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Tue, 15 Apr 2025 22:57:16 +0000 (UTC) Date: Wed, 16 Apr 2025 06:57:07 +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> <1841f2e1-d677-4bb7-b449-78322e52f212@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1841f2e1-d677-4bb7-b449-78322e52f212@amd.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Rspam-User: X-Rspamd-Queue-Id: 41C2F160004 X-Rspamd-Server: rspam04 X-Stat-Signature: ntyk3zhnq6d3a8gbc95yb9yaypqw6o4q X-HE-Tag: 1744757841-714906 X-HE-Meta: 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 1YVEXc0x 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 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 04/16/25 at 12:30am, Shivank Garg wrote: > > > On 4/15/2025 6:31 PM, Baoquan He wrote: > > 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. > > > > Please feel free to add following in next version. > > Reviewed-by: Shivank Garg > Tested-by: Shivank Garg Thanks a lot for your careful reviewing and testing. > > >> > >>> + WARN_ONCE(1, "%s error: errno (%d)\n", __func__, ret); > >>> goto recovery; > >>> + } > >>> > >>> /* Allocated area. */ > >>> va = vas[area]; > >> > > >