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 jack@suse.cz
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" tytso@mit.edu Cc: Andreas Dilger adilger.kernel@dilger.ca Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: "Darrick J. Wong" darrick.wong@oracle.com Cc: linux-xfs@vger.kernel.org (supporter:XFS FILESYSTEM) Cc: Matthew Wilcox mawilcox@microsoft.com Cc: Ross Zwisler ross.zwisler@linux.intel.com Cc: stable@vger.kernel.org Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap") Reported-by: Jan Kara jack@suse.cz Signed-off-by: Dan Williams dan.j.williams@intel.com
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);