Hello Matthew Wilcox (Oracle),
Commit ea1be2228bb6 ("proc: rewrite stable_page_flags()") from Mar
26, 2024 (linux-next), leads to the following Smatch static checker
warning:
fs/proc/page.c:156 stable_page_flags() warn: bit shifter 'PG_lru' used for logical '&'
fs/proc/page.c:207 stable_page_flags() warn: bit shifter 'KPF_HUGE' used for logical '&'
fs/proc/page.c
110 u64 stable_page_flags(const struct page *page)
111 {
112 const struct folio *folio;
113 unsigned long k;
114 unsigned long mapping;
115 bool is_anon;
116 u64 u = 0;
117
118 /*
119 * pseudo flag: KPF_NOPAGE
120 * it differentiates a memory hole from a page with no flags
121 */
122 if (!page)
123 return 1 << KPF_NOPAGE;
124 folio = page_folio(page);
125
126 k = folio->flags;
127 mapping = (unsigned long)folio->mapping;
128 is_anon = mapping & PAGE_MAPPING_ANON;
129
130 /*
131 * pseudo flags for the well known (anonymous) memory mapped pages
132 */
133 if (page_mapped(page))
134 u |= 1 << KPF_MMAP;
135 if (is_anon) {
136 u |= 1 << KPF_ANON;
137 if (mapping & PAGE_MAPPING_KSM)
138 u |= 1 << KPF_KSM;
139 }
140
141 /*
142 * compound pages: export both head/tail info
143 * they together define a compound page's start/end pos and order
144 */
145 if (page == &folio->page)
146 u |= kpf_copy_bit(k, KPF_COMPOUND_HEAD, PG_head);
147 else
148 u |= 1 << KPF_COMPOUND_TAIL;
149 if (folio_test_hugetlb(folio))
150 u |= 1 << KPF_HUGE;
^^^^^^^^^^^^^
Here KPF_HUGE is a shifter
151 /*
152 * We need to check PageLRU/PageAnon
153 * to make sure a given page is a thp, not a non-huge compound page.
154 */
155 else if (folio_test_large(folio)) {
--> 156 if ((k & PG_lru) || is_anon)
^^^^^^^^^^
The PG_lru enum isn't used consistently. Should this be?:
if ((k & (1 << PG_lru)) || ...
157 u |= 1 << KPF_THP;
158 else if (is_huge_zero_folio(folio)) {
159 u |= 1 << KPF_ZERO_PAGE;
160 u |= 1 << KPF_THP;
161 }
162 } else if (is_zero_pfn(page_to_pfn(page)))
163 u |= 1 << KPF_ZERO_PAGE;
164
165 /*
166 * Caveats on high order pages: PG_buddy and PG_slab will only be set
167 * on the head page.
168 */
169 if (PageBuddy(page))
170 u |= 1 << KPF_BUDDY;
171 else if (page_count(page) == 0 && is_free_buddy_page(page))
172 u |= 1 << KPF_BUDDY;
173
174 if (PageOffline(page))
175 u |= 1 << KPF_OFFLINE;
176 if (PageTable(page))
177 u |= 1 << KPF_PGTABLE;
178
179 #if defined(CONFIG_PAGE_IDLE_FLAG) && defined(CONFIG_64BIT)
180 u |= kpf_copy_bit(k, KPF_IDLE, PG_idle);
181 #else
182 if (folio_test_idle(folio))
183 u |= 1 << KPF_IDLE;
184 #endif
185
186 u |= kpf_copy_bit(k, KPF_LOCKED, PG_locked);
187 u |= kpf_copy_bit(k, KPF_SLAB, PG_slab);
188 u |= kpf_copy_bit(k, KPF_ERROR, PG_error);
189 u |= kpf_copy_bit(k, KPF_DIRTY, PG_dirty);
190 u |= kpf_copy_bit(k, KPF_UPTODATE, PG_uptodate);
191 u |= kpf_copy_bit(k, KPF_WRITEBACK, PG_writeback);
192
193 u |= kpf_copy_bit(k, KPF_LRU, PG_lru);
194 u |= kpf_copy_bit(k, KPF_REFERENCED, PG_referenced);
195 u |= kpf_copy_bit(k, KPF_ACTIVE, PG_active);
196 u |= kpf_copy_bit(k, KPF_RECLAIM, PG_reclaim);
197
198 #define SWAPCACHE ((1 << PG_swapbacked) | (1 << PG_swapcache))
199 if ((k & SWAPCACHE) == SWAPCACHE)
200 u |= 1 << KPF_SWAPCACHE;
201 u |= kpf_copy_bit(k, KPF_SWAPBACKED, PG_swapbacked);
202
203 u |= kpf_copy_bit(k, KPF_UNEVICTABLE, PG_unevictable);
204 u |= kpf_copy_bit(k, KPF_MLOCKED, PG_mlocked);
205
206 #ifdef CONFIG_MEMORY_FAILURE
207 if (u & KPF_HUGE)
^^^^^^^^^^^^
Here it is a mask.
208 u |= kpf_copy_bit(k, KPF_HWPOISON, PG_hwpoison);
209 else
210 u |= kpf_copy_bit(page->flags, KPF_HWPOISON, PG_hwpoison);
211 #endif
212
213 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
214 u |= kpf_copy_bit(k, KPF_UNCACHED, PG_uncached);
215 #endif
216
217 u |= kpf_copy_bit(k, KPF_RESERVED, PG_reserved);
218 u |= kpf_copy_bit(k, KPF_MAPPEDTODISK, PG_mappedtodisk);
219 u |= kpf_copy_bit(k, KPF_PRIVATE, PG_private);
220 u |= kpf_copy_bit(k, KPF_PRIVATE_2, PG_private_2);
221 u |= kpf_copy_bit(k, KPF_OWNER_PRIVATE, PG_owner_priv_1);
222 u |= kpf_copy_bit(k, KPF_ARCH, PG_arch_1);
223 #ifdef CONFIG_ARCH_USES_PG_ARCH_X
224 u |= kpf_copy_bit(k, KPF_ARCH_2, PG_arch_2);
225 u |= kpf_copy_bit(k, KPF_ARCH_3, PG_arch_3);
226 #endif
227
228 return u;
229 };
regards,
dan carpenter
