[PATCH 1/2 v2] UBI: Add initial support for scatter gather

[PATCH 1/2 v2] UBI: Add initial support for scatter gather

[Richard Weinberger]

Adds a new set of functions to deal with scatter gather.
ubi_eba_read_leb_sg() will read from a LEB into a scatter gather list.
The new data structure struct ubi_sgl will be used within UBI to
hold the scatter gather list itself and metadata to have a cursor
within the list.

Signed-off-by: Richard Weinberger <richard@nod.at>
Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
---
 drivers/mtd/ubi/eba.c   | 56 +++++++++++++++++++++++++++++
 drivers/mtd/ubi/kapi.c  | 95 +++++++++++++++++++++++++++++++++++++++++--------
 drivers/mtd/ubi/ubi.h   |  3 ++
 include/linux/mtd/ubi.h | 46 ++++++++++++++++++++++++
 4 files changed, 185 insertions(+), 15 deletions(-)

diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index b698534..0aaf707 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -481,6 +481,62 @@ out_unlock:
 }
 
 /**
+ * ubi_eba_read_leb_sg - read data into a scatter gather list.
+ * @ubi: UBI device description object
+ * @vol: volume description object
+ * @lnum: logical eraseblock number
+ * @sgl: UBI scatter gather list to store the read data
+ * @offset: offset from where to read
+ * @len: how many bytes to read
+ * @check: data CRC check flag
+ *
+ * This function works exactly like ubi_eba_read_leb(). But instead of
+ * storing the read data into a buffer it writes to an UBI scatter gather
+ * list.
+ */
+int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
+			struct ubi_sgl *sgl, int lnum, int offset, int len,
+			int check)
+{
+	int to_read;
+	int ret;
+	struct scatterlist *sg;
+
+	for (;;) {
+		ubi_assert(sgl->list_pos < UBI_MAX_SG_COUNT);
+		sg = &sgl->sg[sgl->list_pos];
+		if (len < sg->length - sgl->page_pos)
+			to_read = len;
+		else
+			to_read = sg->length - sgl->page_pos;
+
+		ret = ubi_eba_read_leb(ubi, vol, lnum,
+				       sg_virt(sg) + sgl->page_pos, offset,
+				       to_read, check);
+		if (ret < 0)
+			goto out;
+
+		offset += to_read;
+		len -= to_read;
+		if (!len) {
+			sgl->page_pos += to_read;
+			if (sgl->page_pos == sg->length) {
+				sgl->list_pos++;
+				sgl->page_pos = 0;
+			}
+
+			break;
+		}
+
+		sgl->list_pos++;
+		sgl->page_pos = 0;
+	}
+
+out:
+	return ret;
+}
+
+/**
  * recover_peb - recover from write failure.
  * @ubi: UBI device description object
  * @pnum: the physical eraseblock to recover
diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
index f3bab66..d0055a2 100644
--- a/drivers/mtd/ubi/kapi.c
+++ b/drivers/mtd/ubi/kapi.c
@@ -355,6 +355,43 @@ void ubi_close_volume(struct ubi_volume_desc *desc)
 EXPORT_SYMBOL_GPL(ubi_close_volume);
 
 /**
+ * leb_read_sanity_check - does sanity checks on read requests.
+ * @desc: volume descriptor
+ * @lnum: logical eraseblock number to read from
+ * @offset: offset within the logical eraseblock to read from
+ * @len: how many bytes to read
+ *
+ * This function is used by ubi_leb_read() and ubi_leb_read_sg()
+ * to perfrom sanity checks.
+ */
+static int leb_read_sanity_check(struct ubi_volume_desc *desc, int lnum,
+				 int offset, int len)
+{
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+	int vol_id = vol->vol_id;
+
+	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
+	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
+	    offset + len > vol->usable_leb_size)
+		return -EINVAL;
+
+	if (vol->vol_type == UBI_STATIC_VOLUME) {
+		if (vol->used_ebs == 0)
+			/* Empty static UBI volume */
+			return 0;
+		if (lnum == vol->used_ebs - 1 &&
+		    offset + len > vol->last_eb_bytes)
+			return -EINVAL;
+	}
+
+	if (vol->upd_marker)
+		return -EBADF;
+
+	return 0;
+}
+
+/**
  * ubi_leb_read - read data.
  * @desc: volume descriptor
  * @lnum: logical eraseblock number to read from
@@ -390,22 +427,10 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
 
 	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
 
-	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
-	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
-	    offset + len > vol->usable_leb_size)
-		return -EINVAL;
-
-	if (vol->vol_type == UBI_STATIC_VOLUME) {
-		if (vol->used_ebs == 0)
-			/* Empty static UBI volume */
-			return 0;
-		if (lnum == vol->used_ebs - 1 &&
-		    offset + len > vol->last_eb_bytes)
-			return -EINVAL;
-	}
+	err = leb_read_sanity_check(desc, lnum, offset, len);
+	if (err < 0)
+		return err;
 
-	if (vol->upd_marker)
-		return -EBADF;
 	if (len == 0)
 		return 0;
 
@@ -419,6 +444,46 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
 }
 EXPORT_SYMBOL_GPL(ubi_leb_read);
 
+
+/**
+ * ubi_leb_read_sg - read data into a scatter gather list.
+ * @desc: volume descriptor
+ * @lnum: logical eraseblock number to read from
+ * @buf: buffer where to store the read data
+ * @offset: offset within the logical eraseblock to read from
+ * @len: how many bytes to read
+ * @check: whether UBI has to check the read data's CRC or not.
+ *
+ * This function works exactly like ubi_leb_read_sg(). But instead of
+ * storing the read data into a buffer it writes to an UBI scatter gather
+ * list.
+ */
+int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
+		    int offset, int len, int check)
+{
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+	int err, vol_id = vol->vol_id;
+
+	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
+
+	err = leb_read_sanity_check(desc, lnum, offset, len);
+	if (err < 0)
+		return err;
+
+	if (len == 0)
+		return 0;
+
+	err = ubi_eba_read_leb_sg(ubi, vol, sgl, lnum, offset, len, check);
+	if (err && mtd_is_eccerr(err) && vol->vol_type == UBI_STATIC_VOLUME) {
+		ubi_warn(ubi, "mark volume %d as corrupted", vol_id);
+		vol->corrupted = 1;
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(ubi_leb_read_sg);
+
 /**
  * ubi_leb_write - write data.
  * @desc: volume descriptor
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index ee7ac0b..a5283cf 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -791,6 +791,9 @@ int ubi_eba_unmap_leb(struct ubi_device *ubi, struct ubi_volume *vol,
 		      int lnum);
 int ubi_eba_read_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
 		     void *buf, int offset, int len, int check);
+int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
+			struct ubi_sgl *sgl, int lnum, int offset, int len,
+			int check);
 int ubi_eba_write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
 		      const void *buf, int offset, int len);
 int ubi_eba_write_leb_st(struct ubi_device *ubi, struct ubi_volume *vol,
diff --git a/include/linux/mtd/ubi.h b/include/linux/mtd/ubi.h
index c3918a0..3d5916d 100644
--- a/include/linux/mtd/ubi.h
+++ b/include/linux/mtd/ubi.h
@@ -23,11 +23,16 @@
 
 #include <linux/ioctl.h>
 #include <linux/types.h>
+#include <linux/scatterlist.h>
 #include <mtd/ubi-user.h>
 
 /* All voumes/LEBs */
 #define UBI_ALL -1
 
+/* Maximum number of scatter gather list entries,
+ * we use only 64 to have a lower memory foot print. */
+#define UBI_MAX_SG_COUNT 64
+
 /*
  * enum ubi_open_mode - UBI volume open mode constants.
  *
@@ -116,6 +121,35 @@ struct ubi_volume_info {
 };
 
 /**
+ * struct ubi_sgl - UBI scatter gather list data structure.
+ * @list_pos: current position in @sg[]
+ * @page_pos: current position in @sg[@list_pos]
+ * @sg: the scatter gather list itself
+ *
+ * ubi_sgl is a wrapper around a scatter list which keeps track of the
+ * current position in the list and the current list item such that
+ * it can be used across multiple ubi_leb_read_sg() calls.
+ */
+struct ubi_sgl {
+	int list_pos;
+	int page_pos;
+	struct scatterlist sg[UBI_MAX_SG_COUNT];
+};
+
+/**
+ * ubi_sgl_init - initialize an UBI scatter gather list data structure.
+ * @usgl: the UBI scatter gather struct itself
+ *
+ * Please note that you still have to use sg_init_table() or any adequate
+ * function to initialize the unterlaying struct scatterlist.
+ */
+static inline void ubi_sgl_init(struct ubi_sgl *usgl)
+{
+	usgl->list_pos = 0;
+	usgl->page_pos = 0;
+}
+
+/**
  * struct ubi_device_info - UBI device description data structure.
  * @ubi_num: ubi device number
  * @leb_size: logical eraseblock size on this UBI device
@@ -210,6 +244,8 @@ int ubi_unregister_volume_notifier(struct notifier_block *nb);
 void ubi_close_volume(struct ubi_volume_desc *desc);
 int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
 		 int len, int check);
+int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
+		   int offset, int len, int check);
 int ubi_leb_write(struct ubi_volume_desc *desc, int lnum, const void *buf,
 		  int offset, int len);
 int ubi_leb_change(struct ubi_volume_desc *desc, int lnum, const void *buf,
@@ -230,4 +266,14 @@ static inline int ubi_read(struct ubi_volume_desc *desc, int lnum, char *buf,
 {
 	return ubi_leb_read(desc, lnum, buf, offset, len, 0);
 }
+
+/*
+ * This function is the same as the 'ubi_leb_read_sg()' function, but it does
+ * not provide the checking capability.
+ */
+static inline int ubi_read_sg(struct ubi_volume_desc *desc, int lnum,
+			      struct ubi_sgl *sgl, int offset, int len)
+{
+	return ubi_leb_read_sg(desc, lnum, sgl, offset, len, 0);
+}
 #endif /* !__LINUX_UBI_H__ */
-- 
1.8.4.5

[PATCH 1/2 v2] UBI: Add initial support for scatter gather

[Richard Weinberger]

Adds a new set of functions to deal with scatter gather.
ubi_eba_read_leb_sg() will read from a LEB into a scatter gather list.
The new data structure struct ubi_sgl will be used within UBI to
hold the scatter gather list itself and metadata to have a cursor
within the list.

Signed-off-by: Richard Weinberger <richard@nod.at>
Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
---
 drivers/mtd/ubi/eba.c   | 56 +++++++++++++++++++++++++++++
 drivers/mtd/ubi/kapi.c  | 95 +++++++++++++++++++++++++++++++++++++++++--------
 drivers/mtd/ubi/ubi.h   |  3 ++
 include/linux/mtd/ubi.h | 46 ++++++++++++++++++++++++
 4 files changed, 185 insertions(+), 15 deletions(-)

diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index b698534..0aaf707 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -481,6 +481,62 @@ out_unlock:
 }
 
 /**
+ * ubi_eba_read_leb_sg - read data into a scatter gather list.
+ * @ubi: UBI device description object
+ * @vol: volume description object
+ * @lnum: logical eraseblock number
+ * @sgl: UBI scatter gather list to store the read data
+ * @offset: offset from where to read
+ * @len: how many bytes to read
+ * @check: data CRC check flag
+ *
+ * This function works exactly like ubi_eba_read_leb(). But instead of
+ * storing the read data into a buffer it writes to an UBI scatter gather
+ * list.
+ */
+int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
+			struct ubi_sgl *sgl, int lnum, int offset, int len,
+			int check)
+{
+	int to_read;
+	int ret;
+	struct scatterlist *sg;
+
+	for (;;) {
+		ubi_assert(sgl->list_pos < UBI_MAX_SG_COUNT);
+		sg = &sgl->sg[sgl->list_pos];
+		if (len < sg->length - sgl->page_pos)
+			to_read = len;
+		else
+			to_read = sg->length - sgl->page_pos;
+
+		ret = ubi_eba_read_leb(ubi, vol, lnum,
+				       sg_virt(sg) + sgl->page_pos, offset,
+				       to_read, check);
+		if (ret < 0)
+			goto out;
+
+		offset += to_read;
+		len -= to_read;
+		if (!len) {
+			sgl->page_pos += to_read;
+			if (sgl->page_pos == sg->length) {
+				sgl->list_pos++;
+				sgl->page_pos = 0;
+			}
+
+			break;
+		}
+
+		sgl->list_pos++;
+		sgl->page_pos = 0;
+	}
+
+out:
+	return ret;
+}
+
+/**
  * recover_peb - recover from write failure.
  * @ubi: UBI device description object
  * @pnum: the physical eraseblock to recover
diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
index f3bab66..d0055a2 100644
--- a/drivers/mtd/ubi/kapi.c
+++ b/drivers/mtd/ubi/kapi.c
@@ -355,6 +355,43 @@ void ubi_close_volume(struct ubi_volume_desc *desc)
 EXPORT_SYMBOL_GPL(ubi_close_volume);
 
 /**
+ * leb_read_sanity_check - does sanity checks on read requests.
+ * @desc: volume descriptor
+ * @lnum: logical eraseblock number to read from
+ * @offset: offset within the logical eraseblock to read from
+ * @len: how many bytes to read
+ *
+ * This function is used by ubi_leb_read() and ubi_leb_read_sg()
+ * to perfrom sanity checks.
+ */
+static int leb_read_sanity_check(struct ubi_volume_desc *desc, int lnum,
+				 int offset, int len)
+{
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+	int vol_id = vol->vol_id;
+
+	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
+	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
+	    offset + len > vol->usable_leb_size)
+		return -EINVAL;
+
+	if (vol->vol_type == UBI_STATIC_VOLUME) {
+		if (vol->used_ebs == 0)
+			/* Empty static UBI volume */
+			return 0;
+		if (lnum == vol->used_ebs - 1 &&
+		    offset + len > vol->last_eb_bytes)
+			return -EINVAL;
+	}
+
+	if (vol->upd_marker)
+		return -EBADF;
+
+	return 0;
+}
+
+/**
  * ubi_leb_read - read data.
  * @desc: volume descriptor
  * @lnum: logical eraseblock number to read from
@@ -390,22 +427,10 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
 
