Message-Id: <20180815194811.9423-23-krisman@collabora.co.uk>
Date:   Wed, 15 Aug 2018 15:48:08 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.co.uk>
To:     tytso@....edu
Cc:     linux-ext4@...r.kernel.org, kernel@...labora.com,
        Gabriel Krisman Bertazi <krisman@...labora.co.uk>
Subject: [PATCH v2 22/25] ext4: Support encoding-aware file name lookups

This patch implements the actual support for encoding-aware file name
lookups in ext4, based on the feature bit and the encoding stored in the
superblock.

A filesystem that has the encoding feature set is able to find files
even if the name used by userspace is not exact, but an equivalent
string.  This operation will be called and inexact-match name search.

Ext4 will only store exact-match names in the cache. Even if an
inexact-match is issued, the exact-match name is what will be stored in
the dcache.  This is done to prevent unintentional duplications of
dentries in the dcache, and is the same approach used by filesystems
doing case-insensitive lookups already.  We use d_add_ci(), to fix the
names and prevent such duplication.

For now, negative lookups are not inserted in the dcache, since they
would need to be invalidated anyway, because we can't trust missing file
dentries.  This is bad for performance but requires some leveraging of
the vfs layer to fix.  We can live without that for now.

DX is supported by modifying the hashes to make them encoding-aware.
The new hashes are calculated as the hash of the normalized string,
instead of the string directly.  This allows us to efficiently search
for file names without requiring the user to provide the exact name.

Changes since v1:
  - Support normalized htree hashes.
  - Guard code with CONFIG_NLS.

Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.co.uk>
---
 fs/ext4/ext4.h   |  6 ++--
 fs/ext4/hash.c   | 34 +++++++++++++++++-
 fs/ext4/ialloc.c |  2 +-
 fs/ext4/inline.c |  2 +-
 fs/ext4/namei.c  | 92 ++++++++++++++++++++++++++++++++++++++++++------
 5 files changed, 119 insertions(+), 17 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 80e3bc57db6b..0ad59422f4a6 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1182,7 +1182,7 @@ extern void ext4_set_bits(void *bm, int cur, int len);
 
 /* Be careful when modifying these flags.  The lower byte must match the
  * NLS flags. */
-
+#define EXT4_ENC_STRICT_MODE_FL	0x0001
 #define EXT4_ENC_NLS_FL_MASK	0x00FF
 
 /*
@@ -2379,8 +2379,8 @@ extern int ext4_check_all_de(struct inode *dir, struct buffer_head *bh,
 extern int ext4_sync_file(struct file *, loff_t, loff_t, int);
 
 /* hash.c */
-extern int ext4fs_dirhash(const char *name, int len, struct
-			  dx_hash_info *hinfo);
+extern int ext4fs_dirhash(const struct inode *dir, const char *name, int len,
+			  struct dx_hash_info *hinfo);
 
 /* ialloc.c */
 extern struct inode *__ext4_new_inode(handle_t *, struct inode *, umode_t,
diff --git a/fs/ext4/hash.c b/fs/ext4/hash.c
index e22dcfab308b..1b3c9a492b14 100644
--- a/fs/ext4/hash.c
+++ b/fs/ext4/hash.c
@@ -6,6 +6,7 @@
  */
 
 #include <linux/fs.h>
+#include <linux/nls.h>
 #include <linux/compiler.h>
 #include <linux/bitops.h>
 #include "ext4.h"
@@ -196,7 +197,8 @@ static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)
  * represented, and whether or not the returned hash is 32 bits or 64
  * bits.  32 bit hashes will return 0 for the minor hash.
  */
-int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
+static int __ext4fs_dirhash(const char *name, int len,
+			    struct dx_hash_info *hinfo)
 {
 	__u32	hash;
 	__u32	minor_hash = 0;
@@ -266,3 +268,33 @@ int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
 	hinfo->minor_hash = minor_hash;
 	return 0;
 }
+
+int ext4fs_dirhash(const struct inode *dir, const char *name, int len,
+		   struct dx_hash_info *hinfo)
+{
+#ifdef CONFIG_NLS
+	const struct nls_table *charset = EXT4_SB(dir->i_sb)->encoding;
+	int r, dlen;
+	unsigned char *buff;
+
+	if (len && charset) {
+		buff = kzalloc(sizeof (char) * PATH_MAX, GFP_KERNEL);
+		if (!buff)
+			return -1;
+
+		dlen = nls_normalize(charset, name, len, buff, PATH_MAX);
+
+		if (dlen < 0) {
+			kfree(buff);
+			goto opaque_seq;
+		}
+
+		r = __ext4fs_dirhash(buff, dlen, hinfo);
+
+		kfree(buff);
+		return r;
+	}
+opaque_seq:
+#endif
+	return __ext4fs_dirhash(name, len, hinfo);
+}
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index fb83750c1a14..70a17ac9e601 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -452,7 +452,7 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
 		if (qstr) {
 			hinfo.hash_version = DX_HASH_HALF_MD4;
 			hinfo.seed = sbi->s_hash_seed;
-			ext4fs_dirhash(qstr->name, qstr->len, &hinfo);
+			ext4fs_dirhash(parent, qstr->name, qstr->len, &hinfo);
 			grp = hinfo.hash;
 		} else
 			grp = prandom_u32();
diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index e55a8bc870bd..8f2aa5d7b669 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -1401,7 +1401,7 @@ int htree_inlinedir_to_tree(struct file *dir_file,
 			}
 		}
 
