[PATCH] exfat: optimize dir-cache

From: Tetsuhiro Kohada
Date: Wed May 20 2020 - 03:57:11 EST

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@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
---
fs/exfat/dir.c | 197 +++++++++++++++++---------------------------
fs/exfat/exfat_fs.h | 27 +++---
fs/exfat/file.c | 15 ++--
fs/exfat/inode.c | 53 +++++-------
fs/exfat/namei.c | 14 ++--
5 files changed, 124 insertions(+), 182 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;
}

diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index 294aa7792bc3..5caad1380818 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -71,10 +71,8 @@ enum {
#define MAX_NAME_LENGTH 255 /* max len of file name excluding NULL */
#define MAX_VFSNAME_BUF_SIZE ((MAX_NAME_LENGTH + 1) * MAX_CHARSET_SIZE)

-#define FAT_CACHE_SIZE 128
-#define FAT_CACHE_HASH_SIZE 64
-#define BUF_CACHE_SIZE 256
-#define BUF_CACHE_HASH_SIZE 64
+/* Enough size to hold 256 dentry (even 512 Byte sector) */
+#define DIR_CACHE_SIZE (256*sizeof(struct exfat_dentry)/512+1)

#define EXFAT_HINT_NONE -1
#define EXFAT_MIN_SUBDIR 2
@@ -170,14 +168,12 @@ struct exfat_hint {
};

struct exfat_entry_set_cache {
- /* sector number that contains file_entry */
- sector_t sector;
- /* byte offset in the sector */
- unsigned int offset;
- /* flag in stream entry. 01 for cluster chain, 03 for contig. */
- int alloc_flag;
+ struct super_block *sb;
+ bool modified;
+ unsigned int start_off;
+ int num_bh;
+ struct buffer_head *bh[DIR_CACHE_SIZE];
unsigned int num_entries;
- struct exfat_dentry entries[];
};

struct exfat_dir_entry {
@@ -451,8 +447,7 @@ int exfat_remove_entries(struct inode *inode, struct exfat_chain *p_dir,
int entry, int order, int num_entries);
int exfat_update_dir_chksum(struct inode *inode, struct exfat_chain *p_dir,
int entry);
-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);
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,
@@ -463,9 +458,11 @@ int exfat_find_location(struct super_block *sb, struct exfat_chain *p_dir,
struct exfat_dentry *exfat_get_dentry(struct super_block *sb,
struct exfat_chain *p_dir, int entry, struct buffer_head **bh,
sector_t *sector);
+struct exfat_dentry *exfat_get_dentry_cached(
+ struct exfat_entry_set_cache *es, int num);
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);
+void exfat_free_dentry_set(struct exfat_entry_set_cache *es, int sync);
int exfat_count_dir_entries(struct super_block *sb, struct exfat_chain *p_dir);

/* inode.c */
diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 84f3d31a3a55..8e3f0eef45d7 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -96,11 +96,9 @@ int __exfat_truncate(struct inode *inode, loff_t new_size)
unsigned int num_clusters_new, num_clusters_phys;
unsigned int last_clu = EXFAT_FREE_CLUSTER;
struct exfat_chain clu;
- struct exfat_dentry *ep, *ep2;
struct super_block *sb = inode->i_sb;
struct exfat_sb_info *sbi = EXFAT_SB(sb);
struct exfat_inode_info *ei = EXFAT_I(inode);
- struct exfat_entry_set_cache *es = NULL;
int evict = (ei->dir.dir == DIR_DELETED) ? 1 : 0;

/* check if the given file ID is opened */
@@ -153,12 +151,15 @@ int __exfat_truncate(struct inode *inode, loff_t new_size)
/* update the directory entry */
if (!evict) {
struct timespec64 ts;
+ struct exfat_dentry *ep, *ep2;
+ struct exfat_entry_set_cache *es;

es = exfat_get_dentry_set(sb, &(ei->dir), ei->entry,
- ES_ALL_ENTRIES, &ep);
+ ES_ALL_ENTRIES);
if (!es)
return -EIO;
- ep2 = ep + 1;
+ ep = exfat_get_dentry_cached(es, 0);
+ ep2 = exfat_get_dentry_cached(es, 1);

ts = current_time(inode);
exfat_set_entry_time(sbi, &ts,
@@ -185,10 +186,8 @@ int __exfat_truncate(struct inode *inode, loff_t new_size)
ep2->dentry.stream.start_clu = EXFAT_FREE_CLUSTER;
}

- if (exfat_update_dir_chksum_with_entry_set(sb, es,
- inode_needs_sync(inode)))
- return -EIO;
- kfree(es);
+ exfat_update_dir_chksum_with_entry_set(es);
+ exfat_free_dentry_set(es, inode_needs_sync(inode));
}

/* cut off from the FAT chain */
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index 3f367d081cd6..ef7cf7a6d187 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -19,7 +19,6 @@

static int __exfat_write_inode(struct inode *inode, int sync)
{
- int ret = -EIO;
unsigned long long on_disk_size;
struct exfat_dentry *ep, *ep2;
struct exfat_entry_set_cache *es = NULL;
@@ -43,11 +42,11 @@ static int __exfat_write_inode(struct inode *inode, int sync)
exfat_set_vol_flags(sb, VOL_DIRTY);

