* [djwong-xfs:realtime-rmap 245/249] fs/xfs/scrub/repair.c:2202:6: warning: variable 'is_free' is uninitialized when used here
@ 2020-12-21 19:22 kernel test robot
2020-12-21 22:19 ` Nathan Chancellor
0 siblings, 1 reply; 3+ messages in thread
From: kernel test robot @ 2020-12-21 19:22 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 3037 bytes --]
tree: https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git realtime-rmap
head: 62eb0024d510607ecb04789e8b4f8c0975efb08b
commit: f4188e5ab1984e1b140433a80f223ab4644801af [245/249] xfs: online repair of realtime file bmaps
config: x86_64-randconfig-a011-20201217 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project cee1e7d14f4628d6174b33640d502bff3b54ae45)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install x86_64 cross compiling tool for clang build
# apt-get install binutils-x86-64-linux-gnu
# https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/commit/?id=f4188e5ab1984e1b140433a80f223ab4644801af
git remote add djwong-xfs https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git
git fetch --no-tags djwong-xfs realtime-rmap
git checkout f4188e5ab1984e1b140433a80f223ab4644801af
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All warnings (new ones prefixed by >>):
>> fs/xfs/scrub/repair.c:2202:6: warning: variable 'is_free' is uninitialized when used here [-Wuninitialized]
if (is_free)
^~~~~~~
fs/xfs/scrub/repair.c:2189:16: note: initialize the variable 'is_free' to silence this warning
bool is_free;
^
= 0
1 warning generated.
vim +/is_free +2202 fs/xfs/scrub/repair.c
2173
2174 /*
2175 * Check if any part of this range of rt blocks is free, so that we don't
2176 * rebuild things with bad records. Returns -EFSCORRUPTED if bad.
2177 */
2178 int
2179 xrep_rtext_is_free(
2180 struct xfs_scrub *sc,
2181 xfs_rtblock_t rtbno,
2182 xfs_filblks_t len)
2183 {
2184 struct xfs_mount *mp = sc->mp;
2185 xfs_rtblock_t startext;
2186 xfs_rtblock_t endext;
2187 xfs_rtblock_t extcount;
2188 uint32_t mod;
2189 bool is_free;
2190 int error;
2191
2192 /* Convert rt blocks to rt extents. */
2193 startext = div_u64_rem(rtbno, mp->m_sb.sb_rextsize, &mod);
2194 endext = div_u64_rem(rtbno + len - 1, mp->m_sb.sb_rextsize, &mod);
2195
2196 /* Make sure this isn't free space. */
2197 extcount = endext - startext + 1;
2198 error = xfs_rtalloc_extent_is_free(mp, sc->tp, startext, extcount,
2199 &is_free);
2200 if (error)
2201 return error;
> 2202 if (is_free)
2203 return -EFSCORRUPTED;
2204
2205 return 0;
2206 }
2207
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
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^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [djwong-xfs:realtime-rmap 245/249] fs/xfs/scrub/repair.c:2202:6: warning: variable 'is_free' is uninitialized when used here
2020-12-21 19:22 [djwong-xfs:realtime-rmap 245/249] fs/xfs/scrub/repair.c:2202:6: warning: variable 'is_free' is uninitialized when used here kernel test robot
@ 2020-12-21 22:19 ` Nathan Chancellor
2021-01-04 22:29 ` Darrick J. Wong
0 siblings, 1 reply; 3+ messages in thread
From: Nathan Chancellor @ 2020-12-21 22:19 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 4348 bytes --]
On Tue, Dec 22, 2020 at 03:22:03AM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git realtime-rmap
> head: 62eb0024d510607ecb04789e8b4f8c0975efb08b
> commit: f4188e5ab1984e1b140433a80f223ab4644801af [245/249] xfs: online repair of realtime file bmaps
> config: x86_64-randconfig-a011-20201217 (attached as .config)
> compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project cee1e7d14f4628d6174b33640d502bff3b54ae45)
> reproduce (this is a W=1 build):
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # install x86_64 cross compiling tool for clang build
> # apt-get install binutils-x86-64-linux-gnu
> # https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/commit/?id=f4188e5ab1984e1b140433a80f223ab4644801af
> git remote add djwong-xfs https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git
> git fetch --no-tags djwong-xfs realtime-rmap
> git checkout f4188e5ab1984e1b140433a80f223ab4644801af
> # save the attached .config to linux build tree
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All warnings (new ones prefixed by >>):
>
> >> fs/xfs/scrub/repair.c:2202:6: warning: variable 'is_free' is uninitialized when used here [-Wuninitialized]
> if (is_free)
> ^~~~~~~
> fs/xfs/scrub/repair.c:2189:16: note: initialize the variable 'is_free' to silence this warning
> bool is_free;
> ^
> = 0
> 1 warning generated.
