On 11.01.2017 20:00, Eric Blake wrote: > On 11/29/2016 07:18 PM, Max Reitz wrote: >> If the backing file is overridden, this most probably does change the >> guest-visible data of a BDS. Therefore, we will need to consider this in >> bdrv_refresh_filename(). >> >> Adding a new field to the BDS is not nice, but it is very simple and >> exactly keeps track of whether the backing file has been overridden. >> >> This commit adds a FIXME which will be remedied by a follow-up commit. >> Until then, the respective piece of code will not result in any behavior >> that is worse than what we currently have. >> >> Signed-off-by: Max Reitz <[email protected]> >> --- > >> +++ b/include/block/block_int.h >> @@ -461,6 +461,7 @@ struct BlockDriverState { >> char backing_file[PATH_MAX]; /* if non zero, the image is a diff of >> this file image */ >> char backing_format[16]; /* if non-zero and backing_file exists */ >> + bool backing_overridden; /* backing file has been specified by the user >> */ > > Should we group all of the bool in this struct so as to reduce its size > and improve cache locality? But it's already clunky, so that may be > appropriate as a separate patch. > > Reviewed-by: Eric Blake <[email protected]>
Yep, makes sense, but we should do that in a separate patch. (Or maybe we should fix the compiler to automatically do that reordering? O:-)) Max
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