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UBI: Add initial support for scatter gather
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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 <[email protected]>
Tested-by: Ezequiel Garcia <[email protected]>
Reviewed-by: Ezequiel Garcia <[email protected]>
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richardweinberger committed Jan 28, 2015
1 parent 892abde commit 9ff0897
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Showing 4 changed files with 186 additions and 15 deletions.
55 changes: 55 additions & 0 deletions drivers/mtd/ubi/eba.c
Original file line number Diff line number Diff line change
Expand Up @@ -479,6 +479,61 @@ int ubi_eba_read_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
return err;
}

/**
* 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)
return ret;

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;
}

return ret;
}

/**
* recover_peb - recover from write failure.
* @ubi: UBI device description object
Expand Down
95 changes: 80 additions & 15 deletions drivers/mtd/ubi/kapi.c
Original file line number Diff line number Diff line change
Expand Up @@ -365,6 +365,43 @@ 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 perform 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
Expand Down Expand Up @@ -401,22 +438,10 @@ 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;

Expand All @@ -430,6 +455,46 @@ 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
Expand Down
3 changes: 3 additions & 0 deletions drivers/mtd/ubi/ubi.h
Original file line number Diff line number Diff line change
Expand Up @@ -795,6 +795,9 @@ 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,
Expand Down
48 changes: 48 additions & 0 deletions include/linux/mtd/ubi.h
Original file line number Diff line number Diff line change
Expand Up @@ -23,11 +23,18 @@

#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.
*
Expand Down Expand Up @@ -118,6 +125,35 @@ struct ubi_volume_info {
dev_t cdev;
};

/**
* 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
Expand Down Expand Up @@ -213,6 +249,8 @@ 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,
Expand All @@ -233,4 +271,14 @@ 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__ */

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