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Message-ID: <202207041123.5l995xnn-lkp@intel.com>
Date: Mon, 4 Jul 2022 11:53:30 +0800
From: kernel test robot <lkp@...el.com>
To: Jakub Matěna <matenajakub@...il.com>
Cc: kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Memory Management List <linux-mm@...ck.org>,
Vlastimil Babka <vbabka@...e.cz>
Subject: [akpm-mm:mm-unstable 102/232] mm/mmap.c:1084:14: warning: unused
variable 'merge_next'
tree: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
head: ff9d7221f1fc9bddb4f71f7501154c68b6942b9b
commit: 24a134b0c0a857bbf193eb7b3d8fcbbf77517c5f [102/232] mm: refactor of vma_merge()
config: x86_64-defconfig
compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
reproduce (this is a W=1 build):
# https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?id=24a134b0c0a857bbf193eb7b3d8fcbbf77517c5f
git remote add akpm-mm https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git
git fetch --no-tags akpm-mm mm-unstable
git checkout 24a134b0c0a857bbf193eb7b3d8fcbbf77517c5f
# save the config file
mkdir build_dir && cp config build_dir/.config
make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@...el.com>
All warnings (new ones prefixed by >>):
mm/mmap.c: In function 'vma_merge':
mm/mmap.c:1094:9: error: 'area' undeclared (first use in this function)
1094 | area = next;
| ^~~~
mm/mmap.c:1094:9: note: each undeclared identifier is reported only once for each function it appears in
>> mm/mmap.c:1084:14: warning: unused variable 'merge_next' [-Wunused-variable]
1084 | bool merge_next = false;
| ^~~~~~~~~~
>> mm/mmap.c:1083:14: warning: unused variable 'merge_prev' [-Wunused-variable]
1083 | bool merge_prev = false;
| ^~~~~~~~~~
>> mm/mmap.c:1081:45: warning: unused variable 'res' [-Wunused-variable]
1081 | struct vm_area_struct *mid, *next, *res;
| ^~~
>> mm/mmap.c:1081:32: warning: unused variable 'mid' [-Wunused-variable]
1081 | struct vm_area_struct *mid, *next, *res;
| ^~~
vim +/merge_next +1084 mm/mmap.c
1028
1029 /*
1030 * Given a mapping request (addr,end,vm_flags,file,pgoff,anon_name),
1031 * figure out whether that can be merged with its predecessor or its
1032 * successor. Or both (it neatly fills a hole).
1033 *
1034 * In most cases - when called for mmap, brk or mremap - [addr,end) is
1035 * certain not to be mapped by the time vma_merge is called; but when
1036 * called for mprotect, it is certain to be already mapped (either at
1037 * an offset within prev, or at the start of next), and the flags of
1038 * this area are about to be changed to vm_flags - and the no-change
1039 * case has already been eliminated.
1040 *
1041 * The following mprotect cases have to be considered, where AAAA is
1042 * the area passed down from mprotect_fixup, never extending beyond one
1043 * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
1044 *
1045 * AAAA AAAA AAAA
1046 * PPPPPPNNNNNN PPPPPPNNNNNN PPPPPPNNNNNN
1047 * cannot merge might become might become
1048 * PPNNNNNNNNNN PPPPPPPPPPNN
1049 * mmap, brk or case 4 below case 5 below
1050 * mremap move:
1051 * AAAA AAAA
1052 * PPPP NNNN PPPPNNNNXXXX
1053 * might become might become
1054 * PPPPPPPPPPPP 1 or PPPPPPPPPPPP 6 or
1055 * PPPPPPPPNNNN 2 or PPPPPPPPXXXX 7 or
1056 * PPPPNNNNNNNN 3 PPPPXXXXXXXX 8
1057 *
1058 * It is important for case 8 that the vma NNNN overlapping the
1059 * region AAAA is never going to extended over XXXX. Instead XXXX must
1060 * be extended in region AAAA and NNNN must be removed. This way in
1061 * all cases where vma_merge succeeds, the moment vma_adjust drops the
1062 * rmap_locks, the properties of the merged vma will be already
1063 * correct for the whole merged range. Some of those properties like
1064 * vm_page_prot/vm_flags may be accessed by rmap_walks and they must
1065 * be correct for the whole merged range immediately after the
1066 * rmap_locks are released. Otherwise if XXXX would be removed and
1067 * NNNN would be extended over the XXXX range, remove_migration_ptes
1068 * or other rmap walkers (if working on addresses beyond the "end"
1069 * parameter) may establish ptes with the wrong permissions of NNNN
1070 * instead of the right permissions of XXXX.
