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Wed, 01 Oct 2025 12:26:51 -0700 (PDT) From: "Uladzislau Rezki (Sony)" To: linux-mm@kvack.org, Andrew Morton Cc: Michal Hocko , Baoquan He , LKML , Uladzislau Rezki , Michal Hocko Subject: [PATCH v3 03/10] mm/vmalloc: Support non-blocking GFP flags in alloc_vmap_area() Date: Wed, 1 Oct 2025 21:26:39 +0200 Message-ID: <20251001192647.195204-4-urezki@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251001192647.195204-1-urezki@gmail.com> References: <20251001192647.195204-1-urezki@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" alloc_vmap_area() currently assumes that sleeping is allowed during allocation. This is not true for callers which pass non-blocking GFP flags, such as GFP_ATOMIC or GFP_NOWAIT. This patch adds logic to detect whether the given gfp_mask permits blocking. It avoids invoking might_sleep() or falling back to reclaim path if blocking is not allowed. This makes alloc_vmap_area() safer for use in non-sleeping contexts, where previously it could hit unexpected sleeps, trigger warnings. It is a preparation and adjustment step to later allow both GFP_ATOMIC and GFP_NOWAIT allocations in this series. Acked-by: Michal Hocko Reviewed-by: Baoquan He Signed-off-by: Uladzislau Rezki (Sony) --- mm/vmalloc.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 798b2ed21e46..d83c01caaabe 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2017,6 +2017,7 @@ static struct vmap_area *alloc_vmap_area(unsigned lon= g size, unsigned long freed; unsigned long addr; unsigned int vn_id; + bool allow_block; int purged =3D 0; int ret; =20 @@ -2028,7 +2029,8 @@ static struct vmap_area *alloc_vmap_area(unsigned lon= g size, =20 /* Only reclaim behaviour flags are relevant. */ gfp_mask =3D gfp_mask & GFP_RECLAIM_MASK; - might_sleep(); + allow_block =3D gfpflags_allow_blocking(gfp_mask); + might_sleep_if(allow_block); =20 /* * If a VA is obtained from a global heap(if it fails here) @@ -2062,7 +2064,8 @@ static struct vmap_area *alloc_vmap_area(unsigned lon= g size, * This is not a fast path. Check if yielding is needed. This * is the only reschedule point in the vmalloc() path. */ - cond_resched(); + if (allow_block) + cond_resched(); } =20 trace_alloc_vmap_area(addr, size, align, vstart, vend, IS_ERR_VALUE(addr)= ); @@ -2071,8 +2074,16 @@ static struct vmap_area *alloc_vmap_area(unsigned lo= ng size, * If an allocation fails, the error value is * returned. Therefore trigger the overflow path. */ - if (IS_ERR_VALUE(addr)) - goto overflow; + if (IS_ERR_VALUE(addr)) { + if (allow_block) + goto overflow; + + /* + * We can not trigger any reclaim logic because + * sleeping is not allowed, thus fail an allocation. + */ + goto out_free_va; + } =20 va->va_start =3D addr; va->va_end =3D addr + size; @@ -2122,6 +2133,7 @@ static struct vmap_area *alloc_vmap_area(unsigned lon= g size, pr_warn("vmalloc_node_range for size %lu failed: Address range restricte= d to %#lx - %#lx\n", size, vstart, vend); =20 +out_free_va: kmem_cache_free(vmap_area_cachep, va); return ERR_PTR(-EBUSY); } --=20 2.47.3