 	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
 
-	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
-	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
-	    offset + len > vol->usable_leb_size)
-		return -EINVAL;
-
-	if (vol->vol_type == UBI_STATIC_VOLUME) {
-		if (vol->used_ebs == 0)
-			/* Empty static UBI volume */
-			return 0;
-		if (lnum == vol->used_ebs - 1 &&
-		    offset + len > vol->last_eb_bytes)
-			return -EINVAL;
-	}
+	err = leb_read_sanity_check(desc, lnum, offset, len);
+	if (err < 0)
+		return err;
 
-	if (vol->upd_marker)
-		return -EBADF;
 	if (len == 0)
 		return 0;
 
@@ -419,6 +444,46 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
 }
 EXPORT_SYMBOL_GPL(ubi_leb_read);
 
+
+/**
+ * ubi_leb_read_sg - read data into a scatter gather list.
+ * @desc: volume descriptor
+ * @lnum: logical eraseblock number to read from
+ * @buf: buffer where to store the read data
+ * @offset: offset within the logical eraseblock to read from
+ * @len: how many bytes to read
+ * @check: whether UBI has to check the read data's CRC or not.
+ *
+ * This function works exactly like ubi_leb_read_sg(). But instead of
+ * storing the read data into a buffer it writes to an UBI scatter gather
+ * list.
+ */
+int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
+		    int offset, int len, int check)
+{
+	struct ubi_volume *vol = desc->vol;
+	struct ubi_device *ubi = vol->ubi;
+	int err, vol_id = vol->vol_id;
+
+	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
+
+	err = leb_read_sanity_check(desc, lnum, offset, len);
+	if (err < 0)
+		return err;
+
+	if (len == 0)
+		return 0;
+
+	err = ubi_eba_read_leb_sg(ubi, vol, sgl, lnum, offset, len, check);
+	if (err && mtd_is_eccerr(err) && vol->vol_type == UBI_STATIC_VOLUME) {
+		ubi_warn(ubi, "mark volume %d as corrupted", vol_id);
+		vol->corrupted = 1;
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(ubi_leb_read_sg);
+
 /**
  * ubi_leb_write - write data.
  * @desc: volume descriptor
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index ee7ac0b..a5283cf 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -791,6 +791,9 @@ int ubi_eba_unmap_leb(struct ubi_device *ubi, struct ubi_volume *vol,
 		      int lnum);
 int ubi_eba_read_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
 		     void *buf, int offset, int len, int check);
+int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
+			struct ubi_sgl *sgl, int lnum, int offset, int len,
+			int check);
 int ubi_eba_write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
 		      const void *buf, int offset, int len);
 int ubi_eba_write_leb_st(struct ubi_device *ubi, struct ubi_volume *vol,
diff --git a/include/linux/mtd/ubi.h b/include/linux/mtd/ubi.h
index c3918a0..3d5916d 100644
--- a/include/linux/mtd/ubi.h
+++ b/include/linux/mtd/ubi.h
@@ -23,11 +23,16 @@
 
 #include <linux/ioctl.h>
 #include <linux/types.h>
+#include <linux/scatterlist.h>
 #include <mtd/ubi-user.h>
 
 /* All voumes/LEBs */
 #define UBI_ALL -1
 
+/* Maximum number of scatter gather list entries,
+ * we use only 64 to have a lower memory foot print. */
+#define UBI_MAX_SG_COUNT 64
+
 /*
  * enum ubi_open_mode - UBI volume open mode constants.
  *
@@ -116,6 +121,35 @@ struct ubi_volume_info {
 };
 
 /**
+ * struct ubi_sgl - UBI scatter gather list data structure.
+ * @list_pos: current position in @sg[]
+ * @page_pos: current position in @sg[@list_pos]
+ * @sg: the scatter gather list itself
+ *
+ * ubi_sgl is a wrapper around a scatter list which keeps track of the
+ * current position in the list and the current list item such that
+ * it can be used across multiple ubi_leb_read_sg() calls.
+ */
+struct ubi_sgl {
+	int list_pos;
+	int page_pos;
+	struct scatterlist sg[UBI_MAX_SG_COUNT];
+};
+
+/**
+ * ubi_sgl_init - initialize an UBI scatter gather list data structure.
+ * @usgl: the UBI scatter gather struct itself
+ *
+ * Please note that you still have to use sg_init_table() or any adequate
+ * function to initialize the unterlaying struct scatterlist.
+ */
+static inline void ubi_sgl_init(struct ubi_sgl *usgl)
+{
+	usgl->list_pos = 0;
+	usgl->page_pos = 0;
+}
+
+/**
  * struct ubi_device_info - UBI device description data structure.
  * @ubi_num: ubi device number
  * @leb_size: logical eraseblock size on this UBI device
@@ -210,6 +244,8 @@ int ubi_unregister_volume_notifier(struct notifier_block *nb);
 void ubi_close_volume(struct ubi_volume_desc *desc);
 int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
 		 int len, int check);
+int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
+		   int offset, int len, int check);
 int ubi_leb_write(struct ubi_volume_desc *desc, int lnum, const void *buf,
 		  int offset, int len);
 int ubi_leb_change(struct ubi_volume_desc *desc, int lnum, const void *buf,
@@ -230,4 +266,14 @@ static inline int ubi_read(struct ubi_volume_desc *desc, int lnum, char *buf,
 {
 	return ubi_leb_read(desc, lnum, buf, offset, len, 0);
 }
+
+/*
+ * This function is the same as the 'ubi_leb_read_sg()' function, but it does
+ * not provide the checking capability.
+ */
+static inline int ubi_read_sg(struct ubi_volume_desc *desc, int lnum,
+			      struct ubi_sgl *sgl, int offset, int len)
+{
+	return ubi_leb_read_sg(desc, lnum, sgl, offset, len, 0);
+}
 #endif /* !__LINUX_UBI_H__ */
-- 
1.8.4.5

[PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Convert the driver to blk-mq.
Beside of moving to the modern block interface this change boosts
also the performance of the driver.

nand: device found, Manufacturer ID: 0x2c, Chip ID: 0xda
nand: Micron NAND 256MiB 3,3V 8-bit
nand: 256MiB, SLC, page size: 2048, OOB size: 64

root@debian-armhf:~# dd if=/dev/ubiblock0_0 of=/dev/zero bs=1M
243+1 records in
243+1 records out
255080448 bytes (255 MB) copied, 4.39295 s, 58.1 MB/s

vs.

root@debian-armhf:~# dd if=/dev/ubiblock0_0 of=/dev/zero bs=1M
243+1 records in
243+1 records out
255080448 bytes (255 MB) copied, 2.87676 s, 88.7 MB/s

Cc: hch@infradead.org
Cc: axboe@fb.com
Cc: tom.leiming@gmail.com
Signed-off-by: Richard Weinberger <richard@nod.at>
Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
---
 drivers/mtd/ubi/block.c | 202 ++++++++++++++++++++++--------------------------
 1 file changed, 94 insertions(+), 108 deletions(-)

diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
index 6b6bce2..00caf46 100644
--- a/drivers/mtd/ubi/block.c
+++ b/drivers/mtd/ubi/block.c
@@ -42,11 +42,12 @@
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
-#include <linux/vmalloc.h>
 #include <linux/mtd/ubi.h>
 #include <linux/workqueue.h>
 #include <linux/blkdev.h>
+#include <linux/blk-mq.h>
 #include <linux/hdreg.h>
+#include <linux/scatterlist.h>
 #include <asm/div64.h>
 
 #include "ubi-media.h"
@@ -67,6 +68,11 @@ struct ubiblock_param {
 	char name[UBIBLOCK_PARAM_LEN+1];
 };
 
+struct ubiblock_pdu {
+	struct work_struct work;
+	struct ubi_sgl usgl;
+};
+
 /* Numbers of elements set in the @ubiblock_param array */
 static int ubiblock_devs __initdata;
 
@@ -84,11 +90,10 @@ struct ubiblock {
 	struct request_queue *rq;
 
 	struct workqueue_struct *wq;
-	struct work_struct work;
 
 	struct mutex dev_mutex;
-	spinlock_t queue_lock;
 	struct list_head list;
+	struct blk_mq_tag_set tag_set;
 };
 
 /* Linked list of all ubiblock instances */
@@ -181,31 +186,20 @@ static struct ubiblock *find_dev_nolock(int ubi_num, int vol_id)
 	return NULL;
 }
 
-static int ubiblock_read_to_buf(struct ubiblock *dev, char *buffer,
-				int leb, int offset, int len)
+static int ubiblock_read(struct ubiblock_pdu *pdu)
 {
-	int ret;
+	int ret, leb, offset, bytes_left, to_read;
+	u64 pos;
+	struct request *req = blk_mq_rq_from_pdu(pdu);
+	struct ubiblock *dev = req->q->queuedata;
 
-	ret = ubi_read(dev->desc, leb, buffer, offset, len);
-	if (ret) {
-		dev_err(disk_to_dev(dev->gd), "%d while reading from LEB %d (offset %d, length %d)",
-			ret, leb, offset, len);
-		return ret;
-	}
-	return 0;
-}
-
-static int ubiblock_read(struct ubiblock *dev, char *buffer,
-			 sector_t sec, int len)
-{
-	int ret, leb, offset;
-	int bytes_left = len;
-	int to_read = len;
-	u64 pos = sec << 9;
+	to_read = blk_rq_bytes(req);
+	pos = blk_rq_pos(req) << 9;
 
 	/* Get LEB:offset address to read from */
 	offset = do_div(pos, dev->leb_size);
 	leb = pos;
+	bytes_left = to_read;
 
 	while (bytes_left) {
 		/*
@@ -215,11 +209,10 @@ static int ubiblock_read(struct ubiblock *dev, char *buffer,
 		if (offset + to_read > dev->leb_size)
 			to_read = dev->leb_size - offset;
 
-		ret = ubiblock_read_to_buf(dev, buffer, leb, offset, to_read);
-		if (ret)
+		ret = ubi_read_sg(dev->desc, leb, &pdu->usgl, offset, to_read);
+		if (ret < 0)
 			return ret;
 
-		buffer += to_read;
 		bytes_left -= to_read;
 		to_read = bytes_left;
 		leb += 1;
@@ -228,79 +221,6 @@ static int ubiblock_read(struct ubiblock *dev, char *buffer,
 	return 0;
 }
 
-static int do_ubiblock_request(struct ubiblock *dev, struct request *req)
-{
-	int len, ret;
-	sector_t sec;
-
-	if (req->cmd_type != REQ_TYPE_FS)
-		return -EIO;
-
-	if (blk_rq_pos(req) + blk_rq_cur_sectors(req) >
-	    get_capacity(req->rq_disk))
-		return -EIO;
-
-	if (rq_data_dir(req) != READ)
-		return -ENOSYS; /* Write not implemented */
-
-	sec = blk_rq_pos(req);
-	len = blk_rq_cur_bytes(req);
-
-	/*
-	 * Let's prevent the device from being removed while we're doing I/O
-	 * work. Notice that this means we serialize all the I/O operations,
-	 * but it's probably of no impact given the NAND core serializes
-	 * flash access anyway.
-	 */
-	mutex_lock(&dev->dev_mutex);
-	ret = ubiblock_read(dev, bio_data(req->bio), sec, len);
-	mutex_unlock(&dev->dev_mutex);
-
-	return ret;
-}
-
-static void ubiblock_do_work(struct work_struct *work)
-{
-	struct ubiblock *dev =
-		container_of(work, struct ubiblock, work);
-	struct request_queue *rq = dev->rq;
-	struct request *req;
-	int res;
-
-	spin_lock_irq(rq->queue_lock);
-
-	req = blk_fetch_request(rq);
-	while (req) {
-
-		spin_unlock_irq(rq->queue_lock);
-		res = do_ubiblock_request(dev, req);
-		spin_lock_irq(rq->queue_lock);
-
-		/*
-		 * If we're done with this request,
-		 * we need to fetch a new one
-		 */
-		if (!__blk_end_request_cur(req, res))
-			req = blk_fetch_request(rq);
-	}
-
-	spin_unlock_irq(rq->queue_lock);
-}
-
-static void ubiblock_request(struct request_queue *rq)
-{
-	struct ubiblock *dev;
-	struct request *req;
-
-	dev = rq->queuedata;
-
-	if (!dev)
-		while ((req = blk_fetch_request(rq)) != NULL)
-			__blk_end_request_all(req, -ENODEV);
-	else
-		queue_work(dev->wq, &dev->work);
-}
-
 static int ubiblock_open(struct block_device *bdev, fmode_t mode)
 {
 	struct ubiblock *dev = bdev->bd_disk->private_data;
@@ -374,6 +294,57 @@ static const struct block_device_operations ubiblock_ops = {
 	.getgeo	= ubiblock_getgeo,
 };
 
+static void ubiblock_do_work(struct work_struct *work)
+{
+	int ret;
+	struct ubiblock_pdu *pdu = container_of(work, struct ubiblock_pdu, work);
+	struct request *req = blk_mq_rq_from_pdu(pdu);
+
+	blk_mq_start_request(req);
+	blk_rq_map_sg(req->q, req, pdu->usgl.sg);
+
+	ret = ubiblock_read(pdu);
+	blk_mq_end_request(req, ret);
+}
+
+static int ubiblock_queue_rq(struct blk_mq_hw_ctx *hctx,
+			     const struct blk_mq_queue_data *bd)
+{
+	struct request *req = bd->rq;
+	struct ubiblock *dev = hctx->queue->queuedata;
+	struct ubiblock_pdu *pdu = blk_mq_rq_to_pdu(req);
+
+	if (req->cmd_type != REQ_TYPE_FS)
+		return BLK_MQ_RQ_QUEUE_ERROR;
+
+	if (rq_data_dir(req) != READ)
+		return BLK_MQ_RQ_QUEUE_ERROR; /* Write not implemented */
+
+	ubi_sgl_init(&pdu->usgl);
+	queue_work(dev->wq, &pdu->work);
+
+	return BLK_MQ_RQ_QUEUE_OK;
+}
+
+static int ubiblock_init_request(void *data, struct request *req,
+				 unsigned int hctx_idx,
+				 unsigned int request_idx,
+				 unsigned int numa_node)
+{
+	struct ubiblock_pdu *pdu = blk_mq_rq_to_pdu(req);
+
+	sg_init_table(pdu->usgl.sg, UBI_MAX_SG_COUNT);
+	INIT_WORK(&pdu->work, ubiblock_do_work);
+
+	return 0;
+}
+
+static struct blk_mq_ops ubiblock_mq_ops = {
+	.queue_rq       = ubiblock_queue_rq,
+	.init_request	= ubiblock_init_request,
+	.map_queue      = blk_mq_map_queue,
+};
+
 int ubiblock_create(struct ubi_volume_info *vi)
 {
 	struct ubiblock *dev;
@@ -417,13 +388,27 @@ int ubiblock_create(struct ubi_volume_info *vi)
 	set_capacity(gd, disk_capacity);
 	dev->gd = gd;
 
