[andrea-aa:main 44/48] mm/ksm.c:2134 cmp_and_merge_page() error: uninitialized symbol 'checksum'.

From: Dan Carpenter
Date: Wed Jan 05 2022 - 05:03:26 EST

Next message: Jonathan Cameron: "Re: [PATCH 3/8] PM: core: Add EXPORT[_GPL]_SIMPLE_DEV_PM_OPS macros"
Previous message: Andy Shevchenko: "Re: [PATCH] platform: finally disallow IRQ0 in platform_get_irq() and its ilk"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

tree: https://git.kernel.org/pub/scm/linux/kernel/git/andrea/aa.git main
head: 2f1336124b54750df7ae428da9352e4d8091f31e
commit: fec43fa50ccf8365ae2a8d9f150970ab6ca42b18 [44/48] KSM: only attempt to merge with KSM pages if the payload doesn't change
config: i386-randconfig-m021-20211218 (https://download.01.org/0day-ci/archive/20211219/202112190517.NPcuhEOX-lkp@xxxxxxxxx/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

smatch warnings:
mm/ksm.c:2134 cmp_and_merge_page() error: uninitialized symbol 'checksum'.

vim +/checksum +2134 mm/ksm.c

31dbd01f314364 Izik Eidus 2009-09-21 2059 static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
31dbd01f314364 Izik Eidus 2009-09-21 2060 {
4b22927f0cbd58 Kirill Tkhai 2017-10-03 2061 struct mm_struct *mm = rmap_item->mm;
31dbd01f314364 Izik Eidus 2009-09-21 2062 struct rmap_item *tree_rmap_item;
8dd3557a52f0bc Hugh Dickins 2009-12-14 2063 struct page *tree_page = NULL;
7b6ba2c7d3baf8 Hugh Dickins 2009-12-14 2064 struct stable_node *stable_node;
8dd3557a52f0bc Hugh Dickins 2009-12-14 2065 struct page *kpage;
31dbd01f314364 Izik Eidus 2009-09-21 2066 unsigned int checksum;
31dbd01f314364 Izik Eidus 2009-09-21 2067 int err;
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2068 bool max_page_sharing_bypass = false;
31dbd01f314364 Izik Eidus 2009-09-21 2069
4146d2d673e8d6 Hugh Dickins 2013-02-22 2070 stable_node = page_stable_node(page);
4146d2d673e8d6 Hugh Dickins 2013-02-22 2071 if (stable_node) {
4146d2d673e8d6 Hugh Dickins 2013-02-22 2072 if (stable_node->head != &migrate_nodes &&
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2073 get_kpfn_nid(READ_ONCE(stable_node->kpfn)) !=
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2074 NUMA(stable_node->nid)) {
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2075 stable_node_dup_del(stable_node);
4146d2d673e8d6 Hugh Dickins 2013-02-22 2076 stable_node->head = &migrate_nodes;
4146d2d673e8d6 Hugh Dickins 2013-02-22 2077 list_add(&stable_node->list, stable_node->head);
4146d2d673e8d6 Hugh Dickins 2013-02-22 2078 }
4146d2d673e8d6 Hugh Dickins 2013-02-22 2079 if (stable_node->head != &migrate_nodes &&
4146d2d673e8d6 Hugh Dickins 2013-02-22 2080 rmap_item->head == stable_node)
4146d2d673e8d6 Hugh Dickins 2013-02-22 2081 return;
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2082 /*
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2083 * If it's a KSM fork, allow it to go over the sharing limit
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2084 * without warnings.
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2085 */
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2086 if (!is_page_sharing_candidate(stable_node))
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2087 max_page_sharing_bypass = true;
fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2088 } else {
fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2089 /*
fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2090 * If the hash value of the page has changed from the last
fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2091 * time we calculated it, this page is changing frequently:
fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2092 * therefore we don't want to write protect it.
fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2093 */
fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2094 checksum = calc_checksum(page);

"checksum" initialized here. Not intialized for stable_node.

fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2095 if (rmap_item->oldchecksum != checksum) {
fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2096 rmap_item->oldchecksum = checksum;
fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2097 remove_rmap_item_from_tree(rmap_item);
fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2098 return;
fec43fa50ccf83 Andrea Arcangeli 2021-11-23 2099 }
4146d2d673e8d6 Hugh Dickins 2013-02-22 2100 }
31dbd01f314364 Izik Eidus 2009-09-21 2101
31dbd01f314364 Izik Eidus 2009-09-21 2102 /* We first start with searching the page inside the stable tree */
62b61f611eb5e2 Hugh Dickins 2009-12-14 2103 kpage = stable_tree_search(page);
4146d2d673e8d6 Hugh Dickins 2013-02-22 2104 if (kpage == page && rmap_item->head == stable_node) {
4146d2d673e8d6 Hugh Dickins 2013-02-22 2105 put_page(kpage);
4146d2d673e8d6 Hugh Dickins 2013-02-22 2106 return;
4146d2d673e8d6 Hugh Dickins 2013-02-22 2107 }
4146d2d673e8d6 Hugh Dickins 2013-02-22 2108
4146d2d673e8d6 Hugh Dickins 2013-02-22 2109 remove_rmap_item_from_tree(rmap_item);
4146d2d673e8d6 Hugh Dickins 2013-02-22 2110
62b61f611eb5e2 Hugh Dickins 2009-12-14 2111 if (kpage) {
2cee57d1b08877 Yang Shi 2019-03-05 2112 if (PTR_ERR(kpage) == -EBUSY)
2cee57d1b08877 Yang Shi 2019-03-05 2113 return;
2cee57d1b08877 Yang Shi 2019-03-05 2114
08beca44dfb0ab Hugh Dickins 2009-12-14 2115 err = try_to_merge_with_ksm_page(rmap_item, page, kpage);
31dbd01f314364 Izik Eidus 2009-09-21 2116 if (!err) {
31dbd01f314364 Izik Eidus 2009-09-21 2117 /*
31dbd01f314364 Izik Eidus 2009-09-21 2118 * The page was successfully merged:
31dbd01f314364 Izik Eidus 2009-09-21 2119 * add its rmap_item to the stable tree.
31dbd01f314364 Izik Eidus 2009-09-21 2120 */
5ad6468801d28c Hugh Dickins 2009-12-14 2121 lock_page(kpage);
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2122 stable_tree_append(rmap_item, page_stable_node(kpage),
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2123 max_page_sharing_bypass);
5ad6468801d28c Hugh Dickins 2009-12-14 2124 unlock_page(kpage);
31dbd01f314364 Izik Eidus 2009-09-21 2125 }
8dd3557a52f0bc Hugh Dickins 2009-12-14 2126 put_page(kpage);
31dbd01f314364 Izik Eidus 2009-09-21 2127 return;
31dbd01f314364 Izik Eidus 2009-09-21 2128 }
31dbd01f314364 Izik Eidus 2009-09-21 2129
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2130 /*
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2131 * Same checksum as an empty page. We attempt to merge it with the
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2132 * appropriate zero page if the user enabled this via sysfs.
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2133 */
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 @2134 if (ksm_use_zero_pages && (checksum == zero_checksum)) {

uninitialized here. Smatch cannot see how ksm_use_zero_pages and
stable_node are related. (Neither can I but I have not looked at the
context).