1071 */
1072 struct vm_area_struct *vma_merge(struct mm_struct *mm,
1073 struct vm_area_struct *prev, unsigned long addr,
1074 unsigned long end, unsigned long vm_flags,
1075 struct anon_vma *anon_vma, struct file *file,
1076 pgoff_t pgoff, struct mempolicy *policy,
1077 struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
1078 struct anon_vma_name *anon_name)
1079 {
1080 pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
> 1081 struct vm_area_struct *mid, *next, *res;
1082 int err = -1;
> 1083 bool merge_prev = false;
> 1084 bool merge_next = false;
1085
1086 /*
1087 * We later require that vma->vm_flags == vm_flags,
1088 * so this tests vma->vm_flags & VM_SPECIAL, too.
1089 */
1090 if (vm_flags & VM_SPECIAL)
1091 return NULL;
1092
1093 next = find_vma(mm, prev ? prev->vm_end : 0);
1094 area = next;
1095 if (area && area->vm_end == end) /* cases 6, 7, 8 */
1096 next = find_vma(mm, next->vm_end);
1097
1098 /* verify some invariant that must be enforced by the caller */
1099 VM_WARN_ON(prev && addr <= prev->vm_start);
1100 VM_WARN_ON(area && end > area->vm_end);
1101 VM_WARN_ON(addr >= end);
1102
1103 /*
1104 * Can it merge with the predecessor?
1105 */
1106 if (prev && prev->vm_end == addr &&
1107 mpol_equal(vma_policy(prev), policy) &&
1108 can_vma_merge_after(prev, vm_flags,
1109 anon_vma, file, pgoff,
1110 vm_userfaultfd_ctx, anon_name)) {
1111 /*
1112 * OK, it can. Can we now merge in the successor as well?
1113 */
1114 if (next && end == next->vm_start &&
1115 mpol_equal(policy, vma_policy(next)) &&
1116 can_vma_merge_before(next, vm_flags,
1117 anon_vma, file,
1118 pgoff+pglen,
1119 vm_userfaultfd_ctx, anon_name) &&
1120 is_mergeable_anon_vma(prev->anon_vma,
1121 next->anon_vma, NULL)) {
1122 /* cases 1, 6 */
1123 err = __vma_adjust(prev, prev->vm_start,
1124 next->vm_end, prev->vm_pgoff, NULL,
1125 prev);
1126 } else /* cases 2, 5, 7 */
1127 err = __vma_adjust(prev, prev->vm_start,
1128 end, prev->vm_pgoff, NULL, prev);
1129 if (err)
1130 return NULL;
1131 khugepaged_enter_vma(prev, vm_flags);
1132 return prev;
1133 }
1134
1135 /*
1136 * Can this new request be merged in front of next?
1137 */
1138 if (next && end == next->vm_start &&
1139 mpol_equal(policy, vma_policy(next)) &&
1140 can_vma_merge_before(next, vm_flags,
1141 anon_vma, file, pgoff+pglen,
1142 vm_userfaultfd_ctx, anon_name)) {
1143 if (prev && addr < prev->vm_end) /* case 4 */
1144 err = __vma_adjust(prev, prev->vm_start,
1145 addr, prev->vm_pgoff, NULL, next);
1146 else { /* cases 3, 8 */
1147 err = __vma_adjust(area, addr, next->vm_end,
1148 next->vm_pgoff - pglen, NULL, next);
1149 /*
1150 * In case 3 area is already equal to next and
1151 * this is a noop, but in case 8 "area" has
1152 * been removed and next was expanded over it.
1153 */
1154 area = next;
1155 }
1156 if (err)
1157 return NULL;
1158 khugepaged_enter_vma(area, vm_flags);
1159 return area;
1160 }
1161
1162 return NULL;
1163 }
1164
--
0-DAY CI Kernel Test Service
https://01.org/lkp
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