Re: [patch 05/13] mm/pagemap: Clenaup PREEMPT_COUNT leftovers

From: kernel test robot
Date: Mon Sep 14 2020 - 20:52:40 EST

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Hi Thomas,

I love your patch! Yet something to improve:

[auto build test ERROR on drm-intel/for-linux-next]
[also build test ERROR on linus/master v5.9-rc5 next-20200914]
[cannot apply to rcu/dev arm/for-next tip/sched/core linux/master]
[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]

url: https://github.com/0day-ci/linux/commits/Thomas-Gleixner/preempt-Make-preempt-count-unconditional/20200915-044640
base: git://anongit.freedesktop.org/drm-intel for-linux-next
config: arm-randconfig-r002-20200914 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project b2c32c90bab09a6e2c1f370429db26017a182143)
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 arm cross compiling tool for clang build
# apt-get install binutils-arm-linux-gnueabi
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm

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

All error/warnings (new ones prefixed by >>):

In file included from drivers/scsi/scsi.c:47:
In file included from include/linux/blkdev.h:13:
>> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer
VM_BUG_ON_PAGE(page_count(page) == 0, page);
^
include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE'
#define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond)
^
include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON'
#define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond)
^
include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID'
#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
^
In file included from drivers/scsi/scsi.c:62:
In file included from include/scsi/scsi_cmnd.h:5:
include/linux/dma-mapping.h:632:9: warning: implicit conversion from 'unsigned long long' to 'unsigned long' changes value from 18446744073709551615 to 4294967295 [-Wconstant-conversion]
return DMA_BIT_MASK(32);
~~~~~~ ^~~~~~~~~~~~~~~~
include/linux/dma-mapping.h:139:40: note: expanded from macro 'DMA_BIT_MASK'
#define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
^~~~~
1 warning and 1 error generated.
--
In file included from drivers/scsi/scsicam.c:19:
In file included from include/linux/blkdev.h:13:
>> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer
VM_BUG_ON_PAGE(page_count(page) == 0, page);
^
include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE'
#define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond)
^
include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON'
#define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond)
^
include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID'
#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
^
1 error generated.
--
In file included from drivers/scsi/scsi_sysfs.c:13:
In file included from include/linux/blkdev.h:13:
>> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer
VM_BUG_ON_PAGE(page_count(page) == 0, page);
^
include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE'
#define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond)
^
include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON'
#define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond)
^
include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID'
#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
^
In file included from drivers/scsi/scsi_sysfs.c:20:
In file included from include/scsi/scsi_tcq.h:6:
In file included from include/scsi/scsi_cmnd.h:5:
include/linux/dma-mapping.h:632:9: warning: implicit conversion from 'unsigned long long' to 'unsigned long' changes value from 18446744073709551615 to 4294967295 [-Wconstant-conversion]
return DMA_BIT_MASK(32);
~~~~~~ ^~~~~~~~~~~~~~~~
include/linux/dma-mapping.h:139:40: note: expanded from macro 'DMA_BIT_MASK'
#define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
^~~~~
drivers/scsi/scsi_sysfs.c:373:1: warning: format specifies type 'short' but the argument has type 'int' [-Wformat]
shost_rd_attr(can_queue, "%hd\n");
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
%d
drivers/scsi/scsi_sysfs.c:176:45: note: expanded from macro 'shost_rd_attr'
#define shost_rd_attr(field, format_string) \
^
drivers/scsi/scsi_sysfs.c:173:2: note: expanded from macro '\
shost_rd_attr2'
shost_show_function(name, field, format_string) \
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/scsi/scsi_sysfs.c:165:43: note: expanded from macro 'shost_show_function'
return snprintf (buf, 20, format_string, shost->field); \
~~~~~~~~~~~~~ ^~~~~~~~~~~~
2 warnings and 1 error generated.
--
In file included from drivers/scsi/ufs/ufshcd.c:18:
In file included from drivers/scsi/ufs/ufshcd.h:32:
In file included from include/linux/regulator/consumer.h:35:
