Re: [kbuild-all] Re: [PATCH v6 7/7] kernfs: Replace per-fs rwsem with hashed ones.

From: Chen, Rong A
Date: Wed Feb 16 2022 - 03:57:50 EST

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On 2/15/2022 1:49 AM, Nathan Chancellor wrote:

On Tue, Feb 15, 2022 at 01:19:23AM +0800, kernel test robot wrote:

Hi Imran,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on 6d9bd4ad4ca08b1114e814c2c42383b8b13be631]

url: https://github.com/0day-ci/linux/commits/Imran-Khan/kernfs-Introduce-hashed-mutexes-to-replace-global-kernfs_open_file_mutex/20220214-200700
base: 6d9bd4ad4ca08b1114e814c2c42383b8b13be631
config: hexagon-randconfig-r012-20220213 (https://download.01.org/0day-ci/archive/20220214/202202142322.OezS0EtW-lkp@xxxxxxxxx/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project ea071884b0cc7210b3cc5fe858f0e892a779a23b)
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
# https://github.com/0day-ci/linux/commit/48eab913f80f1555d57b964ef7cdba17f5ec5d1f
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Imran-Khan/kernfs-Introduce-hashed-mutexes-to-replace-global-kernfs_open_file_mutex/20220214-200700
git checkout 48eab913f80f1555d57b964ef7cdba17f5ec5d1f
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash fs/kernfs/

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

All warnings (new ones prefixed by >>):

fs/kernfs/dir.c:1619:7: warning: variable 'old_parent' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]

if (!new_name)
^~~~~~~~~
fs/kernfs/dir.c:1653:50: note: uninitialized use occurs here
up_write_kernfs_rwsem_rename_ns(kn, new_parent, old_parent);
^~~~~~~~~~
fs/kernfs/dir.c:1619:3: note: remove the 'if' if its condition is always false
if (!new_name)
^~~~~~~~~~~~~~
fs/kernfs/dir.c:1612:6: warning: variable 'old_parent' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
if (kernfs_find_ns(new_parent, new_name, new_ns))
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fs/kernfs/dir.c:1653:50: note: uninitialized use occurs here
up_write_kernfs_rwsem_rename_ns(kn, new_parent, old_parent);
^~~~~~~~~~
fs/kernfs/dir.c:1612:2: note: remove the 'if' if its condition is always false
if (kernfs_find_ns(new_parent, new_name, new_ns))
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fs/kernfs/dir.c:1607:6: warning: variable 'old_parent' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fs/kernfs/dir.c:1653:50: note: uninitialized use occurs here
up_write_kernfs_rwsem_rename_ns(kn, new_parent, old_parent);
^~~~~~~~~~
fs/kernfs/dir.c:1607:2: note: remove the 'if' if its condition is always false
if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fs/kernfs/dir.c:1602:6: warning: variable 'old_parent' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fs/kernfs/dir.c:1653:50: note: uninitialized use occurs here
up_write_kernfs_rwsem_rename_ns(kn, new_parent, old_parent);
^~~~~~~~~~
fs/kernfs/dir.c:1602:2: note: remove the 'if' if its condition is always false
if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

fs/kernfs/dir.c:1602:6: warning: variable 'old_parent' is used uninitialized whenever '||' condition is true [-Wsometimes-uninitialized]

if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fs/kernfs/dir.c:1653:50: note: uninitialized use occurs here
up_write_kernfs_rwsem_rename_ns(kn, new_parent, old_parent);
^~~~~~~~~~
fs/kernfs/dir.c:1602:6: note: remove the '||' if its condition is always false
if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

fs/kernfs/dir.c:1602:6: warning: variable 'old_parent' is used uninitialized whenever '||' condition is true [-Wsometimes-uninitialized]

if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
^~~~~~~~~~~~~~~~~~
fs/kernfs/dir.c:1653:50: note: uninitialized use occurs here
up_write_kernfs_rwsem_rename_ns(kn, new_parent, old_parent);
^~~~~~~~~~
fs/kernfs/dir.c:1602:6: note: remove the '||' if its condition is always false
if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
^~~~~~~~~~~~~~~~~~~~~
fs/kernfs/dir.c:1591:32: note: initialize the variable 'old_parent' to silence this warning
struct kernfs_node *old_parent;
^
= NULL
6 warnings generated.

