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Tue, 15 Apr 2025 09:01:58 -0400 X-MC-Unique: Frv93qQoMdO-W_L7a_nk-Q-1 X-Mimecast-MFC-AGG-ID: Frv93qQoMdO-W_L7a_nk-Q_1744722116 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A69951953945; Tue, 15 Apr 2025 13:01:56 +0000 (UTC) Received: from localhost (unknown [10.72.112.38]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 794181955BC0; Tue, 15 Apr 2025 13:01:55 +0000 (UTC) Date: Tue, 15 Apr 2025 21:01:51 +0800 From: Baoquan He To: Shivank Garg Cc: linux-mm@kvack.org, akpm@linux-foundation.org, urezki@gmail.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 5/5] mm/vmalloc.c: return explicit error value in alloc_vmap_area() Message-ID: References: <20250415023952.27850-1-bhe@redhat.com> <20250415023952.27850-6-bhe@redhat.com> <134bd404-d741-40ec-a661-f897da5ca9ca@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <134bd404-d741-40ec-a661-f897da5ca9ca@amd.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 4FB08100009 X-Stat-Signature: fd89gdbxdpmgct483rrbzg4qntw5sufn X-HE-Tag: 1744722133-459234 X-HE-Meta: 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 xjiTN/hN pYyS1Y9rl2YtbiSJWAjo5YA5SLmceLbFiPJTKl8pwDXYiMmFBRTVrxxwD9uYQaJGJ9HcBd4hlZ1L7wc1SrkjOg0yCmu6GxDjdjdiwucK8zi6laTU= 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 04/15/25 at 12:52pm, Shivank Garg wrote: > On 4/15/2025 8:09 AM, Baoquan He wrote: > > In codes of alloc_vmap_area(), it returns the upper bound 'vend' to > > indicate if the allocation is successful or failed. That is not very clear. > > > > Here change to return explicit error values and check them to judge if > > allocation is successful. > > > > IS_ERR_VALUE already uses unlikely() internally > > > > Signed-off-by: Baoquan He > > --- > > mm/vmalloc.c | 34 +++++++++++++++++----------------- > > 1 file changed, 17 insertions(+), 17 deletions(-) > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index 3f38a232663b..5b21cd09b2b4 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -1715,7 +1715,7 @@ va_clip(struct rb_root *root, struct list_head *head, > > */ > > lva = kmem_cache_alloc(vmap_area_cachep, GFP_NOWAIT); > > if (!lva) > > - return -1; > > + return -ENOMEM; > > } > > > > /* > > @@ -1729,7 +1729,7 @@ va_clip(struct rb_root *root, struct list_head *head, > > */ > > va->va_start = nva_start_addr + size; > > } else { > > - return -1; > > + return -EINVAL; > > } Thanks for reviewing. > > Braces around return -EINVAL seem unnecessary. > They can be dropped. This complys with the codeing style required in 3) Placing Braces and Spaces of Documentation/process/coding-style.rst because other branches are multiple statements. > > > > > if (type != FL_FIT_TYPE) { > > @@ -1758,19 +1758,19 @@ va_alloc(struct vmap_area *va, > > > > /* Check the "vend" restriction. */ > > if (nva_start_addr + size > vend) > > - return vend; > > + return -ERANGE; > > > > /* Update the free vmap_area. */ > > ret = va_clip(root, head, va, nva_start_addr, size); > > - if (WARN_ON_ONCE(ret)) > > - return vend; > > + if (ret) > > + return ret; > > Is it safe to remove the warning, or was it critical for debugging? This comes from a reported concern because va_clip() could be failed by NOTHING_FIT or kmem_cache_alloc failure. The warning here could cause confusion misleading people to think vmap area management is failed. > > > > > return nva_start_addr; > > } > > > > /* > > * Returns a start address of the newly allocated area, if success. > > - * Otherwise a vend is returned that indicates failure. > > + * Otherwise an error value is returned that indicates failure. > > */ > > static __always_inline unsigned long > > __alloc_vmap_area(struct rb_root *root, struct list_head *head, > > @@ -1795,14 +1795,13 @@ __alloc_vmap_area(struct rb_root *root, struct list_head *head, > > > > va = find_vmap_lowest_match(root, size, align, vstart, adjust_search_size); > > if (unlikely(!va)) > > - return vend; > > + return -ENOENT; > > > > nva_start_addr = va_alloc(va, root, head, size, align, vstart, vend); > > - if (nva_start_addr == vend) > > - return vend; > > > > #if DEBUG_AUGMENT_LOWEST_MATCH_CHECK > > - find_vmap_lowest_match_check(root, head, size, align); > > + if (!IS_ERR_VALUE(nva_start_addr)) > > + find_vmap_lowest_match_check(root, head, size, align); > > #endif > > > > return nva_start_addr; > > @@ -1932,7 +1931,7 @@ node_alloc(unsigned long size, unsigned long align, > > struct vmap_area *va; > > > > *vn_id = 0; > > - *addr = vend; > > + *addr = -EINVAL; > > > > /* > > * Fallback to a global heap if not vmalloc or there > > @@ -2012,20 +2011,20 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > > } > > > > retry: > > - if (addr == vend) { > > + if (IS_ERR_VALUE(addr)) { > > preload_this_cpu_lock(&free_vmap_area_lock, gfp_mask, node); > > addr = __alloc_vmap_area(&free_vmap_area_root, &free_vmap_area_list, > > size, align, vstart, vend); > > spin_unlock(&free_vmap_area_lock); > > } > > > > - trace_alloc_vmap_area(addr, size, align, vstart, vend, addr == vend); > > + trace_alloc_vmap_area(addr, size, align, vstart, vend, IS_ERR_VALUE(addr)); > > > > /* > > - * If an allocation fails, the "vend" address is > > + * If an allocation fails, the error value is > > * returned. Therefore trigger the overflow path. > > */ > > - if (unlikely(addr == vend)) > > + if (IS_ERR_VALUE(addr)) > > goto overflow; > > > > va->va_start = addr; > > @@ -4753,9 +4752,10 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, > > > > ret = va_clip(&free_vmap_area_root, > > &free_vmap_area_list, va, start, size); > > - if (WARN_ON_ONCE(unlikely(ret))) > > - /* It is a BUG(), but trigger recovery instead. */ > > + if ((unlikely(ret))) { > ^^ ^^ > The extra parentheses are redundant and can be removed for clarity. You are right, I will remove it. Thanks. > > > + WARN_ONCE(1, "%s error: errno (%d)\n", __func__, ret); > > goto recovery; > > + } > > > > /* Allocated area. */ > > va = vas[area]; >