-	spin_lock_init(&dev->queue_lock);
-	dev->rq = blk_init_queue(ubiblock_request, &dev->queue_lock);
+	dev->tag_set.ops = &ubiblock_mq_ops;
+	dev->tag_set.queue_depth = 64;
+	dev->tag_set.numa_node = NUMA_NO_NODE;
+	dev->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
+	dev->tag_set.cmd_size = sizeof(struct ubiblock_pdu);
+	dev->tag_set.driver_data = dev;
+	dev->tag_set.nr_hw_queues = 1;
+
+	ret = blk_mq_alloc_tag_set(&dev->tag_set);
+	if (ret) {
+		dev_err(disk_to_dev(dev->gd), "blk_mq_alloc_tag_set failed");
+		goto out_put_disk;
+	}
+
+	dev->rq = blk_mq_init_queue(&dev->tag_set);
 	if (!dev->rq) {
-		dev_err(disk_to_dev(gd), "blk_init_queue failed");
+		dev_err(disk_to_dev(gd), "blk_mq_init_queue failed");
 		ret = -ENODEV;
-		goto out_put_disk;
+		goto out_free_tags;
 	}
+	blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT);
 
 	dev->rq->queuedata = dev;
 	dev->gd->queue = dev->rq;
@@ -437,7 +422,6 @@ int ubiblock_create(struct ubi_volume_info *vi)
 		ret = -ENOMEM;
 		goto out_free_queue;
 	}
-	INIT_WORK(&dev->work, ubiblock_do_work);
 
 	mutex_lock(&devices_mutex);
 	list_add_tail(&dev->list, &ubiblock_devices);
@@ -451,6 +435,8 @@ int ubiblock_create(struct ubi_volume_info *vi)
 
 out_free_queue:
 	blk_cleanup_queue(dev->rq);
+out_free_tags:
+	blk_mq_free_tag_set(&dev->tag_set);
 out_put_disk:
 	put_disk(dev->gd);
 out_free_dev:
@@ -461,8 +447,13 @@ out_free_dev:
 
 static void ubiblock_cleanup(struct ubiblock *dev)
 {
+	/* Stop new requests to arrive */
 	del_gendisk(dev->gd);
+	/* Flush pending work */
+	destroy_workqueue(dev->wq);
+	/* Finally destroy the blk queue */
 	blk_cleanup_queue(dev->rq);
+	blk_mq_free_tag_set(&dev->tag_set);
 	dev_info(disk_to_dev(dev->gd), "released");
 	put_disk(dev->gd);
 }
@@ -490,9 +481,6 @@ int ubiblock_remove(struct ubi_volume_info *vi)
 	list_del(&dev->list);
 	mutex_unlock(&devices_mutex);
 
-	/* Flush pending work and stop this workqueue */
-	destroy_workqueue(dev->wq);
-
 	ubiblock_cleanup(dev);
 	mutex_unlock(&dev->dev_mutex);
 	kfree(dev);
@@ -620,8 +608,6 @@ static void ubiblock_remove_all(void)
 	struct ubiblock *dev;
 
 	list_for_each_entry_safe(dev, next, &ubiblock_devices, list) {
-		/* Flush pending work and stop workqueue */
-		destroy_workqueue(dev->wq);
 		/* The module is being forcefully removed */
 		WARN_ON(dev->desc);
 		/* Remove from device list */
-- 
1.8.4.5

[PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Convert the driver to blk-mq.
Beside of moving to the modern block interface this change boosts
also the performance of the driver.

nand: device found, Manufacturer ID: 0x2c, Chip ID: 0xda
nand: Micron NAND 256MiB 3,3V 8-bit
nand: 256MiB, SLC, page size: 2048, OOB size: 64

root@debian-armhf:~# dd if=/dev/ubiblock0_0 of=/dev/zero bs=1M
243+1 records in
243+1 records out
255080448 bytes (255 MB) copied, 4.39295 s, 58.1 MB/s

vs.

root@debian-armhf:~# dd if=/dev/ubiblock0_0 of=/dev/zero bs=1M
243+1 records in
243+1 records out
255080448 bytes (255 MB) copied, 2.87676 s, 88.7 MB/s

Cc: hch@infradead.org
Cc: axboe@fb.com
Cc: tom.leiming@gmail.com
Signed-off-by: Richard Weinberger <richard@nod.at>
Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
---
 drivers/mtd/ubi/block.c | 202 ++++++++++++++++++++++--------------------------
 1 file changed, 94 insertions(+), 108 deletions(-)

diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
index 6b6bce2..00caf46 100644
--- a/drivers/mtd/ubi/block.c
+++ b/drivers/mtd/ubi/block.c
@@ -42,11 +42,12 @@
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
-#include <linux/vmalloc.h>
 #include <linux/mtd/ubi.h>
 #include <linux/workqueue.h>
 #include <linux/blkdev.h>
+#include <linux/blk-mq.h>
 #include <linux/hdreg.h>
+#include <linux/scatterlist.h>
 #include <asm/div64.h>
 
 #include "ubi-media.h"
@@ -67,6 +68,11 @@ struct ubiblock_param {
 	char name[UBIBLOCK_PARAM_LEN+1];
 };
 
+struct ubiblock_pdu {
+	struct work_struct work;
+	struct ubi_sgl usgl;
+};
+
 /* Numbers of elements set in the @ubiblock_param array */
 static int ubiblock_devs __initdata;
 
@@ -84,11 +90,10 @@ struct ubiblock {
 	struct request_queue *rq;
 
 	struct workqueue_struct *wq;
-	struct work_struct work;
 
 	struct mutex dev_mutex;
-	spinlock_t queue_lock;
 	struct list_head list;
+	struct blk_mq_tag_set tag_set;
 };
 
 /* Linked list of all ubiblock instances */
@@ -181,31 +186,20 @@ static struct ubiblock *find_dev_nolock(int ubi_num, int vol_id)
 	return NULL;
 }
 
-static int ubiblock_read_to_buf(struct ubiblock *dev, char *buffer,
-				int leb, int offset, int len)
+static int ubiblock_read(struct ubiblock_pdu *pdu)
 {
-	int ret;
+	int ret, leb, offset, bytes_left, to_read;
+	u64 pos;
+	struct request *req = blk_mq_rq_from_pdu(pdu);
+	struct ubiblock *dev = req->q->queuedata;
 
-	ret = ubi_read(dev->desc, leb, buffer, offset, len);
-	if (ret) {
-		dev_err(disk_to_dev(dev->gd), "%d while reading from LEB %d (offset %d, length %d)",
-			ret, leb, offset, len);
-		return ret;
-	}
-	return 0;
-}
-
-static int ubiblock_read(struct ubiblock *dev, char *buffer,
-			 sector_t sec, int len)
-{
-	int ret, leb, offset;
-	int bytes_left = len;
-	int to_read = len;
-	u64 pos = sec << 9;
+	to_read = blk_rq_bytes(req);
+	pos = blk_rq_pos(req) << 9;
 
 	/* Get LEB:offset address to read from */
 	offset = do_div(pos, dev->leb_size);
 	leb = pos;
+	bytes_left = to_read;
 
 	while (bytes_left) {
 		/*
@@ -215,11 +209,10 @@ static int ubiblock_read(struct ubiblock *dev, char *buffer,
 		if (offset + to_read > dev->leb_size)
 			to_read = dev->leb_size - offset;
 
-		ret = ubiblock_read_to_buf(dev, buffer, leb, offset, to_read);
-		if (ret)
+		ret = ubi_read_sg(dev->desc, leb, &pdu->usgl, offset, to_read);
+		if (ret < 0)
 			return ret;
 
-		buffer += to_read;
 		bytes_left -= to_read;
 		to_read = bytes_left;
 		leb += 1;
@@ -228,79 +221,6 @@ static int ubiblock_read(struct ubiblock *dev, char *buffer,
 	return 0;
 }
 
-static int do_ubiblock_request(struct ubiblock *dev, struct request *req)
-{
-	int len, ret;
-	sector_t sec;
-
-	if (req->cmd_type != REQ_TYPE_FS)
-		return -EIO;
-
-	if (blk_rq_pos(req) + blk_rq_cur_sectors(req) >
-	    get_capacity(req->rq_disk))
-		return -EIO;
-
-	if (rq_data_dir(req) != READ)
-		return -ENOSYS; /* Write not implemented */
-
-	sec = blk_rq_pos(req);
-	len = blk_rq_cur_bytes(req);
-
-	/*
-	 * Let's prevent the device from being removed while we're doing I/O
-	 * work. Notice that this means we serialize all the I/O operations,
-	 * but it's probably of no impact given the NAND core serializes
-	 * flash access anyway.
-	 */
-	mutex_lock(&dev->dev_mutex);
-	ret = ubiblock_read(dev, bio_data(req->bio), sec, len);
-	mutex_unlock(&dev->dev_mutex);
-
-	return ret;
-}
-
-static void ubiblock_do_work(struct work_struct *work)
-{
-	struct ubiblock *dev =
-		container_of(work, struct ubiblock, work);
-	struct request_queue *rq = dev->rq;
-	struct request *req;
-	int res;
-
-	spin_lock_irq(rq->queue_lock);
-
-	req = blk_fetch_request(rq);
-	while (req) {
-
-		spin_unlock_irq(rq->queue_lock);
-		res = do_ubiblock_request(dev, req);
-		spin_lock_irq(rq->queue_lock);
-
-		/*
-		 * If we're done with this request,
-		 * we need to fetch a new one
-		 */
-		if (!__blk_end_request_cur(req, res))
-			req = blk_fetch_request(rq);
-	}
-
-	spin_unlock_irq(rq->queue_lock);
-}
-
-static void ubiblock_request(struct request_queue *rq)
-{
-	struct ubiblock *dev;
-	struct request *req;
-
-	dev = rq->queuedata;
-
-	if (!dev)
-		while ((req = blk_fetch_request(rq)) != NULL)
-			__blk_end_request_all(req, -ENODEV);
-	else
-		queue_work(dev->wq, &dev->work);
-}
-
 static int ubiblock_open(struct block_device *bdev, fmode_t mode)
 {
 	struct ubiblock *dev = bdev->bd_disk->private_data;
@@ -374,6 +294,57 @@ static const struct block_device_operations ubiblock_ops = {
 	.getgeo	= ubiblock_getgeo,
 };
 
+static void ubiblock_do_work(struct work_struct *work)
+{
+	int ret;
+	struct ubiblock_pdu *pdu = container_of(work, struct ubiblock_pdu, work);
+	struct request *req = blk_mq_rq_from_pdu(pdu);
+
+	blk_mq_start_request(req);
+	blk_rq_map_sg(req->q, req, pdu->usgl.sg);
+
+	ret = ubiblock_read(pdu);
+	blk_mq_end_request(req, ret);
+}
+
+static int ubiblock_queue_rq(struct blk_mq_hw_ctx *hctx,
+			     const struct blk_mq_queue_data *bd)
+{
+	struct request *req = bd->rq;
+	struct ubiblock *dev = hctx->queue->queuedata;
+	struct ubiblock_pdu *pdu = blk_mq_rq_to_pdu(req);
+
+	if (req->cmd_type != REQ_TYPE_FS)
+		return BLK_MQ_RQ_QUEUE_ERROR;
+
+	if (rq_data_dir(req) != READ)
+		return BLK_MQ_RQ_QUEUE_ERROR; /* Write not implemented */
+
+	ubi_sgl_init(&pdu->usgl);
+	queue_work(dev->wq, &pdu->work);
+
+	return BLK_MQ_RQ_QUEUE_OK;
+}
+
+static int ubiblock_init_request(void *data, struct request *req,
+				 unsigned int hctx_idx,
+				 unsigned int request_idx,
+				 unsigned int numa_node)
+{
+	struct ubiblock_pdu *pdu = blk_mq_rq_to_pdu(req);
+
+	sg_init_table(pdu->usgl.sg, UBI_MAX_SG_COUNT);
+	INIT_WORK(&pdu->work, ubiblock_do_work);
+
+	return 0;
+}
+
+static struct blk_mq_ops ubiblock_mq_ops = {
+	.queue_rq       = ubiblock_queue_rq,
+	.init_request	= ubiblock_init_request,
+	.map_queue      = blk_mq_map_queue,
+};
+
 int ubiblock_create(struct ubi_volume_info *vi)
 {
 	struct ubiblock *dev;
@@ -417,13 +388,27 @@ int ubiblock_create(struct ubi_volume_info *vi)
 	set_capacity(gd, disk_capacity);
 	dev->gd = gd;
 
-	spin_lock_init(&dev->queue_lock);
-	dev->rq = blk_init_queue(ubiblock_request, &dev->queue_lock);
+	dev->tag_set.ops = &ubiblock_mq_ops;
+	dev->tag_set.queue_depth = 64;
+	dev->tag_set.numa_node = NUMA_NO_NODE;
+	dev->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
+	dev->tag_set.cmd_size = sizeof(struct ubiblock_pdu);
+	dev->tag_set.driver_data = dev;
+	dev->tag_set.nr_hw_queues = 1;
+
+	ret = blk_mq_alloc_tag_set(&dev->tag_set);
+	if (ret) {
+		dev_err(disk_to_dev(dev->gd), "blk_mq_alloc_tag_set failed");
+		goto out_put_disk;
+	}
+
+	dev->rq = blk_mq_init_queue(&dev->tag_set);
 	if (!dev->rq) {
-		dev_err(disk_to_dev(gd), "blk_init_queue failed");
+		dev_err(disk_to_dev(gd), "blk_mq_init_queue failed");
 		ret = -ENODEV;
-		goto out_put_disk;
+		goto out_free_tags;
 	}
+	blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT);
 
 	dev->rq->queuedata = dev;
 	dev->gd->queue = dev->rq;
@@ -437,7 +422,6 @@ int ubiblock_create(struct ubi_volume_info *vi)
 		ret = -ENOMEM;
 		goto out_free_queue;
 	}
-	INIT_WORK(&dev->work, ubiblock_do_work);
 
 	mutex_lock(&devices_mutex);
 	list_add_tail(&dev->list, &ubiblock_devices);
@@ -451,6 +435,8 @@ int ubiblock_create(struct ubi_volume_info *vi)
 
 out_free_queue:
 	blk_cleanup_queue(dev->rq);
+out_free_tags:
+	blk_mq_free_tag_set(&dev->tag_set);
 out_put_disk:
 	put_disk(dev->gd);
 out_free_dev:
@@ -461,8 +447,13 @@ out_free_dev:
 
 static void ubiblock_cleanup(struct ubiblock *dev)
 {
+	/* Stop new requests to arrive */
 	del_gendisk(dev->gd);
+	/* Flush pending work */
+	destroy_workqueue(dev->wq);
+	/* Finally destroy the blk queue */
 	blk_cleanup_queue(dev->rq);
+	blk_mq_free_tag_set(&dev->tag_set);
 	dev_info(disk_to_dev(dev->gd), "released");
 	put_disk(dev->gd);
 }
@@ -490,9 +481,6 @@ int ubiblock_remove(struct ubi_volume_info *vi)
 	list_del(&dev->list);
 	mutex_unlock(&devices_mutex);
 
-	/* Flush pending work and stop this workqueue */
-	destroy_workqueue(dev->wq);
-
 	ubiblock_cleanup(dev);
 	mutex_unlock(&dev->dev_mutex);
 	kfree(dev);
@@ -620,8 +608,6 @@ static void ubiblock_remove_all(void)
 	struct ubiblock *dev;
 
 	list_for_each_entry_safe(dev, next, &ubiblock_devices, list) {
-		/* Flush pending work and stop workqueue */
-		destroy_workqueue(dev->wq);
 		/* The module is being forcefully removed */
 		WARN_ON(dev->desc);
 		/* Remove from device list */
-- 
1.8.4.5

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Christoph Hellwig]

> +	struct ubi_sgl usgl;

Btw, what's in struct ubi_sgl?  Can't find that in my tree.

