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 new
        version of VFS to take advantage of vnode cache and path cache.

close: #I3S0CP

FAT12/FAT16 partition has no FSINFO sector storing the free cluster number,
so scanning the FAT is necessary to get the free clusters nums.

Close #I3Q0VS

Change-Id: I2205bbf42e7c2339f81443ace6924b12f4fa1c09

Change-Id: I1146ab12b02aeef3f9a2a0422ee45936f5e4c105

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

PathCacheMemoryDump miscalculate the RAM usage of PathCache for not
counting the name field of PathCache, which is allocated with PathCache

Close #I3OBXY

Change-Id: I8662952ac9d7912aaf2e2e72f779b3def41d14c4

if fatfs_mkfs returns a error, format may return without drop the vnode mutex, which may cause deadlock

Close #I3OFAY

The errno of unrecognized fat filesystem changes from ENOENT to ENOTSUP.

Close #I3O8IF

The name field of struct PathCache is not allocated. It should not try to free it by free(nc->name)

Close #I3NTH9

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

Close #I3NNFA

Change-Id: I3cc042b1fcd00022bc6ba48e2a05d70f351b83de

Close: I3NGBT
Change-Id: I70130c42061e51f5978b48befea66a5925386343

Bug: #I3NEVN
Test:

Close #I3NCDD

Close: I3MZZ6
Change-Id: Iab3919a2eebb44c82531a7fa7a2f688ec4bcc5a0

Close #I3MYP4

Change-Id: I533f4bacaf7e6dd500f5ac3ce4f5343b3b885988

Change-Id: I052d930d54e63179b17b77f02c107a015f3cfc3f

Change-Id: I44981eb9475feb4604ffe91244b4dff00f7d1548

Bug: #I2E08N
Test:

Change-Id: Ic9abc53cd0aafa1fd6272fab8191493c609ea995

Bug: Uninitialized parameter
Test:

Bug: #I3J1IC
Test: io test 1000 time

Change-Id: Ia956fd09f1bd734cd26ab631359c1e2131fe1e37

    buginfo: when try to umount a nfs node, it may casue stack overflow.

Change-Id: I7d96f74a770607c990ca5f51cb92fb2843a08d12

1. Bcache block with high mem address is after lower mem address in RCU list when initing bcache.
2. Format will clear the bcache before writing the FAT.
3. The fatfs_readdir use the bcache writing block to reduce the chance of data switching out
4. Add performance analysing macron switch

Change-Id: I8fbc48418509d2e660d725d2c265266e931c26f8

Change-Id: Ie48b96fe9c8ab036d7234b56a169d6668171a895

add SysFstatat64 SysInfo SysVfork SysGetrusage
fix up SysDup SysFcntl

Change-Id: If41228da62f406312858921e48e2210e04f16a16