Suppose that I have two big filesystems, dest fs and source fs.. I want
to copy whole source fs to dest fs, but I need to keep
source filesystem online I can't mount source fs read only and copy..
The idea is, mount both filesystems "together", and make write/read
operations go on this way
Read operations:
1. See if data is already on dest fs,
2. If is then read data and bright back to caller (lets call this
cold read)
3. If is not, then read file from source fs, put it on page cache,
and change the backstorage of that page..
3.1 So when this page get dirty or too old, it will be writed to
dest fs
The problem here is, I need to remap every data and metadata on
step 3 (inodes and stuff), I think that read only data, isn't writed to
disk,
so in case of old page, this page would be freed from memory and
not write to dest fs.. so I need read only pages to be forced dirty..
Write operations:
1. Write data to dest fs
2. Mark data as present on dest fs
Also I need to know when copy is finished, so I need a tool to
crosscheck both filesystems and say what was copied and what wasn't, and
give me some percent of remaining unsynced data. When I get 100% of data
in sync I can umount source filesystem and use its storage for other
propose.
The go here is move data online, where I can't bring data offline..
I'm a kernel newbie, I have just read a lot about page cache and VSF,
but this seems possible, right?
--
Follow the white rabbit!
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