On Tuesday June 26, nickpiggin@xxxxxxxxxxxx wrote:
> Chris Mason wrote:
> >
> > The block device pagecache isn't special, and certainly isn't that much
> > code. I would suggest keeping it buffer head specific and making a
> > second variant that does only fsblocks. This is mostly to keep the
> > semantics of PagePrivate sane, lets not fuzz the line.
>
> That would require a new inode and address_space for the fsblock
> type blockdev pagecache, wouldn't it? I just can't think of a
> better non-intrusive way of allowing a buffer_head filesystem and
> an fsblock filesystem to live on the same blkdev together.
I don't think they would ever try to. Both filesystems would bd_claim
the blkdev, and only one would win.
The issue is more of a filesystem sharing a blockdev with the
block-special device (i.e. open("/dev/sda1"), read) isn't it?
If a filesystem wants to attach information to the blockdev pagecache
that is different to what blockdev want to attach, then I think "Yes"
- a new inode and address space is what it needs to create.
Then you get into consistency issues between the metadata and direct
blockdevice access. Do we care about those?
NeilBrown
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