Re: [PATCH] cowlinks v2

[Jörn Engel]

On Sat, 3 April 2004 12:47:58 -0700, Eric W. Biederman wrote:
> 
> And a few scenarios to hopefully make things clear.
> 
> So your fs starts out as:
> 
> /file1 -> ino1 (link count 2) -> data block #1
> /file2 -> ino1 (link count 2) -> data block #1
> 
> file1 is only 4K long, so I only need to describe one data block.
> 
> Actions:
> 
> cowcopy(file2, file3):
> 
> /file1 -> ino1 (link count 2) -> ino2 (link count 2) -> data block #1
> /file2 -> ino1 (link count 2) -> ino2 (link count 2) -> data block #1
> /file3 -> ino3 (link count 1) -> ino2 (link count 2) -> data block #1
> 
> 
> copyfile(file3, file4):
> 
> /file1 -> ino1 (link count 2) -> ino2 (link count 3) -> data block #1
> /file2 -> ino1 (link count 2) -> ino2 (link count 3) -> data block #1
> /file3 -> ino3 (link count 1) -> ino2 (link count 3) -> data block #1
> /file4 -> ino4 (link count 1) -> ino2 (link count 3) -> data block #1
> 
> unlink(file2):
> 
> /file1 -> ino1 (link count 1) -> ino2 (link count 3) -> data block #1
> /file3 -> ino3 (link count 1) -> ino2 (link count 3) -> data block #1
> /file4 -> ino4 (link count 1) -> ino2 (link count 3) -> data block #1
> 
> link(file4, file5):
> 
> /file1 -> ino1 (link count 1) -> ino2 (link count 3) -> data block #1
> /file3 -> ino3 (link count 1) -> ino2 (link count 3) -> data block #1
> /file4 -> ino4 (link count 2) -> ino2 (link count 3) -> data block #1
> /file5 -> ino4 (link count 2) -> ino2 (link count 3) -> data block #1
> 
> write(file3):
> 
> /file1 -> ino1 (link count 1) -> ino2 (link count 2) -> data block #1
> /file3 -> ino3 (link count 1) -> data block #2
> /file4 -> ino4 (link count 2) -> ino2 (link count 2) -> data block #1
> /file5 -> ino4 (link count 2) -> ino2 (link count 2) -> data block #1
> 
> write(file5):
> 
> /file1 -> ino1 (link count 1) -> ino2 (link count 1) -> data block #1
> /file3 -> ino3 (link count 1) -> data block #2
> /file4 -> ino4 (link count 2) -> data block #3
> /file5 -> ino4 (link count 2) -> data block #3
> 
> write(file1):
> 
> /file1 -> ino1 (link count 1) -> data block #1 (with modified contents)
> /file3 -> ino3 (link count 1) -> data block #2
> /file4 -> ino4 (link count 2) -> data block #3
> /file5 -> ino4 (link count 2) -> data block #3
> 
> Does this make things clear?

Almost.  What exactly do cowcopy() and copyfile() do?  They look the
same, so why the difference?

Jörn

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