[PATCH NOMERGE 11/13] ext4: Support charset name matching

[Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxxxx>]

Implement generic caseless lookup based on the mount flags using the
charset library.

Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxxxx>
---
 fs/ext4/namei.c | 47 +++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 39 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 3373017e9315..ad7330b82740 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1259,7 +1259,8 @@ static void dx_insert_block(struct dx_frame *frame, u32 hash, ext4_lblk_t block)
  *
  * Return: %true if the directory entry matches, otherwise %false.
  */
-static inline bool ext4_match(const struct ext4_filename *fname,
+static inline bool ext4_match(struct nls_table *charset,
+			      const struct ext4_filename *fname,
 			      const struct ext4_dir_entry_2 *de,
 			      bool casefold)
 {
@@ -1273,7 +1274,8 @@ static inline bool ext4_match(const struct ext4_filename *fname,
 #ifdef CONFIG_EXT4_FS_ENCRYPTION
 	f.crypto_buf = fname->crypto_buf;
 #endif
-	return fscrypt_match_name(&f, de->name, de->name_len);
+	return fscrypt_charset_match_name(charset, &f, de->name,
+					  de->name_len, casefold);
 }
 
 /*
@@ -1287,6 +1289,7 @@ int ext4_search_dir(struct buffer_head *bh, char *search_buf, int buf_size,
 	struct ext4_dir_entry_2 * de;
 	char * dlimit;
 	int de_len;
+	struct super_block *sb = dir->i_sb;
 
 	de = (struct ext4_dir_entry_2 *)search_buf;
 	dlimit = search_buf + buf_size;
@@ -1294,7 +1297,9 @@ int ext4_search_dir(struct buffer_head *bh, char *search_buf, int buf_size,
 		/* this code is executed quadratically often */
 		/* do minimal checking `by hand' */
 		if ((char *) de + de->name_len <= dlimit &&
-		    ext4_match(fname, de, flags & LOOKUP_CASEFOLD)) {
+		    ext4_match(EXT4_SB(sb)->encoding, fname, de,
+			       flags & LOOKUP_CASEFOLD)) {
+
 			/* found a match - just to be sure, do
 			 * a full check */
 			if (ext4_check_dir_entry(dir, NULL, de, bh, bh->b_data,
@@ -1395,11 +1400,13 @@ static struct buffer_head * ext4_find_entry (struct inode *dir,
 	if (is_dx(dir)) {
 		ret = ext4_dx_find_entry(dir, &fname, res_dir, flags);
 		/*
-		 * On success, or if the error was file not found,
-		 * return.  Otherwise, fall back to doing a search the
-		 * old fashioned way.
+		 * On success, or if the file cannot be found, return.
+		 * If an error occurred, or if the file was not found
+		 * but we can do case-insensitive lookups, fall back to
+		 * the linear search.
 		 */
-		if (!IS_ERR(ret) || PTR_ERR(ret) != ERR_BAD_DX_DIR)
+		if ((!IS_ERR(ret) && (ret || !(flags & LOOKUP_CASEFOLD))) ||
+		    (IS_ERR(ret) && PTR_ERR(ret) != ERR_BAD_DX_DIR))
 			goto cleanup_and_exit;
 		dxtrace(printk(KERN_DEBUG "ext4_find_entry: dx failed, "
 			       "falling back\n"));
@@ -1592,6 +1599,29 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsi
 			return ERR_PTR(-EPERM);
 		}
 	}
+
+	if (flags & LOOKUP_CASEFOLD) {
+		struct dentry *new;
+		struct qstr ciname;
+		char *name;
+
+		if (!de)
+			return d_add_ci_negative_dentry(dentry);
+
+		name = kmalloc((sizeof(char) * de->name_len) + 1,
+			       GFP_NOFS);
+		if (!name)
+			return ERR_PTR(-ENOMEM);
+
+		memcpy(name, de->name, de->name_len);
+		name[de->name_len] = '\0';
+		ciname.len = de->name_len;
+		ciname.name = name;
+		new = d_add_ci(dentry, inode, &ciname);
+		kfree(name);
+		return new;
+	}
+
 	return d_splice_alias(inode, dentry);
 }
 
@@ -1795,6 +1825,7 @@ int ext4_find_dest_de(struct inode *dir, struct inode *inode,
 	int nlen, rlen;
 	unsigned int offset = 0;
 	char *top;
+	struct super_block *sb = dir->i_sb;
 
 	de = (struct ext4_dir_entry_2 *)buf;
 	top = buf + buf_size - reclen;
@@ -1802,7 +1833,7 @@ int ext4_find_dest_de(struct inode *dir, struct inode *inode,
 		if (ext4_check_dir_entry(dir, NULL, de, bh,
 					 buf, buf_size, offset))
 			return -EFSCORRUPTED;
-		if (ext4_match(fname, de, false))
+		if (ext4_match(EXT4_SB(sb)->encoding, fname, de, false))
 			return -EEXIST;
 		nlen = EXT4_DIR_REC_LEN(de->name_len);
 		rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
-- 
2.17.0