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Subject[PATCH v2 1/5] exfat: reduce the size of exfat_entry_set_cache
Date
In normal, there are 19 directory entries at most for a file or
a directory.
- A file directory entry
- A stream extension directory entry
- 1~17 file name directory entry

So the directory entries are in 3 sectors at most, it is enough
for struct exfat_entry_set_cache to pre-allocate 3 bh.

This commit changes the size of struct exfat_entry_set_cache as:

Before After
32-bit system 88 32 bytes
64-bit system 168 48 bytes

Signed-off-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Reviewed-by: Andy Wu <Andy.Wu@sony.com>
Reviewed-by: Aoyama Wataru <wataru.aoyama@sony.com>
---
fs/exfat/exfat_fs.h | 25 +++++++++++++++++++++----
1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index a8f8eee4937c..af55018ff22e 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -9,6 +9,7 @@
#include <linux/fs.h>
#include <linux/ratelimit.h>
#include <linux/nls.h>
+#include <linux/blkdev.h>

#define EXFAT_ROOT_INO 1

@@ -41,6 +42,14 @@ enum {
#define ES_2_ENTRIES 2
#define ES_ALL_ENTRIES 0

+#define ES_IDX_FILE 0
+#define ES_IDX_STREAM 1
+#define ES_IDX_FIRST_FILENAME 2
+#define EXFAT_FILENAME_ENTRY_NUM(name_len) \
+ DIV_ROUND_UP(name_len, EXFAT_FILE_NAME_LEN)
+#define ES_IDX_LAST_FILENAME(name_len) \
+ (ES_IDX_FIRST_FILENAME + EXFAT_FILENAME_ENTRY_NUM(name_len) - 1)
+
#define DIR_DELETED 0xFFFF0321

/* type values */
@@ -68,9 +77,6 @@ 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)

-/* 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

@@ -125,6 +131,17 @@ enum {
#define BITS_PER_BYTE_MASK 0x7
#define IGNORED_BITS_REMAINED(clu, clu_base) ((1 << ((clu) - (clu_base))) - 1)

+#define ES_ENTRY_NUM(name_len) (ES_IDX_LAST_FILENAME(name_len) + 1)
+/* 19 entries = 1 file entry + 1 stream entry + 17 filename entries */
+#define ES_MAX_ENTRY_NUM ES_ENTRY_NUM(MAX_NAME_LENGTH)
+
+/*
+ * 19 entries x 32 bytes/entry = 608 bytes.
+ * The 608 bytes are in 3 sectors at most (even 512 Byte sector).
+ */
+#define DIR_CACHE_SIZE \
+ (DIV_ROUND_UP(EXFAT_DEN_TO_B(ES_MAX_ENTRY_NUM), SECTOR_SIZE) + 1)
+
struct exfat_dentry_namebuf {
char *lfn;
int lfnbuf_len; /* usually MAX_UNINAME_BUF_SIZE */
@@ -166,11 +183,11 @@ struct exfat_hint {

struct exfat_entry_set_cache {
struct super_block *sb;
- bool modified;
unsigned int start_off;
int num_bh;
struct buffer_head *bh[DIR_CACHE_SIZE];
unsigned int num_entries;
+ bool modified;
};

struct exfat_dir_entry {
--
2.25.1
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