Re: fragmentation && blocks "realloc"

[Jan Koss <kossjan@gmail.com>]

Hello.

>(They access the block device directly, completely
>bypassing the page cache so you are breaking cache coherency and are 100%
>broken by design.)

Oh... I thought that start from 2.4.x there are no separate implementation
of working with blocks and pages, when you read block, kernel read whole page,
am I wrong?

> They only way to help you
> is to see your whole file system code

If we need some handhold for discussion, lets talk about minix v.1
(my file system derive from this code).
Lets suppose I want make algorigth of allocation blocks in
fs/minix/bitmap.c: minix_new_block more inteligent.

I should say that minix code use sb_bread/brelse and work with pages (for
example fs/minix/dir.c).

So instead of allocation one additional block,
I want "realloc" blocks, so all file will occupy several consecutive blocks.

And we stop on such code
 bh->b_blocknr = newblk;
 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
 mark_buffer_dirty (bh);


And question how should I get this _bh_, if I can not use sb_bread?