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author | Eric W. Biederman <ebiederm@xmission.com> | 2014-02-13 07:54:28 -0800 |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2014-10-09 02:38:54 -0400 |
commit | bafc9b754f752ea798c39f9b099a228fd56604e0 (patch) | |
tree | 73116f40eebcf348d3f35ae0350576e5955c7422 /fs/mount.h | |
parent | 3ccb354d641d910309b916b9c856e2a82ced7237 (diff) |
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 <miklos@szeredi.hu>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/mount.h')
0 files changed, 0 insertions, 0 deletions