On Wed, Sep 04, 2019 at 03:38:20PM -0700, Linus Torvalds wrote: > On Wed, Sep 4, 2019 at 3:31 PM David Howells <dhowells@xxxxxxxxxx> wrote: > > > > It ought to be reasonably easy to make them per-sb at least, I think. We > > don't allow cross-super rename, right? > > Right now the sequence count handling very much depends on it being a > global entity on the reader side, at least. > > And while the rename sequence count could (and probably should) be > per-sb, the same is very much not true of the mount one. Huh? That will cost us having to have a per-superblock dentry hash table; recall that lockless lockup can give false negatives if something gets moved from chain to chain, and rename_lock is first and foremost used to catch those and retry. If we split it on per-superblock basis, we can't have dentries from different superblocks in the same chain anymore...
