exfat: optimize dir-cache

Optimize directory access based on exfat_entry_set_cache.
 - Hold bh instead of copied d-entry.
 - Modify bh->data directly instead of the copied d-entry.
 - Write back the retained bh instead of rescanning the d-entry-set.
And
 - Remove unused cache related definitions.

Signed-off-by: Tetsuhiro Kohada <kohada.tetsuhiro@dc.mitsubishielectric.co.jp>
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

1 files changed, 75 insertions, 122 deletions

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index b5a237c33d50..2902d285bf20 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -32,35 +32,30 @@ static void exfat_get_uniname_from_ext_entry(struct super_block *sb,
 		struct exfat_chain *p_dir, int entry, unsigned short *uniname)
 {
 	int i;
-	struct exfat_dentry *ep;
 	struct exfat_entry_set_cache *es;
 
-	es = exfat_get_dentry_set(sb, p_dir, entry, ES_ALL_ENTRIES, &ep);
+	es = exfat_get_dentry_set(sb, p_dir, entry, ES_ALL_ENTRIES);
 	if (!es)
 		return;
 
-	if (es->num_entries < 3)
-		goto free_es;
-
-	ep += 2;
-
 	/*
 	 * First entry  : file entry
 	 * Second entry : stream-extension entry
 	 * Third entry  : first file-name entry
 	 * So, the index of first file-name dentry should start from 2.
 	 */
-	for (i = 2; i < es->num_entries; i++, ep++) {
+	for (i = 2; i < es->num_entries; i++) {
+		struct exfat_dentry *ep = exfat_get_dentry_cached(es, i);
+
 		/* end of name entry */
 		if (exfat_get_entry_type(ep) != TYPE_EXTEND)
-			goto free_es;
+			break;
 
 		exfat_extract_uni_name(ep, uniname);
 		uniname += EXFAT_FILE_NAME_LEN;
 	}
 
-free_es:
-	kfree(es);
+	exfat_free_dentry_set(es, false);
 }
 
 /* read a directory entry from the opened directory */
@@ -590,62 +585,33 @@ int exfat_remove_entries(struct inode *inode, struct exfat_chain *p_dir,
 	return 0;
 }
 
-int exfat_update_dir_chksum_with_entry_set(struct super_block *sb,
-		struct exfat_entry_set_cache *es, int sync)
+void exfat_update_dir_chksum_with_entry_set(struct exfat_entry_set_cache *es)
 {
-	struct exfat_sb_info *sbi = EXFAT_SB(sb);
-	struct buffer_head *bh;
-	sector_t sec = es->sector;
-	unsigned int off = es->offset;
-	int chksum_type = CS_DIR_ENTRY, i, num_entries = es->num_entries;
-	unsigned int buf_off = (off - es->offset);
-	unsigned int remaining_byte_in_sector, copy_entries, clu;
+	int chksum_type = CS_DIR_ENTRY, i;
 	unsigned short chksum = 0;
+	struct exfat_dentry *ep;
 
-	for (i = 0; i < num_entries; i++) {
-		chksum = exfat_calc_chksum_2byte(&es->entries[i], DENTRY_SIZE,
-			chksum, chksum_type);
+	for (i = 0; i < es->num_entries; i++) {
+		ep = exfat_get_dentry_cached(es, i);
+		chksum = exfat_calc_chksum_2byte(ep, DENTRY_SIZE, chksum,
+						 chksum_type);
 		chksum_type = CS_DEFAULT;
 	}
+	ep = exfat_get_dentry_cached(es, 0);
+	ep->dentry.file.checksum = cpu_to_le16(chksum);
+	es->modified = true;
+}
 
-	es->entries[0].dentry.file.checksum = cpu_to_le16(chksum);
+void exfat_free_dentry_set(struct exfat_entry_set_cache *es, int sync)
+{
+	int i;
 
