[PATCH] ubi: Make recover_peb power cut aware

[PATCH] ubi: Make recover_peb power cut aware

[Richard Weinberger]

recover_peb() was never power cut aware,
if a power cut happened right after writing the VID header
upon next attach UBI would blindly use the new partial written
PEB and all data from the old PEB is lost.

In order to make recover_peb() power cut aware, write the new
VID with a proper crc and copy_flag set such that the UBI attach
process will detect whether the new PEB is completely written
or not.
We cannot directly use ubi_eba_atomic_leb_change() since we'd
have to unlock the LEB which is facing a write error.

Cc: stable@vger.kernel.org
Reported-by: Jörg Pfähler <pfaehler@isse.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
---
 drivers/mtd/ubi/eba.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index 5780dd1..b6b0714 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -575,6 +575,7 @@ static int recover_peb(struct ubi_device *ubi, int pnum, int vol_id, int lnum,
 	int err, idx = vol_id2idx(ubi, vol_id), new_pnum, data_size, tries = 0;
 	struct ubi_volume *vol = ubi->volumes[idx];
 	struct ubi_vid_hdr *vid_hdr;
+	uint32_t crc;
 
 	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
 	if (!vid_hdr)
@@ -599,14 +600,8 @@ retry:
 		goto out_put;
 	}
 
-	vid_hdr->sqnum = cpu_to_be64(ubi_next_sqnum(ubi));
-	err = ubi_io_write_vid_hdr(ubi, new_pnum, vid_hdr);
-	if (err) {
-		up_read(&ubi->fm_eba_sem);
-		goto write_error;
-	}
+	ubi_assert(vid_hdr->vol_type == UBI_VID_DYNAMIC);
 
-	data_size = offset + len;
 	mutex_lock(&ubi->buf_mutex);
 	memset(ubi->peb_buf + offset, 0xFF, len);
 
@@ -621,6 +616,18 @@ retry:
 
 	memcpy(ubi->peb_buf + offset, buf, len);
 
+	data_size = offset + len;
+	crc = crc32(UBI_CRC32_INIT, ubi->peb_buf, data_size);
+	vid_hdr->sqnum = cpu_to_be64(ubi_next_sqnum(ubi));
+	vid_hdr->copy_flag = 1;
+	vid_hdr->data_size = cpu_to_be32(data_size);
+	vid_hdr->data_crc = cpu_to_be32(crc);
+	err = ubi_io_write_vid_hdr(ubi, new_pnum, vid_hdr);
+	if (err) {
+		up_read(&ubi->fm_eba_sem);
+		goto out_unlock;
+	}
+
 	err = ubi_io_write_data(ubi, ubi->peb_buf, new_pnum, 0, data_size);
 	if (err) {
 		mutex_unlock(&ubi->buf_mutex);
-- 
2.7.3

Re: [PATCH] ubi: Make recover_peb power cut aware

[Richard Weinberger]

Am 21.06.2016 um 00:25 schrieb Richard Weinberger:
> recover_peb() was never power cut aware,
> if a power cut happened right after writing the VID header
> upon next attach UBI would blindly use the new partial written
> PEB and all data from the old PEB is lost.
> 
> In order to make recover_peb() power cut aware, write the new
> VID with a proper crc and copy_flag set such that the UBI attach
> process will detect whether the new PEB is completely written
> or not.
> We cannot directly use ubi_eba_atomic_leb_change() since we'd
> have to unlock the LEB which is facing a write error.
> 
> Cc: stable@vger.kernel.org
> Reported-by: Jörg Pfähler <pfaehler@isse.de>
> Signed-off-by: Richard Weinberger <richard@nod.at>
> ---
>  drivers/mtd/ubi/eba.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
> index 5780dd1..b6b0714 100644
> --- a/drivers/mtd/ubi/eba.c
> +++ b/drivers/mtd/ubi/eba.c
> @@ -575,6 +575,7 @@ static int recover_peb(struct ubi_device *ubi, int pnum, int vol_id, int lnum,
>  	int err, idx = vol_id2idx(ubi, vol_id), new_pnum, data_size, tries = 0;
>  	struct ubi_volume *vol = ubi->volumes[idx];
>  	struct ubi_vid_hdr *vid_hdr;
> +	uint32_t crc;
>  
>  	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
>  	if (!vid_hdr)
> @@ -599,14 +600,8 @@ retry:
>  		goto out_put;
>  	}
>  
> -	vid_hdr->sqnum = cpu_to_be64(ubi_next_sqnum(ubi));
> -	err = ubi_io_write_vid_hdr(ubi, new_pnum, vid_hdr);
> -	if (err) {
> -		up_read(&ubi->fm_eba_sem);
> -		goto write_error;
> -	}
> +	ubi_assert(vid_hdr->vol_type == UBI_VID_DYNAMIC);
>  
> -	data_size = offset + len;
>  	mutex_lock(&ubi->buf_mutex);
>  	memset(ubi->peb_buf + offset, 0xFF, len);
>  
> @@ -621,6 +616,18 @@ retry:
>  
>  	memcpy(ubi->peb_buf + offset, buf, len);
>  
> +	data_size = offset + len;
> +	crc = crc32(UBI_CRC32_INIT, ubi->peb_buf, data_size);
> +	vid_hdr->sqnum = cpu_to_be64(ubi_next_sqnum(ubi));
> +	vid_hdr->copy_flag = 1;
> +	vid_hdr->data_size = cpu_to_be32(data_size);
> +	vid_hdr->data_crc = cpu_to_be32(crc);
> +	err = ubi_io_write_vid_hdr(ubi, new_pnum, vid_hdr);
> +	if (err) {
> +		up_read(&ubi->fm_eba_sem);
> +		goto out_unlock;

As always, right after sending a patch I spot an issue... ;-\
We need to goto write_error here (and release buf_mutex first).

Thanks,
//richard