>
>
> vim +/is_free +2202 fs/xfs/scrub/repair.c
>
> 2173
> 2174 /*
> 2175 * Check if any part of this range of rt blocks is free, so that we don't
> 2176 * rebuild things with bad records. Returns -EFSCORRUPTED if bad.
> 2177 */
> 2178 int
> 2179 xrep_rtext_is_free(
> 2180 struct xfs_scrub *sc,
> 2181 xfs_rtblock_t rtbno,
> 2182 xfs_filblks_t len)
> 2183 {
> 2184 struct xfs_mount *mp = sc->mp;
> 2185 xfs_rtblock_t startext;
> 2186 xfs_rtblock_t endext;
> 2187 xfs_rtblock_t extcount;
> 2188 uint32_t mod;
> 2189 bool is_free;
> 2190 int error;
> 2191
> 2192 /* Convert rt blocks to rt extents. */
> 2193 startext = div_u64_rem(rtbno, mp->m_sb.sb_rextsize, &mod);
> 2194 endext = div_u64_rem(rtbno + len - 1, mp->m_sb.sb_rextsize, &mod);
> 2195
> 2196 /* Make sure this isn't free space. */
> 2197 extcount = endext - startext + 1;
> 2198 error = xfs_rtalloc_extent_is_free(mp, sc->tp, startext, extcount,
> 2199 &is_free);
> 2200 if (error)
> 2201 return error;
> > 2202 if (is_free)
> 2203 return -EFSCORRUPTED;
> 2204
> 2205 return 0;
> 2206 }
> 2207
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
>
This appears to be a false positive. From the config:
# CONFIG_XFS_RT is not set
which means xfs_rtalloc_extent_is_free evaluates to ENOSYS and we never
actually make it to that if statement evaluation; however, clang cannot
see this because it is doing simple static analysis at this stage of the
pipeline, not seeing that it will never have to use is_free in this
configuration. A simple reproducer:
$ cat test.c
#define func(a) 22
int main() {
int error;
_Bool is_free;
error = func(&is_free);
if (error)
return error;
if (is_free)
return -117;
return 0;
}
$ clang -Wuninitialized -fsyntax-only test.c
test.c:10:9: warning: variable 'is_free' is uninitialized when used here [-Wuninitialized]
if (is_free)
^~~~~~~
test.c:5:18: note: initialize the variable 'is_free' to silence this warning
_Bool is_free;
^
= 0
1 warning generated.
Obviously initializing is_free to false will avoid this warning, which
is probably the simplest fix.
Cheers,
Nathan
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [djwong-xfs:realtime-rmap 245/249] fs/xfs/scrub/repair.c:2202:6: warning: variable 'is_free' is uninitialized when used here
2020-12-21 22:19 ` Nathan Chancellor
@ 2021-01-04 22:29 ` Darrick J. Wong
0 siblings, 0 replies; 3+ messages in thread
From: Darrick J. Wong @ 2021-01-04 22:29 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 4966 bytes --]
On Mon, Dec 21, 2020 at 03:19:21PM -0700, Nathan Chancellor wrote:
> On Tue, Dec 22, 2020 at 03:22:03AM +0800, kernel test robot wrote:
> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git realtime-rmap
> > head: 62eb0024d510607ecb04789e8b4f8c0975efb08b
> > commit: f4188e5ab1984e1b140433a80f223ab4644801af [245/249] xfs: online repair of realtime file bmaps
> > config: x86_64-randconfig-a011-20201217 (attached as .config)
> > compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project cee1e7d14f4628d6174b33640d502bff3b54ae45)
> > reproduce (this is a W=1 build):
> > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > chmod +x ~/bin/make.cross
> > # install x86_64 cross compiling tool for clang build
> > # apt-get install binutils-x86-64-linux-gnu
> > # https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/commit/?id=f4188e5ab1984e1b140433a80f223ab4644801af
> > git remote add djwong-xfs https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git
> > git fetch --no-tags djwong-xfs realtime-rmap
> > git checkout f4188e5ab1984e1b140433a80f223ab4644801af
> > # save the attached .config to linux build tree
> > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64
> >
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@intel.com>
> >
> > All warnings (new ones prefixed by >>):
> >
> > >> fs/xfs/scrub/repair.c:2202:6: warning: variable 'is_free' is uninitialized when used here [-Wuninitialized]
> > if (is_free)
> > ^~~~~~~
> > fs/xfs/scrub/repair.c:2189:16: note: initialize the variable 'is_free' to silence this warning
> > bool is_free;
> > ^
> > = 0
> > 1 warning generated.
