From: Eric W. Biederman Date: Thu, 13 Feb 2014 15:54:28 +0000 (-0800) Subject: vfs: More precise tests in d_invalidate X-Git-Tag: fixes-against-v3.18-rc2~105^2~54 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bafc9b754f75;p=pandora-kernel.git vfs: More precise tests in d_invalidate The current comments in d_invalidate about what and why it is doing what it is doing are wildly off-base. Which is not surprising as the comments date back to last minute bug fix of the 2.2 kernel. The big fat lie of a comment said: If it's a directory, we can't drop it for fear of somebody re-populating it with children (even though dropping it would make it unreachable from that root, we still might repopulate it if it was a working directory or similar). [AV] What we really need to avoid is multiple dentry aliases of the same directory inode; on all filesystems that have ->d_revalidate() we either declare all positive dentries always valid (and thus never fed to d_invalidate()) or use d_materialise_unique() and/or d_splice_alias(), which take care of alias prevention. The current rules are: - To prevent mount point leaks dentries that are mount points or that have childrent that are mount points may not be be unhashed. - All dentries may be unhashed. - Directories may be rehashed with d_materialise_unique check_submounts_and_drop implements this already for well maintained remote filesystems so implement the current rules in d_invalidate by just calling check_submounts_and_drop. The one difference between d_invalidate and check_submounts_and_drop is that d_invalidate must respect it when a d_revalidate method has earlier called d_drop so preserve the d_unhashed check in d_invalidate. Reviewed-by: Miklos Szeredi Signed-off-by: "Eric W. Biederman" Signed-off-by: Al Viro --- Reading git-diff-tree failed