Pathname Traversal

When a pathname is passed as an argument to a system call, the syscall layer must “convert it to a vnode”.

Pathname traversal is a sequence of vop_lookup calls to descend the tree to the named file or directory.

open(“/tmp/zot”)

vp = get vnode for / (rootdir)

vp->vop_lookup(&cvp, “tmp”);

vp = cvp;

vp->vop_lookup(&cvp, “zot”);

Issues:

1. crossing mount points

2. obtaining root vnode (or current dir)

3. finding resident vnodes in memory

4. caching name->vnode translations

5. symbolic (soft) links

6. disk implementation of directories

7. locking/referencing to handle races

with name create and delete operations

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