Re: PATCH ext2 unbork fs.h (part 1/7)

From: Jeff Garzik (
Date: Mon Jan 07 2002 - 18:48:50 EST

Daniel Phillips wrote:
> On January 7, 2002 02:21 pm, Jeff Garzik wrote:
> > Here's my idea for the solution. Each patch in the series has been
> > tested individually and can be applied individually, as long as all
> > preceding patches are applied. (ie. to apply and testing patch N,
> > patches 1 through N-1 must also be applied) The light testing consisted
> > of unpacking, catting, and removing kernel trees, along with a fillmem
> > runs to ensure that slab caches are properly purged. An fsck was forced
> > after each run of tests.
> >
> > This is the first of seven steps in the Make Fs.h Happy program.
> > It borrows direction from Daniel and Linus as well as my own.
> >
> > patch1 (this patch): use accessor function ext2_i to access inode->u.ext2_i
> > The rest of the patches borrows ideas but no code. This patch
> > is the only exception: it borrows substantially Daniel's ext2_i
> > patch.
> > patch2: use accessor function ext2_sb to access sb->u.ext2_sb
> > patch3: dynamically allocate sb->u.ext2_sbp
> > patch4: dynamically allocate inode->u.ext2_ip
> > patch5: move include/linux/ext2*.h to fs/ext2
> >
> > at this point we've reached the limits of how far the current
> > VFS API will go. inode and superblock fs-level private info
> > is dynamically allocated.
> >
> > patch6: add sb->s_op->{alloc,destroy}_inode to VFS API
> > patch7: implement ext2 use of s_op->{alloc,destroy}
> The two main problems I see with this are:
> - If a filesystem doesn't want to use genericp_ip/sbp then fs.h has
> to know about it. Why should fs.h know about every filesystem in
> the world?
> - You are dreferencing a pointer, and have two allocations for every
> inode instead of one.
> It's not horrible, it's just not optimal.

new patch fixes both of these objections

> Moving the ext2 headers from include/linux to fs/ext2 is an interesting
> feature of your patch, though it isn't essential to the idea you're
> presenting. But is there a good reason why ext2_fs_i.h and ext2_fs_sb.h
> should remain separate from ext2_fs.h? It looks like gratuitous
> modularity to me.

apparently userspace includes them, which is the reason for the strange
types. good reason to continue to keep them separate. That's also why
my patch7 adds an ifdef __KERNEL__.


Jeff Garzik      | Alternate titles for LOTR:
Building 1024    | Fast Times at Uruk-Hai
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                 | Samwise Gamgee: International Hobbit of Mystery
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