Re: [PATCH 0/9] Switch defines to enums

[David Sterba <dsterba@suse.cz>]

On Wed, Nov 28, 2018 at 09:33:50AM +0800, Qu Wenruo wrote:
> On 2018/11/28 上午3:53, David Sterba wrote:
> > This is motivated by a merging mistake that happened a few releases ago.
> > Two patches updated BTRFS_FS_* flags independently to the same value,
> > git did not see any direct merge conflict. The two values got mixed at
> > runtime and caused crash.
> > 
> > Update all #define sequential values, the above merging problem would
> > not happen as there would be a conflict and the enum value
> > auto-increment would prevent duplicated values anyway.
> 
> Just one small question for the bitmap usage.
> 
> For enum we won't directly know the last number is, my concern is if
> we're using u16 as bitmap and there is some enum over 15, will we get a
> warning at compile time or some bug would just sneak into kernel?

Do you have a concrete example where this would happen? Most bits are
used in 'long' that should be at least 32. I'm not aware of 16bit bits
flags.