> +static void ubiblock_do_work(struct work_struct *work)
> +{
> +	int ret;
> +	struct ubiblock_pdu *pdu = container_of(work, struct ubiblock_pdu, work);
> +	struct request *req = blk_mq_rq_from_pdu(pdu);
> +
> +	blk_mq_start_request(req);
> +	blk_rq_map_sg(req->q, req, pdu->usgl.sg);

blk_rq_map_sg returns the number of entries actually mapped, which
might be smaller than the number passed in due to merging.

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Christoph Hellwig]

> +	struct ubi_sgl usgl;

Btw, what's in struct ubi_sgl?  Can't find that in my tree.

> +static void ubiblock_do_work(struct work_struct *work)
> +{
> +	int ret;
> +	struct ubiblock_pdu *pdu = container_of(work, struct ubiblock_pdu, work);
> +	struct request *req = blk_mq_rq_from_pdu(pdu);
> +
> +	blk_mq_start_request(req);
> +	blk_rq_map_sg(req->q, req, pdu->usgl.sg);

blk_rq_map_sg returns the number of entries actually mapped, which
might be smaller than the number passed in due to merging.

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Am 13.01.2015 um 17:25 schrieb Christoph Hellwig:
>> +	struct ubi_sgl usgl;
> 
> Btw, what's in struct ubi_sgl?  Can't find that in my tree.

"[PATCH 1/2] UBI: Add initial support for scatter gather" adds it.

/**
 * struct ubi_sgl - UBI scatter gather list data structure.
 * @list_pos: current position in @sg[]
 * @page_pos: current position in @sg[@list_pos]
 * @sg: the scatter gather list itself
 *
 * ubi_sgl is a wrapper around a scatter list which keeps track of the
 * current position in the list and the current list item such that
 * it can be used across multiple ubi_leb_read_sg() calls.
 */
struct ubi_sgl {
        int list_pos;
        int page_pos;
        struct scatterlist sg[UBI_MAX_SG_COUNT];
};

>> +static void ubiblock_do_work(struct work_struct *work)
>> +{
>> +	int ret;
>> +	struct ubiblock_pdu *pdu = container_of(work, struct ubiblock_pdu, work);
>> +	struct request *req = blk_mq_rq_from_pdu(pdu);
>> +
>> +	blk_mq_start_request(req);
>> +	blk_rq_map_sg(req->q, req, pdu->usgl.sg);
> 
> blk_rq_map_sg returns the number of entries actually mapped, which
> might be smaller than the number passed in due to merging.

Yep, but the ubi_sql has a fixed number of scatterlist entries, UBI_MAX_SG_COUNT.
And I limit it also to that using: blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT);

Is there another reason why I should use the return value of blk_rq_map_sg()?
Please also note that the UBI block driver is read-only.

Thanks,
//richard

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Am 13.01.2015 um 17:25 schrieb Christoph Hellwig:
>> +	struct ubi_sgl usgl;
> 
> Btw, what's in struct ubi_sgl?  Can't find that in my tree.

"[PATCH 1/2] UBI: Add initial support for scatter gather" adds it.

/**
 * struct ubi_sgl - UBI scatter gather list data structure.
 * @list_pos: current position in @sg[]
 * @page_pos: current position in @sg[@list_pos]
 * @sg: the scatter gather list itself
 *
 * ubi_sgl is a wrapper around a scatter list which keeps track of the
 * current position in the list and the current list item such that
 * it can be used across multiple ubi_leb_read_sg() calls.
 */
struct ubi_sgl {
        int list_pos;
        int page_pos;
        struct scatterlist sg[UBI_MAX_SG_COUNT];
};

>> +static void ubiblock_do_work(struct work_struct *work)
>> +{
>> +	int ret;
>> +	struct ubiblock_pdu *pdu = container_of(work, struct ubiblock_pdu, work);
>> +	struct request *req = blk_mq_rq_from_pdu(pdu);
>> +
>> +	blk_mq_start_request(req);
>> +	blk_rq_map_sg(req->q, req, pdu->usgl.sg);
> 
> blk_rq_map_sg returns the number of entries actually mapped, which
> might be smaller than the number passed in due to merging.

Yep, but the ubi_sql has a fixed number of scatterlist entries, UBI_MAX_SG_COUNT.
And I limit it also to that using: blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT);

Is there another reason why I should use the return value of blk_rq_map_sg()?
Please also note that the UBI block driver is read-only.

Thanks,
//richard

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Jens Axboe]

On 01/13/2015 03:51 PM, Richard Weinberger wrote:
> Am 13.01.2015 um 17:25 schrieb Christoph Hellwig:
>>> +	struct ubi_sgl usgl;
>>
>> Btw, what's in struct ubi_sgl?  Can't find that in my tree.
> 
> "[PATCH 1/2] UBI: Add initial support for scatter gather" adds it.
> 
> /**
>  * struct ubi_sgl - UBI scatter gather list data structure.
>  * @list_pos: current position in @sg[]
>  * @page_pos: current position in @sg[@list_pos]
>  * @sg: the scatter gather list itself
>  *
>  * ubi_sgl is a wrapper around a scatter list which keeps track of the
>  * current position in the list and the current list item such that
>  * it can be used across multiple ubi_leb_read_sg() calls.
>  */
> struct ubi_sgl {
>         int list_pos;
>         int page_pos;
>         struct scatterlist sg[UBI_MAX_SG_COUNT];
> };
> 
>>> +static void ubiblock_do_work(struct work_struct *work)
>>> +{
>>> +	int ret;
>>> +	struct ubiblock_pdu *pdu = container_of(work, struct ubiblock_pdu, work);
>>> +	struct request *req = blk_mq_rq_from_pdu(pdu);
>>> +
>>> +	blk_mq_start_request(req);
>>> +	blk_rq_map_sg(req->q, req, pdu->usgl.sg);
>>
>> blk_rq_map_sg returns the number of entries actually mapped, which
>> might be smaller than the number passed in due to merging.
> 
> Yep, but the ubi_sql has a fixed number of scatterlist entries, UBI_MAX_SG_COUNT.
> And I limit it also to that using: blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT);
> 
> Is there another reason why I should use the return value of blk_rq_map_sg()?
> Please also note that the UBI block driver is read-only.

It can return less than what you asked for, if segments are coalesced.
Read/write, doesn't matter. You should always use the returned value as
the indication of how many segments to access in pdu->usgl.sg for data
transfer.

-- 
Jens Axboe

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Jens Axboe]

On 01/13/2015 03:51 PM, Richard Weinberger wrote:
> Am 13.01.2015 um 17:25 schrieb Christoph Hellwig:
>>> +	struct ubi_sgl usgl;
>>
>> Btw, what's in struct ubi_sgl?  Can't find that in my tree.
> 
> "[PATCH 1/2] UBI: Add initial support for scatter gather" adds it.
> 
> /**
>  * struct ubi_sgl - UBI scatter gather list data structure.
>  * @list_pos: current position in @sg[]
>  * @page_pos: current position in @sg[@list_pos]
>  * @sg: the scatter gather list itself
>  *
>  * ubi_sgl is a wrapper around a scatter list which keeps track of the
>  * current position in the list and the current list item such that
>  * it can be used across multiple ubi_leb_read_sg() calls.
>  */
> struct ubi_sgl {
>         int list_pos;
>         int page_pos;
>         struct scatterlist sg[UBI_MAX_SG_COUNT];
> };
> 
>>> +static void ubiblock_do_work(struct work_struct *work)
>>> +{
>>> +	int ret;
>>> +	struct ubiblock_pdu *pdu = container_of(work, struct ubiblock_pdu, work);
>>> +	struct request *req = blk_mq_rq_from_pdu(pdu);
>>> +
>>> +	blk_mq_start_request(req);
>>> +	blk_rq_map_sg(req->q, req, pdu->usgl.sg);
>>
>> blk_rq_map_sg returns the number of entries actually mapped, which
>> might be smaller than the number passed in due to merging.
> 
> Yep, but the ubi_sql has a fixed number of scatterlist entries, UBI_MAX_SG_COUNT.
> And I limit it also to that using: blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT);
> 
> Is there another reason why I should use the return value of blk_rq_map_sg()?
> Please also note that the UBI block driver is read-only.

It can return less than what you asked for, if segments are coalesced.
Read/write, doesn't matter. You should always use the returned value as
the indication of how many segments to access in pdu->usgl.sg for data
transfer.

-- 
Jens Axboe

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Am 13.01.2015 um 23:54 schrieb Jens Axboe:
>>> blk_rq_map_sg returns the number of entries actually mapped, which
>>> might be smaller than the number passed in due to merging.
>>
>> Yep, but the ubi_sql has a fixed number of scatterlist entries, UBI_MAX_SG_COUNT.
>> And I limit it also to that using: blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT);
>>
>> Is there another reason why I should use the return value of blk_rq_map_sg()?
>> Please also note that the UBI block driver is read-only.
> 
> It can return less than what you asked for, if segments are coalesced.
> Read/write, doesn't matter. You should always use the returned value as
> the indication of how many segments to access in pdu->usgl.sg for data
> transfer.

Sorry, I don't fully understand.

Currently the driver does:
to_read = blk_rq_bytes(req);
Then it fills pdu->usgl.sg up to to_read bytes
and calls blk_mq_end_request().

If I understand you correctly it can happen that blk_rq_bytes() returns
more bytes than blk_rq_map_sg() allocated, right?

Thanks,
//richard

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Am 13.01.2015 um 23:54 schrieb Jens Axboe:
>>> blk_rq_map_sg returns the number of entries actually mapped, which
>>> might be smaller than the number passed in due to merging.
>>
>> Yep, but the ubi_sql has a fixed number of scatterlist entries, UBI_MAX_SG_COUNT.
>> And I limit it also to that using: blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT);
>>
>> Is there another reason why I should use the return value of blk_rq_map_sg()?
>> Please also note that the UBI block driver is read-only.
> 
> It can return less than what you asked for, if segments are coalesced.
> Read/write, doesn't matter. You should always use the returned value as
> the indication of how many segments to access in pdu->usgl.sg for data
> transfer.

Sorry, I don't fully understand.

Currently the driver does:
to_read = blk_rq_bytes(req);
Then it fills pdu->usgl.sg up to to_read bytes
and calls blk_mq_end_request().

If I understand you correctly it can happen that blk_rq_bytes() returns
more bytes than blk_rq_map_sg() allocated, right?

Thanks,
//richard

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Jens Axboe]

On 01/13/2015 04:17 PM, Richard Weinberger wrote:
> Am 13.01.2015 um 23:54 schrieb Jens Axboe:
>>>> blk_rq_map_sg returns the number of entries actually mapped, which
>>>> might be smaller than the number passed in due to merging.
>>>
>>> Yep, but the ubi_sql has a fixed number of scatterlist entries, UBI_MAX_SG_COUNT.
>>> And I limit it also to that using: blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT);
>>>
>>> Is there another reason why I should use the return value of blk_rq_map_sg()?
>>> Please also note that the UBI block driver is read-only.
>>
>> It can return less than what you asked for, if segments are coalesced.
>> Read/write, doesn't matter. You should always use the returned value as
>> the indication of how many segments to access in pdu->usgl.sg for data
>> transfer.
> 
> Sorry, I don't fully understand.
> 
> Currently the driver does:
> to_read = blk_rq_bytes(req);
> Then it fills pdu->usgl.sg up to to_read bytes
> and calls blk_mq_end_request().
> 
> If I understand you correctly it can happen that blk_rq_bytes() returns
> more bytes than blk_rq_map_sg() allocated, right?

No, the number of bytes will be the same, no magic is involved :-)

But lets say the initial request has 4 bios, with each 2 pages, for a
total of 8 segments. Lets further assume that the pages in each bio are
contiguous, so that blk_rq_map_sg() will map this to 4 sg elements, each
2xpages long.

Now, this may already be handled just fine, and you don't need to
update/store the actual sg count. I just looked at the source, and I'm
assuming it'll do the right thing (ubi_read_sg() will bump the active sg
element, when that size has been consumed), but I don't have
ubi_read_sg() in my tree to verify.

-- 
Jens Axboe

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Jens Axboe]

On 01/13/2015 04:17 PM, Richard Weinberger wrote:
> Am 13.01.2015 um 23:54 schrieb Jens Axboe:
>>>> blk_rq_map_sg returns the number of entries actually mapped, which
>>>> might be smaller than the number passed in due to merging.
>>>
>>> Yep, but the ubi_sql has a fixed number of scatterlist entries, UBI_MAX_SG_COUNT.
>>> And I limit it also to that using: blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT);
>>>
>>> Is there another reason why I should use the return value of blk_rq_map_sg()?
>>> Please also note that the UBI block driver is read-only.
>>
>> It can return less than what you asked for, if segments are coalesced.
>> Read/write, doesn't matter. You should always use the returned value as
>> the indication of how many segments to access in pdu->usgl.sg for data
>> transfer.
> 
> Sorry, I don't fully understand.
> 
> Currently the driver does:
> to_read = blk_rq_bytes(req);
> Then it fills pdu->usgl.sg up to to_read bytes
> and calls blk_mq_end_request().
> 
> If I understand you correctly it can happen that blk_rq_bytes() returns
> more bytes than blk_rq_map_sg() allocated, right?

