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[109.81.80.221]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3b79c3abf33sm26573824f8f.7.2025.08.07.04.25.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Aug 2025 04:25:02 -0700 (PDT) Date: Thu, 7 Aug 2025 13:25:01 +0200 From: Michal Hocko To: "Uladzislau Rezki (Sony)" Cc: linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Baoquan He , LKML Subject: Re: [PATCH 6/8] mm/vmalloc: Defer freeing partly initialized vm_struct Message-ID: References: <20250807075810.358714-1-urezki@gmail.com> <20250807075810.358714-7-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: <20250807075810.358714-7-urezki@gmail.com> On Thu 07-08-25 09:58:08, Uladzislau Rezki wrote: > __vmalloc_area_node() may call free_vmap_area() or vfree() on > error paths, both of which can sleep. This becomes problematic > if the function is invoked from an atomic context, such as when > GFP_ATOMIC or GFP_NOWAIT is passed via gfp_mask. > > To fix this, unify error paths and defer the cleanup of partly > initialized vm_struct objects to a workqueue. This ensures that > freeing happens in a process context and avoids invalid sleeps > in atomic regions. > > Signed-off-by: Uladzislau Rezki (Sony) LGTM Acked-by: Michal Hocko Thanks! > --- > include/linux/vmalloc.h | 6 +++++- > mm/vmalloc.c | 34 +++++++++++++++++++++++++++++++--- > 2 files changed, 36 insertions(+), 4 deletions(-) > > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h > index fdc9aeb74a44..b1425fae8cbf 100644 > --- a/include/linux/vmalloc.h > +++ b/include/linux/vmalloc.h > @@ -50,7 +50,11 @@ struct iov_iter; /* in uio.h */ > #endif > > struct vm_struct { > - struct vm_struct *next; > + union { > + struct vm_struct *next; /* Early registration of vm_areas. */ > + struct llist_node llnode; /* Asynchronous freeing on error paths. */ > + }; > + > void *addr; > unsigned long size; > unsigned long flags; > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 7f48a54ec108..2424f80d524a 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3680,6 +3680,35 @@ vm_area_alloc_pages(gfp_t gfp, int nid, > return nr_allocated; > } > > +static LLIST_HEAD(pending_vm_area_cleanup); > +static void cleanup_vm_area_work(struct work_struct *work) > +{ > + struct vm_struct *area, *tmp; > + struct llist_node *head; > + > + head = llist_del_all(&pending_vm_area_cleanup); > + if (!head) > + return; > + > + llist_for_each_entry_safe(area, tmp, head, llnode) { > + if (!area->pages) > + free_vm_area(area); > + else > + vfree(area->addr); > + } > +} > + > +/* > + * Helper for __vmalloc_area_node() to defer cleanup > + * of partially initialized vm_struct in error paths. > + */ > +static DECLARE_WORK(cleanup_vm_area, cleanup_vm_area_work); > +static void defer_vm_area_cleanup(struct vm_struct *area) > +{ > + if (llist_add(&area->llnode, &pending_vm_area_cleanup)) > + schedule_work(&cleanup_vm_area); > +} > + > static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, > pgprot_t prot, unsigned int page_shift, > int node) > @@ -3711,8 +3740,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, > warn_alloc(gfp_mask, NULL, > "vmalloc error: size %lu, failed to allocated page array size %lu", > nr_small_pages * PAGE_SIZE, array_size); > - free_vm_area(area); > - return NULL; > + goto fail; > } > > set_vm_area_page_order(area, page_shift - PAGE_SHIFT); > @@ -3789,7 +3817,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, > return area->addr; > > fail: > - vfree(area->addr); > + defer_vm_area_cleanup(area); > return NULL; > } > > -- > 2.39.5 -- Michal Hocko SUSE Labs