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[v6,4/9] fs: Add DCACHE_CASEFOLDED_NAME flag

Message ID 20230816050803.15660-5-krisman@suse.de (mailing list archive)
State New, archived
Headers show
Series Support negative dentries on case-insensitive ext4 and f2fs | expand

Commit Message

Gabriel Krisman Bertazi Aug. 16, 2023, 5:07 a.m. UTC 
From: Gabriel Krisman Bertazi <krisman@collabora.com>

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.

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>

---
Changes since v5:
  - Fix EXPORT_SYMBOL (Eric, kernel test bot)
Changes since v4:
  - Fixup names of functions to reflect flag name change (Eric)

Changes since v2:
  -  Rename DCACHE_CASEFOLD_LOOKUP -> DCACHE_CASEFOLDED_NAME (Eric)
---
 fs/dcache.c            | 8 ++++++++
 include/linux/dcache.h | 8 ++++++++
 2 files changed, 16 insertions(+)

Comments

Al Viro Nov. 22, 2023, 8:32 p.m. UTC | #1 
On Wed, Aug 16, 2023 at 01:07:58AM -0400, Gabriel Krisman Bertazi wrote:
> From: Gabriel Krisman Bertazi <krisman@collabora.com>
> 
> 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.

What should happen to that flag when d_splice_alias() picks an existing
alias?  AFAICS, you set it in ->lookup() for the dentry passed to ->lookup(),
but the alias picked by that sucker won't see anything of that sort, will
it?
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Patch

diff --git a/fs/dcache.c b/fs/dcache.c
index 52e6d5fdab6b..91e5cd4c4237 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1958,6 +1958,14 @@  void d_set_fallthru(struct dentry *dentry)
 }
 EXPORT_SYMBOL(d_set_fallthru);
 
+void d_set_casefolded_name(struct dentry *dentry)
+{
+	spin_lock(&dentry->d_lock);
+	dentry->d_flags |= DCACHE_CASEFOLDED_NAME;
+	spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL(d_set_casefolded_name);
+
 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 9362e4ef0bad..ccbb5c4db7ce 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_CASEFOLDED_NAME		0x08000000 /* Dentry comes from a casefold directory */
 
 #define DCACHE_PAR_LOOKUP		0x10000000 /* being looked up (with parent locked shared) */
 #define DCACHE_DENTRY_CURSOR		0x20000000
@@ -496,6 +497,13 @@  static inline bool d_is_fallthru(const struct dentry *dentry)
 	return dentry->d_flags & DCACHE_FALLTHRU;
 }
 
+extern void d_set_casefolded_name(struct dentry *dentry);
+
+static inline bool d_is_casefolded_name(const struct dentry *dentry)
+{
+	return dentry->d_flags & DCACHE_CASEFOLDED_NAME;
+}
+
 
 extern int sysctl_vfs_cache_pressure;