On Mon 26-02-18 20:20:05, Dan Williams wrote: > The current IS_DAX() helper that checks the S_DAX inode flag is > ambiguous, and currently has the broken assumption that the S_DAX flag
I don't think S_DAX flag is really ambiguous. It is just that in CONFIG_FS_DAX=n + CONFIG_DEV_DAX=y case, the compiler is not able to figure out some calls behind IS_DAX() are dead code and so the kernel won't compile / link. Or is there any other problem I'm missing? If I'm indeed right, then please tell this in the changelog and don't talk about abstract ambiguity of S_DAX flag. As much as I'd prefer to solve link-time problems with stubs instead of relying on dead-code elimination, I can live with split macros so once the changelog is settled, feel free to add: Reviewed-by: Jan Kara <[email protected]> Honza > is only non-zero in the CONFIG_FS_DAX=y case. In preparation for > defining S_DAX to non-zero in the CONFIG_FS_DAX=n + CONFIG_DEV_DAX=y > case, introduce two explicit helpers to replace IS_DAX(). > > Cc: "Theodore Ts'o" <[email protected]> > Cc: Andreas Dilger <[email protected]> > Cc: Alexander Viro <[email protected]> > Cc: "Darrick J. Wong" <[email protected]> > Cc: [email protected] (supporter:XFS FILESYSTEM) > Cc: Matthew Wilcox <[email protected]> > Cc: Ross Zwisler <[email protected]> > Cc: <[email protected]> > Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap") > Reported-by: Jan Kara <[email protected]> > Signed-off-by: Dan Williams <[email protected]> > --- > include/linux/fs.h | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 79c413985305..bd0c46880572 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1909,6 +1909,28 @@ static inline bool sb_rdonly(const struct super_block > *sb) { return sb->s_flags > #define IS_WHITEOUT(inode) (S_ISCHR(inode->i_mode) && \ > (inode)->i_rdev == WHITEOUT_DEV) > > +static inline bool IS_DEVDAX(struct inode *inode) > +{ > + if (!IS_ENABLED(CONFIG_DEV_DAX)) > + return false; > + if ((inode->i_flags & S_DAX) == 0) > + return false; > + if (!S_ISCHR(inode->i_mode)) > + return false; > + return true; > +} > + > +static inline bool IS_FSDAX(struct inode *inode) > +{ > + if (!IS_ENABLED(CONFIG_FS_DAX)) > + return false; > + if ((inode->i_flags & S_DAX) == 0) > + return false; > + if (S_ISCHR(inode->i_mode)) > + return false; > + return true; > +} > + > static inline bool HAS_UNMAPPED_ID(struct inode *inode) > { > return !uid_valid(inode->i_uid) || !gid_valid(inode->i_gid); > -- Jan Kara <[email protected]> SUSE Labs, CR
