linux-ext4 - patch V1 1/10] ex4: Introduce DX_HASH_UNSIGNED

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Date:	23 Sep 2014 06:03:52 -0400
From:	"George Spelvin" <linux@...izon.com>
To:	linux-ext4@...r.kernel.org
Cc:	linux@...izon.com, tytso@....edu
Subject: patch V1 1/10] ex4: Introduce DX_HASH_UNSIGNED_DELTA

This makes it easier to add additional hash algorithms in future.

Signed-off-by: George Spelvin <linux@...izon.com>
---
 fs/ext4/ext4.h  | 17 +++++++++++++----
 fs/ext4/super.c |  7 ++++---
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 1bbe7c31..cda8dd9c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1216,7 +1216,7 @@ struct ext4_sb_info {
 	u32 s_next_generation;
 	u32 s_hash_seed[4];
 	int s_def_hash_version;
-	int s_hash_unsigned;	/* 3 if hash should be signed, 0 if not */
+	int s_hash_unsigned;	/* DX_HASH_UNSIGNED_DELTA, or 0 if signed */
 	struct percpu_counter s_freeclusters_counter;
 	struct percpu_counter s_freeinodes_counter;
 	struct percpu_counter s_dirs_counter;
@@ -1737,9 +1737,18 @@ static inline __le16 ext4_rec_len_to_disk(unsigned len, unsigned blocksize)
 #define DX_HASH_LEGACY		0
 #define DX_HASH_HALF_MD4	1
 #define DX_HASH_TEA		2
-#define DX_HASH_LEGACY_UNSIGNED	3
-#define DX_HASH_HALF_MD4_UNSIGNED	4
-#define DX_HASH_TEA_UNSIGNED		5
+
+/*
+ * For historical reasons, the first three hash algorithms
+ * have signed and unsigned variants.  So, for internal
+ * use only, define some extra values outside the range of
+ * what's allowed on disk.
+ */
+#define DX_HASH_UNSIGNED_DELTA	3
+
+#define DX_HASH_LEGACY_UNSIGNED   (DX_HASH_LEGACY   + DX_HASH_UNSIGNED_DELTA)
+#define DX_HASH_HALF_MD4_UNSIGNED (DX_HASH_HALF_MD4 + DX_HASH_UNSIGNED_DELTA)
+#define DX_HASH_TEA_UNSIGNED      (DX_HASH_TEA      + DX_HASH_UNSIGNED_DELTA)
 
 static inline u32 ext4_chksum(struct ext4_sb_info *sbi, u32 crc,
 			      const void *address, unsigned int length)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 4566c2fe..6eb2c47a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3721,16 +3721,17 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	for (i = 0; i < 4; i++)
 		sbi->s_hash_seed[i] = le32_to_cpu(es->s_hash_seed[i]);
 	sbi->s_def_hash_version = es->s_def_hash_version;
-	if (EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_DIR_INDEX)) {
+	if (sbi->s_def_hash_version <= DX_HASH_TEA &&
+	    EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_DIR_INDEX)) {
 		i = le32_to_cpu(es->s_flags);
 		if (i & EXT2_FLAGS_UNSIGNED_HASH)
-			sbi->s_hash_unsigned = 3;
+			sbi->s_hash_unsigned = DX_HASH_UNSIGNED_DELTA;
 		else if ((i & EXT2_FLAGS_SIGNED_HASH) == 0) {
 #ifdef __CHAR_UNSIGNED__
 			if (!(sb->s_flags & MS_RDONLY))
 				es->s_flags |=
 					cpu_to_le32(EXT2_FLAGS_UNSIGNED_HASH);
-			sbi->s_hash_unsigned = 3;
+			sbi->s_hash_unsigned = DX_HASH_UNSIGNED_DELTA;
 #else
 			if (!(sb->s_flags & MS_RDONLY))
 				es->s_flags |=
-- 
2.1.0

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