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SubjectRe: [PATCH 03/14] ubi: fastmap: Add support for flags
On Wed, 13 Jun 2018 23:23:33 +0200
Richard Weinberger <richard@nod.at> wrote:

> With version 2 of fastmap, flags are supported.
> We fall back to scanning mode if unsupported flags are found.
>
> Signed-off-by: Richard Weinberger <richard@nod.at>
> ---
> drivers/mtd/ubi/fastmap.c | 24 ++++++++++++++++++++----
> drivers/mtd/ubi/ubi-media.h | 11 +++++++++--
> drivers/mtd/ubi/ubi.h | 2 ++
> 3 files changed, 31 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mtd/ubi/fastmap.c b/drivers/mtd/ubi/fastmap.c
> index 768fa8a76867..1ebb5d15ab1a 100644
> --- a/drivers/mtd/ubi/fastmap.c
> +++ b/drivers/mtd/ubi/fastmap.c
> @@ -949,9 +949,24 @@ int ubi_scan_fastmap(struct ubi_device *ubi, struct ubi_attach_info *ai,
> goto free_fm_sb;
> }
>
> - if (fmsb->version != UBI_FM_FMT_VERSION) {
> - ubi_err(ubi, "bad fastmap version: %i, expected: %i",
> - fmsb->version, UBI_FM_FMT_VERSION);
> + fm->flags = be32_to_cpu(fmsb->flags);
> +
> + if (fmsb->version == 1) {
> + if (fm->flags != 0) {
> + ubi_err(ubi, "fastmap flags are non-zero: %#x",
> + fm->flags);
> + ret = UBI_BAD_FASTMAP;
> + goto free_fm_sb;
> + }
> + } else if (fmsb->version == 2) {
> + if ((fm->flags & UBI_FM_SB_FLG_MASK) != UBI_FM_SB_FLG_MASK) {

Do you mean

if (fm->flags & ~UBI_FM_SB_FLG_MASK) {

?

Because you test will return an error if at least one of all the
possible flags are not set, which I guess is a valid case.

> + ubi_err(ubi, "unsupported fastmap flags present: %#x",
> + fm->flags);
> + ret = UBI_BAD_FASTMAP;
> + goto free_fm_sb;
> + }

Is there really a point in supporting FM v2 so early in the patch
series? I mean, the new thing in v2 is flag support, and here you fail
when ->flags != 0. Better add support for at least one flag before
saying you support v2 IMO.

> + } else {
> + ubi_err(ubi, "bad fastmap version: %i", fmsb->version);
> ret = UBI_BAD_FASTMAP;
> goto free_fm_sb;
> }
> @@ -1229,10 +1244,11 @@ static int ubi_write_fastmap(struct ubi_device *ubi,
> ubi_assert(fm_pos <= ubi->fm_size);
>
> fmsb->magic = cpu_to_be32(UBI_FM_SB_MAGIC);
> - fmsb->version = UBI_FM_FMT_VERSION;
> + fmsb->version = UBI_FM_FMT_WRITE_VERSION;
> fmsb->used_blocks = cpu_to_be32(new_fm->used_blocks);
> /* the max sqnum will be filled in while *reading* the fastmap */
> fmsb->sqnum = 0;
> + fmsb->flags = 0;
>
> fmh->magic = cpu_to_be32(UBI_FM_HDR_MAGIC);
> free_peb_count = 0;
> diff --git a/drivers/mtd/ubi/ubi-media.h b/drivers/mtd/ubi/ubi-media.h
> index 195ff8ca8211..6136a97f4844 100644
> --- a/drivers/mtd/ubi/ubi-media.h
> +++ b/drivers/mtd/ubi/ubi-media.h
> @@ -365,7 +365,10 @@ struct ubi_vtbl_record {
> #define UBI_FM_DATA_VOLUME_ID (UBI_LAYOUT_VOLUME_ID + 2)
>
> /* fastmap on-flash data structure format version */
> -#define UBI_FM_FMT_VERSION 1
> +#define UBI_FM_FMT_VERSION 2

How about renaming that one UBI_FM_MAX_SUPPORTED_VERSION or something
like that.

> +
> +/* this implementation writes always version 1 */
> +#define UBI_FM_FMT_WRITE_VERSION 1

It really feels weird to hardcode that. What if you're reading a
fastmap volume that has version 2 set, and need to update it? Does that
mean you'll downgrade the FM to version 1 or will you prevent updating
the it?

>
> #define UBI_FM_SB_MAGIC 0x7B11D69F
> #define UBI_FM_HDR_MAGIC 0xD4B82EF7
> @@ -387,6 +390,8 @@ struct ubi_vtbl_record {
> #define UBI_FM_MIN_POOL_SIZE 8
> #define UBI_FM_MAX_POOL_SIZE 256
>
> +#define UBI_FM_SB_FLG_MASK 0

How about naming that one UBI_FM_SB_SUPPORTED_FLG_MASK since you seem
to add new flags afterwards without changing the version number.

> +
> /**
> * struct ubi_fm_sb - UBI fastmap super block
> * @magic: fastmap super block magic number (%UBI_FM_SB_MAGIC)
> @@ -396,6 +401,7 @@ struct ubi_vtbl_record {
> * @block_loc: an array containing the location of all PEBs of the fastmap
> * @block_ec: the erase counter of each used PEB
> * @sqnum: highest sequence number value at the time while taking the fastmap
> + * @flags: fastmap specific flags, only used with @version > 1, zero otherwise
> *
> */
> struct ubi_fm_sb {
> @@ -407,7 +413,8 @@ struct ubi_fm_sb {
> __be32 block_loc[UBI_FM_MAX_BLOCKS];
> __be32 block_ec[UBI_FM_MAX_BLOCKS];
> __be64 sqnum;
> - __u8 padding2[32];
> + __be32 flags;
> + __u8 padding2[28];
> } __packed;
>
> /**
> diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
> index f5ba97c46160..4fab3790733b 100644
> --- a/drivers/mtd/ubi/ubi.h
> +++ b/drivers/mtd/ubi/ubi.h
> @@ -249,6 +249,7 @@ struct ubi_volume_desc;
> * @used_blocks: number of used PEBs
> * @max_pool_size: maximal size of the user pool
> * @max_wl_pool_size: maximal size of the pool used by the WL sub-system
> + * @flags: fastmap flags
> */
> struct ubi_fastmap_layout {
> struct ubi_wl_entry *e[UBI_FM_MAX_BLOCKS];
> @@ -256,6 +257,7 @@ struct ubi_fastmap_layout {
> int used_blocks;
> int max_pool_size;
> int max_wl_pool_size;
> + int flags;
> };
>
> /**

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