In file included from include/linux/suspend.h:5:
In file included from include/linux/swap.h:9:
In file included from include/linux/memcontrol.h:22:
In file included from include/linux/writeback.h:14:
In file included from include/linux/blk-cgroup.h:23:
In file included from include/linux/blkdev.h:13:
>> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer
VM_BUG_ON_PAGE(page_count(page) == 0, page);
^
include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE'
#define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond)
^
include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON'
#define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond)
^
include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID'
#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
^
In file included from drivers/scsi/ufs/ufshcd.c:18:
In file included from drivers/scsi/ufs/ufshcd.h:41:
In file included from include/scsi/scsi_cmnd.h:5:
include/linux/dma-mapping.h:632:9: warning: implicit conversion from 'unsigned long long' to 'unsigned long' changes value from 18446744073709551615 to 4294967295 [-Wconstant-conversion]
return DMA_BIT_MASK(32);
~~~~~~ ^~~~~~~~~~~~~~~~
include/linux/dma-mapping.h:139:40: note: expanded from macro 'DMA_BIT_MASK'
#define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
^~~~~
>> drivers/scsi/ufs/ufshcd.c:8716:44: warning: shift count >= width of type [-Wshift-count-overflow]
if (!dma_set_mask_and_coherent(hba->dev, DMA_BIT_MASK(64)))
^~~~~~~~~~~~~~~~
include/linux/dma-mapping.h:139:54: note: expanded from macro 'DMA_BIT_MASK'
#define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
^ ~~~
2 warnings and 1 error generated.
--
In file included from drivers/scsi/hisi_sas/hisi_sas_main.c:7:
In file included from drivers/scsi/hisi_sas/hisi_sas.h:16:
In file included from include/linux/libata.h:21:
In file included from include/scsi/scsi_host.h:11:
In file included from include/linux/blk-mq.h:5:
In file included from include/linux/blkdev.h:13:
>> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer
VM_BUG_ON_PAGE(page_count(page) == 0, page);
^
include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE'
#define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond)
^
include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON'
#define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond)
^
include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID'
#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
^
>> drivers/scsi/hisi_sas/hisi_sas_main.c:2579:41: warning: shift count >= width of type [-Wshift-count-overflow]
error = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64));
^~~~~~~~~~~~~~~~
include/linux/dma-mapping.h:139:54: note: expanded from macro 'DMA_BIT_MASK'
#define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
^ ~~~
1 warning and 1 error generated.
--
In file included from drivers/scsi/scsi_sysfs.c:13:
In file included from include/linux/blkdev.h:13:
>> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer
VM_BUG_ON_PAGE(page_count(page) == 0, page);
^
include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE'
#define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond)
^
include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON'
#define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond)
^
include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID'
#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
^
In file included from drivers/scsi/scsi_sysfs.c:20:
In file included from include/scsi/scsi_tcq.h:6:
In file included from include/scsi/scsi_cmnd.h:5:
include/linux/dma-mapping.h:632:9: warning: implicit conversion from 'unsigned long long' to 'unsigned long' changes value from 18446744073709551615 to 4294967295 [-Wconstant-conversion]
return DMA_BIT_MASK(32);
~~~~~~ ^~~~~~~~~~~~~~~~
include/linux/dma-mapping.h:139:40: note: expanded from macro 'DMA_BIT_MASK'
#define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
^~~~~
drivers/scsi/scsi_sysfs.c:373:1: warning: format specifies type 'short' but the argument has type 'int' [-Wformat]
shost_rd_attr(can_queue, "%hd\n");
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
%d
drivers/scsi/scsi_sysfs.c:176:45: note: expanded from macro 'shost_rd_attr'
#define shost_rd_attr(field, format_string) \
^
drivers/scsi/scsi_sysfs.c:173:2: note: expanded from macro '\
shost_rd_attr2'
shost_show_function(name, field, format_string) \
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/scsi/scsi_sysfs.c:165:43: note: expanded from macro 'shost_show_function'
return snprintf (buf, 20, format_string, shost->field); \
~~~~~~~~~~~~~ ^~~~~~~~~~~~
drivers/scsi/scsi_sysfs.c:1027:10: fatal error: 'scsi_devinfo_tbl.c' file not found
#include "scsi_devinfo_tbl.c"
^~~~~~~~~~~~~~~~~~~~
2 warnings and 2 errors generated.