-	while (num_entries) {
-		/* write per sector base */
-		remaining_byte_in_sector = (1 << sb->s_blocksize_bits) - off;
-		copy_entries = min_t(int,
-			EXFAT_B_TO_DEN(remaining_byte_in_sector),
-			num_entries);
-		bh = sb_bread(sb, sec);
-		if (!bh)
-			goto err_out;
-		memcpy(bh->b_data + off,
-			(unsigned char *)&es->entries[0] + buf_off,
-			EXFAT_DEN_TO_B(copy_entries));
-		exfat_update_bh(sb, bh, sync);
-		brelse(bh);
-		num_entries -= copy_entries;
-
-		if (num_entries) {
-			/* get next sector */
-			if (exfat_is_last_sector_in_cluster(sbi, sec)) {
-				clu = exfat_sector_to_cluster(sbi, sec);
-				if (es->alloc_flag == ALLOC_NO_FAT_CHAIN)
-					clu++;
-				else if (exfat_get_next_cluster(sb, &clu))
-					goto err_out;
-				sec = exfat_cluster_to_sector(sbi, clu);
-			} else {
-				sec++;
-			}
-			off = 0;
-			buf_off += EXFAT_DEN_TO_B(copy_entries);
-		}
+	for (i = 0; i < es->num_bh; i++) {
+		if (es->modified)
+			exfat_update_bh(es->sb, es->bh[i], sync);
+		brelse(es->bh[i]);
 	}
-
-	return 0;
-err_out:
-	return -EIO;
+	kfree(es);
 }
 
 static int exfat_walk_fat_chain(struct super_block *sb,
@@ -820,34 +786,40 @@ static bool exfat_validate_entry(unsigned int type,
 	}
 }
 
+struct exfat_dentry *exfat_get_dentry_cached(
+	struct exfat_entry_set_cache *es, int num)
+{
+	int off = es->start_off + num * DENTRY_SIZE;
+	struct buffer_head *bh = es->bh[EXFAT_B_TO_BLK(off, es->sb)];
+	char *p = bh->b_data + EXFAT_BLK_OFFSET(off, es->sb);
+
+	return (struct exfat_dentry *)p;
+}
+
 /*
  * Returns a set of dentries for a file or dir.
  *
- * Note that this is a copy (dump) of dentries so that user should
- * call write_entry_set() to apply changes made in this entry set
- * to the real device.
+ * Note It provides a direct pointer to bh->data via exfat_get_dentry_cached().
+ * User should call exfat_get_dentry_set() after setting 'modified' to apply
+ * changes made in this entry set to the real device.
  *
  * in:
  *   sb+p_dir+entry: indicates a file/dir
  *   type:  specifies how many dentries should be included.
- * out:
- *   file_ep: will point the first dentry(= file dentry) on success
  * return:
  *   pointer of entry set on success,
  *   NULL on failure.
  */
 struct exfat_entry_set_cache *exfat_get_dentry_set(struct super_block *sb,
-		struct exfat_chain *p_dir, int entry, unsigned int type,
-		struct exfat_dentry **file_ep)
+		struct exfat_chain *p_dir, int entry, unsigned int type)
 {
-	int ret;
+	int ret, i, num_bh;
 	unsigned int off, byte_offset, clu = 0;
-	unsigned int entry_type;
 	sector_t sec;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	struct exfat_entry_set_cache *es;
-	struct exfat_dentry *ep, *pos;
-	unsigned char num_entries;
+	struct exfat_dentry *ep;
+	int num_entries;
 	enum exfat_validate_dentry_mode mode = ES_MODE_STARTED;
 	struct buffer_head *bh;
 
@@ -861,11 +833,18 @@ struct exfat_entry_set_cache *exfat_get_dentry_set(struct super_block *sb,
 	if (ret)
 		return NULL;
 
+	es = kzalloc(sizeof(*es), GFP_KERNEL);
+	if (!es)
+		return NULL;
+	es->sb = sb;
+	es->modified = false;
+
 	/* byte offset in cluster */
 	byte_offset = EXFAT_CLU_OFFSET(byte_offset, sbi);
 
