---- 在 星期四, 2020-10-15 12:57:41 Al Viro <viro@xxxxxxxxxxxxxxxxxx> 撰写 ----
> On Thu, Oct 15, 2020 at 11:42:51AM +0800, Chengguang Xu wrote:
> > ---- 在 星期四, 2020-10-15 11:25:01 Al Viro <viro@xxxxxxxxxxxxxxxxxx> 撰写 ----
> > > On Sat, Oct 10, 2020 at 10:23:51PM +0800, Chengguang Xu wrote:
> > > > Currently there is no notification api for kernel about modification
> > > > of vfs inode, in some use cases like overlayfs, this kind of notification
> > > > will be very helpful to implement containerized syncfs functionality.
> > > > As the first attempt, we introduce marking inode dirty notification so that
> > > > overlay's inode could mark itself dirty as well and then only sync dirty
> > > > overlay inode while syncfs.
> > >
> > > Who's responsible for removing the crap from notifier chain? And how does
> > > that affect the lifetime of inode?
> >
> > In this case, overlayfs unregisters call back from the notifier chain of upper inode
> > when evicting it's own inode. It will not affect the lifetime of upper inode because
> > overlayfs inode holds a reference of upper inode that means upper inode will not be
> > evicted while overlayfs inode is still alive.
>
> Let me see if I've got it right:
> * your chain contains 1 (for upper inodes) or 0 (everything else, i.e. the
> vast majority of inodes) recepients
> * recepient pins the inode for as long as the recepient exists
>
> That looks like a massive overkill, especially since all you are propagating is
> dirtying the suckers. All you really need is one bit in your inode + hash table
> indexed by the address of struct inode (well, middle bits thereof, as usual).
> With entries embedded into overlayfs-private part of overlayfs inode. And callback
> to be called stored in that entry...
>
Hi AI, Jack, Amir
Based on your feedback, I would to change the inode dirty notification
something like below, is it acceptable?
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 1492271..48473d9 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2249,6 +2249,14 @@ void __mark_inode_dirty(struct inode *inode, int flags)
trace_writeback_mark_inode_dirty(inode, flags);
+ if (inode->state & I_OVL_INUSE) {
+ struct inode *ovl_inode;
+
+ ovl_inode = ilookup5(NULL, (unsigned long)inode, ovl_inode_test, inode);
+ if (ovl_inode)
+ __mark_inode_dirty(ovl_inode, flags);
+ }
+
/*
* Don't do this for I_DIRTY_PAGES - that doesn't actually
* dirty the inode itself
diff --git a/fs/inode.c b/fs/inode.c
index 72c4c34..ed6c85e 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -820,7 +820,7 @@ static struct inode *find_inode(struct super_block *sb,
repeat:
hlist_for_each_entry(inode, head, i_hash) {
- if (inode->i_sb != sb)
+ if (sb && inode->i_sb != sb)
continue;
if (!test(inode, data))
continue;
Thanks,
Chengguang
