Re: [Libguestfs] [PATCH 5/5 v3] fuse: Add tests for guestmount.
On Wed, Nov 18, 2009 at 09:44:10AM +0000, Matthew Booth wrote:
> +stage Checking file modes of initial content
> +[ "$(stat -c %a empty)" = "644" ]
> +[ "$(stat -c %a hello.txt)" = "644" ]
> +[ "$(stat -c %a world.txt)" = "644" ]
You need to explicitly set the umask to 022 at the beginning of the
script for this to be reliable.
libguestfs guarantees the initial umask already:
http://libguestfs.org/guestfs.3.html#guestfs_umask
http://git.annexia.org/?p=libguestfs.git;a=blob;f=daemon/guestfsd.c;h=db0...
> +stage Checking sizes of initial content
> +[ "$(stat -c %s empty)" -eq 0 ]
> +[ "$(stat -c %s hello.txt)" -eq 5 ]
> +[ "$(stat -c %s world.txt)" -eq 11 ]
While you're at it, you could add tests for every other stat field.
Yup, I've checked most of them, but more would be better.
> +# This fails because of caching. The problem is that the linked
file
> +# ("hello.txt") is cached with a link count of 2.
unlink("link")
> +# invalidates the cache for "link", but_not_ for "hello.txt"
which
> +# still has the now-incorrect cached value. However there's not much
> +# we can do about this since searching for all linked inodes of a file
> +# is an O(n) operation.
> +#[ "$(stat -c %h hello.txt)" -eq 1 ]
Eurgh. What's the impact of not caching?
It's really really slow.
Note that the problem here is fairly minor. You'll see a link count
of 2 instead of 1 for just a few seconds.
Alternatively, inotify can spot an updated link count. What's the
potential for adding asynchronous cache invalidation from the daemon?
I don't think inotify helps here ... The linked file could be
anywhere in the whole filesystem, so you'd have to have inotify
watches in every single directory in the filesystem.
I really don't think there's a good way to solve this ...
Rich.
--
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