fat: small optimization to __fat_readdir()

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 39 insertions, 32 deletions

diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 96a1cad30da4..4c35477bc94c 100644
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -481,11 +481,11 @@ static int __fat_readdir(struct inode *inode, struct file *filp, void *dirent,
         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_super(sb);
@@ -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;