Messages in this thread | | | From | Miklos Szeredi <> | Date | Thu, 26 Apr 2018 17:21:40 +0200 | Subject | Re: [RFC PATCH 09/35] ovl: stack file ops |
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On Thu, Apr 26, 2018 at 5:13 PM, Vivek Goyal <vgoyal@redhat.com> wrote:
> Aha, cool. thanks. While I am at it, let me just ask one more stupid > question. > > I am wondering while opening the underlying realfile, why do we pass > in the path/dentry of ovl layer (and not underlying real layer). > > realfile = path_open(&file->f_path, file->f_flags | O_NOATIME, > realinode, current_cred(), false); > > This forces us to do file_dentry() in ovl_open() later to map top level > dentry to underlying dentry. > > We know the realinode and should be figure out real dentry. Can't we > construct path from underlying dentry and mount point and use that > to open underlying real file. I am sure there is some reason for doing > this way, just trying to understand it.
The logical thing would be to just use the real path (as returned by ovl_path_real()).
The reason we don't do that is because mmap stores the real file in vma->vm_file and vm_file->f_path is used in various places (e.g. /proc/PID/maps).
We could have a separate realfile for mmap, but that would be additional complexity and memory use, so I don't think it makes sense.
Thanks, Miklos
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