No, the number of bytes will be the same, no magic is involved :-)

But lets say the initial request has 4 bios, with each 2 pages, for a
total of 8 segments. Lets further assume that the pages in each bio are
contiguous, so that blk_rq_map_sg() will map this to 4 sg elements, each
2xpages long.

Now, this may already be handled just fine, and you don't need to
update/store the actual sg count. I just looked at the source, and I'm
assuming it'll do the right thing (ubi_read_sg() will bump the active sg
element, when that size has been consumed), but I don't have
ubi_read_sg() in my tree to verify.

-- 
Jens Axboe

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Am 14.01.2015 um 00:30 schrieb Jens Axboe:
>> If I understand you correctly it can happen that blk_rq_bytes() returns
>> more bytes than blk_rq_map_sg() allocated, right?
> 
> No, the number of bytes will be the same, no magic is involved :-)

Good to know. :)

> But lets say the initial request has 4 bios, with each 2 pages, for a
> total of 8 segments. Lets further assume that the pages in each bio are
> contiguous, so that blk_rq_map_sg() will map this to 4 sg elements, each
> 2xpages long.
> 
> Now, this may already be handled just fine, and you don't need to
> update/store the actual sg count. I just looked at the source, and I'm
> assuming it'll do the right thing (ubi_read_sg() will bump the active sg
> element, when that size has been consumed), but I don't have
> ubi_read_sg() in my tree to verify.

Currently the sg count is hard coded to UBI_MAX_SG_COUNT.

I'm sorry, I forgot to CC you and hch to this patch:
https://lkml.org/lkml/2015/1/10/204

Thanks,
//richard

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Am 14.01.2015 um 00:30 schrieb Jens Axboe:
>> If I understand you correctly it can happen that blk_rq_bytes() returns
>> more bytes than blk_rq_map_sg() allocated, right?
> 
> No, the number of bytes will be the same, no magic is involved :-)

Good to know. :)

> But lets say the initial request has 4 bios, with each 2 pages, for a
> total of 8 segments. Lets further assume that the pages in each bio are
> contiguous, so that blk_rq_map_sg() will map this to 4 sg elements, each
> 2xpages long.
> 
> Now, this may already be handled just fine, and you don't need to
> update/store the actual sg count. I just looked at the source, and I'm
> assuming it'll do the right thing (ubi_read_sg() will bump the active sg
> element, when that size has been consumed), but I don't have
> ubi_read_sg() in my tree to verify.

Currently the sg count is hard coded to UBI_MAX_SG_COUNT.

I'm sorry, I forgot to CC you and hch to this patch:
https://lkml.org/lkml/2015/1/10/204

Thanks,
//richard

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Jens Axboe]

On 01/13/2015 04:36 PM, Richard Weinberger wrote:
> 
> 
> Am 14.01.2015 um 00:30 schrieb Jens Axboe:
>>> If I understand you correctly it can happen that blk_rq_bytes() returns
>>> more bytes than blk_rq_map_sg() allocated, right?
>>
>> No, the number of bytes will be the same, no magic is involved :-)
> 
> Good to know. :)
> 
>> But lets say the initial request has 4 bios, with each 2 pages, for a
>> total of 8 segments. Lets further assume that the pages in each bio are
>> contiguous, so that blk_rq_map_sg() will map this to 4 sg elements, each
>> 2xpages long.
>>
>> Now, this may already be handled just fine, and you don't need to
>> update/store the actual sg count. I just looked at the source, and I'm
>> assuming it'll do the right thing (ubi_read_sg() will bump the active sg
>> element, when that size has been consumed), but I don't have
>> ubi_read_sg() in my tree to verify.
> 
> Currently the sg count is hard coded to UBI_MAX_SG_COUNT.

The max count doesn't matter, that just provides you a guarantee that
you'll never receive a request that maps to more than that. The point
I'm trying to make is that if you receive 8 segments and it maps to 4,
then you better not look at segments 5..8 after it being mapped.
Whatever the max is, doesn't matter in this conversation.

> I'm sorry, I forgot to CC you and hch to this patch:

Which is as I suspected, you'll do each segment to the length specified,
hence you don't need to track the returned count from blk_rq_map_sg().

-- 
Jens Axboe

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Jens Axboe]

On 01/13/2015 04:36 PM, Richard Weinberger wrote:
> 
> 
> Am 14.01.2015 um 00:30 schrieb Jens Axboe:
>>> If I understand you correctly it can happen that blk_rq_bytes() returns
>>> more bytes than blk_rq_map_sg() allocated, right?
>>
>> No, the number of bytes will be the same, no magic is involved :-)
> 
> Good to know. :)
> 
>> But lets say the initial request has 4 bios, with each 2 pages, for a
>> total of 8 segments. Lets further assume that the pages in each bio are
>> contiguous, so that blk_rq_map_sg() will map this to 4 sg elements, each
>> 2xpages long.
>>
>> Now, this may already be handled just fine, and you don't need to
>> update/store the actual sg count. I just looked at the source, and I'm
>> assuming it'll do the right thing (ubi_read_sg() will bump the active sg
>> element, when that size has been consumed), but I don't have
>> ubi_read_sg() in my tree to verify.
> 
> Currently the sg count is hard coded to UBI_MAX_SG_COUNT.

The max count doesn't matter, that just provides you a guarantee that
you'll never receive a request that maps to more than that. The point
I'm trying to make is that if you receive 8 segments and it maps to 4,
then you better not look at segments 5..8 after it being mapped.
Whatever the max is, doesn't matter in this conversation.

> I'm sorry, I forgot to CC you and hch to this patch:

Which is as I suspected, you'll do each segment to the length specified,
hence you don't need to track the returned count from blk_rq_map_sg().

-- 
Jens Axboe

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Am 14.01.2015 um 01:23 schrieb Jens Axboe:
> On 01/13/2015 04:36 PM, Richard Weinberger wrote:
>>
>>
>> Am 14.01.2015 um 00:30 schrieb Jens Axboe:
>>>> If I understand you correctly it can happen that blk_rq_bytes() returns
>>>> more bytes than blk_rq_map_sg() allocated, right?
>>>
>>> No, the number of bytes will be the same, no magic is involved :-)
>>
>> Good to know. :)
>>
>>> But lets say the initial request has 4 bios, with each 2 pages, for a
>>> total of 8 segments. Lets further assume that the pages in each bio are
>>> contiguous, so that blk_rq_map_sg() will map this to 4 sg elements, each
>>> 2xpages long.
>>>
>>> Now, this may already be handled just fine, and you don't need to
>>> update/store the actual sg count. I just looked at the source, and I'm
>>> assuming it'll do the right thing (ubi_read_sg() will bump the active sg
>>> element, when that size has been consumed), but I don't have
>>> ubi_read_sg() in my tree to verify.
>>
>> Currently the sg count is hard coded to UBI_MAX_SG_COUNT.
> 
> The max count doesn't matter, that just provides you a guarantee that
> you'll never receive a request that maps to more than that. The point
> I'm trying to make is that if you receive 8 segments and it maps to 4,
> then you better not look at segments 5..8 after it being mapped.
> Whatever the max is, doesn't matter in this conversation.
> 
>> I'm sorry, I forgot to CC you and hch to this patch:
> 
> Which is as I suspected, you'll do each segment to the length specified,
> hence you don't need to track the returned count from blk_rq_map_sg().

Thanks a lot for the kind explanation, Jens!
I'll add a comment the usage of blk_rq_map_sg() to avoid further confusion.
Am I allowed to add your Reviewed-by too?

Thanks,
//richard

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Am 14.01.2015 um 01:23 schrieb Jens Axboe:
> On 01/13/2015 04:36 PM, Richard Weinberger wrote:
>>
>>
>> Am 14.01.2015 um 00:30 schrieb Jens Axboe:
>>>> If I understand you correctly it can happen that blk_rq_bytes() returns
>>>> more bytes than blk_rq_map_sg() allocated, right?
>>>
>>> No, the number of bytes will be the same, no magic is involved :-)
>>
>> Good to know. :)
>>
>>> But lets say the initial request has 4 bios, with each 2 pages, for a
>>> total of 8 segments. Lets further assume that the pages in each bio are
>>> contiguous, so that blk_rq_map_sg() will map this to 4 sg elements, each
>>> 2xpages long.
>>>
>>> Now, this may already be handled just fine, and you don't need to
>>> update/store the actual sg count. I just looked at the source, and I'm
>>> assuming it'll do the right thing (ubi_read_sg() will bump the active sg
>>> element, when that size has been consumed), but I don't have
>>> ubi_read_sg() in my tree to verify.
>>
>> Currently the sg count is hard coded to UBI_MAX_SG_COUNT.
> 
> The max count doesn't matter, that just provides you a guarantee that
> you'll never receive a request that maps to more than that. The point
> I'm trying to make is that if you receive 8 segments and it maps to 4,
> then you better not look at segments 5..8 after it being mapped.
> Whatever the max is, doesn't matter in this conversation.
> 
>> I'm sorry, I forgot to CC you and hch to this patch:
> 
> Which is as I suspected, you'll do each segment to the length specified,
> hence you don't need to track the returned count from blk_rq_map_sg().

Thanks a lot for the kind explanation, Jens!
I'll add a comment the usage of blk_rq_map_sg() to avoid further confusion.
Am I allowed to add your Reviewed-by too?

Thanks,
//richard

Re: [PATCH 1/2 v2] UBI: Add initial support for scatter gather

[Richard Weinberger]

Am 10.01.2015 um 22:52 schrieb Richard Weinberger:
> Adds a new set of functions to deal with scatter gather.
> ubi_eba_read_leb_sg() will read from a LEB into a scatter gather list.
> The new data structure struct ubi_sgl will be used within UBI to
> hold the scatter gather list itself and metadata to have a cursor
> within the list.
> 
> Signed-off-by: Richard Weinberger <richard@nod.at>
> Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

Can I please get a Reviewed-by for this patch?

Thanks,
//richard

Re: [PATCH 1/2 v2] UBI: Add initial support for scatter gather

[Richard Weinberger]

Am 10.01.2015 um 22:52 schrieb Richard Weinberger:
> Adds a new set of functions to deal with scatter gather.
> ubi_eba_read_leb_sg() will read from a LEB into a scatter gather list.
> The new data structure struct ubi_sgl will be used within UBI to
> hold the scatter gather list itself and metadata to have a cursor
> within the list.
> 
> Signed-off-by: Richard Weinberger <richard@nod.at>
> Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

Can I please get a Reviewed-by for this patch?

Thanks,
//richard

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Am 14.01.2015 um 09:39 schrieb Richard Weinberger:
> Am 14.01.2015 um 01:23 schrieb Jens Axboe:
>> Which is as I suspected, you'll do each segment to the length specified,
>> hence you don't need to track the returned count from blk_rq_map_sg().
> 
> Thanks a lot for the kind explanation, Jens!
> I'll add a comment the usage of blk_rq_map_sg() to avoid further confusion.
> Am I allowed to add your Reviewed-by too?

Ping?
I'd like to add a Reviewed-by to this patch.

Thanks,
//richard

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Richard Weinberger]

Am 14.01.2015 um 09:39 schrieb Richard Weinberger:
> Am 14.01.2015 um 01:23 schrieb Jens Axboe:
>> Which is as I suspected, you'll do each segment to the length specified,
>> hence you don't need to track the returned count from blk_rq_map_sg().
> 
> Thanks a lot for the kind explanation, Jens!
> I'll add a comment the usage of blk_rq_map_sg() to avoid further confusion.
> Am I allowed to add your Reviewed-by too?

Ping?
I'd like to add a Reviewed-by to this patch.

Thanks,
//richard

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Jens Axboe]

On 01/26/2015 04:55 PM, Richard Weinberger wrote:
> Am 14.01.2015 um 09:39 schrieb Richard Weinberger:
>> Am 14.01.2015 um 01:23 schrieb Jens Axboe:
>>> Which is as I suspected, you'll do each segment to the length specified,
>>> hence you don't need to track the returned count from blk_rq_map_sg().
>>
>> Thanks a lot for the kind explanation, Jens!
>> I'll add a comment the usage of blk_rq_map_sg() to avoid further confusion.
>> Am I allowed to add your Reviewed-by too?
>
> Ping?
> I'd like to add a Reviewed-by to this patch.

Yup sorry, looks OK to go in from my point of view. You can add my 
reviewed-by.


-- 
Jens Axboe

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Jens Axboe]

On 01/26/2015 04:55 PM, Richard Weinberger wrote:
> Am 14.01.2015 um 09:39 schrieb Richard Weinberger:
>> Am 14.01.2015 um 01:23 schrieb Jens Axboe:
>>> Which is as I suspected, you'll do each segment to the length specified,
>>> hence you don't need to track the returned count from blk_rq_map_sg().
>>
>> Thanks a lot for the kind explanation, Jens!
>> I'll add a comment the usage of blk_rq_map_sg() to avoid further confusion.
>> Am I allowed to add your Reviewed-by too?
>
> Ping?
> I'd like to add a Reviewed-by to this patch.

Yup sorry, looks OK to go in from my point of view. You can add my 
reviewed-by.


