Messages in this thread | | | From | Linus Torvalds <> | Date | Sat, 8 May 2021 15:42:00 -0700 | Subject | Re: [PATCH RFC 1/3] fs: introduce helper d_path_fast() |
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On Sat, May 8, 2021 at 2:06 PM Al Viro <viro@zeniv.linux.org.uk> wrote: > > FWIW, if we go that way, I would make that > > while (dentry != root->dentry || &mnt->mnt != root->mnt) { > int error; > struct dentry *parent = READ_ONCE(dentry->d_parent);
Side note: you've added that READ_ONCE() to the parent reading, and I think that's a bug-fix regardless. The old code does that plain
parent = dentry->d_parent;
(after doing the mountpoint stuff). And d_parent isn't actually guaranteed stable here.
It probably does not matter - we are in a RCU read-locked section, so it's not like parent will go away, but in theory we might end up with (for example) pre-fetching a different parent than the one we then walk down.
But your READ_ONCE() is definitely the right thing to do (whether we do your re-org or not, and whether we do this "prepend_buffer" thing or not).
Do you want to do a final version with your fixes?
Linus
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