Re: [Xen-devel] [PATCH V3 2/6] libxl_read_file_contents: fix reading sysfs file

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, May 18, 2015 at 03:23:38PM +0100, Ian Jackson wrote:
> Chunyan Liu writes ("[PATCH V3 2/6] libxl_read_file_contents: fix reading 
> sysfs file"):
> > Sysfs file has size=4096 but actual file content is less than that.
> 
> Wow.
> 
> Is there any danger that the actual size might be >4096 ?
> 
> 
> > Current libxl_read_file_contents will treat it as error when file size
> > and actual file content differs, so reading sysfs file content with
> > this function always fails. Fix it so that we can reuse this function
> > to get sysfs file content in later pvusb work.
> 
> I'm uncomfortable with removing an error check from this function for
> all its call sites.
> 
> I think, sadly, that we are going to need a new function - at least, a
> new entrypoint.
> 
> 
> We don't want to repeat the whole of libxl__read_file_contents.
> 
> Perhaps the bulk should be made into libxl__read_file_contents_core
> which takes a boolean instructing whether to tolerate magically
> shrinking files ?
> 
> Setting that boolean probably ought to arrange to insist that the
> function gets eof, in case the file is actually bigger rather than
> smaller than the size.
> 
> 
> Ian, Wei ?
> 

Yes, we need a new entry point.

Wei.

> Ian.

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