> >
> >
> > vim +/is_free +2202 fs/xfs/scrub/repair.c
> >
> > 2173
> > 2174 /*
> > 2175 * Check if any part of this range of rt blocks is free, so that we don't
> > 2176 * rebuild things with bad records. Returns -EFSCORRUPTED if bad.
> > 2177 */
> > 2178 int
> > 2179 xrep_rtext_is_free(
> > 2180 struct xfs_scrub *sc,
> > 2181 xfs_rtblock_t rtbno,
> > 2182 xfs_filblks_t len)
> > 2183 {
> > 2184 struct xfs_mount *mp = sc->mp;
> > 2185 xfs_rtblock_t startext;
> > 2186 xfs_rtblock_t endext;
> > 2187 xfs_rtblock_t extcount;
> > 2188 uint32_t mod;
> > 2189 bool is_free;
> > 2190 int error;
> > 2191
> > 2192 /* Convert rt blocks to rt extents. */
> > 2193 startext = div_u64_rem(rtbno, mp->m_sb.sb_rextsize, &mod);
> > 2194 endext = div_u64_rem(rtbno + len - 1, mp->m_sb.sb_rextsize, &mod);
> > 2195
> > 2196 /* Make sure this isn't free space. */
> > 2197 extcount = endext - startext + 1;
> > 2198 error = xfs_rtalloc_extent_is_free(mp, sc->tp, startext, extcount,
> > 2199 &is_free);
> > 2200 if (error)
> > 2201 return error;
> > > 2202 if (is_free)
> > 2203 return -EFSCORRUPTED;
> > 2204
> > 2205 return 0;
> > 2206 }
> > 2207
> >
> > ---
> > 0-DAY CI Kernel Test Service, Intel Corporation
> > https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
> >
>
> This appears to be a false positive. From the config:
>
> # CONFIG_XFS_RT is not set
>
> which means xfs_rtalloc_extent_is_free evaluates to ENOSYS and we never
> actually make it to that if statement evaluation; however, clang cannot
> see this because it is doing simple static analysis at this stage of the
> pipeline, not seeing that it will never have to use is_free in this
> configuration. A simple reproducer:
>
> $ cat test.c
> #define func(a) 22
>
> int main() {
> int error;
> _Bool is_free;
>
> error = func(&is_free);
> if (error)
> return error;
> if (is_free)
> return -117;
>
> return 0;
> }
>
> $ clang -Wuninitialized -fsyntax-only test.c
> test.c:10:9: warning: variable 'is_free' is uninitialized when used here [-Wuninitialized]
> if (is_free)
> ^~~~~~~
> test.c:5:18: note: initialize the variable 'is_free' to silence this warning
> _Bool is_free;
> ^
> = 0
> 1 warning generated.
>
> Obviously initializing is_free to false will avoid this warning, which
> is probably the simplest fix.
I don't mind making that change (and in fact already did), but uh...
shouldn't clang be analyzing the C source code /after/ the preprocessing
step? I bet there's a fair amount of #define soup in the kernel that
clang would /love/ to sink its teeth into. ;)
Insofar as one doesn't need teeth for soup.
--D
> Cheers,
> Nathan
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-01-04 22:29 UTC | newest]
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2020-12-21 19:22 [djwong-xfs:realtime-rmap 245/249] fs/xfs/scrub/repair.c:2202:6: warning: variable 'is_free' is uninitialized when used here kernel test robot
2020-12-21 22:19 ` Nathan Chancellor
2021-01-04 22:29 ` Darrick J. Wong
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