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authorEric W. Biederman <ebiederm@xmission.com>2014-02-13 19:54:28 +0400
committerAl Viro <viro@zeniv.linux.org.uk>2014-10-09 10:38:54 +0400
commitbafc9b754f752ea798c39f9b099a228fd56604e0 (patch)
tree73116f40eebcf348d3f35ae0350576e5955c7422 /fs/dcache.c
parent3ccb354d641d910309b916b9c856e2a82ced7237 (diff)
downloadlinux-bafc9b754f752ea798c39f9b099a228fd56604e0.tar.xz
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/dcache.c')
-rw-r--r--fs/dcache.c38
1 files changed, 4 insertions, 34 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 1f8e6acb0ea4..8150e4e9e88b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -650,9 +650,8 @@ EXPORT_SYMBOL(dput);
* @dentry: dentry to invalidate
*
* Try to invalidate the dentry if it turns out to be
- * possible. If there are other dentries that can be
- * reached through this one we can't delete it and we
- * return -EBUSY. On success we return 0.
+ * possible. If there are reasons not to delete it
+ * return -EBUSY. On success return 0.
*
* no dcache lock.
*/
@@ -667,38 +666,9 @@ int d_invalidate(struct dentry * dentry)
spin_unlock(&dentry->d_lock);
return 0;
}
- /*
- * Check whether to do a partial shrink_dcache
- * to get rid of unused child entries.
- */
- if (!list_empty(&dentry->d_subdirs)) {
- spin_unlock(&dentry->d_lock);
- shrink_dcache_parent(dentry);
- spin_lock(&dentry->d_lock);
- }
-
- /*
- * Somebody else still using it?
- *
- * 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 the root,
- * we might still populate it if it was a
- * working directory or similar).
- * We also need to leave mountpoints alone,
- * directory or not.
- */
- if (dentry->d_lockref.count > 1 && dentry->d_inode) {
- if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
- spin_unlock(&dentry->d_lock);
- return -EBUSY;
- }
- }
-
- __d_drop(dentry);
spin_unlock(&dentry->d_lock);
- return 0;
+
+ return check_submounts_and_drop(dentry);
}
EXPORT_SYMBOL(d_invalidate);