-		ext4fs_dirhash(de->name, de->name_len, hinfo);
+		ext4fs_dirhash(dir, de->name, de->name_len, hinfo);
 		if ((hinfo->hash < start_hash) ||
 		    ((hinfo->hash == start_hash) &&
 		     (hinfo->minor_hash < start_minor_hash)))
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 2a4c25c4681d..87f3ccec42e2 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -35,6 +35,7 @@
 #include <linux/buffer_head.h>
 #include <linux/bio.h>
 #include <linux/iversion.h>
+#include <linux/nls.h>
 #include "ext4.h"
 #include "ext4_jbd2.h"
 
@@ -628,7 +629,7 @@ static struct stats dx_show_leaf(struct inode *dir,
 				}
 				if (!fscrypt_has_encryption_key(dir)) {
 					/* Directory is not encrypted */
-					ext4fs_dirhash(de->name,
+					ext4fs_dirhash(dir, de->name,
 						de->name_len, &h);
 					printk("%*.s:(U)%x.%u ", len,
 					       name, h.hash,
@@ -661,8 +662,8 @@ static struct stats dx_show_leaf(struct inode *dir,
 						name = fname_crypto_str.name;
 						len = fname_crypto_str.len;
 					}
-					ext4fs_dirhash(de->name, de->name_len,
-						       &h);
+					ext4fs_dirhash(dir, de->name,
+						       de->name_len, &h);
 					printk("%*.s:(E)%x.%u ", len, name,
 					       h.hash, (unsigned) ((char *) de
 								   - base));
@@ -672,7 +673,7 @@ static struct stats dx_show_leaf(struct inode *dir,
 #else
 				int len = de->name_len;
 				char *name = de->name;
-				ext4fs_dirhash(de->name, de->name_len, &h);
+				ext4fs_dirhash(dir, de->name, de->name_len, &h);
 				printk("%*.s:%x.%u ", len, name, h.hash,
 				       (unsigned) ((char *) de - base));
 #endif
@@ -761,7 +762,7 @@ dx_probe(struct ext4_filename *fname, struct inode *dir,
 		hinfo->hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
 	hinfo->seed = EXT4_SB(dir->i_sb)->s_hash_seed;
 	if (fname && fname_name(fname))
-		ext4fs_dirhash(fname_name(fname), fname_len(fname), hinfo);
+		ext4fs_dirhash(dir, fname_name(fname), fname_len(fname), hinfo);
 	hash = hinfo->hash;
 
 	if (root->info.unused_flags & 1) {
@@ -1007,7 +1008,7 @@ static int htree_dirblock_to_tree(struct file *dir_file,
 			/* silently ignore the rest of the block */
 			break;
 		}
-		ext4fs_dirhash(de->name, de->name_len, hinfo);
+		ext4fs_dirhash(dir, de->name, de->name_len, hinfo);
 		if ((hinfo->hash < start_hash) ||
 		    ((hinfo->hash == start_hash) &&
 		     (hinfo->minor_hash < start_minor_hash)))
@@ -1196,7 +1197,7 @@ static int dx_make_map(struct inode *dir, struct ext4_dir_entry_2 *de,
 
 	while ((char *) de < base + blocksize) {
 		if (de->name_len && de->inode) {
-			ext4fs_dirhash(de->name, de->name_len, &h);
+			ext4fs_dirhash(dir, de->name, de->name_len, &h);
 			map_tail--;
 			map_tail->hash = h.hash;
 			map_tail->offs = ((char *) de - base)>>2;
@@ -1256,10 +1257,14 @@ 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(const struct inode *parent,
+			      const struct ext4_filename *fname,
 			      const struct ext4_dir_entry_2 *de)
 {
 	struct fscrypt_name f;
+#ifdef CONFIG_NLS
+	const struct ext4_sb_info *sbi = EXT4_SB(parent->i_sb);
+#endif
 
 	if (!de->inode)
 		return false;
@@ -1269,6 +1274,15 @@ static inline bool ext4_match(const struct ext4_filename *fname,
 #ifdef CONFIG_EXT4_FS_ENCRYPTION
 	f.crypto_buf = fname->crypto_buf;
 #endif
+
+#ifdef CONFIG_NLS
+	if (sbi->encoding) {
+		return !nls_strncmp(sbi->encoding,
+				    de->name, de->name_len,
+				    f.disk_name.name, f.disk_name.len);
+	}
+#endif
+
 	return fscrypt_match_name(&f, de->name, de->name_len);
 }
 
