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Subject[PATCH 6/7] fat: small optimaize __fat_readdir()
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This removes unnecessary parsing for directory entries.

If short_only, we don't need to parse longname. And if !both and it
found the longname, we don't need shortname.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---
fs/fat/dir.c | 71 +++++++++++++++++++++++++++++++---------------------------
1 file changed, 39 insertions(+), 32 deletions(-)
diff -puN fs/fat/dir.c~fat_dir-optimize fs/fat/dir.c
--- linux-2.6/fs/fat/dir.c~fat_dir-optimize 2008-07-01 10:12:23.000000000 +0900
+++ linux-2.6-hirofumi/fs/fat/dir.c 2008-07-01 10:12:23.000000000 +0900
@@ -481,11 +481,11 @@ static int __fat_readdir(struct inode *i
unsigned short opt_shortname = sbi->options.shortname;
int isvfat = sbi->options.isvfat;
int nocase = sbi->options.nocase;
- const char *fill_name;
+ const char *fill_name = NULL;
unsigned long inum;
unsigned long lpos, dummy, *furrfu = &lpos;
loff_t cpos;
- int chi, chl, i, i2, j, last, last_u, dotoffset = 0, fill_len;
+ int chi, chl, i, i2, j, last, last_u, dotoffset = 0, fill_len = 0;
int ret = 0;

lock_kernel();
@@ -516,8 +516,11 @@ get_new:
goto end_of_dir;
parse_record:
nr_slots = 0;
- /* Check for long filename entry */
- if (isvfat) {
+ /*
+ * Check for long filename entry, but if short_only, we don't
+ * need to parse long filename.
+ */
+ if (isvfat && !short_only) {
if (de->name[0] == DELETED_FLAG)
goto record_end;
if (de->attr != ATTR_EXT && (de->attr & ATTR_VOLUME))
@@ -542,6 +545,18 @@ parse_record:
goto parse_record;
else if (status == PARSE_EOF)
goto end_of_dir;
+
+ if (nr_slots) {
+ void *longname = unicode + FAT_MAX_UNI_CHARS;
+ int size = PATH_MAX - FAT_MAX_UNI_SIZE;
+ int len = fat_uni_to_x8(sbi, unicode, longname, size);
+
+ fill_name = longname;
+ fill_len = len;
+ /* !both && !short_only, so we don't need shortname. */
+ if (!both)
+ goto start_filldir;
+ }
}

if (sbi->options.dotsOK) {
@@ -608,6 +623,26 @@ parse_record:
i = last + dotoffset;
j = last_u;

+ if (isvfat) {
+ bufuname[j] = 0x0000;
+ i = fat_uni_to_x8(sbi, bufuname, bufname, sizeof(bufname));
+ }
+ if (nr_slots) {
+ /* hack for fat_ioctl_filldir() */
+ struct fat_ioctl_filldir_callback *p = dirent;
+
+ p->longname = fill_name;
+ p->long_len = fill_len;
+ p->shortname = bufname;
+ p->short_len = i;
+ fill_name = NULL;
+ fill_len = 0;
+ } else {
+ fill_name = bufname;
+ fill_len = i;
+ }
+
+start_filldir:
lpos = cpos - (nr_slots + 1) * sizeof(struct msdos_dir_entry);
if (!memcmp(de->name, MSDOS_DOT, MSDOS_NAME))
inum = inode->i_ino;
@@ -623,34 +658,6 @@ parse_record:
inum = iunique(sb, MSDOS_ROOT_INO);
}

- if (isvfat) {
- bufuname[j] = 0x0000;
- i = fat_uni_to_x8(sbi, bufuname, bufname, sizeof(bufname));
- }
-
- fill_name = bufname;
- fill_len = i;
- if (!short_only && nr_slots) {
- void *longname = unicode + FAT_MAX_UNI_CHARS;
- int long_len, size = PATH_MAX - FAT_MAX_UNI_SIZE;
-
- long_len = fat_uni_to_x8(sbi, unicode, longname, size);
-
- if (!both) {
- fill_name = longname;
- fill_len = long_len;
- } else {
- /* hack for fat_ioctl_filldir() */
- struct fat_ioctl_filldir_callback *p = dirent;
-
- p->longname = longname;
- p->long_len = long_len;
- p->shortname = bufname;
- p->short_len = i;
- fill_name = NULL;
- fill_len = 0;
- }
- }
if (filldir(dirent, fill_name, fill_len, *furrfu, inum,
(de->attr & ATTR_DIR) ? DT_DIR : DT_REG) < 0)
goto fill_failed;
_

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