pick_link(): pass it struct path already with normal refcounting rules

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step_into() tries to avoid grabbing and dropping mount references
on the steps that do not involve crossing mountpoints (which is
obviously the majority of cases).  So it uses a local struct path
with unusual refcounting rules - path.mnt is pinned if and only if
it's not equal to nd->path.mnt.

We used to have similar beasts all over the place and we had quite
a few bugs crop up in their handling - it's easy to get confused
when changing e.g. cleanup on failure exits (or adding a new check,
etc.)

Now that's mostly gone - the step_into() instance (which is what
we need them for) is the only one left.  It is exposed to mount
traversal and it's (shortly) seen by pick_link().  Since pick_link()
needs to store it in link stack, where the normal rules apply,
it has to make sure that mount is pinned regardless of nd->path.mnt
value.  That's done on all calls of pick_link() and very early
in those.  Let's do that in the caller (step_into()) instead -
that way the fewer places need to be aware of such struct path
instances.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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Al Viro 2020-03-03 10:14:30 -05:00

parent 19f6028a01

commit 84f0cd9e83

1 changed files with 6 additions and 6 deletions

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fs/namei.c

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