vim +1619 fs/kernfs/dir.c

fd7b9f7b9776b1 Tejun Heo 2013-11-28 1580
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1581 /**
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1582 * kernfs_rename_ns - move and rename a kernfs_node
324a56e16e44ba Tejun Heo 2013-12-11 1583 * @kn: target node
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1584 * @new_parent: new parent to put @sd under
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1585 * @new_name: new name
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1586 * @new_ns: new namespace tag
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1587 */
324a56e16e44ba Tejun Heo 2013-12-11 1588 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1589 const char *new_name, const void *new_ns)
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1590 {
3eef34ad7dc369 Tejun Heo 2014-02-07 1591 struct kernfs_node *old_parent;
3eef34ad7dc369 Tejun Heo 2014-02-07 1592 const char *old_name = NULL;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1593 int error;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1594
3eef34ad7dc369 Tejun Heo 2014-02-07 1595 /* can't move or rename root */
3eef34ad7dc369 Tejun Heo 2014-02-07 1596 if (!kn->parent)
3eef34ad7dc369 Tejun Heo 2014-02-07 1597 return -EINVAL;
3eef34ad7dc369 Tejun Heo 2014-02-07 1598
48eab913f80f15 Imran Khan 2022-02-14 1599 down_write_kernfs_rwsem_rename_ns(kn, kn->parent, new_parent);
798c75a0d44cdb Greg Kroah-Hartman 2014-01-13 1600
d0ae3d4347ee02 Tejun Heo 2013-12-11 1601 error = -ENOENT;
ea015218f2f7ac Eric W. Biederman 2015-05-13 @1602 if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
ea015218f2f7ac Eric W. Biederman 2015-05-13 1603 (new_parent->flags & KERNFS_EMPTY_DIR))
d0ae3d4347ee02 Tejun Heo 2013-12-11 1604 goto out;
d0ae3d4347ee02 Tejun Heo 2013-12-11 1605
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1606 error = 0;
adc5e8b58f4886 Tejun Heo 2013-12-11 1607 if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
adc5e8b58f4886 Tejun Heo 2013-12-11 1608 (strcmp(kn->name, new_name) == 0))
798c75a0d44cdb Greg Kroah-Hartman 2014-01-13 1609 goto out; /* nothing to rename */
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1610
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1611 error = -EEXIST;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1612 if (kernfs_find_ns(new_parent, new_name, new_ns))
798c75a0d44cdb Greg Kroah-Hartman 2014-01-13 1613 goto out;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1614
324a56e16e44ba Tejun Heo 2013-12-11 1615 /* rename kernfs_node */
adc5e8b58f4886 Tejun Heo 2013-12-11 1616 if (strcmp(kn->name, new_name) != 0) {
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1617 error = -ENOMEM;
75287a677ba1be Andrzej Hajda 2015-02-13 1618 new_name = kstrdup_const(new_name, GFP_KERNEL);
fd7b9f7b9776b1 Tejun Heo 2013-11-28 @1619 if (!new_name)
798c75a0d44cdb Greg Kroah-Hartman 2014-01-13 1620 goto out;
3eef34ad7dc369 Tejun Heo 2014-02-07 1621 } else {
3eef34ad7dc369 Tejun Heo 2014-02-07 1622 new_name = NULL;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1623 }
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1624
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1625 /*
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1626 * Move to the appropriate place in the appropriate directories rbtree.
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1627 */
c637b8acbe079e Tejun Heo 2013-12-11 1628 kernfs_unlink_sibling(kn);
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1629 kernfs_get(new_parent);
3eef34ad7dc369 Tejun Heo 2014-02-07 1630
3eef34ad7dc369 Tejun Heo 2014-02-07 1631 /* rename_lock protects ->parent and ->name accessors */
3eef34ad7dc369 Tejun Heo 2014-02-07 1632 spin_lock_irq(&kernfs_rename_lock);
3eef34ad7dc369 Tejun Heo 2014-02-07 1633
3eef34ad7dc369 Tejun Heo 2014-02-07 1634 old_parent = kn->parent;
adc5e8b58f4886 Tejun Heo 2013-12-11 1635 kn->parent = new_parent;
3eef34ad7dc369 Tejun Heo 2014-02-07 1636
3eef34ad7dc369 Tejun Heo 2014-02-07 1637 kn->ns = new_ns;
3eef34ad7dc369 Tejun Heo 2014-02-07 1638 if (new_name) {
3eef34ad7dc369 Tejun Heo 2014-02-07 1639 old_name = kn->name;
3eef34ad7dc369 Tejun Heo 2014-02-07 1640 kn->name = new_name;
3eef34ad7dc369 Tejun Heo 2014-02-07 1641 }
3eef34ad7dc369 Tejun Heo 2014-02-07 1642
3eef34ad7dc369 Tejun Heo 2014-02-07 1643 spin_unlock_irq(&kernfs_rename_lock);
3eef34ad7dc369 Tejun Heo 2014-02-07 1644
9561a8961c708f Tejun Heo 2014-02-10 1645 kn->hash = kernfs_name_hash(kn->name, kn->ns);
c637b8acbe079e Tejun Heo 2013-12-11 1646 kernfs_link_sibling(kn);
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1647
3eef34ad7dc369 Tejun Heo 2014-02-07 1648 kernfs_put(old_parent);
75287a677ba1be Andrzej Hajda 2015-02-13 1649 kfree_const(old_name);
3eef34ad7dc369 Tejun Heo 2014-02-07 1650
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1651 error = 0;
ae34372eb8408b Tejun Heo 2014-01-10 1652 out:
48eab913f80f15 Imran Khan 2022-02-14 1653 up_write_kernfs_rwsem_rename_ns(kn, new_parent, old_parent);
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1654 return error;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1655 }
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1656

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

I am forwarding this along as a reply to the original posting so that
this patch series is not picked up in its current form. This warning
looks legitimate to me and it will break allmodconfig due to -Werror.

Intel folks, why did this get sent to the author privately, rather than
as a reply to the original posting, given the patch is still in review?

Hi Nathan,

Thanks for the notice, it should be a bug in our system, will fix it asap.

Best Regards,
Rong Chen

Cheers,
Nathan
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