2009-12-31 02:29:47

by Haibo

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Subject: a question about the ext3fs reserve window

I am a newer to linux kernel.I have read some code of the ext3fs.
I found a new word "reserve window".I have not known much about it.
All of I known is :

1."reserve window" is used to help extfs to allocate the block(for
regular file only).
2.One inode can have some reserve window,and it can store the allocate
info of some ranges.
3.It used rb_tree to link thoses "reserve window",so if you want to find
a new "reserve window",
it will be fast.
4.The info of the "reserve window" store in memory only,not in disk.
5.You can control the "reserve window" through the ioctl();

I not sure above and I have some questions:

1.Before the "reserve window" ,extfs allocate the block through
searching the block bitmap.
Between these two methods, who is better?
2.When was "reserve window" been code to the extfs?

Thank you very much for your answer.