From: Eric Biggers <ebiggers@xxxxxxxxxx>
When a filesystem encryption key is removed, we need all files which had
been "unlocked" (had ->i_crypt_info set up) with it to appear "locked"
again. This is most easily done by evicting the inodes. This can
currently be done using 'echo 2 > /proc/sys/vm/drop_caches'; however,
that is overkill and not usable by non-root users.
To evict just the needed inodes we also need the ability to evict those
inodes' dentries, since an inode is pinned by its dentries. Therefore,
add a function shrink_dcache_inode() which iterates through an inode's
dentries and evicts any unused ones as well as any unused descendants
(since there may be negative dentries pinning the inode's dentries).
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
fs/dcache.c | 32 ++++++++++++++++++++++++++++++++
include/linux/dcache.h | 1 +
2 files changed, 33 insertions(+)
diff --git a/fs/dcache.c b/fs/dcache.c
index aac41adf47433..1d940484c2d17 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1507,6 +1507,38 @@ void shrink_dcache_parent(struct dentry *parent)
}
EXPORT_SYMBOL(shrink_dcache_parent);
+/**
+ * shrink_dcache_inode - prune dcache for inode
+ * @inode: inode to prune
+ *
+ * Evict all unused aliases of the specified inode from the dcache. This is
+ * intended to be used when trying to evict a specific inode, since inodes are
+ * pinned by their dentries. We also have to descend to ->d_subdirs for each
+ * alias, since aliases may be pinned by negative child dentries.
+ */
+void shrink_dcache_inode(struct inode *inode)
+{
+ for (;;) {
+ struct select_data data;
+ struct dentry *dentry;
+
+ INIT_LIST_HEAD(&data.dispose);
+ data.start = NULL;
+ data.found = 0;
+
+ spin_lock(&inode->i_lock);
+ hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias)
+ d_walk(dentry, &data, select_collect);
+ spin_unlock(&inode->i_lock);
+
+ if (!data.found)
+ break;
+
+ shrink_dentry_list(&data.dispose);
+ cond_resched();
+ }
+}
+
static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
{
/* it has busy descendents; complain about those instead */
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 60996e64c5798..1b5f295dc1156 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -246,6 +246,7 @@ extern struct dentry * d_obtain_alias(struct inode *);
extern struct dentry * d_obtain_root(struct inode *);
extern void shrink_dcache_sb(struct super_block *);
extern void shrink_dcache_parent(struct dentry *);
+extern void shrink_dcache_inode(struct inode *);
extern void shrink_dcache_for_umount(struct super_block *);
extern void d_invalidate(struct dentry *);
--
2.21.0
