Re: linux-2.4.10-pre5

[Andrea Arcangeli]

On Sat, Sep 08, 2001 at 03:15:39PM -0600, Andreas Dilger wrote:
> On Sep 08, 2001  10:30 -0700, Linus Torvalds wrote:
> > I'll merge the blkdev in pagecache very early in 2.5.x, but I'm a bit
> > nervous about merging it in 2.4.x.
> > 
> > That said, if you'll give a description of how you fixed the aliasing
> > issues etc, maybe I'd be less nervous. Putting it in the page cache is
> > 100% the right thing to do, so in theory I'd really like to merge it
> > earlier rather than later, but...
> 
> I think this may have bad interactions with the filesystems, which still
> use buffer cache for metadata.  If the block devices move to page cache,
> so should the filesystems.
> 
> For example, the "tune2fs" program will modify parts of the superblock
> from user space (fields that are read-only from the kernel, e.g. label,
> reserved blocks count, etc), because it knows that the data read/written
> on /dev/hda1 is coherent with that in the kernel for the filesystem
> on /dev/hda1.  The same is true with e2fsck - the metadata should be
> kept coherent from user-space and kernel-space or bad things happen.

the patch takes care of that transparently of course, if it didn't you
would keep doing long fsck of the root filesystem forever.

Andrea