/* get the directory entry of given file or directory */
- es = exfat_get_dentry_set(sb, &(ei->dir), ei->entry, ES_ALL_ENTRIES,
- &ep);
+ es = exfat_get_dentry_set(sb, &(ei->dir), ei->entry, ES_ALL_ENTRIES);
if (!es)
return -EIO;
- ep2 = ep + 1;
+ ep = exfat_get_dentry_cached(es, 0);
+ ep2 = exfat_get_dentry_cached(es, 1);

ep->dentry.file.attr = cpu_to_le16(exfat_make_attr(inode));

@@ -77,9 +76,9 @@ static int __exfat_write_inode(struct inode *inode, int sync)
ep2->dentry.stream.valid_size = cpu_to_le64(on_disk_size);
ep2->dentry.stream.size = ep2->dentry.stream.valid_size;

- ret = exfat_update_dir_chksum_with_entry_set(sb, es, sync);
- kfree(es);
- return ret;
+ exfat_update_dir_chksum_with_entry_set(es);
+ exfat_free_dentry_set(es, sync);
+ return 0;
}

int exfat_write_inode(struct inode *inode, struct writeback_control *wbc)
@@ -110,8 +109,6 @@ static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
int ret, modified = false;
unsigned int last_clu;
struct exfat_chain new_clu;
- struct exfat_dentry *ep;
- struct exfat_entry_set_cache *es = NULL;
struct super_block *sb = inode->i_sb;
struct exfat_sb_info *sbi = EXFAT_SB(sb);
struct exfat_inode_info *ei = EXFAT_I(inode);
@@ -222,34 +219,28 @@ static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
num_clusters += num_to_be_allocated;
*clu = new_clu.dir;

- if (ei->dir.dir != DIR_DELETED) {
+ if (ei->dir.dir != DIR_DELETED && modified) {
+ struct exfat_dentry *ep;
+ struct exfat_entry_set_cache *es;
+
es = exfat_get_dentry_set(sb, &(ei->dir), ei->entry,
- ES_ALL_ENTRIES, &ep);
+ ES_ALL_ENTRIES);
if (!es)
return -EIO;
/* get stream entry */
- ep++;
+ ep = exfat_get_dentry_cached(es, 1);

/* update directory entry */
- if (modified) {
- if (ep->dentry.stream.flags != ei->flags)
- ep->dentry.stream.flags = ei->flags;
-
- if (le32_to_cpu(ep->dentry.stream.start_clu) !=
- ei->start_clu)
- ep->dentry.stream.start_clu =
- cpu_to_le32(ei->start_clu);
-
- ep->dentry.stream.valid_size =
- cpu_to_le64(i_size_read(inode));
- ep->dentry.stream.size =
- ep->dentry.stream.valid_size;
- }
-
- if (exfat_update_dir_chksum_with_entry_set(sb, es,
- inode_needs_sync(inode)))
- return -EIO;
- kfree(es);
+ ep->dentry.stream.flags = ei->flags;
+ ep->dentry.stream.start_clu =
+ cpu_to_le32(ei->start_clu);
+ ep->dentry.stream.valid_size =
+ cpu_to_le64(i_size_read(inode));
+ ep->dentry.stream.size =
+ ep->dentry.stream.valid_size;
+
+ exfat_update_dir_chksum_with_entry_set(es);
+ exfat_free_dentry_set(es, inode_needs_sync(inode));

} /* end of if != DIR_DELETED */

diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c
index 48f4df883f3b..5b0f35329d63 100644
--- a/fs/exfat/namei.c
+++ b/fs/exfat/namei.c
@@ -600,8 +600,6 @@ static int exfat_find(struct inode *dir, struct qstr *qname,
int ret, dentry, num_entries, count;
struct exfat_chain cdir;
struct exfat_uni_name uni_name;
- struct exfat_dentry *ep, *ep2;
- struct exfat_entry_set_cache *es = NULL;
struct super_block *sb = dir->i_sb;
struct exfat_sb_info *sbi = EXFAT_SB(sb);
struct exfat_inode_info *ei = EXFAT_I(dir);
@@ -660,10 +658,14 @@ static int exfat_find(struct inode *dir, struct qstr *qname,

info->num_subdirs = count;
} else {
- es = exfat_get_dentry_set(sb, &cdir, dentry, ES_2_ENTRIES, &ep);
+ struct exfat_dentry *ep, *ep2;
+ struct exfat_entry_set_cache *es;
+
+ es = exfat_get_dentry_set(sb, &cdir, dentry, ES_2_ENTRIES);
if (!es)
return -EIO;
- ep2 = ep + 1;
+ ep = exfat_get_dentry_cached(es, 0);
+ ep2 = exfat_get_dentry_cached(es, 1);

info->type = exfat_get_entry_type(ep);
info->attr = le16_to_cpu(ep->dentry.file.attr);
@@ -681,7 +683,7 @@ static int exfat_find(struct inode *dir, struct qstr *qname,
exfat_fs_error(sb,
"non-zero size file starts with zero cluster (size : %llu, p_dir : %u, entry : 0x%08x)",
i_size_read(dir), ei->dir.dir, ei->entry);
- kfree(es);
+ exfat_free_dentry_set(es, false);
return -EIO;
}

@@ -700,7 +702,7 @@ static int exfat_find(struct inode *dir, struct qstr *qname,
ep->dentry.file.access_time,
ep->dentry.file.access_date,
0);
- kfree(es);
+ exfat_free_dentry_set(es, false);

if (info->type == TYPE_DIR) {
exfat_chain_set(&cdir, info->start_clu,
--
2.25.0