e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2135 struct vm_area_struct *vma;
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2136
d8ed45c5dcd455 Michel Lespinasse 2020-06-08 2137 mmap_read_lock(mm);
4b22927f0cbd58 Kirill Tkhai 2017-10-03 2138 vma = find_mergeable_vma(mm, rmap_item->address);
56df70a63ed5d9 Muchun Song 2020-04-20 2139 if (vma) {
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2140 err = try_to_merge_one_page(vma, page,
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2141 ZERO_PAGE(rmap_item->address));
56df70a63ed5d9 Muchun Song 2020-04-20 2142 } else {
56df70a63ed5d9 Muchun Song 2020-04-20 2143 /*
56df70a63ed5d9 Muchun Song 2020-04-20 2144 * If the vma is out of date, we do not need to
56df70a63ed5d9 Muchun Song 2020-04-20 2145 * continue.
56df70a63ed5d9 Muchun Song 2020-04-20 2146 */
56df70a63ed5d9 Muchun Song 2020-04-20 2147 err = 0;
56df70a63ed5d9 Muchun Song 2020-04-20 2148 }
d8ed45c5dcd455 Michel Lespinasse 2020-06-08 2149 mmap_read_unlock(mm);
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2150 /*
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2151 * In case of failure, the page was not really empty, so we
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2152 * need to continue. Otherwise we're done.
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2153 */
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2154 if (!err)
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2155 return;
e86c59b1b12d0d Claudio Imbrenda 2017-02-24 2156 }
8dd3557a52f0bc Hugh Dickins 2009-12-14 2157 tree_rmap_item =
8dd3557a52f0bc Hugh Dickins 2009-12-14 2158 unstable_tree_search_insert(rmap_item, page, &tree_page);
31dbd01f314364 Izik Eidus 2009-09-21 2159 if (tree_rmap_item) {
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2160 bool split;
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2161
8dd3557a52f0bc Hugh Dickins 2009-12-14 2162 kpage = try_to_merge_two_pages(rmap_item, page,
8dd3557a52f0bc Hugh Dickins 2009-12-14 2163 tree_rmap_item, tree_page);
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2164 /*
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2165 * If both pages we tried to merge belong to the same compound
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2166 * page, then we actually ended up increasing the reference
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2167 * count of the same compound page twice, and split_huge_page
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2168 * failed.
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2169 * Here we set a flag if that happened, and we use it later to
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2170 * try split_huge_page again. Since we call put_page right
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2171 * afterwards, the reference count will be correct and
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2172 * split_huge_page should succeed.
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2173 */
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2174 split = PageTransCompound(page)
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2175 && compound_head(page) == compound_head(tree_page);
8dd3557a52f0bc Hugh Dickins 2009-12-14 2176 put_page(tree_page);
bc56620b493496 Hugh Dickins 2013-02-22 2177 if (kpage) {
31dbd01f314364 Izik Eidus 2009-09-21 2178 /*
bc56620b493496 Hugh Dickins 2013-02-22 2179 * The pages were successfully merged: insert new
bc56620b493496 Hugh Dickins 2013-02-22 2180 * node in the stable tree and add both rmap_items.
31dbd01f314364 Izik Eidus 2009-09-21 2181 */
5ad6468801d28c Hugh Dickins 2009-12-14 2182 lock_page(kpage);
7b6ba2c7d3baf8 Hugh Dickins 2009-12-14 2183 stable_node = stable_tree_insert(kpage);
7b6ba2c7d3baf8 Hugh Dickins 2009-12-14 2184 if (stable_node) {
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2185 stable_tree_append(tree_rmap_item, stable_node,
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2186 false);
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2187 stable_tree_append(rmap_item, stable_node,
2c653d0ee2ae78 Andrea Arcangeli 2017-07-06 2188 false);
7b6ba2c7d3baf8 Hugh Dickins 2009-12-14 2189 }
5ad6468801d28c Hugh Dickins 2009-12-14 2190 unlock_page(kpage);
7b6ba2c7d3baf8 Hugh Dickins 2009-12-14 2191
31dbd01f314364 Izik Eidus 2009-09-21 2192 /*
31dbd01f314364 Izik Eidus 2009-09-21 2193 * If we fail to insert the page into the stable tree,
31dbd01f314364 Izik Eidus 2009-09-21 2194 * we will have 2 virtual addresses that are pointing
31dbd01f314364 Izik Eidus 2009-09-21 2195 * to a ksm page left outside the stable tree,
31dbd01f314364 Izik Eidus 2009-09-21 2196 * in which case we need to break_cow on both.
31dbd01f314364 Izik Eidus 2009-09-21 2197 */
7b6ba2c7d3baf8 Hugh Dickins 2009-12-14 2198 if (!stable_node) {
8dd3557a52f0bc Hugh Dickins 2009-12-14 2199 break_cow(tree_rmap_item);
8dd3557a52f0bc Hugh Dickins 2009-12-14 2200 break_cow(rmap_item);
31dbd01f314364 Izik Eidus 2009-09-21 2201 }
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2202 } else if (split) {
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2203 /*
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2204 * We are here if we tried to merge two pages and
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2205 * failed because they both belonged to the same
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2206 * compound page. We will split the page now, but no
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2207 * merging will take place.
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2208 * We do not want to add the cost of a full lock; if
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2209 * the page is locked, it is better to skip it and
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2210 * perhaps try again later.
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2211 */
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2212 if (!trylock_page(page))
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2213 return;
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2214 split_huge_page(page);
77da2ba0648a4f Claudio Imbrenda 2018-04-05 2215 unlock_page(page);
31dbd01f314364 Izik Eidus 2009-09-21 2216 }
31dbd01f314364 Izik Eidus 2009-09-21 2217 }
31dbd01f314364 Izik Eidus 2009-09-21 2218 }

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx

Next message: Jonathan Cameron: "Re: [PATCH 3/8] PM: core: Add EXPORT[_GPL]_SIMPLE_DEV_PM_OPS macros"
Previous message: Andy Shevchenko: "Re: [PATCH] platform: finally disallow IRQ0 in platform_get_irq() and its ilk"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]