* mm/filemap.c:3307 do_sync_mmap_readahead() warn: assigning (-12) to unsigned variable 'ra->order'
@ 2026-01-13 11:12 Dan Carpenter
2026-01-13 12:24 ` Jan Kara
0 siblings, 1 reply; 3+ messages in thread
From: Dan Carpenter @ 2026-01-13 11:12 UTC (permalink / raw)
To: oe-kbuild, Roman Gushchin
Cc: lkp, oe-kbuild-all, linux-kernel, Andrew Morton,
Linux Memory Management List, Dev Jain, Jan Kara
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: b71e635feefc852405b14620a7fc58c4c80c0f73
commit: 9f1edf1aedac1b287355f63f768ba4275de72dca mm: readahead: make thp readahead conditional to mmap_miss logic
config: x86_64-randconfig-161-20260113 (https://download.01.org/0day-ci/archive/20260113/202601131311.g3lyUAks-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
smatch version: v0.5.0-8985-g2614ff1a
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@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202601131311.g3lyUAks-lkp@intel.com/
smatch warnings:
mm/filemap.c:3307 do_sync_mmap_readahead() warn: assigning (-12) to unsigned variable 'ra->order'
vim +3307 mm/filemap.c
6b4c9f4469819a0 Josef Bacik 2019-03-13 3248 static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3249 {
2a1180f1bd389e9 Josef Bacik 2019-03-13 3250 struct file *file = vmf->vma->vm_file;
2a1180f1bd389e9 Josef Bacik 2019-03-13 3251 struct file_ra_state *ra = &file->f_ra;
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3252 struct address_space *mapping = file->f_mapping;
fcd9ae4f7f3b5fb Matthew Wilcox (Oracle 2021-04-07 3253) DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff);
6b4c9f4469819a0 Josef Bacik 2019-03-13 3254 struct file *fpin = NULL;
bfbe71109fa40e8 Lorenzo Stoakes 2025-06-18 3255 vm_flags_t vm_flags = vmf->vma->vm_flags;
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3256 bool force_thp_readahead = false;
f5e8b140cd1324c Ryan Roberts 2025-06-09 3257 unsigned short mmap_miss;
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3258
4687fdbb805a92c Matthew Wilcox (Oracle 2021-07-24 3259) /* Use the readahead code, even if readahead is disabled */
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3260 if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3261 (vm_flags & VM_HUGEPAGE) && HPAGE_PMD_ORDER <= MAX_PAGECACHE_ORDER)
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3262 force_thp_readahead = true;
4687fdbb805a92c Matthew Wilcox (Oracle 2021-07-24 3263)
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3264 if (!force_thp_readahead) {
38b0ece6d76374b Ryan Roberts 2025-06-09 3265 /*
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3266 * If we don't want any read-ahead, don't bother.
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3267 * VM_EXEC case below is already intended for random access.
38b0ece6d76374b Ryan Roberts 2025-06-09 3268 */
38b0ece6d76374b Ryan Roberts 2025-06-09 3269 if ((vm_flags & (VM_RAND_READ | VM_EXEC)) == VM_RAND_READ)
6b4c9f4469819a0 Josef Bacik 2019-03-13 3270 return fpin;
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3271
275b12bf5486f6f Wu Fengguang 2011-05-24 3272 if (!ra->ra_pages)
6b4c9f4469819a0 Josef Bacik 2019-03-13 3273 return fpin;
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3274
dcfa24ba68991ab Matthew Wilcox (Oracle 2022-05-25 3275) if (vm_flags & VM_SEQ_READ) {
6b4c9f4469819a0 Josef Bacik 2019-03-13 3276 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
fcd9ae4f7f3b5fb Matthew Wilcox (Oracle 2021-04-07 3277) page_cache_sync_ra(&ractl, ra->ra_pages);
6b4c9f4469819a0 Josef Bacik 2019-03-13 3278 return fpin;
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3279 }
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3280 }
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3281
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3282 if (!(vm_flags & VM_SEQ_READ)) {
207d04baa3591a3 Andi Kleen 2011-05-24 3283 /* Avoid banging the cache line if not needed */
e630bfac79456d3 Kirill A. Shutemov 2020-08-14 3284 mmap_miss = READ_ONCE(ra->mmap_miss);
e630bfac79456d3 Kirill A. Shutemov 2020-08-14 3285 if (mmap_miss < MMAP_LOTSAMISS * 10)
e630bfac79456d3 Kirill A. Shutemov 2020-08-14 3286 WRITE_ONCE(ra->mmap_miss, ++mmap_miss);
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3287
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3288 /*
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3289 * Do we miss much more than hit in this file? If so,
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3290 * stop bothering with read-ahead. It will only hurt.
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3291 */
e630bfac79456d3 Kirill A. Shutemov 2020-08-14 3292 if (mmap_miss > MMAP_LOTSAMISS)
6b4c9f4469819a0 Josef Bacik 2019-03-13 3293 return fpin;
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3294 }
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3295
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3296 if (force_thp_readahead) {
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3297 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3298 ractl._index &= ~((unsigned long)HPAGE_PMD_NR - 1);
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3299 ra->size = HPAGE_PMD_NR;
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3300 /*
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3301 * Fetch two PMD folios, so we get the chance to actually
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3302 * readahead, unless we've been told not to.
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3303 */
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3304 if (!(vm_flags & VM_RAND_READ))
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3305 ra->size *= 2;
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3306 ra->async_size = HPAGE_PMD_NR;
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 @3307 ra->order = HPAGE_PMD_ORDER;
HPAGE_PMD_SHIFT is zero in this config?
ra->order is a u16.
