[fuse] Relevance of st_ino values

[Nikolaus Rath <Nikolaus@rath.org>]

Hello,

For several requests, FUSE userspace returns a struct stat to the
kernel. struct stat includes an st_ino field, but FUSE generally has a
separate field for the inode (e.g. fuse_entry_param.ino vs
fuse_entry_param.attr.st_ino).

Does the kernel use the st_ino value at all, or is just passed through
to userspace?

If it is just passed through, is there a need for st_ino to match the
"real" inode?

Background:

Given that userspace has no use for inode values other than comparing
them for equality, I would have expected that st_ino can basically be
anything as long as there's some 1:1 mapping to kernel inodes. However,
I have seen changes in userspace behavior when setting st_ino to the
kernel inode (previously it was set to some other value by accident).


Thanks!
-Nikolaus

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