[U-Boot] [BUG] cb8af8af5ba0 "fs: fat: support write with non-zero offset" fatwrite followed by fatload and then cmp fails

[Akashi, Takahiro]

Hi Faiz,

On Tue, Mar 12, 2019 at 02:11:08PM +0530, Faiz Abbas wrote:
> Hi Akashi,
> 
> On 11/09/18 12:29 PM, Akashi, Takahiro wrote:
> > From: AKASHI Takahiro <takahiro.akashi at linaro.org>
> > 
> > The current write implementation is quite simple: remove existing clusters
> > and then allocating new ones and filling them with data. This, inevitably,
> > enforces always writing from the beginning of a file.
> > 
> > As the first step to lift this restriction, fat_file_write() and
> > set_contents() are modified to accept an additional parameter, file offset
> > and further re-factored so that, in the next patch, all the necessary code
> > will be put into set_contents().
> > 
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> > ---
> 
> My fatwrite, fatload and compare tests are failing in MMC with this
> commit. This is what I see:
> 
> => fatwrite mmc 0 ${loadaddr} test 0x2000000
> 33554432 bytes written
> => fatload mmc 0 84000000 test
> 33554432 bytes read in 2149 ms (14.9 MiB/s)
> => cmp.b 82000000 84000000 0x2000000
> byte at 0x820c5000 (0x85) != byte at 0x840c5000 (0x9d)
> Total of 806912 byte(s) were the same
> =>

I tried, but could not reproduce this issue.
(v2019.04-rc2)

What I did was:
- On host, create a vfat file system and a random data file.
     dd of=vfat128M.img bs=1M count=128
     mkfs -t vfat vfat128M.img ; mount ...
     head -c 32m /dev/urandom > 32m.data

- On qemu, try fatwrite
  (try 1)
  => fatload scsi 0:0 50000000 /32m.data 2000000
  33554432 bytes read in 539 ms (59.4 MiB/s)
  => fatwrite scsi 0:0 50000000 /32m_w.data 2000000
  33554432 bytes written
  => fatls scsi 0:0 /
  33554432   32m.data
  33554432   32m_w.data

  2 file(s), 0 dir(s)

  => fatload scsi 0:0 52000000 /32m_w.data
  33554432 bytes read in 537 ms (59.6 MiB/s)
  => cmp.b 50000000 52000000 2000000
  Total of 33554432 byte(s) were the same

  (try 2)
  => fatwrite scsi 0:0 54000000 /32m_w2.data 2000000
  33554432 bytes written
  => fatload scsi 0:0 56000000 /32m_w2.data    
  33554432 bytes read in 537 ms (59.6 MiB/s)
  => cmp.b 54000000 56000000 2000000
  Total of 33554432 byte(s) were the same

- I also confirmed that 32m.data and 32m_w.data are the same
  on the host.

> Reverting this commit fixes this issue for me.

So, first let me ask some questions:
- What is the size of your mmc memory?
- How did you format it?
- How many files are already there in the root directory?

Thanks,
-Takahiro Akashi


> Thanks,
> Faiz
> 
> 
> 
> 
>