Re: UAPI value collision: STATX_ATTR_MOUNT_ROOT vs STATX_ATTR_DAX

[Andreas Dilger]

On Nov 25, 2020, at 12:26 PM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> 
> On Wed, Nov 25, 2020 at 5:57 PM David Howells <dhowells@xxxxxxxxxx> wrote:
>> 
>> Hi Linus, Miklos, Ira,
>> 
>> It seems that two patches that got merged in the 5.8 merge window collided and
>> no one noticed until now:
>> 
>> 80340fe3605c0 (Miklos Szeredi     2020-05-14 184) #define STATX_ATTR_MOUNT_ROOT         0x00002000 /* Root of a mount */
>> ...
>> 712b2698e4c02 (Ira Weiny          2020-04-30 186) #define STATX_ATTR_DAX                        0x00002000 /* [I] File is DAX */
>> 
>> The question is, what do we do about it?  Renumber one or both of the
>> constants?
> 
> <uapi/linux/stat.h>:
> * Note that the flags marked [I] correspond to generic FS_IOC_FLAGS
> * semantically.  Where possible, the numerical value is picked to correspond
> * also.
> 
> <uapi/linux/fs.h>:
> #define FS_DAX_FL 0x02000000 /* Inode is DAX */
> 
> The DAX one can be the same value as FS_DAX_FL, the placement (after
> STATX_ATTR_VERITY, instead of before) seems to confirm this intention.

Yes, this looks like a bug in the STATX_ATTR_DAX value.  It should be the same
as FS_DAX_FL, like all of the other STATX_ATTR_* [I] values are.

Cheers, Andreas

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