[PATCH v2 1/8] dcache: Add helper to disable d_revalidate for a specific dentry

[Gabriel Krisman Bertazi <krisman@suse.de>]

Case-insensitive wants d_compare/d_hash for every dentry in the
filesystem, while fscrypt needs d_revalidate only for DCACHE_NOKEY_NAME.
This means we currently can't use sb->s_d_op to set case-insensitive
hooks in fscrypt+case-insensitive filesystems without paying the cost to
call d_revalidate for every dentry in the filesystem.

In preparation to doing exactly that, add a way to disable d_revalidate
later.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
---
 fs/dcache.c            | 10 ++++++++++
 include/linux/dcache.h |  1 +
 2 files changed, 11 insertions(+)

diff --git a/fs/dcache.c b/fs/dcache.c
index c82ae731df9a..1f5464cd3bd1 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1911,6 +1911,16 @@ struct dentry *d_alloc_name(struct dentry *parent, const char *name)
 }
 EXPORT_SYMBOL(d_alloc_name);
 
+void d_set_always_valid(struct dentry *dentry)
+{
+	if (!(dentry->d_flags & DCACHE_OP_REVALIDATE))
+		return;
+
+	spin_lock(&dentry->d_lock);
+	dentry->d_flags &= ~DCACHE_OP_REVALIDATE;
+	spin_unlock(&dentry->d_lock);
+}
+
 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
 {
 	WARN_ON_ONCE(dentry->d_op);
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 3da2f0545d5d..d2ce151b2d8e 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -225,6 +225,7 @@ extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *);
 extern void __d_drop(struct dentry *dentry);
 extern void d_drop(struct dentry *dentry);
 extern void d_delete(struct dentry *);
+extern void d_set_always_valid(struct dentry *dentry);
 extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
 
 /* allocate/de-allocate */
-- 
2.43.0