# https://github.com/0day-ci/linux/commit/a4a0f54fdd08d95dfe20d684b405db8a47fb61d8
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Thomas-Gleixner/preempt-Make-preempt-count-unconditional/20200915-044640
git checkout a4a0f54fdd08d95dfe20d684b405db8a47fb61d8
vim +/void +181 include/linux/pagemap.h

^1da177e4c3f41 Linus Torvalds 2005-04-16 123
e286781d5f2e9c Nick Piggin 2008-07-25 124 /*
e286781d5f2e9c Nick Piggin 2008-07-25 125 * speculatively take a reference to a page.
0139aa7b7fa12c Joonsoo Kim 2016-05-19 126 * If the page is free (_refcount == 0), then _refcount is untouched, and 0
0139aa7b7fa12c Joonsoo Kim 2016-05-19 127 * is returned. Otherwise, _refcount is incremented by 1 and 1 is returned.
e286781d5f2e9c Nick Piggin 2008-07-25 128 *
e286781d5f2e9c Nick Piggin 2008-07-25 129 * This function must be called inside the same rcu_read_lock() section as has
e286781d5f2e9c Nick Piggin 2008-07-25 130 * been used to lookup the page in the pagecache radix-tree (or page table):
0139aa7b7fa12c Joonsoo Kim 2016-05-19 131 * this allows allocators to use a synchronize_rcu() to stabilize _refcount.
e286781d5f2e9c Nick Piggin 2008-07-25 132 *
e286781d5f2e9c Nick Piggin 2008-07-25 133 * Unless an RCU grace period has passed, the count of all pages coming out
e286781d5f2e9c Nick Piggin 2008-07-25 134 * of the allocator must be considered unstable. page_count may return higher
e286781d5f2e9c Nick Piggin 2008-07-25 135 * than expected, and put_page must be able to do the right thing when the
e286781d5f2e9c Nick Piggin 2008-07-25 136 * page has been finished with, no matter what it is subsequently allocated
e286781d5f2e9c Nick Piggin 2008-07-25 137 * for (because put_page is what is used here to drop an invalid speculative
e286781d5f2e9c Nick Piggin 2008-07-25 138 * reference).
e286781d5f2e9c Nick Piggin 2008-07-25 139 *
e286781d5f2e9c Nick Piggin 2008-07-25 140 * This is the interesting part of the lockless pagecache (and lockless
e286781d5f2e9c Nick Piggin 2008-07-25 141 * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page)
e286781d5f2e9c Nick Piggin 2008-07-25 142 * has the following pattern:
e286781d5f2e9c Nick Piggin 2008-07-25 143 * 1. find page in radix tree
e286781d5f2e9c Nick Piggin 2008-07-25 144 * 2. conditionally increment refcount
e286781d5f2e9c Nick Piggin 2008-07-25 145 * 3. check the page is still in pagecache (if no, goto 1)
e286781d5f2e9c Nick Piggin 2008-07-25 146 *
0139aa7b7fa12c Joonsoo Kim 2016-05-19 147 * Remove-side that cares about stability of _refcount (eg. reclaim) has the
b93b016313b3ba Matthew Wilcox 2018-04-10 148 * following (with the i_pages lock held):
e286781d5f2e9c Nick Piggin 2008-07-25 149 * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg)
e286781d5f2e9c Nick Piggin 2008-07-25 150 * B. remove page from pagecache
e286781d5f2e9c Nick Piggin 2008-07-25 151 * C. free the page
e286781d5f2e9c Nick Piggin 2008-07-25 152 *
e286781d5f2e9c Nick Piggin 2008-07-25 153 * There are 2 critical interleavings that matter:
e286781d5f2e9c Nick Piggin 2008-07-25 154 * - 2 runs before A: in this case, A sees elevated refcount and bails out
e286781d5f2e9c Nick Piggin 2008-07-25 155 * - A runs before 2: in this case, 2 sees zero refcount and retries;
e286781d5f2e9c Nick Piggin 2008-07-25 156 * subsequently, B will complete and 1 will find no page, causing the
e286781d5f2e9c Nick Piggin 2008-07-25 157 * lookup to return NULL.
e286781d5f2e9c Nick Piggin 2008-07-25 158 *
e286781d5f2e9c Nick Piggin 2008-07-25 159 * It is possible that between 1 and 2, the page is removed then the exact same
e286781d5f2e9c Nick Piggin 2008-07-25 160 * page is inserted into the same position in pagecache. That's OK: the
b93b016313b3ba Matthew Wilcox 2018-04-10 161 * old find_get_page using a lock could equally have run before or after
e286781d5f2e9c Nick Piggin 2008-07-25 162 * such a re-insertion, depending on order that locks are granted.
e286781d5f2e9c Nick Piggin 2008-07-25 163 *
e286781d5f2e9c Nick Piggin 2008-07-25 164 * Lookups racing against pagecache insertion isn't a big problem: either 1
e286781d5f2e9c Nick Piggin 2008-07-25 165 * will find the page or it will not. Likewise, the old find_get_page could run
e286781d5f2e9c Nick Piggin 2008-07-25 166 * either before the insertion or afterwards, depending on timing.
e286781d5f2e9c Nick Piggin 2008-07-25 167 */
494eec70f05496 john.hubbard@xxxxxxxxx 2019-03-05 168 static inline int __page_cache_add_speculative(struct page *page, int count)
e286781d5f2e9c Nick Piggin 2008-07-25 169 {
8375ad98cc1def Paul E. McKenney 2013-04-29 170 #ifdef CONFIG_TINY_RCU
a4a0f54fdd08d9 Thomas Gleixner 2020-09-14 171 VM_BUG_ON(preemptible())
e286781d5f2e9c Nick Piggin 2008-07-25 172 /*
e286781d5f2e9c Nick Piggin 2008-07-25 173 * Preempt must be disabled here - we rely on rcu_read_lock doing
e286781d5f2e9c Nick Piggin 2008-07-25 174 * this for us.
e286781d5f2e9c Nick Piggin 2008-07-25 175 *
e286781d5f2e9c Nick Piggin 2008-07-25 176 * Pagecache won't be truncated from interrupt context, so if we have
e286781d5f2e9c Nick Piggin 2008-07-25 177 * found a page in the radix tree here, we have pinned its refcount by
e286781d5f2e9c Nick Piggin 2008-07-25 178 * disabling preempt, and hence no need for the "speculative get" that
e286781d5f2e9c Nick Piggin 2008-07-25 179 * SMP requires.
e286781d5f2e9c Nick Piggin 2008-07-25 180 */
309381feaee564 Sasha Levin 2014-01-23 @181 VM_BUG_ON_PAGE(page_count(page) == 0, page);
494eec70f05496 john.hubbard@xxxxxxxxx 2019-03-05 182 page_ref_add(page, count);
e286781d5f2e9c Nick Piggin 2008-07-25 183

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