linux-ext4 - [PATCH RFC 2/7] fs: Add DCACHE_CASEFOLD

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Date:   Wed,  1 Jun 2022 16:44:32 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     viro@...iv.linux.org.uk, tytso@....edu, jaegeuk@...nel.org
Cc:     ebiggers@...nel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel@...labora.com
Subject: [PATCH RFC 2/7] fs: Add DCACHE_CASEFOLD_LOOKUP flag

This flag marks a negative or positive dentry as being created after a
case-insensitive lookup operation.  It is useful to differentiate
dentries this way to detect whether the negative dentry can be trusted
during a case-insensitive lookup.

Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
---
 fs/dcache.c            | 7 +++++++
 include/linux/dcache.h | 8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/fs/dcache.c b/fs/dcache.c
index a0fe9e3676fb..518ddb7fbe0c 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1958,6 +1958,13 @@ void d_set_fallthru(struct dentry *dentry)
 }
 EXPORT_SYMBOL(d_set_fallthru);
 
+void d_set_casefold_lookup(struct dentry *dentry)
+{
+	spin_lock(&dentry->d_lock);
+	dentry->d_flags |= DCACHE_CASEFOLD_LOOKUP;
+	spin_unlock(&dentry->d_lock);
+}
+
 static unsigned d_flags_for_inode(struct inode *inode)
 {
 	unsigned add_flags = DCACHE_REGULAR_TYPE;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 871f65c8ef7f..8b71c5e418c2 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -208,6 +208,7 @@ struct dentry_operations {
 #define DCACHE_FALLTHRU			0x01000000 /* Fall through to lower layer */
 #define DCACHE_NOKEY_NAME		0x02000000 /* Encrypted name encoded without key */
 #define DCACHE_OP_REAL			0x04000000
+#define DCACHE_CASEFOLD_LOOKUP		0x08000000 /* Dentry comes from a casefold directory */
 
 #define DCACHE_PAR_LOOKUP		0x10000000 /* being looked up (with parent locked shared) */
 #define DCACHE_DENTRY_CURSOR		0x20000000
@@ -497,6 +498,13 @@ static inline bool d_is_fallthru(const struct dentry *dentry)
 	return dentry->d_flags & DCACHE_FALLTHRU;
 }
 
+extern void d_set_casefold_lookup(struct dentry *dentry);
+
+static inline bool d_is_casefold_lookup(const struct dentry *dentry)
+{
+	return dentry->d_flags & DCACHE_CASEFOLD_LOOKUP;
+}
+
 
 extern int sysctl_vfs_cache_pressure;
 
-- 
2.36.1