[PATCH RFC 1/7] fs: Expose name under lookup to d_revalidate hook

[Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>]

Negative dentries support on case-insensitive ext4/f2fs will require
access to the name under lookup to ensure it matches the dentry.  This
adds an optional new flavor of cached dentry revalidation hook to expose
this extra parameter.

I'm fine with extending d_revalidate instead of adding a new hook, if
it is considered cleaner and the approach is accepted.  I wrote a new
hook to simplify reviewing.

Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
---
 fs/dcache.c            |  2 +-
 fs/namei.c             | 23 ++++++++++++++---------
 include/linux/dcache.h |  1 +
 3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 93f4f5ee07bf..a0fe9e3676fb 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1928,7 +1928,7 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
 		dentry->d_flags |= DCACHE_OP_HASH;
 	if (op->d_compare)
 		dentry->d_flags |= DCACHE_OP_COMPARE;
-	if (op->d_revalidate)
+	if (op->d_revalidate || op->d_revalidate_name)
 		dentry->d_flags |= DCACHE_OP_REVALIDATE;
 	if (op->d_weak_revalidate)
 		dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
diff --git a/fs/namei.c b/fs/namei.c
index 509657fdf4f5..b2a2e715c1a8 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -848,11 +848,16 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsi
 	return false;
 }
 
-static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
+static inline int d_revalidate(struct dentry *dentry,
+			       const struct qstr *name,
+			       unsigned int flags)
 {
-	if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
+
+	if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
+		if (dentry->d_op->d_revalidate_name)
+			return dentry->d_op->d_revalidate_name(dentry, name, flags);
 		return dentry->d_op->d_revalidate(dentry, flags);
-	else
+	} else
 		return 1;
 }
 
@@ -1569,7 +1574,7 @@ static struct dentry *lookup_dcache(const struct qstr *name,
 {
 	struct dentry *dentry = d_lookup(dir, name);
 	if (dentry) {
-		int error = d_revalidate(dentry, flags);
+		int error = d_revalidate(dentry, name, flags);
 		if (unlikely(error <= 0)) {
 			if (!error)
 				d_invalidate(dentry);
@@ -1653,19 +1658,19 @@ static struct dentry *lookup_fast(struct nameidata *nd,
 			return ERR_PTR(-ECHILD);
 
 		*seqp = seq;
-		status = d_revalidate(dentry, nd->flags);
+		status = d_revalidate(dentry, &nd->last, nd->flags);
 		if (likely(status > 0))
 			return dentry;
 		if (!try_to_unlazy_next(nd, dentry, seq))
 			return ERR_PTR(-ECHILD);
 		if (status == -ECHILD)
 			/* we'd been told to redo it in non-rcu mode */
-			status = d_revalidate(dentry, nd->flags);
+			status = d_revalidate(dentry, &nd->last, nd->flags);
 	} else {
 		dentry = __d_lookup(parent, &nd->last);
 		if (unlikely(!dentry))
 			return NULL;
-		status = d_revalidate(dentry, nd->flags);
+		status = d_revalidate(dentry, &nd->last, nd->flags);
 	}
 	if (unlikely(status <= 0)) {
 		if (!status)
@@ -1693,7 +1698,7 @@ static struct dentry *__lookup_slow(const struct qstr *name,
 	if (IS_ERR(dentry))
 		return dentry;
 	if (unlikely(!d_in_lookup(dentry))) {
-		int error = d_revalidate(dentry, flags);
+		int error = d_revalidate(dentry, name, flags);
 		if (unlikely(error <= 0)) {
 			if (!error) {
 				d_invalidate(dentry);
@@ -3258,7 +3263,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
 		if (d_in_lookup(dentry))
 			break;
 
-		error = d_revalidate(dentry, nd->flags);
+		error = d_revalidate(dentry, &nd->last, nd->flags);
 		if (likely(error > 0))
 			break;
 		if (error)
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index f5bba51480b2..871f65c8ef7f 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -126,6 +126,7 @@ enum dentry_d_lock_class
 
 struct dentry_operations {
 	int (*d_revalidate)(struct dentry *, unsigned int);
+	int (*d_revalidate_name)(struct dentry *, const struct qstr *, unsigned int);
 	int (*d_weak_revalidate)(struct dentry *, unsigned int);
 	int (*d_hash)(const struct dentry *, struct qstr *);
 	int (*d_compare)(const struct dentry *,
-- 
2.36.1