Failed writes to block devices don't report an error

[Arnout Vandecappelle]

On Wednesday 23 June 2010 03:18:02, Chris Johns wrote:
> I see us needing both of these. Further the 'write' has:
> 
>   "[SIO] If the O_DSYNC bit has been set, write I/O operations
>    on the file descriptor shall complete as defined by synchronized
>    I/O data integrity completion."
> 
> This is an extension. I cannot find any further detail about the SIO
> extensions but to me it makes sense that we look at a standards base way
> of managing this. We have an AIO effort underway so we should consider
> the O_DSYNC flag.

 Agreed, but that's a lot more effort as it requires support all over the 
filesystem.

[snip]

> > 1. Make sure rtems_bdbuf_sync() returns an error if the write fails.
> > rtems_bdbuf_sync() is called when disks or files are sync'ed.  It
> > writes back a block and waits for the writeback to finish.  Currently,
> > it always returns successfully but we could put error detection code
> > in here.
> 
> This would be good to have. I see it being needed which ever way we go.
> I also see the following:
> 
>   if (write(fd, buf, size) != size)
>     goto handle_error
>   if (sync_call(..) < 0)
>     goto handle_error
> 
> in an application could be a work around until a more standard approach
> is made. I prefer this over the other suggestions.

...which is why I put it as the first one :-)

[snip]


> 
> > 4. In the block device driver itself (spi-sd-card.c in my case), detect
> > that the media is removed and take appropriate action.  I'm not
> > entirely sure, though, what 'appropriate action' would be.
> 
> I know Sebastian has something like this for USB devices. Maybe he can
> help here.

 As I feared, "appropriate action" turns out to be quite complex.  And 
detecting that the SD card has disappeared isn't trivial if the card detect 
pin isn't connected...

 Regards,
 Arnout
-- 
Arnout Vandecappelle                               arnout at mind be
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