On Mon, Jan 08, 2007 at 10:34:45AM -0800, Dave Hansen wrote: > Removing it had a few side-effects. First of all, it made me move > all of the operations on the counts of writers to underneath the > spinlock that was already there. I guess this could be a cause > for potential contention because there _are_ locks in the common > code paths now. But, I do agree with Christoph that it would be > awfully hard to get it contended. > > The other side-effect is that we can't have the bit in mnt_flags > to be a shortcut to the superblock's writeable state since we > don't have a way to go find the mounts and that bit when a fs > changes writeable state. This causes a potential cache miss > when we have to check the superblock directly during the > relatively common __mnt_is_readonly() function.
Why? We _only_ need to check the vfsmount flag. vfsmount can become r/w if the superblock is marked r/o which means the underlying (block/network/etc) device is fundamentally not writeable. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
