On Wed, Aug 18, 2010 at 11:20 AM, David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote: > > Um, can't you? You can't *store* timestamps which are more precise, but > they can be in cache can't they? No. That is how Linux used to work, and it caused many problems, which is why the current_fs_time() function was invented. > And since you're not going to drop it from cache and bring it back in > again within 4ms, that ought to suffice? Not the problem. As usual, the problem is out-of-order timestamps: 1) Modify file A 2) Modify file B 3) File B's inode gets evicted, truncating its timestamp to disk resolution 4) Call stat() on B, bringing it back in with truncated resolution And boom, B appears to be OLDER than A. Which is not allowed. This is exactly what happened when Linux first added sub-second timestamps to the generic VFS layer. Many complaints about "make" rebuilding files unecessarily, among other things. Eventually it got fixed by the introduction of current_fs_time(). - Pat -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
