Re: [PATCH] mm/slab: pass __GFP_NOWARN to refill_sheaf() if fallback is available

[Chris Bainbridge <chris.bainbridge@gmail.com>]

On Tue, Feb 24, 2026 at 12:30:11PM +0100, Vlastimil Babka (SUSE) wrote:
> On 2/23/26 20:46, Chris Bainbridge wrote:
> > On Mon, Feb 23, 2026 at 05:48:25PM +0100, Vlastimil Babka (SUSE) wrote:
> >> On 2/23/26 14:33, Harry Yoo wrote:
> >> > When refill_sheaf() is called, failing to refill the sheaf doesn't
> >> > necessarily mean the allocation will fail because a fallback path
> >> > might be available and serve the allocation request.
> >> > 
> >> > Suppress spurious warnings by passing __GFP_NOWARN along with
> >> > __GFP_NOMEMALLOC whenever a fallback path is available.
> >> > 
> >> > When the caller is alloc_full_sheaf() or __pcs_replace_empty_main(),
> >> > the kernel always falls back to the slowpath (__slab_alloc_node()).
> >> > For __prefill_sheaf_pfmemalloc(), the fallback path is available
> >> > only when gfp_pfmemalloc_allowed() returns true.
> >> > 
> >> > Reported-by: Chris Bainbridge <chris.bainbridge@gmail.com>
> >> > Closes: https://lore.kernel.org/linux-mm/aZt2-oS9lkmwT7Ch@debian.local
> >> > Fixes: 1ce20c28eafd ("slab: handle pfmemalloc slabs properly with sheaves")
> >> > Link: https://lore.kernel.org/linux-mm/aZwSreGj9-HHdD-j@hyeyoo
> >> > Signed-off-by: Harry Yoo <harry.yoo@oracle.com>
> >> 
> >> Thanks, added to slab/for-next-fixes.
> >> Hopefully Chris can confirm it works (without adding the __NOWARN to btrfs code)
> > 
> > Yes, it works for my test case.
> 
> Great, can we add your Tested-by:  then?
> Thanks!

Sure.

Reported-and-tested-by: Chris Bainbridge <chris.bainbridge@gmail.com>