-- 
Jens Axboe

Re: [PATCH 1/2 v2] UBI: Add initial support for scatter gather

[Ezequiel Garcia]

On 01/10/2015 06:52 PM, Richard Weinberger wrote:
> Adds a new set of functions to deal with scatter gather.
> ubi_eba_read_leb_sg() will read from a LEB into a scatter gather list.
> The new data structure struct ubi_sgl will be used within UBI to
> hold the scatter gather list itself and metadata to have a cursor
> within the list.
> 
> Signed-off-by: Richard Weinberger <richard@nod.at>
> Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

Three nitpicks below, and my

Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

> ---
>  drivers/mtd/ubi/eba.c   | 56 +++++++++++++++++++++++++++++
>  drivers/mtd/ubi/kapi.c  | 95 +++++++++++++++++++++++++++++++++++++++++--------
>  drivers/mtd/ubi/ubi.h   |  3 ++
>  include/linux/mtd/ubi.h | 46 ++++++++++++++++++++++++
>  4 files changed, 185 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
> index b698534..0aaf707 100644
> --- a/drivers/mtd/ubi/eba.c
> +++ b/drivers/mtd/ubi/eba.c
> @@ -481,6 +481,62 @@ out_unlock:
>  }
>  
>  /**
> + * ubi_eba_read_leb_sg - read data into a scatter gather list.
> + * @ubi: UBI device description object
> + * @vol: volume description object
> + * @lnum: logical eraseblock number
> + * @sgl: UBI scatter gather list to store the read data
> + * @offset: offset from where to read
> + * @len: how many bytes to read
> + * @check: data CRC check flag
> + *
> + * This function works exactly like ubi_eba_read_leb(). But instead of
> + * storing the read data into a buffer it writes to an UBI scatter gather
> + * list.
> + */
> +int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
> +			struct ubi_sgl *sgl, int lnum, int offset, int len,
> +			int check)
> +{
> +	int to_read;
> +	int ret;
> +	struct scatterlist *sg;
> +
> +	for (;;) {
> +		ubi_assert(sgl->list_pos < UBI_MAX_SG_COUNT);
> +		sg = &sgl->sg[sgl->list_pos];
> +		if (len < sg->length - sgl->page_pos)
> +			to_read = len;
> +		else
> +			to_read = sg->length - sgl->page_pos;
> +
> +		ret = ubi_eba_read_leb(ubi, vol, lnum,
> +				       sg_virt(sg) + sgl->page_pos, offset,
> +				       to_read, check);
> +		if (ret < 0)
> +			goto out;

Matter of taste, but isn't it better to just return here?

> +
> +		offset += to_read;
> +		len -= to_read;
> +		if (!len) {
> +			sgl->page_pos += to_read;
> +			if (sgl->page_pos == sg->length) {
> +				sgl->list_pos++;
> +				sgl->page_pos = 0;
> +			}
> +
> +			break;
> +		}
> +
> +		sgl->list_pos++;
> +		sgl->page_pos = 0;
> +	}
> +
> +out:
> +	return ret;
> +}
> +
> +/**
>   * recover_peb - recover from write failure.
>   * @ubi: UBI device description object
>   * @pnum: the physical eraseblock to recover
> diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
> index f3bab66..d0055a2 100644
> --- a/drivers/mtd/ubi/kapi.c
> +++ b/drivers/mtd/ubi/kapi.c
> @@ -355,6 +355,43 @@ void ubi_close_volume(struct ubi_volume_desc *desc)
>  EXPORT_SYMBOL_GPL(ubi_close_volume);
>  
>  /**
> + * leb_read_sanity_check - does sanity checks on read requests.
> + * @desc: volume descriptor
> + * @lnum: logical eraseblock number to read from
> + * @offset: offset within the logical eraseblock to read from
> + * @len: how many bytes to read
> + *
> + * This function is used by ubi_leb_read() and ubi_leb_read_sg()
> + * to perfrom sanity checks.

s/perfrom/perform

> + */
> +static int leb_read_sanity_check(struct ubi_volume_desc *desc, int lnum,
> +				 int offset, int len)
> +{
> +	struct ubi_volume *vol = desc->vol;
> +	struct ubi_device *ubi = vol->ubi;
> +	int vol_id = vol->vol_id;
> +
> +	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
> +	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
> +	    offset + len > vol->usable_leb_size)
> +		return -EINVAL;
> +
> +	if (vol->vol_type == UBI_STATIC_VOLUME) {
> +		if (vol->used_ebs == 0)
> +			/* Empty static UBI volume */
> +			return 0;
> +		if (lnum == vol->used_ebs - 1 &&
> +		    offset + len > vol->last_eb_bytes)
> +			return -EINVAL;
> +	}
> +
> +	if (vol->upd_marker)
> +		return -EBADF;
> +
> +	return 0;
> +}
> +
> +/**
>   * ubi_leb_read - read data.
>   * @desc: volume descriptor
>   * @lnum: logical eraseblock number to read from
> @@ -390,22 +427,10 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
>  
>  	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
>  
> -	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
> -	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
> -	    offset + len > vol->usable_leb_size)
> -		return -EINVAL;
> -
> -	if (vol->vol_type == UBI_STATIC_VOLUME) {
> -		if (vol->used_ebs == 0)
> -			/* Empty static UBI volume */
> -			return 0;
> -		if (lnum == vol->used_ebs - 1 &&
> -		    offset + len > vol->last_eb_bytes)
> -			return -EINVAL;
> -	}
> +	err = leb_read_sanity_check(desc, lnum, offset, len);
> +	if (err < 0)
> +		return err;
>  
> -	if (vol->upd_marker)
> -		return -EBADF;
>  	if (len == 0)
>  		return 0;
>  
> @@ -419,6 +444,46 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
>  }
>  EXPORT_SYMBOL_GPL(ubi_leb_read);
>  
> +
> +/**
> + * ubi_leb_read_sg - read data into a scatter gather list.
> + * @desc: volume descriptor
> + * @lnum: logical eraseblock number to read from
> + * @buf: buffer where to store the read data
> + * @offset: offset within the logical eraseblock to read from
> + * @len: how many bytes to read
> + * @check: whether UBI has to check the read data's CRC or not.
> + *
> + * This function works exactly like ubi_leb_read_sg(). But instead of
> + * storing the read data into a buffer it writes to an UBI scatter gather
> + * list.
> + */
> +int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
> +		    int offset, int len, int check)
> +{
> +	struct ubi_volume *vol = desc->vol;
> +	struct ubi_device *ubi = vol->ubi;
> +	int err, vol_id = vol->vol_id;
> +
> +	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
> +
> +	err = leb_read_sanity_check(desc, lnum, offset, len);
> +	if (err < 0)
> +		return err;
> +
> +	if (len == 0)
> +		return 0;
> +
> +	err = ubi_eba_read_leb_sg(ubi, vol, sgl, lnum, offset, len, check);
> +	if (err && mtd_is_eccerr(err) && vol->vol_type == UBI_STATIC_VOLUME) {
> +		ubi_warn(ubi, "mark volume %d as corrupted", vol_id);
> +		vol->corrupted = 1;
> +	}
> +
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(ubi_leb_read_sg);
> +
>  /**
>   * ubi_leb_write - write data.
>   * @desc: volume descriptor
> diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
> index ee7ac0b..a5283cf 100644
> --- a/drivers/mtd/ubi/ubi.h
> +++ b/drivers/mtd/ubi/ubi.h
> @@ -791,6 +791,9 @@ int ubi_eba_unmap_leb(struct ubi_device *ubi, struct ubi_volume *vol,
>  		      int lnum);
>  int ubi_eba_read_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
>  		     void *buf, int offset, int len, int check);
> +int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
> +			struct ubi_sgl *sgl, int lnum, int offset, int len,
> +			int check);
>  int ubi_eba_write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
>  		      const void *buf, int offset, int len);
>  int ubi_eba_write_leb_st(struct ubi_device *ubi, struct ubi_volume *vol,
> diff --git a/include/linux/mtd/ubi.h b/include/linux/mtd/ubi.h
> index c3918a0..3d5916d 100644
> --- a/include/linux/mtd/ubi.h
> +++ b/include/linux/mtd/ubi.h
> @@ -23,11 +23,16 @@
>  
>  #include <linux/ioctl.h>
>  #include <linux/types.h>
> +#include <linux/scatterlist.h>
>  #include <mtd/ubi-user.h>
>  
>  /* All voumes/LEBs */
>  #define UBI_ALL -1
>  
> +/* Maximum number of scatter gather list entries,
> + * we use only 64 to have a lower memory foot print. */

Multilines comments style is:

/*
 *
 */

> +#define UBI_MAX_SG_COUNT 64
> +
>  /*
>   * enum ubi_open_mode - UBI volume open mode constants.
>   *
> @@ -116,6 +121,35 @@ struct ubi_volume_info {
>  };
>  
>  /**
> + * struct ubi_sgl - UBI scatter gather list data structure.
> + * @list_pos: current position in @sg[]
> + * @page_pos: current position in @sg[@list_pos]
> + * @sg: the scatter gather list itself
> + *
> + * ubi_sgl is a wrapper around a scatter list which keeps track of the
> + * current position in the list and the current list item such that
> + * it can be used across multiple ubi_leb_read_sg() calls.
> + */
> +struct ubi_sgl {
> +	int list_pos;
> +	int page_pos;
> +	struct scatterlist sg[UBI_MAX_SG_COUNT];
> +};
> +
> +/**
> + * ubi_sgl_init - initialize an UBI scatter gather list data structure.
> + * @usgl: the UBI scatter gather struct itself
> + *
> + * Please note that you still have to use sg_init_table() or any adequate
> + * function to initialize the unterlaying struct scatterlist.
> + */
> +static inline void ubi_sgl_init(struct ubi_sgl *usgl)
> +{
> +	usgl->list_pos = 0;
> +	usgl->page_pos = 0;
> +}
> +
> +/**
>   * struct ubi_device_info - UBI device description data structure.
>   * @ubi_num: ubi device number
>   * @leb_size: logical eraseblock size on this UBI device
> @@ -210,6 +244,8 @@ int ubi_unregister_volume_notifier(struct notifier_block *nb);
>  void ubi_close_volume(struct ubi_volume_desc *desc);
>  int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
>  		 int len, int check);
> +int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
> +		   int offset, int len, int check);
>  int ubi_leb_write(struct ubi_volume_desc *desc, int lnum, const void *buf,
>  		  int offset, int len);
>  int ubi_leb_change(struct ubi_volume_desc *desc, int lnum, const void *buf,
> @@ -230,4 +266,14 @@ static inline int ubi_read(struct ubi_volume_desc *desc, int lnum, char *buf,
>  {
>  	return ubi_leb_read(desc, lnum, buf, offset, len, 0);
>  }
> +
> +/*
> + * This function is the same as the 'ubi_leb_read_sg()' function, but it does
> + * not provide the checking capability.
> + */
> +static inline int ubi_read_sg(struct ubi_volume_desc *desc, int lnum,
> +			      struct ubi_sgl *sgl, int offset, int len)
> +{
> +	return ubi_leb_read_sg(desc, lnum, sgl, offset, len, 0);
> +}
>  #endif /* !__LINUX_UBI_H__ */
> 


-- 
Ezequiel Garcia, VanguardiaSur
www.vanguardiasur.com.ar

Re: [PATCH 1/2 v2] UBI: Add initial support for scatter gather

[Ezequiel Garcia]

On 01/10/2015 06:52 PM, Richard Weinberger wrote:
> Adds a new set of functions to deal with scatter gather.
> ubi_eba_read_leb_sg() will read from a LEB into a scatter gather list.
> The new data structure struct ubi_sgl will be used within UBI to
> hold the scatter gather list itself and metadata to have a cursor
> within the list.
> 
> Signed-off-by: Richard Weinberger <richard@nod.at>
> Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

Three nitpicks below, and my

Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

> ---
>  drivers/mtd/ubi/eba.c   | 56 +++++++++++++++++++++++++++++
>  drivers/mtd/ubi/kapi.c  | 95 +++++++++++++++++++++++++++++++++++++++++--------
>  drivers/mtd/ubi/ubi.h   |  3 ++
>  include/linux/mtd/ubi.h | 46 ++++++++++++++++++++++++
>  4 files changed, 185 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
> index b698534..0aaf707 100644
> --- a/drivers/mtd/ubi/eba.c
> +++ b/drivers/mtd/ubi/eba.c
> @@ -481,6 +481,62 @@ out_unlock:
>  }
>  
>  /**
> + * ubi_eba_read_leb_sg - read data into a scatter gather list.
> + * @ubi: UBI device description object
> + * @vol: volume description object
> + * @lnum: logical eraseblock number
> + * @sgl: UBI scatter gather list to store the read data
> + * @offset: offset from where to read
> + * @len: how many bytes to read
> + * @check: data CRC check flag
> + *
> + * This function works exactly like ubi_eba_read_leb(). But instead of
> + * storing the read data into a buffer it writes to an UBI scatter gather
> + * list.
> + */
> +int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
> +			struct ubi_sgl *sgl, int lnum, int offset, int len,
> +			int check)
> +{
> +	int to_read;
> +	int ret;
> +	struct scatterlist *sg;
> +
> +	for (;;) {
> +		ubi_assert(sgl->list_pos < UBI_MAX_SG_COUNT);
> +		sg = &sgl->sg[sgl->list_pos];
> +		if (len < sg->length - sgl->page_pos)
> +			to_read = len;
> +		else
> +			to_read = sg->length - sgl->page_pos;
> +
> +		ret = ubi_eba_read_leb(ubi, vol, lnum,
> +				       sg_virt(sg) + sgl->page_pos, offset,
> +				       to_read, check);
> +		if (ret < 0)
> +			goto out;

Matter of taste, but isn't it better to just return here?

