[PATCH v3 13/16] isofs: Implement fileattr_get for case sensitivity

[Chuck Lever <cel@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

Upper layers such as NFSD need a way to query whether a
filesystem handles filenames in a case-sensitive manner so
they can provide correct semantics to remote clients. Without
this information, NFS exports of ISO 9660 filesystems cannot
properly advertise their filename case behavior.

Implement isofs_fileattr_get() to report ISO 9660 case
handling behavior. The 'check=r' (relaxed) mount option
enables case-insensitive lookups, and this setting determines
the value reported through the file_kattr structure. By
default, Joliet extensions operate in relaxed mode while plain
ISO 9660 uses strict (case-sensitive) mode. All ISO 9660
variants are case-preserving, meaning filenames are stored
exactly as they appear on the disc.

The callback is registered only on isofs_dir_inode_operations
because isofs has no custom inode_operations for regular
files, and symlinks use the generic page_symlink_inode_operations.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/isofs/dir.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/isofs/dir.c b/fs/isofs/dir.c
index 09df40b612fb..717cdf726e83 100644
--- a/fs/isofs/dir.c
+++ b/fs/isofs/dir.c
@@ -12,6 +12,7 @@
  *  isofs directory handling functions
  */
 #include <linux/gfp.h>
+#include <linux/fileattr.h>
 #include "isofs.h"
 
 int isofs_name_translate(struct iso_directory_record *de, char *new, struct inode *inode)
@@ -266,6 +267,15 @@ static int isofs_readdir(struct file *file, struct dir_context *ctx)
 	return result;
 }
 
+static int isofs_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
+{
+	struct isofs_sb_info *sbi = ISOFS_SB(dentry->d_sb);
+
+	fa->case_insensitive = sbi->s_check == 'r';
+	fa->case_preserving = true;
+	return 0;
+}
+
 const struct file_operations isofs_dir_operations =
 {
 	.llseek = generic_file_llseek,
@@ -279,6 +289,7 @@ const struct file_operations isofs_dir_operations =
 const struct inode_operations isofs_dir_inode_operations =
 {
 	.lookup = isofs_lookup,
+	.fileattr_get = isofs_fileattr_get,
 };
 
 
-- 
2.52.0