@@ -1289,7 +1303,7 @@ 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)) {
+		    ext4_match(dir, fname, de)) {
 			/* found a match - just to be sure, do
 			 * a full check */
 			if (ext4_check_dir_entry(dir, NULL, de, bh, bh->b_data,
@@ -1586,6 +1600,31 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsi
 			return ERR_PTR(-EPERM);
 		}
 	}
+
+#ifdef CONFIG_NLS
+	if (EXT4_SB(dir->i_sb)->encoding) {
+		if (inode) {
+			struct dentry *new;
+			struct qstr ciname;
+
+			ciname.len = de->name_len;
+			ciname.name = kstrndup(de->name, ciname.len, GFP_NOFS);
+			if (!ciname.name)
+				return ERR_PTR(-ENOMEM);
+
+			new = d_add_ci(dentry, inode, &ciname);
+			kfree(ciname.name);
+			return new;
+		} else {
+			/* Eventually we want to call d_add_ci(dentry, NULL)
+			 * for negative dentries in the encoding case as
+			 * well.  For now, prevent the negative dentry
+			 * from being cached.
+			 */
+			return NULL;
+		}
+	}
+#endif
 	return d_splice_alias(inode, dentry);
 }
 
@@ -1796,7 +1835,7 @@ 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))
+		if (ext4_match(dir, fname, de))
 			return -EEXIST;
 		nlen = EXT4_DIR_REC_LEN(de->name_len);
 		rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
@@ -1981,7 +2020,7 @@ static int make_indexed_dir(handle_t *handle, struct ext4_filename *fname,
 	if (fname->hinfo.hash_version <= DX_HASH_TEA)
 		fname->hinfo.hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
 	fname->hinfo.seed = EXT4_SB(dir->i_sb)->s_hash_seed;
-	ext4fs_dirhash(fname_name(fname), fname_len(fname), &fname->hinfo);
+	ext4fs_dirhash(dir, fname_name(fname), fname_len(fname), &fname->hinfo);
 
 	memset(frames, 0, sizeof(frames));
 	frame = frames;
@@ -2034,6 +2073,7 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
 	struct ext4_dir_entry_2 *de;
 	struct ext4_dir_entry_tail *t;
 	struct super_block *sb;
+	struct ext4_sb_info *sbi;
 	struct ext4_filename fname;
 	int	retval;
 	int	dx_fallback=0;
@@ -2045,10 +2085,18 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
 		csum_size = sizeof(struct ext4_dir_entry_tail);
 
 	sb = dir->i_sb;
+	sbi = EXT4_SB(sb);
 	blocksize = sb->s_blocksize;
 	if (!dentry->d_name.len)
 		return -EINVAL;
 
+#ifdef CONFIG_NLS
+	if (sbi->encoding_flags & EXT4_ENC_STRICT_MODE_FL &&
+	    nls_validate(sbi->encoding, dentry->d_name.name,
+			 dentry->d_name.len))
+		return -EINVAL;
+#endif
+
 	retval = ext4_fname_setup_filename(dir, &dentry->d_name, 0, &fname);
 	if (retval)
 		return retval;
@@ -2971,6 +3019,17 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
 	ext4_update_dx_flag(dir);
 	ext4_mark_inode_dirty(handle, dir);
 
+#ifdef CONFIG_NLS
+	/* VFS negative dentries are incompatible with Encoding and
+	 * Case-insensitiveness. Eventually we'll want avoid
+	 * invalidating the dentries here, alongside with returning the
+	 * negative dentries at ext4_lookup(), when it is better
+	 * supported by the VFS for the CI case.
+	 */
+	if (EXT4_SB(dir->i_sb)->encoding)
+		d_invalidate(dentry);
+#endif
+
 end_rmdir:
 	brelse(bh);
 	if (handle)
@@ -3040,6 +3099,17 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
 	inode->i_ctime = current_time(inode);
 	ext4_mark_inode_dirty(handle, inode);
 
+#ifdef CONFIG_NLS
+	/* VFS negative dentries are incompatible with Encoding and
+	 * Case-insensitiveness. Eventually we'll want avoid
+	 * invalidating the dentries here, alongside with returning the
+	 * negative dentries at ext4_lookup(), when it is  better
+	 * supported by the VFS for the CI case.
+	 */
+	if (EXT4_SB(dir->i_sb)->encoding)
+		d_invalidate(dentry);
+#endif
+
 end_unlink:
 	brelse(bh);
 	if (handle)
-- 
2.18.0

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