> +
> +		offset += to_read;
> +		len -= to_read;
> +		if (!len) {
> +			sgl->page_pos += to_read;
> +			if (sgl->page_pos == sg->length) {
> +				sgl->list_pos++;
> +				sgl->page_pos = 0;
> +			}
> +
> +			break;
> +		}
> +
> +		sgl->list_pos++;
> +		sgl->page_pos = 0;
> +	}
> +
> +out:
> +	return ret;
> +}
> +
> +/**
>   * recover_peb - recover from write failure.
>   * @ubi: UBI device description object
>   * @pnum: the physical eraseblock to recover
> diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
> index f3bab66..d0055a2 100644
> --- a/drivers/mtd/ubi/kapi.c
> +++ b/drivers/mtd/ubi/kapi.c
> @@ -355,6 +355,43 @@ void ubi_close_volume(struct ubi_volume_desc *desc)
>  EXPORT_SYMBOL_GPL(ubi_close_volume);
>  
>  /**
> + * leb_read_sanity_check - does sanity checks on read requests.
> + * @desc: volume descriptor
> + * @lnum: logical eraseblock number to read from
> + * @offset: offset within the logical eraseblock to read from
> + * @len: how many bytes to read
> + *
> + * This function is used by ubi_leb_read() and ubi_leb_read_sg()
> + * to perfrom sanity checks.

s/perfrom/perform

> + */
> +static int leb_read_sanity_check(struct ubi_volume_desc *desc, int lnum,
> +				 int offset, int len)
> +{
> +	struct ubi_volume *vol = desc->vol;
> +	struct ubi_device *ubi = vol->ubi;
> +	int vol_id = vol->vol_id;
> +
> +	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
> +	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
> +	    offset + len > vol->usable_leb_size)
> +		return -EINVAL;
> +
> +	if (vol->vol_type == UBI_STATIC_VOLUME) {
> +		if (vol->used_ebs == 0)
> +			/* Empty static UBI volume */
> +			return 0;
> +		if (lnum == vol->used_ebs - 1 &&
> +		    offset + len > vol->last_eb_bytes)
> +			return -EINVAL;
> +	}
> +
> +	if (vol->upd_marker)
> +		return -EBADF;
> +
> +	return 0;
> +}
> +
> +/**
>   * ubi_leb_read - read data.
>   * @desc: volume descriptor
>   * @lnum: logical eraseblock number to read from
> @@ -390,22 +427,10 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
>  
>  	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
>  
> -	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
> -	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
> -	    offset + len > vol->usable_leb_size)
> -		return -EINVAL;
> -
> -	if (vol->vol_type == UBI_STATIC_VOLUME) {
> -		if (vol->used_ebs == 0)
> -			/* Empty static UBI volume */
> -			return 0;
> -		if (lnum == vol->used_ebs - 1 &&
> -		    offset + len > vol->last_eb_bytes)
> -			return -EINVAL;
> -	}
> +	err = leb_read_sanity_check(desc, lnum, offset, len);
> +	if (err < 0)
> +		return err;
>  
> -	if (vol->upd_marker)
> -		return -EBADF;
>  	if (len == 0)
>  		return 0;
>  
> @@ -419,6 +444,46 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
>  }
>  EXPORT_SYMBOL_GPL(ubi_leb_read);
>  
> +
> +/**
> + * ubi_leb_read_sg - read data into a scatter gather list.
> + * @desc: volume descriptor
> + * @lnum: logical eraseblock number to read from
> + * @buf: buffer where to store the read data
> + * @offset: offset within the logical eraseblock to read from
> + * @len: how many bytes to read
> + * @check: whether UBI has to check the read data's CRC or not.
> + *
> + * This function works exactly like ubi_leb_read_sg(). But instead of
> + * storing the read data into a buffer it writes to an UBI scatter gather
> + * list.
> + */
> +int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
> +		    int offset, int len, int check)
> +{
> +	struct ubi_volume *vol = desc->vol;
> +	struct ubi_device *ubi = vol->ubi;
> +	int err, vol_id = vol->vol_id;
> +
> +	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
> +
> +	err = leb_read_sanity_check(desc, lnum, offset, len);
> +	if (err < 0)
> +		return err;
> +
> +	if (len == 0)
> +		return 0;
> +
> +	err = ubi_eba_read_leb_sg(ubi, vol, sgl, lnum, offset, len, check);
> +	if (err && mtd_is_eccerr(err) && vol->vol_type == UBI_STATIC_VOLUME) {
> +		ubi_warn(ubi, "mark volume %d as corrupted", vol_id);
> +		vol->corrupted = 1;
> +	}
> +
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(ubi_leb_read_sg);
> +
>  /**
>   * ubi_leb_write - write data.
>   * @desc: volume descriptor
> diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
> index ee7ac0b..a5283cf 100644
> --- a/drivers/mtd/ubi/ubi.h
> +++ b/drivers/mtd/ubi/ubi.h
> @@ -791,6 +791,9 @@ int ubi_eba_unmap_leb(struct ubi_device *ubi, struct ubi_volume *vol,
>  		      int lnum);
>  int ubi_eba_read_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
>  		     void *buf, int offset, int len, int check);
> +int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
> +			struct ubi_sgl *sgl, int lnum, int offset, int len,
> +			int check);
>  int ubi_eba_write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
>  		      const void *buf, int offset, int len);
>  int ubi_eba_write_leb_st(struct ubi_device *ubi, struct ubi_volume *vol,
> diff --git a/include/linux/mtd/ubi.h b/include/linux/mtd/ubi.h
> index c3918a0..3d5916d 100644
> --- a/include/linux/mtd/ubi.h
> +++ b/include/linux/mtd/ubi.h
> @@ -23,11 +23,16 @@
>  
>  #include <linux/ioctl.h>
>  #include <linux/types.h>
> +#include <linux/scatterlist.h>
>  #include <mtd/ubi-user.h>
>  
>  /* All voumes/LEBs */
>  #define UBI_ALL -1
>  
> +/* Maximum number of scatter gather list entries,
> + * we use only 64 to have a lower memory foot print. */

Multilines comments style is:

/*
 *
 */

> +#define UBI_MAX_SG_COUNT 64
> +
>  /*
>   * enum ubi_open_mode - UBI volume open mode constants.
>   *
> @@ -116,6 +121,35 @@ struct ubi_volume_info {
>  };
>  
>  /**
> + * struct ubi_sgl - UBI scatter gather list data structure.
> + * @list_pos: current position in @sg[]
> + * @page_pos: current position in @sg[@list_pos]
> + * @sg: the scatter gather list itself
> + *
> + * ubi_sgl is a wrapper around a scatter list which keeps track of the
> + * current position in the list and the current list item such that
> + * it can be used across multiple ubi_leb_read_sg() calls.
> + */
> +struct ubi_sgl {
> +	int list_pos;
> +	int page_pos;
> +	struct scatterlist sg[UBI_MAX_SG_COUNT];
> +};
> +
> +/**
> + * ubi_sgl_init - initialize an UBI scatter gather list data structure.
> + * @usgl: the UBI scatter gather struct itself
> + *
> + * Please note that you still have to use sg_init_table() or any adequate
> + * function to initialize the unterlaying struct scatterlist.
> + */
> +static inline void ubi_sgl_init(struct ubi_sgl *usgl)
> +{
> +	usgl->list_pos = 0;
> +	usgl->page_pos = 0;
> +}
> +
> +/**
>   * struct ubi_device_info - UBI device description data structure.
>   * @ubi_num: ubi device number
>   * @leb_size: logical eraseblock size on this UBI device
> @@ -210,6 +244,8 @@ int ubi_unregister_volume_notifier(struct notifier_block *nb);
>  void ubi_close_volume(struct ubi_volume_desc *desc);
>  int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
>  		 int len, int check);
> +int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
> +		   int offset, int len, int check);
>  int ubi_leb_write(struct ubi_volume_desc *desc, int lnum, const void *buf,
>  		  int offset, int len);
>  int ubi_leb_change(struct ubi_volume_desc *desc, int lnum, const void *buf,
> @@ -230,4 +266,14 @@ static inline int ubi_read(struct ubi_volume_desc *desc, int lnum, char *buf,
>  {
>  	return ubi_leb_read(desc, lnum, buf, offset, len, 0);
>  }
> +
> +/*
> + * This function is the same as the 'ubi_leb_read_sg()' function, but it does
> + * not provide the checking capability.
> + */
> +static inline int ubi_read_sg(struct ubi_volume_desc *desc, int lnum,
> +			      struct ubi_sgl *sgl, int offset, int len)
> +{
> +	return ubi_leb_read_sg(desc, lnum, sgl, offset, len, 0);
> +}
>  #endif /* !__LINUX_UBI_H__ */
> 


-- 
Ezequiel Garcia, VanguardiaSur
www.vanguardiasur.com.ar

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Ezequiel Garcia]

On 01/10/2015 06:52 PM, Richard Weinberger wrote:
> Convert the driver to blk-mq.
> Beside of moving to the modern block interface this change boosts
> also the performance of the driver.
> 
> nand: device found, Manufacturer ID: 0x2c, Chip ID: 0xda
> nand: Micron NAND 256MiB 3,3V 8-bit
> nand: 256MiB, SLC, page size: 2048, OOB size: 64
> 
> root@debian-armhf:~# dd if=/dev/ubiblock0_0 of=/dev/zero bs=1M
> 243+1 records in
> 243+1 records out
> 255080448 bytes (255 MB) copied, 4.39295 s, 58.1 MB/s
> 
> vs.
> 
> root@debian-armhf:~# dd if=/dev/ubiblock0_0 of=/dev/zero bs=1M
> 243+1 records in
> 243+1 records out
> 255080448 bytes (255 MB) copied, 2.87676 s, 88.7 MB/s
> 
> Cc: hch@infradead.org
> Cc: axboe@fb.com
> Cc: tom.leiming@gmail.com
> Signed-off-by: Richard Weinberger <richard@nod.at>
> Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

Acked-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

And thanks a lot for the good work!

-- 
Ezequiel Garcia, VanguardiaSur
www.vanguardiasur.com.ar

Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support

[Ezequiel Garcia]

On 01/10/2015 06:52 PM, Richard Weinberger wrote:
> Convert the driver to blk-mq.
> Beside of moving to the modern block interface this change boosts
> also the performance of the driver.
> 
> nand: device found, Manufacturer ID: 0x2c, Chip ID: 0xda
> nand: Micron NAND 256MiB 3,3V 8-bit
> nand: 256MiB, SLC, page size: 2048, OOB size: 64
> 
> root@debian-armhf:~# dd if=/dev/ubiblock0_0 of=/dev/zero bs=1M
> 243+1 records in
> 243+1 records out
> 255080448 bytes (255 MB) copied, 4.39295 s, 58.1 MB/s
> 
> vs.
> 
> root@debian-armhf:~# dd if=/dev/ubiblock0_0 of=/dev/zero bs=1M
> 243+1 records in
> 243+1 records out
> 255080448 bytes (255 MB) copied, 2.87676 s, 88.7 MB/s
> 
> Cc: hch@infradead.org
> Cc: axboe@fb.com
> Cc: tom.leiming@gmail.com
> Signed-off-by: Richard Weinberger <richard@nod.at>
> Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

Acked-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

And thanks a lot for the good work!

-- 
Ezequiel Garcia, VanguardiaSur
www.vanguardiasur.com.ar

Re: [PATCH 1/2 v2] UBI: Add initial support for scatter gather

[Richard Weinberger]

Am 28.01.2015 um 00:36 schrieb Ezequiel Garcia:
> On 01/10/2015 06:52 PM, Richard Weinberger wrote:
>> Adds a new set of functions to deal with scatter gather.
>> ubi_eba_read_leb_sg() will read from a LEB into a scatter gather list.
>> The new data structure struct ubi_sgl will be used within UBI to
>> hold the scatter gather list itself and metadata to have a cursor
>> within the list.
>>
>> Signed-off-by: Richard Weinberger <richard@nod.at>
>> Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
> 
> Three nitpicks below, and my
> 
> Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
> 
>> ---
>>  drivers/mtd/ubi/eba.c   | 56 +++++++++++++++++++++++++++++
>>  drivers/mtd/ubi/kapi.c  | 95 +++++++++++++++++++++++++++++++++++++++++--------
>>  drivers/mtd/ubi/ubi.h   |  3 ++
>>  include/linux/mtd/ubi.h | 46 ++++++++++++++++++++++++
>>  4 files changed, 185 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
>> index b698534..0aaf707 100644
>> --- a/drivers/mtd/ubi/eba.c
>> +++ b/drivers/mtd/ubi/eba.c
>> @@ -481,6 +481,62 @@ out_unlock:
>>  }
>>  
>>  /**
>> + * ubi_eba_read_leb_sg - read data into a scatter gather list.
>> + * @ubi: UBI device description object
>> + * @vol: volume description object
>> + * @lnum: logical eraseblock number
>> + * @sgl: UBI scatter gather list to store the read data
>> + * @offset: offset from where to read
>> + * @len: how many bytes to read
>> + * @check: data CRC check flag
>> + *
>> + * This function works exactly like ubi_eba_read_leb(). But instead of
>> + * storing the read data into a buffer it writes to an UBI scatter gather
>> + * list.
>> + */
>> +int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
>> +			struct ubi_sgl *sgl, int lnum, int offset, int len,
>> +			int check)
>> +{
>> +	int to_read;
>> +	int ret;
>> +	struct scatterlist *sg;
>> +
>> +	for (;;) {
>> +		ubi_assert(sgl->list_pos < UBI_MAX_SG_COUNT);
>> +		sg = &sgl->sg[sgl->list_pos];
>> +		if (len < sg->length - sgl->page_pos)
>> +			to_read = len;
>> +		else
>> +			to_read = sg->length - sgl->page_pos;
>> +
>> +		ret = ubi_eba_read_leb(ubi, vol, lnum,
>> +				       sg_virt(sg) + sgl->page_pos, offset,
>> +				       to_read, check);
>> +		if (ret < 0)
>> +			goto out;
> 
> Matter of taste, but isn't it better to just return here?

After dealing with a lot of nasty bugs in error paths in other projects I've started
using the principle of a single function exit path.
But in this case a "return ret;" is also perfectly fine as the "out" label does no cleanup.

Will fix before pushing.

>> +
>> +		offset += to_read;
>> +		len -= to_read;
>> +		if (!len) {
>> +			sgl->page_pos += to_read;
>> +			if (sgl->page_pos == sg->length) {
>> +				sgl->list_pos++;
>> +				sgl->page_pos = 0;
>> +			}
>> +
>> +			break;
>> +		}
>> +
>> +		sgl->list_pos++;
>> +		sgl->page_pos = 0;
>> +	}
>> +
>> +out:
>> +	return ret;
>> +}
>> +
>> +/**
>>   * recover_peb - recover from write failure.
>>   * @ubi: UBI device description object
>>   * @pnum: the physical eraseblock to recover
>> diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
>> index f3bab66..d0055a2 100644
>> --- a/drivers/mtd/ubi/kapi.c
>> +++ b/drivers/mtd/ubi/kapi.c
>> @@ -355,6 +355,43 @@ void ubi_close_volume(struct ubi_volume_desc *desc)
>>  EXPORT_SYMBOL_GPL(ubi_close_volume);
>>  
>>  /**
>> + * leb_read_sanity_check - does sanity checks on read requests.
>> + * @desc: volume descriptor
>> + * @lnum: logical eraseblock number to read from
>> + * @offset: offset within the logical eraseblock to read from
>> + * @len: how many bytes to read
>> + *
>> + * This function is used by ubi_leb_read() and ubi_leb_read_sg()
>> + * to perfrom sanity checks.
> 
> s/perfrom/perform

Thx.

