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Date: Wed, 28 Jan 2015 00:46:59 +0100
From: Richard Weinberger <richard@....at>
To: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
dedekind1@...il.com
CC: dwmw2@...radead.org, computersforpeace@...il.com,
linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2 v2] UBI: Add initial support for scatter gather
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@....at>
>> Tested-by: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
>
> Three nitpicks below, and my
>
> Reviewed-by: Ezequiel Garcia <ezequiel@...guardiasur.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
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