1，VFS代码中不修改参数增加const修饰
2，fs_file_mapping.c: 增加安全函数的判空
3，path_cache.c: sizeof改为使用类型
4，fs_syscall.c: 对NULL解引用

close: I3UMWD
Signed-off-by: yansira <yansira@hotmail.com>

1, this RomFS's codebase is Nuttx romfs, then it is compatible with
   Linux RomFS and you can create such a file system using the tool
   genromfs.
2, there are two major changes against with the original Nuttx romfs:
   1), it is memory-based: all contents of the fs are stored in the
       memory in the very first stage of "mount".
   2), this version of romfs is altered to be compatible with our
       version of VFS to take advantage of vnode cache and path cache.

close: #I3S0CP

Change-Id: I05564abac3f0a8f7881ebe8b5b72c1b6abbbe448

Change-Id: Id5d0019550abb395d56b254d3eb260316fe983e4

Function VnodeInUseIter and VnodeFreeAll used to be recursive.
Now we traverse the current in-use vnode list to find the vnode in
1 filesystem

Close #I3NN3U

Change-Id: Ia46512ceb07333b3c51ff57d41ef8993f1ca6495

Change-Id: Ib99e937093336cfb16c44d0f811613d90f1b2f13

When tmpfs_lookup find a vnode from hashlist, the field parent of vnode should be updated,
because the old parent may be reclaimed.

Close #I3NNFA

Close: I3NGBT
Change-Id: I0c3ae0f389cabccc6ffa7a79b96ba6b028168dca

Close #I3MYP4

Change-Id: I03b19a74ae5340aa6c7cdc84d044c469873c1648

Change-Id: If876cf6e9cba695906fa4a562c34027bd044aed6

Change-Id: I256c6d908bce019698d349456109c8437ba751fc

Change-Id: Id48e780054f8df37e27acf2b5fdb700d01490160

Change-Id: I832a8c1d4110b414214e88d09483ec4f5d7bf4a4

Description:Delete VM to support only kernel mode.
Sig:liteos_a
Feature or Bugfix:Feature
Binary Source:No

Change-Id: Ie1029c8fbc0c1b85c138663933118d2d148b7769

Change-Id: I19322f5dd90eb4a6642c97df8710958819eb9d98

Change-Id: I9802b6f9f0db6d137c0d4e3fa83f9ea7a3ecaa32

Description: fix deadlock when opening a block device while frequently openning and closing a normal file

Change-Id: I02e5574f522c2c51297ff10b63b0890dda5a8fca

fix:compatible with the old version of nfs server, add unmount ops.

Feature or Bugfix:Feature
Binary Source:Huawei
PrivateCode(Yes/No):Yes

Change-Id: I175d2648bc6f9078c34de2c0a5c93fda10b86c47
ChangeID:13306420

Signed-off-by: NZbigniew Bodek <zbigniew.bodek@huawei.com>
Change-Id: I36cf1ea70a6e58e248328e189a2b9aa801fd88e7