Trouble with RFS

Joel Sherrill joel.sherrill at
Thu Jun 9 14:56:49 UTC 2011

Is this with 4.10.0?  There is a bug which sounds
like this.


On 06/09/2011 09:14 AM, Oleg Moroz wrote:
> Hello.
> I've discovered a possible bug with RFS, though I have no idea why 
> does it happening.
> My goal was to develop event logger based on ring buffer, which is 
> stored in a file of static size (say, 2048 bytes). It didn't take a 
> lot of time, and I've tested it on debian linux first, so I'm pretty 
> much sured my logger is OK. After that, I've reconfigured it for using 
> with RTEMS. Everything did work fine while I was using IMFS or dosfs 
> to store the file with logs. But when I tried to use it with RFS, I 
> experienced the following case: it truncates my file, when I try to 
> write more than 1536 bytes of data. For example, if I write 1024 bytes 
> and close the file, it's size stays unchanged and equals 2048. But if 
> I write 1700 bytes, RFS truncates my file to size of 1700. That 
> doesn't fit me at all, since I need my ring buffer size to be fixed 
> for obvious reasons.
> Now let's forget about ring buffer and consider a simple example:
> FILE* test = fopen("/nv/testfile","wb");
> void* buf = malloc(2048);
> memset(buf,0,2048);
> fwrite(buf,2048,1,test);
> fclose(test);
> test = fopen("/nv/testfile","wb");
> rewind(test);
> fwrite(buf,1700,1,test);
> fclose(test);
> Size of "test" after such operations will be equal to 1700. But if u 
> replace
> fwrite(buf,1700,1,test);
> with
> fwrite(buf,1200,1,test);
> the size of file will remain unchanged and will be equal to 2048. So 
> it seems that RFS truncates the file, if file pointer stops in last 
> block (in my example size of block is 512 bytes). Personally, I don't 
> think that it's normal, since no other FS does change the size of file 
> in such case.
> As I've said, I have no idea, why and what for does it happening. I'm 
> going to use another FS for further development, but I hope this 
> information about RFS can be usefull.
> Best regards, Oleg Moroz.

Joel Sherrill, Ph.D.             Director of Research&  Development
joel.sherrill at        On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
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