Block IO
设备层
内核态
....
Block-based FS
b3
exFat
Stackable FS
ASM
ext4
用户进程 (Application)
内存映射
Other FS
用户态
xfs
外置设备
b2
Page Cache
b1
File
块设备(Disk/USB/Flash..etc)
overlayFS
Direct_IO API
Block IO 层
page 1
imbajin
page 2
mmap/malloc
直接 IO
Buffered IO(标准IO)
4~8k
unionFS
0~4k
span style=\"font-size: inherit;\
system call
buffer
VFS
read/write
