On Thu, Jun 08, 2023 at 06:50:15AM -0700, Christoph Hellwig wrote: > On Thu, Jun 08, 2023 at 02:37:34PM +0100, Matthew Wilcox wrote: > > On Wed, Jun 07, 2023 at 08:24:04PM -0700, Luis Chamberlain wrote: > > > We currently share a single super_block for the block device cache, > > > each block device corresponds to one inode on that super_block. This > > > implicates sharing one aops operation though, and in the near future > > > we want to be able to instead support using iomap on the super_block > > > for different block devices. > > > > > -struct super_block *blockdev_superblock __read_mostly; > > > > Did we consider adding > > > > +struct super_block *blockdev_sb_iomap __read_mostly; > > > > and then considering only two superblocks instead of having a list of > > all bdevs? > > Or why the heck we would even do this to start with? That's what I gathered you suggested at LSFMM on hallway talk. > iomap has absolutely nothing to do with superblocks. > > Now maybe it might make sense to have a superblock per gendisk just > to remove all the weird special casing for the bdev inode in the > writeback code. But that's something entirely different than this > patch. The goal behind this is to allow block devices to have its bdev cache use iomap, right now now we show-horn in the buffer-head aops if we have to build buffer-heads. If this sort of approach is not desirable, let me know what alternative you would prefer to see, because clearly, I must not have understood your suggestion. Luis
