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From:   Andreas Dilger <adilger@dilger.ca>
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Subject: Re: UAPI value collision: STATX_ATTR_MOUNT_ROOT vs STATX_ATTR_DAX
Date:   Wed, 25 Nov 2020 20:00:02 -0700
In-Reply-To: <CAJfpegvc5FjU-X1DxNtPjJLgEp_gT228kqk2Va31nk7GjZbPBQ@mail.gmail.com>
Cc:     David Howells <dhowells@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Miklos Szeredi <mszeredi@redhat.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Eric Sandeen <sandeen@redhat.com>,
        linux-fsdevel@vger.kernel.org,
        linux-man <linux-man@vger.kernel.org>,
        linux-kernel@vger.kernel.org
To:     Miklos Szeredi <miklos@szeredi.hu>
References: <1927370.1606323014@warthog.procyon.org.uk>
 <CAJfpegvc5FjU-X1DxNtPjJLgEp_gT228kqk2Va31nk7GjZbPBQ@mail.gmail.com>
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On Nov 25, 2020, at 12:26 PM, Miklos Szeredi <miklos@szeredi.hu> wrote:
>=20
> On Wed, Nov 25, 2020 at 5:57 PM David Howells <dhowells@redhat.com> =
wrote:
>>=20
>> Hi Linus, Miklos, Ira,
>>=20
>> It seems that two patches that got merged in the 5.8 merge window =
collided and
>> no one noticed until now:
>>=20
>> 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 */
>>=20
>> The question is, what do we do about it?  Renumber one or both of the
>> constants?
>=20
> <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.
>=20
> <uapi/linux/fs.h>:
> #define FS_DAX_FL 0x02000000 /* Inode is DAX */
>=20
> 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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