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[109.81.80.221]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3b79c3ac158sm26896024f8f.4.2025.08.07.04.20.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Aug 2025 04:20:55 -0700 (PDT) Date: Thu, 7 Aug 2025 13:20:54 +0200 From: Michal Hocko To: "Uladzislau Rezki (Sony)" Cc: linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Baoquan He , LKML Subject: Re: [PATCH 3/8] mm/vmalloc: Support non-blocking GFP flags in alloc_vmap_area() Message-ID: References: <20250807075810.358714-1-urezki@gmail.com> <20250807075810.358714-4-urezki@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250807075810.358714-4-urezki@gmail.com> On Thu 07-08-25 09:58:05, Uladzislau Rezki wrote: > 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. Those are currently not allowed so it would be better to mention this is a preparation for those to _be_ supported later in the series. > 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. > > Signed-off-by: Uladzislau Rezki (Sony) With the changelog clarified Acked-by: Michal Hocko Thanks! > --- > mm/vmalloc.c | 17 ++++++++++++++--- > 1 file changed, 14 insertions(+), 3 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 6dbcdceecae1..81b6d3bde719 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2017,6 +2017,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > unsigned long freed; > unsigned long addr; > unsigned int vn_id; > + bool allow_block; > int purged = 0; > int ret; > > @@ -2026,7 +2027,8 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > if (unlikely(!vmap_initialized)) > return ERR_PTR(-EBUSY); > > - might_sleep(); > + allow_block = gfpflags_allow_blocking(gfp_mask); > + might_sleep_if(allow_block); > > /* > * If a VA is obtained from a global heap(if it fails here) > @@ -2065,8 +2067,16 @@ static struct vmap_area *alloc_vmap_area(unsigned long 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 error; > + } > > va->va_start = addr; > va->va_end = addr + size; > @@ -2116,6 +2126,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > pr_warn("vmalloc_node_range for size %lu failed: Address range restricted to %#lx - %#lx\n", > size, vstart, vend); > > +error: > kmem_cache_free(vmap_area_cachep, va); > return ERR_PTR(-EBUSY); > } > -- > 2.39.5 -- Michal Hocko SUSE Labs