From c6e2f52e3051e8d898d38840104638ca8bbcdec2 Mon Sep 17 00:00:00 2001

From: Hyeongseok Kim <hyeongseok@gmail.com>

Date: Mon, 22 Mar 2021 12:53:36 +0900

Subject: [Backport c6e2f52e3051] exfat: speed up iterate/lookup by fixing

 start point of traversing cluster chain

When directory iterate and lookup is called, there's a buggy rewinding

of start point for traversing cluster chain to the parent directory

entry's first cluster. This caused repeated cluster chain traversing

from the first entry of the parent directory that would show worse

performance if huge amounts of files exist under the parent directory.

Fix not to rewind, make continue from currently referenced cluster and

dir entry.

Tested with 50,000 files under single directory / 256GB sdcard,

with command "time ls -l > /dev/null",

Before :     0m08.69s real     0m00.27s user     0m05.91s system

After  :     0m07.01s real     0m00.25s user     0m04.34s system

Signed-off-by: Hyeongseok Kim <hyeongseok@gmail.com>

Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

---

 src/dir.c      | 19 +++++++++++++------

 src/exfat_fs.h |  2 +-

 src/namei.c    |  9 ++++++++-

 3 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/src/dir.c b/src/dir.c

index 7efb1c6d480846937da5436277b6220dd26f2f7c..c4523648472a088a2477ea9c3ffe7416c498b523 100644

--- a/src/dir.c

+++ b/src/dir.c

@@ -147,7 +147,7 @@ static int exfat_readdir(struct inode *inode, loff_t *cpos, struct exfat_dir_ent

 					0);

 			*uni_name.name = 0x0;

-			exfat_get_uniname_from_ext_entry(sb, &dir, dentry,

+			exfat_get_uniname_from_ext_entry(sb, &clu, i,

 				uni_name.name);

 			exfat_utf16_to_nls(sb, &uni_name,

 				dir_entry->namebuf.lfn,

@@ -911,14 +911,19 @@ enum {

 };

 /*

- * return values:

- *   >= 0	: return dir entiry position with the name in dir

- *   -ENOENT	: entry with the name does not exist

- *   -EIO	: I/O error

+ * @ei:         inode info of parent directory

+ * @p_dir:      directory structure of parent directory

+ * @num_entries:entry size of p_uniname

+ * @hint_opt:   If p_uniname is found, filled with optimized dir/entry

+ *              for traversing cluster chain.

+ * @return:

+ *   >= 0:      file directory entry position where the name exists

+ *   -ENOENT:   entry with the name does not exist

+ *   -EIO:      I/O error

  */

 int exfat_find_dir_entry(struct super_block *sb, struct exfat_inode_info *ei,

 		struct exfat_chain *p_dir, struct exfat_uni_name *p_uniname,

-		int num_entries, unsigned int type)

+		int num_entries, unsigned int type, struct exfat_hint *hint_opt)

 {

 	int i, rewind = 0, dentry = 0, end_eidx = 0, num_ext = 0, len;

 	int order, step, name_len = 0;

@@ -995,6 +1000,8 @@ int exfat_find_dir_entry(struct super_block *sb, struct exfat_inode_info *ei,

 			if (entry_type == TYPE_FILE || entry_type == TYPE_DIR) {

 				step = DIRENT_STEP_FILE;

+				hint_opt->clu = clu.dir;

+				hint_opt->eidx = i;

 				if (type == TYPE_ALL || type == entry_type) {

 					num_ext = ep->dentry.file.num_ext;

 					step = DIRENT_STEP_STRM;

diff --git a/src/exfat_fs.h b/src/exfat_fs.h

index e77fe2f45cf28fe8533276426a73c657446863f6..1d6da61157c9364996da966537da92681cae5e31 100644

--- a/src/exfat_fs.h

+++ b/src/exfat_fs.h

@@ -457,7 +457,7 @@ void exfat_update_dir_chksum_with_entry_set(struct exfat_entry_set_cache *es);

 int exfat_calc_num_entries(struct exfat_uni_name *p_uniname);

 int exfat_find_dir_entry(struct super_block *sb, struct exfat_inode_info *ei,

 		struct exfat_chain *p_dir, struct exfat_uni_name *p_uniname,

-		int num_entries, unsigned int type);

+		int num_entries, unsigned int type, struct exfat_hint *hint_opt);

 int exfat_alloc_new_dir(struct inode *inode, struct exfat_chain *clu);

 int exfat_find_location(struct super_block *sb, struct exfat_chain *p_dir,

 		int entry, sector_t *sector, int *offset);

diff --git a/src/namei.c b/src/namei.c

index 1f7b3dc66fcd6fd5507f9d52d73d01cb69433afd..24b41103d1cc08cbfc967cba9d60d14b579a932b 100644

--- a/src/namei.c

+++ b/src/namei.c

@@ -596,6 +596,8 @@ static int exfat_find(struct inode *dir, struct qstr *qname,

 	struct exfat_inode_info *ei = EXFAT_I(dir);

 	struct exfat_dentry *ep, *ep2;

 	struct exfat_entry_set_cache *es;

+	/* for optimized dir & entry to prevent long traverse of cluster chain */

+	struct exfat_hint hint_opt;

 	if (qname->len == 0)

 		return -ENOENT;

@@ -619,7 +621,7 @@ static int exfat_find(struct inode *dir, struct qstr *qname,

 	/* search the file name for directories */

 	dentry = exfat_find_dir_entry(sb, ei, &cdir, &uni_name,

-			num_entries, TYPE_ALL);

+			num_entries, TYPE_ALL, &hint_opt);

 	if (dentry < 0)

 		return dentry; /* -error value */

@@ -628,6 +630,11 @@ static int exfat_find(struct inode *dir, struct qstr *qname,

 	info->entry = dentry;

 	info->num_subdirs = 0;

+	/* adjust cdir to the optimized value */

+	cdir.dir = hint_opt.clu;

+	if (cdir.flags & ALLOC_NO_FAT_CHAIN)

+		cdir.size -= dentry / sbi->dentries_per_clu;

+	dentry = hint_opt.eidx;

 	es = exfat_get_dentry_set(sb, &cdir, dentry, ES_2_ENTRIES);

 	if (!es)

 		return -EIO;

-- 

2.31.1