @@ struct pmcraid_sglist {
 	u32 order;
 	u32 num_sg;
 	u32 num_dma_sg;
-	struct scatterlist scatterlist[1];
+	struct scatterlist *scatterlist;
 };
 
 /* page D0 inquiry data of focal point resource */
-- 
2.14.2

Re: [PATCH 1/8] lib: Introduce sgl_alloc() and sgl_free()

[Jens Axboe]

On 10/12/2017 04:45 PM, Bart Van Assche wrote:
> Many kernel drivers contain code that allocate and free both a
> scatterlist and the pages that populate that scatterlist.
> Introduce functions under lib/ that perform these tasks instead
> of duplicating this functionality in multiple drivers.
> 
> Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
> ---
>  include/linux/sgl_alloc.h |  16 ++++++++
>  lib/Kconfig               |   4 ++
>  lib/Makefile              |   1 +
>  lib/sgl_alloc.c           | 102 ++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 123 insertions(+)
>  create mode 100644 include/linux/sgl_alloc.h
>  create mode 100644 lib/sgl_alloc.c
> 
> diff --git a/include/linux/sgl_alloc.h b/include/linux/sgl_alloc.h
> new file mode 100644
> index 000000000000..a0f719690c9e
> --- /dev/null
> +++ b/include/linux/sgl_alloc.h
> @@ -0,0 +1,16 @@
> +#ifndef _SGL_ALLOC_H_
> +#define _SGL_ALLOC_H_
> +
> +#include <linux/types.h> /* bool, gfp_t */
> +
> +struct scatterlist;
> +
> +struct scatterlist *sgl_alloc_order(unsigned long long length,
> +				    unsigned int order, unsigned int *nent_p,
> +				    gfp_t gfp, bool chainable);
> +struct scatterlist *sgl_alloc(unsigned long long length, unsigned int *nent_p,
> +			      gfp_t gfp);
> +void sgl_free_order(struct scatterlist *sgl, int order);
> +void sgl_free(struct scatterlist *sgl);
> +
> +#endif /* _SGL_ALLOC_H_ */

Should this just go into linux/scatterlist.h instead of creating a new header
file?

-- 
Jens Axboe

Re: [PATCH 1/8] lib: Introduce sgl_alloc() and sgl_free()

[Bart Van Assche]

On Thu, 2017-10-12 at 16:52 -0600, Jens Axboe wrote:
> On 10/12/2017 04:45 PM, Bart Van Assche wrote:
> > +++ b/include/linux/sgl_alloc.h
> > @@ -0,0 +1,16 @@
> > +#ifndef _SGL_ALLOC_H_
> > +#define _SGL_ALLOC_H_
> > +
> > +#include <linux/types.h> /* bool, gfp_t */
> > +
> > +struct scatterlist;
> > +
> > +struct scatterlist *sgl_alloc_order(unsigned long long length,
> > +				    unsigned int order, unsigned int *nent_p,
> > +				    gfp_t gfp, bool chainable);
> > +struct scatterlist *sgl_alloc(unsigned long long length, unsigned int *nent_p,
> > +			      gfp_t gfp);
> > +void sgl_free_order(struct scatterlist *sgl, int order);
> > +void sgl_free(struct scatterlist *sgl);
> > +
> > +#endif /* _SGL_ALLOC_H_ */
> 
> Should this just go into linux/scatterlist.h instead of creating a new header
> file?

That's something I can change. I don't have a strong opinion about whether
these declarations should go into a new header file or into linux/scatterlist.h.

Bart.

Re: [PATCH 3/8] nvmet/fc: Use sgl_alloc() and sgl_free()

[Johannes Thumshirn]

Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
-- 
Johannes Thumshirn                                          Storage
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH 4/8] nvmet/rdma: Use sgl_alloc() and sgl_free()

[Johannes Thumshirn]

Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
-- 
Johannes Thumshirn                                          Storage
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH 1/8] lib: Introduce sgl_alloc() and sgl_free()

[Johannes Thumshirn]