 	/* byte offset in sector */
 	off = EXFAT_BLK_OFFSET(byte_offset, sb);
+	es->start_off = off;
 
 	/* sector offset in cluster */
 	sec = EXFAT_B_TO_BLK(byte_offset, sb);
@@ -873,72 +852,46 @@ struct exfat_entry_set_cache *exfat_get_dentry_set(struct super_block *sb,
 
 	bh = sb_bread(sb, sec);
 	if (!bh)
-		return NULL;
-
-	ep = (struct exfat_dentry *)(bh->b_data + off);
-	entry_type = exfat_get_entry_type(ep);
+		goto free_es;
+	es->bh[es->num_bh++] = bh;
 
-	if (entry_type != TYPE_FILE && entry_type != TYPE_DIR)
-		goto release_bh;
+	ep = exfat_get_dentry_cached(es, 0);
+	if (!exfat_validate_entry(exfat_get_entry_type(ep), &mode))
+		goto free_es;
 
 	num_entries = type == ES_ALL_ENTRIES ?
 		ep->dentry.file.num_ext + 1 : type;
-	es = kmalloc(struct_size(es, entries, num_entries), GFP_KERNEL);
-	if (!es)
-		goto release_bh;
-
 	es->num_entries = num_entries;
-	es->sector = sec;
-	es->offset = off;
-	es->alloc_flag = p_dir->flags;
-
-	pos = &es->entries[0];
-
-	while (num_entries) {
-		if (!exfat_validate_entry(exfat_get_entry_type(ep), &mode))
-			goto free_es;
 
-		/* copy dentry */
-		memcpy(pos, ep, sizeof(struct exfat_dentry));
-
-		if (--num_entries == 0)
-			break;
-
-		if (((off + DENTRY_SIZE) & (sb->s_blocksize - 1)) <
-		    (off & (sb->s_blocksize - 1))) {
-			/* get the next sector */
-			if (exfat_is_last_sector_in_cluster(sbi, sec)) {
-				if (es->alloc_flag == ALLOC_NO_FAT_CHAIN)
-					clu++;
-				else if (exfat_get_next_cluster(sb, &clu))
-					goto free_es;
-				sec = exfat_cluster_to_sector(sbi, clu);
-			} else {
-				sec++;
-			}
-
-			brelse(bh);
-			bh = sb_bread(sb, sec);
-			if (!bh)
+	num_bh = EXFAT_B_TO_BLK_ROUND_UP(off + num_entries * DENTRY_SIZE, sb);
+	for (i = 1; i < num_bh; i++) {
+		/* get the next sector */
+		if (exfat_is_last_sector_in_cluster(sbi, sec)) {
+			if (p_dir->flags == ALLOC_NO_FAT_CHAIN)
+				clu++;
+			else if (exfat_get_next_cluster(sb, &clu))
 				goto free_es;
-			off = 0;
-			ep = (struct exfat_dentry *)bh->b_data;
+			sec = exfat_cluster_to_sector(sbi, clu);
 		} else {
-			ep++;
-			off += DENTRY_SIZE;
+			sec++;
 		}
-		pos++;
+
+		bh = sb_bread(sb, sec);
+		if (!bh)
+			goto free_es;
+		es->bh[es->num_bh++] = bh;
 	}
 
-	if (file_ep)
-		*file_ep = &es->entries[0];
-	brelse(bh);
+	/* validiate cached dentries */
+	for (i = 1; i < num_entries; i++) {
+		ep = exfat_get_dentry_cached(es, i);
+		if (!exfat_validate_entry(exfat_get_entry_type(ep), &mode))
+			goto free_es;
+	}
 	return es;
 
 free_es:
-	kfree(es);
-release_bh:
-	brelse(bh);
+	exfat_free_dentry_set(es, false);
 	return NULL;
 }