On Tue, Sep 19, 2023 at 06:17:21AM +0100, Matthew Wilcox wrote: > Frustratingly, it looks like buffer_heads were intended to be used as > extents; each one has a b_size of its own. But there's a ridiculous > amount of code that assumes that all BHs attached to a folio have the > same b_size as each other. The primary reason why we need a per-bh b_size is for the benefit of non-iomap O_DIRECT code paths. If that goes away, then we can simplify this significantly, since we flush the buffer cache whenever we change the blocksize used in the buffer cache; the O_DIRECT bh's aren't part of the buffer cache, which is when you might have bh's with a b_size of 8200k (when doing a 8200k O_DIRECT read or write). Cheers, - Ted
