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

[Tom Rini <trini@konsulko.com>]

On Mon, Mar 18, 2019 at 10:42:31AM +0900, Akashi, Takahiro wrote:
> 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@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@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?

Since I think there's some timezone mismatches here, can you please try
your test in a loop?  And this is likely showing up on something like
am335x_evm or dra7xx_evm.  Thanks!

-- 
Tom
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