On Fri, May 20, 2016 at 05:45:12AM +0200, Adam Borowski wrote:
> (Only btrfs currently implements dedupe_file_range.)
>
> Instead of checking the mode of the file descriptor, let's check whether
> it could have been opened rw. This allows fixing failures when deduping
> a live system: anyone trying to exec a file currently being deduped gets
> ETXTBSY.
>
> Issuing this ioctl on a ro file was already allowed for root/cap.
>
> Signed-off-by: Adam Borowski <kilob...@angband.pl>
Hi Adam, this patch seems reasonable to me but I have to admit to being
worried about 'unintended consequences'. I poked around the code in fs/ for
a bit and saw mostly checks against file open mode. It might be that dedupe
is a special case due to the potential for longer running operations, but
theoretically you'd see the same problem if trying to exec against a file
being cloned too, correct? If that's the case then I wonder how this issue
gets solved for other ioctls.
--Mark
--
Mark Fasheh
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