Re: [RFC] atomic create+open

[Miklos Szeredi]

> > > The reason why we do it as a lookup intent is because this has to be
> > > atomic lookup+create+open in order to be at all useful to NFS.
> > 
> > Oh, and btw there's a problem with atomic lookup+create+open: mounts.
> > Do you want to follow mounts inside ->lookup().  Ugly.
> 
> No. Why do you think you would need to? The VFS is supposed to protect
> you against races with mount and other local objects (dcache races,
> inode races,...). The problem is remote objects.

Say you have NFS mount on /mnt and a bind mount over the regular file
/mnt/foo.  You do open("/mnt/foo", O_RDWR | O_CREAT, 0644).  How do
you solve the atomic open case.

If you open in ->lookup("foo") you will be opening the wrong file,
unless you want to follow mounts inside ->lookup.

Miklos
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