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Thu, 17 Apr 2025 03:02:10 +0000 (UTC) Date: Thu, 17 Apr 2025 11:02:06 +0800 From: Baoquan He To: Uladzislau Rezki Cc: linux-mm@kvack.org, akpm@linux-foundation.org, 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 X-Rspamd-Queue-Id: AC26412000E X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 4p4aa3nidkanm7zy55156xyk1zd48qit X-HE-Tag: 1744858937-292581 X-HE-Meta: U2FsdGVkX19XWmd/Za7nULh9XMn1wku+UF85H6cyQvZ7aMzUSC8iBJnw9wxa3rih8rHv6Ob9qcfUpAwjDBbPjSqcuVshKjv4m9IRWeV0BNHhTS3NLy5f9uJS04VgNe8RE2Y8rcjj2RJbWIViVc5HiKKBxrf77P9xNqgg08WXMCBUcB4Ah6LY3bPWODEOIWWwK3tkkQ4rGhlrLWOLUVNOKC/3CPNGHO7GlQoJybAyzQUUs0fishQWKWQ3hgMfUjBJgaU5lmExchuh3abEdXtjitwcjOrfC6aCrZ0U0BEMIhJPt/RNdT/uFPTzuX032BydobhGQIIg+eAzfkBnSicpkBIIMXX6zLH7CBDDoUENjPL6E+cegDEX2a+lZeEWh7Xx2xY2RKYAk1iZaYu7o25kEOFc/hd3qbAK9CkuJ7aIsk2Cx3Njc1TA4/bvdcmW5KUW3G7ozy62AmsG8InSKQkvsnI+HsxgZNh4f9SrIJn6ra601wQf6tz8VShnfGkQTNJPMB6OoYcJIrAQ2PiWNlkeRcyJGT9GUIsNTrjYGoiZphypS0iqGdm9jaw5r/+PNqa/+fS5rbXureWm3r87+D8g9UHr3F8wamMP0BH+GP5nJ/gENgkt+QGtFdki7dnps94RohAr6Ku8IuU3o4E/YSymJLs26k6uLpAoduECJ/SqVZrm42oL1K3UFD84HeXNQSpw8r0ZsNmjnaSYJ2pOVUZVj41jdQB2JwWxl1xytMRUv21yCxz+KSjFZM5VP3TJcayeAPHQ0Pafk1AzTBSaWdkVuoKOWEQhJKOI/DIpHqjV1mCN8n1Q6e5uPgn96bSxa+XIdUdfGuE8GKdPSK2g5G44P4Xu0N6LdDtnXaGrRYBdD9VDSUMN3T7/nf6dpS3SZidB/lNk5OyUdH0yTPkf+L66ukR16ncdMmAn6OFV3R66Skgveoaf5d1pBDVnY7r1uGC5k59XM2fiOhHq4OeOXwv gZqXWWMn BCi7Lj+ELrXc5k5mUv/7peyeGhXQbtGZmeFVC7j5k665bxBTyiiCnbz94m1PozxtXEQAtFt3f77wO7mwmkl+zSC3qpVA+0umazn8HKjVnjR9JDVHtEaxXBV5OInja1MLfziw0gT9N9Ghj76oARct5hh6SzuzAgqn7rQP+JMlKhJJp19Dxm46zm8dP9TOOcIm3YtSvqylT0BbCsizkDQL9LTXjMbyMNd+uH2Iftqrq2yNvrVStuY9sMaUPUUCP8gkA8VnEDt7+/zDkR5LoNDN9OEP675isz1T7av47UZ9wT6hvrZLU1PpiEOtbOA+s7G6oLrvJ1r91z87aRR1aaftJAZ7Oy0Fj1eE5ZnZkzccEheouCtD2lwXnc8ALslLsNdsdyuwcVZF3jYuFMxDIZPFf6/IERUFFlYEHk1NgH/WDqBRSx58SezqGPC8lspmNM3LV6B8+ii9MUC4dUasabYRPNU8usmOU2zVIxuDx 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 04:28pm, Uladzislau Rezki wrote: > On Tue, Apr 15, 2025 at 10:39:52AM +0800, 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; > > } > > > > 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; > > > Not clear why you remove this WARN_ON by this patch. It should be > a separate patch or just keep it as is. The warning here can mean > that something is really wrong, especially if NOTHING_FIT. So we > definitely want the warning. I remember one time someone reported that the slab allocation failure triggered this warning which is confusing to them. But yes, it should be discussed in a separate post or thread, not appropriate to remove it silently. I will add it back in v2. > > > + if (ret) > > + return ret; > > > > 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)) > > > Just keep it as it was. No need to check if addr is valid or not. This is to keep consistent with the old code. Before this patch, if va_alloc() return vend, it returns directly, no find_vmap_lowest_match_check() invocation is done. I tried to keep the behaviour unchanged. That code is for debugging, both is fine to me. > > > + 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. */ > Keep the comment. OK, will add it back. > > > + if ((unlikely(ret))) { > > + WARN_ONCE(1, "%s error: errno (%d)\n", __func__, ret); > > goto recovery; > > + } > > > > -- > Uladzislau Rezki >