Hi Suren, kernel test robot noticed the following build warnings: [auto build test WARNING on akpm-mm/mm-everything] [also build test WARNING on next-20231027] [cannot apply to linus/master v6.6-rc7] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch#_base_tree_information] url: https://github.com/intel-lab-lkp/linux/commits/Suren-Baghdasaryan/mm-rmap-support-move-to-different-root-anon_vma-in-folio_move_anon_rmap/20231028-084120 base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything patch link: https://lore.kernel.org/r/20231028003819.652322-3-surenb%40google.com patch subject: [PATCH v4 2/5] userfaultfd: UFFDIO_MOVE uABI config: m68k-allyesconfig (https://download.01.org/0day-ci/archive/20231028/202310281500.latmtbJs-lkp@xxxxxxxxx/config) compiler: m68k-linux-gcc (GCC) 13.2.0 reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231028/202310281500.latmtbJs-lkp@xxxxxxxxx/reproduce) If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <lkp@xxxxxxxxx> | Closes: https://lore.kernel.org/oe-kbuild-all/202310281500.latmtbJs-lkp@xxxxxxxxx/ All warnings (new ones prefixed by >>): >> mm/userfaultfd.c:1289: warning: Function parameter or member 'ctx' not described in 'move_pages' >> mm/userfaultfd.c:1289: warning: Function parameter or member 'mm' not described in 'move_pages' >> mm/userfaultfd.c:1289: warning: Function parameter or member 'mode' not described in 'move_pages' vim +1289 mm/userfaultfd.c 1211 1212 /** 1213 * move_pages - move arbitrary anonymous pages of an existing vma 1214 * @dst_start: start of the destination virtual memory range 1215 * @src_start: start of the source virtual memory range 1216 * @len: length of the virtual memory range 1217 * 1218 * Must be called with mmap_lock held for read. 1219 * 1220 * move_pages() remaps arbitrary anonymous pages atomically in zero 1221 * copy. It only works on non shared anonymous pages because those can 1222 * be relocated without generating non linear anon_vmas in the rmap 1223 * code. 1224 * 1225 * It provides a zero copy mechanism to handle userspace page faults. 1226 * The source vma pages should have mapcount == 1, which can be 1227 * enforced by using madvise(MADV_DONTFORK) on src vma. 1228 * 1229 * The thread receiving the page during the userland page fault 1230 * will receive the faulting page in the source vma through the network, 1231 * storage or any other I/O device (MADV_DONTFORK in the source vma 1232 * avoids move_pages() to fail with -EBUSY if the process forks before 1233 * move_pages() is called), then it will call move_pages() to map the 1234 * page in the faulting address in the destination vma. 1235 * 1236 * This userfaultfd command works purely via pagetables, so it's the 1237 * most efficient way to move physical non shared anonymous pages 1238 * across different virtual addresses. Unlike mremap()/mmap()/munmap() 1239 * it does not create any new vmas. The mapping in the destination 1240 * address is atomic. 1241 * 1242 * It only works if the vma protection bits are identical from the 1243 * source and destination vma. 1244 * 1245 * It can remap non shared anonymous pages within the same vma too. 1246 * 1247 * If the source virtual memory range has any unmapped holes, or if 1248 * the destination virtual memory range is not a whole unmapped hole, 1249 * move_pages() will fail respectively with -ENOENT or -EEXIST. This 1250 * provides a very strict behavior to avoid any chance of memory 1251 * corruption going unnoticed if there are userland race conditions. 1252 * Only one thread should resolve the userland page fault at any given 1253 * time for any given faulting address. This means that if two threads 1254 * try to both call move_pages() on the same destination address at the 1255 * same time, the second thread will get an explicit error from this 1256 * command. 1257 * 1258 * The command retval will return "len" is successful. The command 1259 * however can be interrupted by fatal signals or errors. If 1260 * interrupted it will return the number of bytes successfully 1261 * remapped before the interruption if any, or the negative error if 1262 * none. It will never return zero. Either it will return an error or 1263 * an amount of bytes successfully moved. If the retval reports a 1264 * "short" remap, the move_pages() command should be repeated by 1265 * userland with src+retval, dst+reval, len-retval if it wants to know 1266 * about the error that interrupted it. 1267 * 1268 * The UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES flag can be specified to 1269 * prevent -ENOENT errors to materialize if there are holes in the 1270 * source virtual range that is being remapped. The holes will be 1271 * accounted as successfully remapped in the retval of the 1272 * command. This is mostly useful to remap hugepage naturally aligned 1273 * virtual regions without knowing if there are transparent hugepage 1274 * in the regions or not, but preventing the risk of having to split 1275 * the hugepmd during the remap. 1276 * 1277 * If there's any rmap walk that is taking the anon_vma locks without 1278 * first obtaining the folio lock (the only current instance is 1279 * folio_referenced), they will have to verify if the folio->mapping 1280 * has changed after taking the anon_vma lock. If it changed they 1281 * should release the lock and retry obtaining a new anon_vma, because 1282 * it means the anon_vma was changed by move_pages() before the lock 1283 * could be obtained. This is the only additional complexity added to 1284 * the rmap code to provide this anonymous page remapping functionality. 1285 */ 1286 ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, 1287 unsigned long dst_start, unsigned long src_start, 1288 unsigned long len, __u64 mode) > 1289 { -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
