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b=QpiREUdB6lYUmHAJPgwXeRaN+Gy+bUrQKbfvQHImDodRXHOR71W4pk4DGEGuTFNbv lRBRuQP2JSSTJJhwGur3aGJKeAjEhtVrWaFm3yJFpd/HCbJgCfZJAH5oCp7AOl/sUj 58klYWV6MYgqVd+9PWEiIwRkgGrZOPy/MO9cF0sziBvjdFCI8Z441ScY2xbtxlVS+s aWqZZLh1ZlUAhV3ywK3n1RB9gwNhmd1YsUqfnVM8+y8lzLju4kLstfogH8UdfxoOC7 tpx8zAFcNnvtljhq0SddX/oZqIBLeR6KVfxaP5deWui2d7E4PacZUlgMgpNuGJ2Wn7 Km1PkF011LcJQ== Message-ID: Date: Mon, 23 Feb 2026 17:48:25 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slab: pass __GFP_NOWARN to refill_sheaf() if fallback is available Content-Language: en-US To: Harry Yoo , Vlastimil Babka , Andrew Morton Cc: Christoph Lameter , David Rientjes , Roman Gushchin , Hao Li , linux-mm@kvack.org, Chris Bainbridge References: <20260223133322.16705-1-harry.yoo@oracle.com> From: "Vlastimil Babka (SUSE)" In-Reply-To: <20260223133322.16705-1-harry.yoo@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspam-User: X-Rspamd-Queue-Id: 81BC08000B X-Stat-Signature: di5eqyuzuihsoge6q9j94mhh66yjmboa X-HE-Tag: 1771865310-809605 X-HE-Meta: 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 zQz6dKvW JvL5PA4/oeSNqbWaXiyDBX4/OvkhkWmRdcx0lsc8EADFMUbEfsikZ9UEeFnO3IK0gNPa4z8Vi7vccVhmuiOWZetdh2+HB7JsjBwXDvNUxgeOGaGqKIAI9sY2SyAZA7bdzBoZU0wUCBwqFHj8jkj956fTqsOiEqoDXkF1j+ICXyBwvIhnYSBDKhmvESjWnXasz6Enx6CRp7nFpLWDVaxNtsZuVQxO9g728nkf6+VVE299JIGS5lN+R+OsNlIno18Jd6b1TuKSqSWnJZfsGC9Ui7j+ii78qDjmubEFopVB9qDhTzsED2otOHAv00Y6VO8KM1Nsx0pZw46pJC5TtfEsg7Q7V6yQNU+4L8btwG0KgMF3TcK8nIezGhxO8cWuvL1RDV9pWonhPxyz0GeqrsHs+bR2PazguIwDLqQlnsjqCtOUfgEW28qgpvt3xuO9Hnh0030kW X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 > 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 Thanks, added to slab/for-next-fixes. Hopefully Chris can confirm it works (without adding the __NOWARN to btrfs code) > --- > mm/slub.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index afa98065d74f..0c986c240bf6 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2823,7 +2823,7 @@ static struct slab_sheaf *alloc_full_sheaf(struct kmem_cache *s, gfp_t gfp) > if (!sheaf) > return NULL; > > - if (refill_sheaf(s, sheaf, gfp | __GFP_NOMEMALLOC)) { > + if (refill_sheaf(s, sheaf, gfp | __GFP_NOMEMALLOC | __GFP_NOWARN)) { > free_empty_sheaf(s, sheaf); > return NULL; > } > @@ -4576,7 +4576,7 @@ __pcs_replace_empty_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs, > return NULL; > > if (empty) { > - if (!refill_sheaf(s, empty, gfp | __GFP_NOMEMALLOC)) { > + if (!refill_sheaf(s, empty, gfp | __GFP_NOMEMALLOC | __GFP_NOWARN)) { > full = empty; > } else { > /* > @@ -4891,9 +4891,14 @@ EXPORT_SYMBOL(kmem_cache_alloc_node_noprof); > static int __prefill_sheaf_pfmemalloc(struct kmem_cache *s, > struct slab_sheaf *sheaf, gfp_t gfp) > { > - int ret = 0; > + gfp_t gfp_nomemalloc; > + int ret; > + > + gfp_nomemalloc = gfp | __GFP_NOMEMALLOC; > + if (gfp_pfmemalloc_allowed(gfp)) > + gfp_nomemalloc |= __GFP_NOWARN; > > - ret = refill_sheaf(s, sheaf, gfp | __GFP_NOMEMALLOC); > + ret = refill_sheaf(s, sheaf, gfp_nomemalloc); > > if (likely(!ret || !gfp_pfmemalloc_allowed(gfp))) > return ret;