refactor: 文件系统Open性能优化

优化包括：
1. 提供VnodeLookupFullpath接口，如果路径是规范化的路径，则调用此接口可减少一次vfs_normalizepath接口的调用;
2. fatfs open钩子函数FIL和buffer同时malloc，减少一次malloc调用，同时去除不必要的数据写回;
3. 其他小细节的优化。

Close #I4E0CT

Signed-off-by: Far <yesiyuan2@huawei.com>

fs/fat/os_adapt/fatfs.c

@@ -606,7 +606,7 @@ int fatfs_open(struct file *filep)
     FIL *fp;
     int ret;
 
-    fp = (FIL *)zalloc(sizeof(FIL));
+    fp = (FIL *)zalloc(sizeof(FIL) + SS(fs));
     if (fp == NULL) {
         ret = ENOMEM;
         goto ERROR_EXIT;
@@ -630,19 +630,13 @@ int fatfs_open(struct file *filep)
     fp->err = 0;
     fp->sect = 0;
     fp->fptr = 0;
-    fp->buf = (BYTE*) ff_memalloc(SS(fs));
-    if (fp->buf == NULL) {
-        ret = ENOMEM;
-        goto ERROR_UNLOCK;
-    }
+    fp->buf = (BYTE *)fp + sizeof(FIL);
     LOS_ListAdd(&finfo->fp_list, &fp->fp_entry);
     unlock_fs(fs, FR_OK);
 
     filep->f_priv = fp;
-    return fatfs_sync(vp->originMount->mountFlags, fs);
+    return 0;
 
-ERROR_UNLOCK:
-    unlock_fs(fs, FR_OK);
 ERROR_FREE:
     free(fp);
 ERROR_EXIT:
@@ -672,7 +666,6 @@ int fatfs_close(struct file *filep)
     }
 #endif
     LOS_ListDelete(&fp->fp_entry);
-    ff_memfree(fp->buf);
     free(fp);
     filep->f_priv = NULL;
 EXIT:

fs/vfs/include/vnode.h

@@ -163,6 +163,7 @@ int VnodeDevInit(void);
 int VnodeAlloc(struct VnodeOps *vop, struct Vnode **vnode);
 int VnodeFree(struct Vnode *vnode);
 int VnodeLookup(const char *path, struct Vnode **vnode, uint32_t flags);
+int VnodeLookupFullpath(const char *fullpath, struct Vnode **vnode, uint32_t flags);
 int VnodeLookupAt(const char *path, struct Vnode **vnode, uint32_t flags, struct Vnode *orgVnode);
 int VnodeHold(void);
 int VnodeDrop(void);

fs/vfs/vnode.c

@@ -388,7 +388,7 @@ int VnodeLookupAt(const char *path, struct Vnode **result, uint32_t flags, struc
         }
     }
 
-    if (normalizedPath[0] == '/' && normalizedPath[1] == '\0') {
+    if (normalizedPath[1] == '\0' && normalizedPath[0] == '/') {
         *result = g_rootVnode;
         free(normalizedPath);
         return LOS_OK;
@@ -447,6 +447,11 @@ int VnodeLookup(const char *path, struct Vnode **vnode, uint32_t flags)
     return VnodeLookupAt(path, vnode, flags, NULL);
 }
 
+int VnodeLookupFullpath(const char *fullpath, struct Vnode **vnode, uint32_t flags)
+{
+    return VnodeLookupAt(fullpath, vnode, flags, g_rootVnode);
+}
+
 static void ChangeRootInternal(struct Vnode *rootOld, char *dirname)
 {
     int ret;