Re: ubifs_decompress: cannot decompress 2293 bytes, compressor lzo, error -22

[Scott Zhang <macromarship@gmail.com>]

Dear Miquel:
     I have fixed the nuc980 nand driver, now the nandbiterrors works.

# ./nandbiterrs /dev/mtd3 -i
incremental biterrors test
Successfully corrected 0 bit errors per subpage
Inserted biterror @ 0/5
Read reported 1 corrected bit errors
Successfully corrected 1 bit errors per subpage
Inserted biterror @ 0/2
Read reported 2 corrected bit errors
Successfully corrected 2 bit errors per subpage
Inserted biterror @ 0/0
Read reported 3 corrected bit errors
Successfully corrected 3 bit errors per subpage
Inserted biterror @ 1/7
Read reported 4 corrected bit errors
Successfully corrected 4 bit errors per subpage
Inserted biterror @ 1/5
Read reported 5 corrected bit errors
Successfully corrected 5 bit errors per subpage
Inserted biterror @ 1/2
Read reported 6 corrected bit errors
Successfully corrected 6 bit errors per subpage
Inserted biterror @ 1/0
Read reported 7 corrected bit errors
Successfully corrected 7 bit errors per subpage
Inserted biterror @ 2/6
Read reported 8 corrected bit errors
Successfully corrected 8 bit errors per subpage
Inserted biterror @ 2/5
Failed to recover 1 bitflips
Read error after 9 bit errors per page

But I noticed the lzo decompress error is still there.
I did  following actions to test.
/dev/mtd3 is mounted on /opt using ubifs.
tar zcvf /root/opt.tar.gz /opt  (done without error)
format /opt.
tar zxvf /root/opt.tar.gz -C /

Then when I run php program which is in opt. I saw dmesg
[  118.850000] UBIFS error (ubi0:0 pid 1526): ubifs_decompress: cannot
decompress 2293 bytes, compressor lzo, error -22
[  118.860000] UBIFS error (ubi0:0 pid 1526): do_readpage: bad data
node (block 15, inode 396)
[  118.870000] UBIFS error (ubi0:0 pid 1526): do_readpage: cannot read
page 15 of inode 396, error -22
[  118.880000] UBIFS error (ubi0:0 pid 1526): ubifs_decompress: cannot
decompress 2293 bytes, compressor lzo, error -22
[  118.900000] UBIFS error (ubi0:0 pid 1526): do_readpage: bad data
node (block 15, inode 396)
[  118.900000] UBIFS error (ubi0:0 pid 1526): do_readpage: cannot read
page 15 of inode 396, error -22
[  118.920000] UBIFS error (ubi0:0 pid 1526): ubifs_decompress: cannot
decompress 2293 bytes, compressor lzo, error -22
[  118.930000] UBIFS error (ubi0:0 pid 1526): do_readpage: bad data
node (block 15, inode 396)
[  118.940000] UBIFS error (ubi0:0 pid 1526): do_readpage: cannot read
page 15 of inode 396, error -22

I removed the ubifs_dump_node call to avoid many dump text. The
problem is when I run php program, lots of above logs dumped.
But I don't see any effect of the above logs. the program seems running.
Is there a possibility the underlying nand driver data is ok, but the
lzo compress/decompress code has bugs ?  I am running linux-5.4.y
cloned from kernel.org.

On Fri, Apr 15, 2022 at 4:29 PM Miquel Raynal <miquel.raynal@bootlin.com> wrote:
>
> Hi Scott,
>
> macromarship@gmail.com wrote on Fri, 15 Apr 2022 12:38:09 +0800:
>
> > Hi. Miquèl.
> > Yes. I tried nandbiterrs, the result is below. Looks ecc is not working .
> >
> > [root@jgcx: ~]#./nandbiterrs /dev/mtd2 -i
> > incremental biterrors test
> > Successfully corrected 0 bit errors per subpage
> > Inserted biterror @ 0/5
> > Failed to recover 1 bitflips
> > Read error after 1 bit errors per page
> >
> > By checking the nand driver whichi is nuc980_nand.c
> >
> > https://github.com/OpenNuvoton/NUC980-linux-4.4.y/blob/master/drivers/mtd/nand/nuc980_nand.c
> >
> >
> > * Enable HW ECC : unused on most chips
> > */
> > void nuc980_nand_enable_hwecc(struct mtd_info *mtd, int mode)
> > {
> > ENTER();
> > #ifdef NUC980_NAND_DEBUG
> > {
> > char * ptr=REG_SMRA0;
> > int i=0;
> > if( mode == NAND_ECC_READ )
> > printk("[R]=\n");
> > else
> > printk("[W]=\n");
> >
> > for(i=0; i<mtd->oobsize; i++)
> > {
> > printk("%X ", *(ptr+i) );
> > if ( i % 32 == 31)
> > printk("\n");
> > }
> > printk("\n");
> > }
> > #endif
> > LEAVE();
> > }
> >
> >
> > I guess the nuc980 driver doesn't support ecc correction.
>
> You cannot use NAND without proper ECC handling.
>
> Thanks,
> Miquèl

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