Re: update BDI {io,ra}_pages values based on the RT device limits

[Christoph Hellwig <hch@lst.de>]

On Wed, Jun 24, 2026 at 12:40:50PM +0200, Carlos Maiolino wrote:
> Giving the current tendency of filesystems being multi-device, this
> doesn't sound bad IMHO. Wouldn't accessing io_pages of each BDI also be
> worth even for a journal dev? I wonder if what you ran into wouldn't be
> possible if somebody would be using just a SSD for journal and a non-rt
> XFS on a HDD or a different/slower device.

Nothing looks at the value for the log device.

> 
> I don't know how stupid that sounds but perhaps it wouldn't be that
> complicated to support multiple BDIs without making it unpleasant for
> filesystems that don't care?
> sb->bdi could be turned into a dynamic array and a new sb->s_devcount
> fields to keep track of it on multi-device filesystems. Filesystems who
> don't care about multiple BDIs would have it pointing to a single BDI
> struct. Again I feel I'm missing something, so it might sound really
> stupid :)

This will get complicated really soon..