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Mon, 27 Apr 2026 07:17:59 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 27 Apr 2026 16:17:57 +0200 To: Vlastimil Babka Cc: Herbert Xu , Uladzislau Rezki , Harry Yoo , Hao Li , Thomas Graf , oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, Andrew Morton , Michal Hocko , Baoquan He , Alexander Potapenko , Andrey Ryabinin , Marco Elver , Michal Hocko , linux-mm@kvack.org Subject: Re: [linus:master] [mm] c6307674ed: BUG:sleeping_function_called_from_invalid_context_at_mm/vmalloc.c Message-ID: References: <202604211323.fac1b29e-lkp@intel.com> <4e269fb1-cd6c-46ca-ac2a-168ce9fd06fe@suse.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: <4e269fb1-cd6c-46ca-ac2a-168ce9fd06fe@suse.com> On Mon, Apr 27, 2026 at 10:53:52AM +0200, Vlastimil Babka wrote: > On 4/23/26 05:34, Herbert Xu wrote: > > On Wed, Apr 22, 2026 at 10:32:16AM +0200, Uladzislau Rezki wrote: > >> > >> We have added non-sleeping flags for vmalloc() to extend kvmalloc() > >> functionality as folk need those. > >> > >> Another option, would be: always use vfree_atomic() from the kvfree() > >> path. > >> > >> Any thoughts? > > > > Perhaps add a kvfree_atomic that just calls vfree_atomic? > > kvfree()'s comment says > > " * Context: Either preemptible task context or not-NMI interrupt." > I am not sure the description clearly reflects the intended usage. To me it sounds like all contexts but excluding NMI. For example, calling this under spin_lock() will be invalid, as the vfree() path may invoke cond_resched(). > so this is neither. It might be ok then to create kvfree_atomic(). Always > using vfree_atomic() from kvfree() might be wasteful. > > > For rhashtable it really makes no difference either way. But it > > would eliminate the unsightly call to is_vmalloc_addr in rhashtable. > > Seems atomic version makes sense here: diff --git a/include/linux/slab.h b/include/linux/slab.h index 15a60b501b95..2b5ab488e96b 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -1234,6 +1234,9 @@ void *kvrealloc_node_align_noprof(const void *p, size_t size, unsigned long alig extern void kvfree(const void *addr); DEFINE_FREE(kvfree, void *, if (!IS_ERR_OR_NULL(_T)) kvfree(_T)) +extern void kvfree_atomic(const void *addr); +DEFINE_FREE(kvfree_atomic, void *, if (!IS_ERR_OR_NULL(_T)) kvfree_atomic(_T)) + extern void kvfree_sensitive(const void *addr, size_t len); unsigned int kmem_cache_size(struct kmem_cache *s); diff --git a/mm/slub.c b/mm/slub.c index 2b2d33cc735c..e25a0eab6ff7 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -6802,6 +6802,22 @@ void kvfree(const void *addr) } EXPORT_SYMBOL(kvfree); +/** + * kvfree_atomic() - Free memory. + * @addr: Pointer to allocated memory. + * + * Same as kvfree(), but safe to use in atomic contexts. + * Must not be called from NMI context. + */ +void kvfree_atomic(const void *addr) +{ + if (is_vmalloc_addr(addr)) + vfree_atomic(addr); + else + kfree(addr); +} +EXPORT_SYMBOL(kvfree_atomic); + /** * kvfree_sensitive - Free a data object containing sensitive information. * @addr: address of the data object to be freed. I can post it if no objections. -- Uladzislau Rezki