udf: create common function for tag checksumming

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Acked-by: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 22 insertions, 56 deletions

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 3ce2f6d1aafa..42783da9cfe3 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1440,7 +1440,6 @@ static int udf_update_inode(struct inode *inode, int do_sync)
         uint32_t udfperms;
         uint16_t icbflags;
         uint16_t crclen;
-        int i;
         kernel_timestamp cpu_time;
         int err = 0;
         struct udf_sb_info *sbi = UDF_SB(inode->i_sb);
@@ -1476,12 +1475,7 @@ static int udf_update_inode(struct inode *inode, int do_sync)
                 use->descTag.descCRC = cpu_to_le16(udf_crc((char *)use +
                                                            sizeof(tag), crclen,
                                                            0));
-
-                use->descTag.tagChecksum = 0;
-                for (i = 0; i < 16; i++)
-                        if (i != 4)
-                                use->descTag.tagChecksum +=
-                                                ((uint8_t *)&(use->descTag))[i];
+                use->descTag.tagChecksum = udf_tag_checksum(&use->descTag);
 
                 mark_buffer_dirty(bh);
                 brelse(bh);
@@ -1650,12 +1644,7 @@ static int udf_update_inode(struct inode *inode, int do_sync)
         fe->descTag.descCRCLength = cpu_to_le16(crclen);
         fe->descTag.descCRC = cpu_to_le16(udf_crc((char *)fe + sizeof(tag),
                                                   crclen, 0));
-
-        fe->descTag.tagChecksum = 0;
-        for (i = 0; i < 16; i++)
-                if (i != 4)
-                        fe->descTag.tagChecksum +=
-                                ((uint8_t *)&(fe->descTag))[i];
+        fe->descTag.tagChecksum = udf_tag_checksum(&fe->descTag);
 
         /* write the data blocks */
         mark_buffer_dirty(bh);
diff --git a/fs/udf/misc.c b/fs/udf/misc.c
index a0bf4158f1f1..585e4eaed254 100644
--- a/fs/udf/misc.c
+++ b/fs/udf/misc.c
@@ -51,7 +51,6 @@ struct genericFormat *udf_add_extendedattr(struct inode *inode, uint32_t size,
         uint8_t *ea = NULL, *ad = NULL;
         int offset;
         uint16_t crclen;
-        int i;
 
         ea = UDF_I_DATA(inode);
         if (UDF_I_LENEATTR(inode)) {
@@ -138,11 +137,7 @@ struct genericFormat *udf_add_extendedattr(struct inode *inode, uint32_t size,
                 eahd->descTag.descCRCLength = cpu_to_le16(crclen);
                 eahd->descTag.descCRC = cpu_to_le16(udf_crc((char *)eahd +
                                                 sizeof(tag), crclen, 0));
-                eahd->descTag.tagChecksum = 0;
-                for (i = 0; i < 16; i++)
-                        if (i != 4)
-                                eahd->descTag.tagChecksum +=
-                                        ((uint8_t *)&(eahd->descTag))[i];
+                eahd->descTag.tagChecksum = udf_tag_checksum(&eahd->descTag);
                 UDF_I_LENEATTR(inode) += size;
                 return (struct genericFormat *)&ea[offset];
         }
@@ -207,8 +202,6 @@ struct buffer_head *udf_read_tagged(struct super_block *sb, uint32_t block,
 {
         tag *tag_p;
         struct buffer_head *bh = NULL;
-        register uint8_t checksum;
-        register int i;
         struct udf_sb_info *sbi = UDF_SB(sb);
 
         /* Read the block */
@@ -234,12 +227,7 @@ struct buffer_head *udf_read_tagged(struct super_block *sb, uint32_t block,
         }
 
         /* Verify the tag checksum */
-        checksum = 0U;
-        for (i = 0; i < 4; i++)
-                checksum += (uint8_t)(bh->b_data[i]);
-        for (i = 5; i < 16; i++)
-                checksum += (uint8_t)(bh->b_data[i]);
-        if (checksum != tag_p->tagChecksum) {
+        if (udf_tag_checksum(tag_p) != tag_p->tagChecksum) {
                 printk(KERN_ERR "udf: tag checksum failed block %d\n", block);
                 goto error_out;
         }
@@ -277,17 +265,11 @@ struct buffer_head *udf_read_ptagged(struct super_block *sb, kernel_lb_addr loc,
 void udf_update_tag(char *data, int length)
 {
         tag *tptr = (tag *)data;
-        int i;
-
         length -= sizeof(tag);
 