On Thu, Oct 12, 2017 at 11:00:10PM +0000, Bart Van Assche wrote:
> On Thu, 2017-10-12 at 16:52 -0600, Jens Axboe wrote:
> > On 10/12/2017 04:45 PM, Bart Van Assche wrote:
> > > +++ b/include/linux/sgl_alloc.h
> > > @@ -0,0 +1,16 @@
> > > +#ifndef _SGL_ALLOC_H_
> > > +#define _SGL_ALLOC_H_
> > > +
> > > +#include <linux/types.h> /* bool, gfp_t */
> > > +
> > > +struct scatterlist;
> > > +
> > > +struct scatterlist *sgl_alloc_order(unsigned long long length,
> > > +				    unsigned int order, unsigned int *nent_p,
> > > +				    gfp_t gfp, bool chainable);
> > > +struct scatterlist *sgl_alloc(unsigned long long length, unsigned int *nent_p,
> > > +			      gfp_t gfp);
> > > +void sgl_free_order(struct scatterlist *sgl, int order);
> > > +void sgl_free(struct scatterlist *sgl);
> > > +
> > > +#endif /* _SGL_ALLOC_H_ */
> > 
> > Should this just go into linux/scatterlist.h instead of creating a new header
> > file?
> 
> That's something I can change. I don't have a strong opinion about whether
> these declarations should go into a new header file or into linux/scatterlist.h.

Yes please do (and the implementaion should go into lib/scatterlist.c).
Additionally please get rid of the new CONFIG_SGL_ALLOC as well.

Thanks,
	Johannes
-- 
Johannes Thumshirn                                          Storage
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH 6/8] scsi/ipr: Use sgl_alloc_order() and sgl_free_order()

[Johannes Thumshirn]

Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
-- 
Johannes Thumshirn                                          Storage
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH 7/8] scsi/pmcraid: Remove an unused structure member

[Johannes Thumshirn]

Fair enough,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
-- 
Johannes Thumshirn                                          Storage
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH 8/8] scsi/pmcraid: Use sgl_alloc_order() and sgl_free_order()

[Johannes Thumshirn]

Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
-- 
Johannes Thumshirn                                          Storage
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH 1/8] lib: Introduce sgl_alloc() and sgl_free()

[Jens Axboe]

On 10/12/2017 05:00 PM, Bart Van Assche wrote:
> On Thu, 2017-10-12 at 16:52 -0600, Jens Axboe wrote:
>> On 10/12/2017 04:45 PM, Bart Van Assche wrote:
>>> +++ b/include/linux/sgl_alloc.h
>>> @@ -0,0 +1,16 @@
>>> +#ifndef _SGL_ALLOC_H_
>>> +#define _SGL_ALLOC_H_
>>> +
>>> +#include <linux/types.h> /* bool, gfp_t */
>>> +
>>> +struct scatterlist;
>>> +
>>> +struct scatterlist *sgl_alloc_order(unsigned long long length,
>>> +				    unsigned int order, unsigned int *nent_p,
>>> +				    gfp_t gfp, bool chainable);
>>> +struct scatterlist *sgl_alloc(unsigned long long length, unsigned int *nent_p,
>>> +			      gfp_t gfp);
>>> +void sgl_free_order(struct scatterlist *sgl, int order);
>>> +void sgl_free(struct scatterlist *sgl);
>>> +
>>> +#endif /* _SGL_ALLOC_H_ */
>>
>> Should this just go into linux/scatterlist.h instead of creating a new header
>> file?
> 
> That's something I can change. I don't have a strong opinion about whether
> these declarations should go into a new header file or into linux/scatterlist.h.

I think you should make that change, keep things simpler. As Johannes
suggested, you could move the code to lib/scatterlist.c as well. I would
recommend keeping the kconfig option to only build it when needed, though.

-- 
Jens Axboe

Re: [PATCH 1/8] lib: Introduce sgl_alloc() and sgl_free()

[Randy Dunlap]

On 10/12/17 15:45, Bart Van Assche wrote:

> diff --git a/lib/sgl_alloc.c b/lib/sgl_alloc.c
> new file mode 100644
> index 000000000000..d96b395dd5c8
> --- /dev/null
> +++ b/lib/sgl_alloc.c
> @@ -0,0 +1,102 @@

> +/**
> + * sgl_free_order - free a scatterlist and its pages
> + * @sg: Scatterlist with one or more elements

      @sgl:

> + * @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
> + * @sg: Scatterlist with one or more elements

      @sgl:

> + */
> +void sgl_free(struct scatterlist *sgl)
> +{
> +	sgl_free_order(sgl, 0);
> +}
> +EXPORT_SYMBOL(sgl_free);
> 

ta.
-- 
~Randy

Re: [PATCH 1/8] lib: Introduce sgl_alloc() and sgl_free()

[Bart Van Assche]

On Fri, 2017-10-13 at 10:43 -0700, Randy Dunlap wrote:
> On 10/12/17 15:45, Bart Van Assche wrote:
> > + * @sg: Scatterlist with one or more elements
> 
>       @sgl:

Thanks Randy. I will fix this before I repost this series.

Bart.