Re: [PATCH 1/3] slab, block: generalize bvec_alloc_gfp

[Matthew Wilcox <willy@infradead.org>]

On Mon, Oct 27, 2025 at 07:47:28AM +0100, Christoph Hellwig wrote:
> On Sun, Oct 26, 2025 at 09:19:27PM +0000, Matthew Wilcox wrote:
> > it's quite different.  I am by no stretch of the imagination a GFP
> > flags expert, but it seems to me that we should make the two the same
> > since they're both "try to allocate and we have a fallback if
> > necessary".  I suspect kvmalloc() is called with a wider range of
> > GFP flags than bvec allocation is, so it's probably better tested.
> > 
> > Is there a reason _not_ to use the kvmalloc code for bvec allocations?
> 
> It's using a dedicated slab cache, which makes sense for such a frequent
> and usually short-lived allocation.  We also don't use vmalloc backing
> ever at the moment.

That's not what I meant.

What I was proposing was:

+static inline gfp_t try_alloc_gfp(gfp_t gfp)
+{
+	gfp |= __GFP_NOWARN;
+	if (!(gfp & __GFP_RETRY_MAYFAIL))
+		gfp &= ~__GFP_DIRECT_RECLAIM;
+	gfp &= ~__GFP_NOFAIL;
+
+	return gfp;
+}