> 
>> + */
>> +static int leb_read_sanity_check(struct ubi_volume_desc *desc, int lnum,
>> +				 int offset, int len)
>> +{
>> +	struct ubi_volume *vol = desc->vol;
>> +	struct ubi_device *ubi = vol->ubi;
>> +	int vol_id = vol->vol_id;
>> +
>> +	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
>> +	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
>> +	    offset + len > vol->usable_leb_size)
>> +		return -EINVAL;
>> +
>> +	if (vol->vol_type == UBI_STATIC_VOLUME) {
>> +		if (vol->used_ebs == 0)
>> +			/* Empty static UBI volume */
>> +			return 0;
>> +		if (lnum == vol->used_ebs - 1 &&
>> +		    offset + len > vol->last_eb_bytes)
>> +			return -EINVAL;
>> +	}
>> +
>> +	if (vol->upd_marker)
>> +		return -EBADF;
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>>   * ubi_leb_read - read data.
>>   * @desc: volume descriptor
>>   * @lnum: logical eraseblock number to read from
>> @@ -390,22 +427,10 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
>>  
>>  	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
>>  
>> -	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
>> -	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
>> -	    offset + len > vol->usable_leb_size)
>> -		return -EINVAL;
>> -
>> -	if (vol->vol_type == UBI_STATIC_VOLUME) {
>> -		if (vol->used_ebs == 0)
>> -			/* Empty static UBI volume */
>> -			return 0;
>> -		if (lnum == vol->used_ebs - 1 &&
>> -		    offset + len > vol->last_eb_bytes)
>> -			return -EINVAL;
>> -	}
>> +	err = leb_read_sanity_check(desc, lnum, offset, len);
>> +	if (err < 0)
>> +		return err;
>>  
>> -	if (vol->upd_marker)
>> -		return -EBADF;
>>  	if (len == 0)
>>  		return 0;
>>  
>> @@ -419,6 +444,46 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
>>  }
>>  EXPORT_SYMBOL_GPL(ubi_leb_read);
>>  
>> +
>> +/**
>> + * ubi_leb_read_sg - read data into a scatter gather list.
>> + * @desc: volume descriptor
>> + * @lnum: logical eraseblock number to read from
>> + * @buf: buffer where to store the read data
>> + * @offset: offset within the logical eraseblock to read from
>> + * @len: how many bytes to read
>> + * @check: whether UBI has to check the read data's CRC or not.
>> + *
>> + * This function works exactly like ubi_leb_read_sg(). But instead of
>> + * storing the read data into a buffer it writes to an UBI scatter gather
>> + * list.
>> + */
>> +int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
>> +		    int offset, int len, int check)
>> +{
>> +	struct ubi_volume *vol = desc->vol;
>> +	struct ubi_device *ubi = vol->ubi;
>> +	int err, vol_id = vol->vol_id;
>> +
>> +	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
>> +
>> +	err = leb_read_sanity_check(desc, lnum, offset, len);
>> +	if (err < 0)
>> +		return err;
>> +
>> +	if (len == 0)
>> +		return 0;
>> +
>> +	err = ubi_eba_read_leb_sg(ubi, vol, sgl, lnum, offset, len, check);
>> +	if (err && mtd_is_eccerr(err) && vol->vol_type == UBI_STATIC_VOLUME) {
>> +		ubi_warn(ubi, "mark volume %d as corrupted", vol_id);
>> +		vol->corrupted = 1;
>> +	}
>> +
>> +	return err;
>> +}
>> +EXPORT_SYMBOL_GPL(ubi_leb_read_sg);
>> +
>>  /**
>>   * ubi_leb_write - write data.
>>   * @desc: volume descriptor
>> diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
>> index ee7ac0b..a5283cf 100644
>> --- a/drivers/mtd/ubi/ubi.h
>> +++ b/drivers/mtd/ubi/ubi.h
>> @@ -791,6 +791,9 @@ int ubi_eba_unmap_leb(struct ubi_device *ubi, struct ubi_volume *vol,
>>  		      int lnum);
>>  int ubi_eba_read_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
>>  		     void *buf, int offset, int len, int check);
>> +int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
>> +			struct ubi_sgl *sgl, int lnum, int offset, int len,
>> +			int check);
>>  int ubi_eba_write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
>>  		      const void *buf, int offset, int len);
>>  int ubi_eba_write_leb_st(struct ubi_device *ubi, struct ubi_volume *vol,
>> diff --git a/include/linux/mtd/ubi.h b/include/linux/mtd/ubi.h
>> index c3918a0..3d5916d 100644
>> --- a/include/linux/mtd/ubi.h
>> +++ b/include/linux/mtd/ubi.h
>> @@ -23,11 +23,16 @@
>>  
>>  #include <linux/ioctl.h>
>>  #include <linux/types.h>
>> +#include <linux/scatterlist.h>
>>  #include <mtd/ubi-user.h>
>>  
>>  /* All voumes/LEBs */
>>  #define UBI_ALL -1
>>  
>> +/* Maximum number of scatter gather list entries,
>> + * we use only 64 to have a lower memory foot print. */
> 
> Multilines comments style is:
> 
> /*
>  *
>  */

Correct. I wonder why checkpatch.pl did not bark on that.

Thanks,
//richard

Re: [PATCH 1/2 v2] UBI: Add initial support for scatter gather

[Richard Weinberger]

Am 28.01.2015 um 00:36 schrieb Ezequiel Garcia:
> On 01/10/2015 06:52 PM, Richard Weinberger wrote:
>> Adds a new set of functions to deal with scatter gather.
>> ubi_eba_read_leb_sg() will read from a LEB into a scatter gather list.
>> The new data structure struct ubi_sgl will be used within UBI to
>> hold the scatter gather list itself and metadata to have a cursor
>> within the list.
>>
>> Signed-off-by: Richard Weinberger <richard@nod.at>
>> Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
> 
> Three nitpicks below, and my
> 
> Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
> 
>> ---
>>  drivers/mtd/ubi/eba.c   | 56 +++++++++++++++++++++++++++++
>>  drivers/mtd/ubi/kapi.c  | 95 +++++++++++++++++++++++++++++++++++++++++--------
>>  drivers/mtd/ubi/ubi.h   |  3 ++
>>  include/linux/mtd/ubi.h | 46 ++++++++++++++++++++++++
>>  4 files changed, 185 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
>> index b698534..0aaf707 100644
>> --- a/drivers/mtd/ubi/eba.c
>> +++ b/drivers/mtd/ubi/eba.c
>> @@ -481,6 +481,62 @@ out_unlock:
>>  }
>>  
>>  /**
>> + * ubi_eba_read_leb_sg - read data into a scatter gather list.
>> + * @ubi: UBI device description object
>> + * @vol: volume description object
>> + * @lnum: logical eraseblock number
>> + * @sgl: UBI scatter gather list to store the read data
>> + * @offset: offset from where to read
>> + * @len: how many bytes to read
>> + * @check: data CRC check flag
>> + *
>> + * This function works exactly like ubi_eba_read_leb(). But instead of
>> + * storing the read data into a buffer it writes to an UBI scatter gather
>> + * list.
>> + */
>> +int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
>> +			struct ubi_sgl *sgl, int lnum, int offset, int len,
>> +			int check)
>> +{
>> +	int to_read;
>> +	int ret;
>> +	struct scatterlist *sg;
>> +
>> +	for (;;) {
>> +		ubi_assert(sgl->list_pos < UBI_MAX_SG_COUNT);
>> +		sg = &sgl->sg[sgl->list_pos];
>> +		if (len < sg->length - sgl->page_pos)
>> +			to_read = len;
>> +		else
>> +			to_read = sg->length - sgl->page_pos;
>> +
>> +		ret = ubi_eba_read_leb(ubi, vol, lnum,
>> +				       sg_virt(sg) + sgl->page_pos, offset,
>> +				       to_read, check);
>> +		if (ret < 0)
>> +			goto out;
> 
> Matter of taste, but isn't it better to just return here?

After dealing with a lot of nasty bugs in error paths in other projects I've started
using the principle of a single function exit path.
But in this case a "return ret;" is also perfectly fine as the "out" label does no cleanup.

Will fix before pushing.

>> +
>> +		offset += to_read;
>> +		len -= to_read;
>> +		if (!len) {
>> +			sgl->page_pos += to_read;
>> +			if (sgl->page_pos == sg->length) {
>> +				sgl->list_pos++;
>> +				sgl->page_pos = 0;
>> +			}
>> +
>> +			break;
>> +		}
>> +
>> +		sgl->list_pos++;
>> +		sgl->page_pos = 0;
>> +	}
>> +
>> +out:
>> +	return ret;
>> +}
>> +
>> +/**
>>   * recover_peb - recover from write failure.
>>   * @ubi: UBI device description object
>>   * @pnum: the physical eraseblock to recover
>> diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
>> index f3bab66..d0055a2 100644
>> --- a/drivers/mtd/ubi/kapi.c
>> +++ b/drivers/mtd/ubi/kapi.c
>> @@ -355,6 +355,43 @@ void ubi_close_volume(struct ubi_volume_desc *desc)
>>  EXPORT_SYMBOL_GPL(ubi_close_volume);
>>  
>>  /**
>> + * leb_read_sanity_check - does sanity checks on read requests.
>> + * @desc: volume descriptor
>> + * @lnum: logical eraseblock number to read from
>> + * @offset: offset within the logical eraseblock to read from
>> + * @len: how many bytes to read
>> + *
>> + * This function is used by ubi_leb_read() and ubi_leb_read_sg()
>> + * to perfrom sanity checks.
> 
> s/perfrom/perform

Thx.

> 
>> + */
>> +static int leb_read_sanity_check(struct ubi_volume_desc *desc, int lnum,
>> +				 int offset, int len)
>> +{
>> +	struct ubi_volume *vol = desc->vol;
>> +	struct ubi_device *ubi = vol->ubi;
>> +	int vol_id = vol->vol_id;
>> +
>> +	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
>> +	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
>> +	    offset + len > vol->usable_leb_size)
>> +		return -EINVAL;
>> +
>> +	if (vol->vol_type == UBI_STATIC_VOLUME) {
>> +		if (vol->used_ebs == 0)
>> +			/* Empty static UBI volume */
>> +			return 0;
>> +		if (lnum == vol->used_ebs - 1 &&
>> +		    offset + len > vol->last_eb_bytes)
>> +			return -EINVAL;
>> +	}
>> +
>> +	if (vol->upd_marker)
>> +		return -EBADF;
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>>   * ubi_leb_read - read data.
>>   * @desc: volume descriptor
>>   * @lnum: logical eraseblock number to read from
>> @@ -390,22 +427,10 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
>>  
>>  	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
>>  
>> -	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
>> -	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
>> -	    offset + len > vol->usable_leb_size)
>> -		return -EINVAL;
>> -
>> -	if (vol->vol_type == UBI_STATIC_VOLUME) {
>> -		if (vol->used_ebs == 0)
>> -			/* Empty static UBI volume */
>> -			return 0;
>> -		if (lnum == vol->used_ebs - 1 &&
>> -		    offset + len > vol->last_eb_bytes)
>> -			return -EINVAL;
>> -	}
>> +	err = leb_read_sanity_check(desc, lnum, offset, len);
>> +	if (err < 0)
>> +		return err;
>>  
>> -	if (vol->upd_marker)
>> -		return -EBADF;
>>  	if (len == 0)
>>  		return 0;
>>  
>> @@ -419,6 +444,46 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
>>  }
>>  EXPORT_SYMBOL_GPL(ubi_leb_read);
>>  
>> +
>> +/**
>> + * ubi_leb_read_sg - read data into a scatter gather list.
>> + * @desc: volume descriptor
>> + * @lnum: logical eraseblock number to read from
>> + * @buf: buffer where to store the read data
>> + * @offset: offset within the logical eraseblock to read from
>> + * @len: how many bytes to read
>> + * @check: whether UBI has to check the read data's CRC or not.
>> + *
>> + * This function works exactly like ubi_leb_read_sg(). But instead of
>> + * storing the read data into a buffer it writes to an UBI scatter gather
>> + * list.
>> + */
>> +int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
>> +		    int offset, int len, int check)
>> +{
>> +	struct ubi_volume *vol = desc->vol;
>> +	struct ubi_device *ubi = vol->ubi;
>> +	int err, vol_id = vol->vol_id;
>> +
>> +	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);
>> +
>> +	err = leb_read_sanity_check(desc, lnum, offset, len);
>> +	if (err < 0)
>> +		return err;
>> +
>> +	if (len == 0)
>> +		return 0;
>> +
>> +	err = ubi_eba_read_leb_sg(ubi, vol, sgl, lnum, offset, len, check);
>> +	if (err && mtd_is_eccerr(err) && vol->vol_type == UBI_STATIC_VOLUME) {
>> +		ubi_warn(ubi, "mark volume %d as corrupted", vol_id);
>> +		vol->corrupted = 1;
>> +	}
>> +
>> +	return err;
>> +}
>> +EXPORT_SYMBOL_GPL(ubi_leb_read_sg);
>> +
>>  /**
>>   * ubi_leb_write - write data.
>>   * @desc: volume descriptor
>> diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
>> index ee7ac0b..a5283cf 100644
>> --- a/drivers/mtd/ubi/ubi.h
>> +++ b/drivers/mtd/ubi/ubi.h
>> @@ -791,6 +791,9 @@ int ubi_eba_unmap_leb(struct ubi_device *ubi, struct ubi_volume *vol,
>>  		      int lnum);
>>  int ubi_eba_read_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
>>  		     void *buf, int offset, int len, int check);
>> +int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
>> +			struct ubi_sgl *sgl, int lnum, int offset, int len,
>> +			int check);
>>  int ubi_eba_write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
>>  		      const void *buf, int offset, int len);
>>  int ubi_eba_write_leb_st(struct ubi_device *ubi, struct ubi_volume *vol,
>> diff --git a/include/linux/mtd/ubi.h b/include/linux/mtd/ubi.h
>> index c3918a0..3d5916d 100644
>> --- a/include/linux/mtd/ubi.h
>> +++ b/include/linux/mtd/ubi.h
>> @@ -23,11 +23,16 @@
>>  
>>  #include <linux/ioctl.h>
>>  #include <linux/types.h>
>> +#include <linux/scatterlist.h>
>>  #include <mtd/ubi-user.h>
>>  
>>  /* All voumes/LEBs */
>>  #define UBI_ALL -1
>>  
>> +/* Maximum number of scatter gather list entries,
>> + * we use only 64 to have a lower memory foot print. */
> 
> Multilines comments style is:
> 
> /*
>  *
>  */

Correct. I wonder why checkpatch.pl did not bark on that.

Thanks,
//richard