linux-ext4 - [PATCH v4 04/12] fscrypt: Drop d_revalidate for valid dentries during lookup

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Date: Fri, 26 Jan 2024 21:10:04 -0300
From: Gabriel Krisman Bertazi <krisman@...e.de>
To: ebiggers@...nel.org,
	viro@...iv.linux.org.uk,
	jaegeuk@...nel.org,
	tytso@....edu
Cc: amir73il@...il.com,
	linux-ext4@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net,
	linux-fsdevel@...r.kernel.org,
	Gabriel Krisman Bertazi <krisman@...e.de>
Subject: [PATCH v4 04/12] fscrypt: Drop d_revalidate for valid dentries during lookup

Unencrypted and encrypted-dentries where the key is available don't need
to be revalidated with regards to fscrypt, since they don't go stale
from under VFS and the key cannot be removed for the encrypted case
without evicting the dentry.  Mark them with d_set_always_valid, to
avoid unnecessary revalidation, in preparation to always configuring
d_op through sb->s_d_op.

Since the filesystem might have other features that require
revalidation, only apply this optimization if the d_revalidate handler
is fscrypt_d_revalidate itself.

Signed-off-by: Gabriel Krisman Bertazi <krisman@...e.de>
---
 include/linux/fscrypt.h | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 4aaf847955c0..a22997b9f35c 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -942,11 +942,22 @@ static inline int fscrypt_prepare_rename(struct inode *old_dir,
 static inline void fscrypt_prepare_lookup_dentry(struct dentry *dentry,
 						 bool is_nokey_name)
 {
-	if (is_nokey_name) {
-		spin_lock(&dentry->d_lock);
+	spin_lock(&dentry->d_lock);
+
+	if (is_nokey_name)
 		dentry->d_flags |= DCACHE_NOKEY_NAME;
-		spin_unlock(&dentry->d_lock);
+	else if (dentry->d_flags & DCACHE_OP_REVALIDATE &&
+		 dentry->d_op->d_revalidate == fscrypt_d_revalidate) {
+		/*
+		 * Unencrypted dentries and encrypted dentries where the
+		 * key is available are always valid from fscrypt
+		 * perspective. Avoid the cost of calling
+		 * fscrypt_d_revalidate unnecessarily.
+		 */
+		dentry->d_flags &= ~DCACHE_OP_REVALIDATE;
 	}
+
+	spin_unlock(&dentry->d_lock);
 }
 
 /**
-- 
2.43.0