-        tptr->tagChecksum = 0;
         tptr->descCRCLength = cpu_to_le16(length);
         tptr->descCRC = cpu_to_le16(udf_crc(data + sizeof(tag), length, 0));
-
-        for (i = 0; i < 16; i++)
-                if (i != 4)
-                        tptr->tagChecksum += (uint8_t)(data[i]);
+        tptr->tagChecksum = udf_tag_checksum(tptr);
 }
 
 void udf_new_tag(char *data, uint16_t ident, uint16_t version, uint16_t snum,
@@ -300,3 +282,14 @@ void udf_new_tag(char *data, uint16_t ident, uint16_t version, uint16_t snum,
         tptr->tagLocation = cpu_to_le32(loc);
         udf_update_tag(data, length);
 }
+
+u8 udf_tag_checksum(const tag *t)
+{
+        u8 *data = (u8 *)t;
+        u8 checksum = 0;
+        int i;
+        for (i = 0; i < sizeof(tag); ++i)
+                if (i != 4) /* position of checksum */
+                        checksum += data[i];
+        return checksum;
+}
diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index a126950d79e6..9b5cfc5f725c 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -47,8 +47,6 @@ int udf_write_fi(struct inode *inode, struct fileIdentDesc *cfi,
 {
         uint16_t crclen = fibh->eoffset - fibh->soffset - sizeof(tag);
         uint16_t crc;
-        uint8_t checksum = 0;
-        int i;
         int offset;
         uint16_t liu = le16_to_cpu(cfi->lengthOfImpUse);
         uint8_t lfi = cfi->lengthFileIdent;
@@ -122,13 +120,8 @@ int udf_write_fi(struct inode *inode, struct fileIdentDesc *cfi,
 
         cfi->descTag.descCRC = cpu_to_le16(crc);
         cfi->descTag.descCRCLength = cpu_to_le16(crclen);
+        cfi->descTag.tagChecksum = udf_tag_checksum(&cfi->descTag);
 
-        for (i = 0; i < 16; i++) {
-                if (i != 4)
-                        checksum += ((uint8_t *)&cfi->descTag)[i];
-        }
-
-        cfi->descTag.tagChecksum = checksum;
         if (adinicb || (sizeof(struct fileIdentDesc) <= -fibh->soffset)) {
                 memcpy((uint8_t *)sfi, (uint8_t *)cfi,
                         sizeof(struct fileIdentDesc));
diff --git a/fs/udf/super.c b/fs/udf/super.c
index 7f75a949e152..12fb91d23a83 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -1564,7 +1564,6 @@ static void udf_open_lvid(struct super_block *sb)
         struct udf_sb_info *sbi = UDF_SB(sb);
         struct buffer_head *bh = sbi->s_lvid_bh;
         if (bh) {
-                int i;
                 kernel_timestamp cpu_time;
                 struct logicalVolIntegrityDesc *lvid =
                                 (struct logicalVolIntegrityDesc *)bh->b_data;
@@ -1582,12 +1581,7 @@ static void udf_open_lvid(struct super_block *sb)
                                 le16_to_cpu(lvid->descTag.descCRCLength),
                                 0));
 
-                lvid->descTag.tagChecksum = 0;
-                for (i = 0; i < 16; i++)
-                        if (i != 4)
-                                lvid->descTag.tagChecksum +=
-                                        ((uint8_t *) &(lvid->descTag))[i];
-
+                lvid->descTag.tagChecksum = udf_tag_checksum(&lvid->descTag);
                 mark_buffer_dirty(bh);
         }
 }
@@ -1595,7 +1589,6 @@ static void udf_open_lvid(struct super_block *sb)
 static void udf_close_lvid(struct super_block *sb)
 {
         kernel_timestamp cpu_time;
-        int i;
         struct udf_sb_info *sbi = UDF_SB(sb);
         struct buffer_head *bh = sbi->s_lvid_bh;
         struct logicalVolIntegrityDesc *lvid;
@@ -1626,12 +1619,7 @@ static void udf_close_lvid(struct super_block *sb)
                                 le16_to_cpu(lvid->descTag.descCRCLength),
                                 0));
 
-                lvid->descTag.tagChecksum = 0;
-                for (i = 0; i < 16; i++)
-                        if (i != 4)
-                                lvid->descTag.tagChecksum +=
-                                        ((uint8_t *)&(lvid->descTag))[i];
-
+                lvid->descTag.tagChecksum = udf_tag_checksum(&lvid->descTag);
                 mark_buffer_dirty(bh);
         }
 }
diff --git a/fs/udf/udfdecl.h b/fs/udf/udfdecl.h
index c8016cc9e7e6..bed0a0251389 100644
--- a/fs/udf/udfdecl.h
+++ b/fs/udf/udfdecl.h
@@ -36,6 +36,9 @@
 
 #define udf_get_lb_pblock(sb,loc,offset) udf_get_pblock((sb), (loc).logicalBlockNum, (loc).partitionReferenceNum, (offset))
 
+/* computes tag checksum */
+u8 udf_tag_checksum(const tag *t);
+
 struct dentry;
 struct inode;
 struct task_struct;