On Thu, Sep 15, 2016 at 4:07 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote: > On Thu, Sep 15, 2016 at 10:01:03AM -0700, Dan Williams wrote: >> On Thu, Sep 15, 2016 at 1:26 AM, Christoph Hellwig <hch@xxxxxx> wrote: >> > On Wed, Sep 14, 2016 at 11:54:38PM -0700, Dan Williams wrote: >> >> The DAX property, page cache bypass, of a VMA is only detectable via the >> >> vma_is_dax() helper to check the S_DAX inode flag. However, this is >> >> only available internal to the kernel and is a property that userspace >> >> applications would like to interrogate. >> > >> > They have absolutely no business knowing such an implementation detail. >> >> Hasn't that train already left the station with FS_XFLAG_DAX? > > No, that's an admin flag, not a runtime hint for applications. Just > because that flag is set on an inode, it does not mean that DAX is > actually in use - it will be ignored if the backing dev is not dax > capable. > What's the point of an admin flag if an admin can't do cat /proc/<pid of interest>/smaps, or some other mechanism, to validate that the setting the admin cares about is in effect? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>