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3308 page_cache_ra_order(&ractl, ra);
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3309 return fpin;
9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3310 }
ef00e08e26dd5d8 Linus Torvalds 2009-06-16 3311
38b0ece6d76374b Ryan Roberts 2025-06-09 3312 if (vm_flags & VM_EXEC) {
38b0ece6d76374b Ryan Roberts 2025-06-09 3313 /*
38b0ece6d76374b Ryan Roberts 2025-06-09 3314 * Allow arch to request a preferred minimum folio order for
38b0ece6d76374b Ryan Roberts 2025-06-09 3315 * executable memory. This can often be beneficial to
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: mm/filemap.c:3307 do_sync_mmap_readahead() warn: assigning (-12) to unsigned variable 'ra->order'
2026-01-13 11:12 mm/filemap.c:3307 do_sync_mmap_readahead() warn: assigning (-12) to unsigned variable 'ra->order' Dan Carpenter
@ 2026-01-13 12:24 ` Jan Kara
2026-01-13 12:56 ` Dan Carpenter
0 siblings, 1 reply; 3+ messages in thread
From: Jan Kara @ 2026-01-13 12:24 UTC (permalink / raw)
To: Dan Carpenter
Cc: oe-kbuild, Roman Gushchin, lkp, oe-kbuild-all, linux-kernel,
Andrew Morton, Linux Memory Management List, Dev Jain, Jan Kara
On Tue 13-01-26 14:12:28, Dan Carpenter wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: b71e635feefc852405b14620a7fc58c4c80c0f73
> commit: 9f1edf1aedac1b287355f63f768ba4275de72dca mm: readahead: make thp readahead conditional to mmap_miss logic
> config: x86_64-randconfig-161-20260113 (https://download.01.org/0day-ci/archive/20260113/202601131311.g3lyUAks-lkp@intel.com/config)
> compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> smatch version: v0.5.0-8985-g2614ff1a
>
> 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@intel.com>
> | Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> | Closes: https://lore.kernel.org/r/202601131311.g3lyUAks-lkp@intel.com/
>
> smatch warnings:
> mm/filemap.c:3307 do_sync_mmap_readahead() warn: assigning (-12) to unsigned variable 'ra->order'
...
> 9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3306 ra->async_size = HPAGE_PMD_NR;
> 9f1edf1aedac1b2 Roman Gushchin 2025-10-06 @3307 ra->order = HPAGE_PMD_ORDER;
>
> HPAGE_PMD_SHIFT is zero in this config?
> ra->order is a u16.
What's the config exactly? I suppose CONFIG_TRANSPARENT_HUGEPAGE is
disabled in this case, isn't it? In that case force_thp_readahead will
never be true and thus the branch with the assignment can never be reached
AFAICT...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: mm/filemap.c:3307 do_sync_mmap_readahead() warn: assigning (-12) to unsigned variable 'ra->order'
2026-01-13 12:24 ` Jan Kara
@ 2026-01-13 12:56 ` Dan Carpenter
0 siblings, 0 replies; 3+ messages in thread
From: Dan Carpenter @ 2026-01-13 12:56 UTC (permalink / raw)
To: Jan Kara
Cc: oe-kbuild, Roman Gushchin, lkp, oe-kbuild-all, linux-kernel,
Andrew Morton, Linux Memory Management List, Dev Jain
On Tue, Jan 13, 2026 at 01:24:20PM +0100, Jan Kara wrote:
> On Tue 13-01-26 14:12:28, Dan Carpenter wrote:
> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head: b71e635feefc852405b14620a7fc58c4c80c0f73
> > commit: 9f1edf1aedac1b287355f63f768ba4275de72dca mm: readahead: make thp readahead conditional to mmap_miss logic
> > config: x86_64-randconfig-161-20260113 (https://download.01.org/0day-ci/archive/20260113/202601131311.g3lyUAks-lkp@intel.com/config)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> > smatch version: v0.5.0-8985-g2614ff1a
> >
> > 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@intel.com>
> > | Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > | Closes: https://lore.kernel.org/r/202601131311.g3lyUAks-lkp@intel.com/
> >
> > smatch warnings:
> > mm/filemap.c:3307 do_sync_mmap_readahead() warn: assigning (-12) to unsigned variable 'ra->order'
> ...
> > 9f1edf1aedac1b2 Roman Gushchin 2025-10-06 3306 ra->async_size = HPAGE_PMD_NR;
> > 9f1edf1aedac1b2 Roman Gushchin 2025-10-06 @3307 ra->order = HPAGE_PMD_ORDER;
> >
> > HPAGE_PMD_SHIFT is zero in this config?
> > ra->order is a u16.
>
> What's the config exactly? I suppose CONFIG_TRANSPARENT_HUGEPAGE is
> disabled in this case, isn't it? In that case force_thp_readahead will
> never be true and thus the branch with the assignment can never be reached
> AFAICT...
>
Ah, yes. You are right. force_thp_readahead is false in this
config.
The truth is, I could easily disable these kinds of warnings in smatch
because this is marked as an impossible path. if (is_impossible_path())
return... I've done that on a case by case basis in the past but maybe I
should just do it globally.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 3+ messages in thread
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2026-01-13 11:12 mm/filemap.c:3307 do_sync_mmap_readahead() warn: assigning (-12) to unsigned variable 'ra->order' Dan Carpenter
2026-01-13 12:24 ` Jan Kara
2026-01-13 12:56 ` Dan Carpenter
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