* mm/shmem.c:2223 shmem_split_large_entry() error: uninitialized symbol 'entry_order'.
@ 2025-06-18 17:42 Dan Carpenter
2025-06-18 17:47 ` Matthew Wilcox
0 siblings, 1 reply; 3+ messages in thread
From: Dan Carpenter @ 2025-06-18 17:42 UTC (permalink / raw)
To: oe-kbuild, Zi Yan
Cc: lkp, oe-kbuild-all, linux-kernel, Andrew Morton,
Linux Memory Management List, Baolin Wang
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 4774cfe3543abb8ee98089f535e28ebfd45b975a
commit: d53c78fffe7ad364397c693522ceb4d152c2aacd mm/shmem: use xas_try_split() in shmem_split_large_entry()
config: x86_64-randconfig-161-20250614 (https://download.01.org/0day-ci/archive/20250614/202506141535.tjdnCMqW-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
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/202506141535.tjdnCMqW-lkp@intel.com/
smatch warnings:
mm/shmem.c:2223 shmem_split_large_entry() error: uninitialized symbol 'entry_order'.
vim +/entry_order +2223 mm/shmem.c
12885cbe88ddf6 Baolin Wang 2024-08-12 2151 static int shmem_split_large_entry(struct inode *inode, pgoff_t index,
12885cbe88ddf6 Baolin Wang 2024-08-12 2152 swp_entry_t swap, gfp_t gfp)
12885cbe88ddf6 Baolin Wang 2024-08-12 2153 {
12885cbe88ddf6 Baolin Wang 2024-08-12 2154 struct address_space *mapping = inode->i_mapping;
12885cbe88ddf6 Baolin Wang 2024-08-12 2155 XA_STATE_ORDER(xas, &mapping->i_pages, index, 0);
d53c78fffe7ad3 Zi Yan 2025-03-14 2156 int split_order = 0, entry_order;
d53c78fffe7ad3 Zi Yan 2025-03-14 2157 int i;
12885cbe88ddf6 Baolin Wang 2024-08-12 2158
12885cbe88ddf6 Baolin Wang 2024-08-12 2159 /* Convert user data gfp flags to xarray node gfp flags */
12885cbe88ddf6 Baolin Wang 2024-08-12 2160 gfp &= GFP_RECLAIM_MASK;
12885cbe88ddf6 Baolin Wang 2024-08-12 2161
12885cbe88ddf6 Baolin Wang 2024-08-12 2162 for (;;) {
12885cbe88ddf6 Baolin Wang 2024-08-12 2163 void *old = NULL;
d53c78fffe7ad3 Zi Yan 2025-03-14 2164 int cur_order;
d53c78fffe7ad3 Zi Yan 2025-03-14 2165 pgoff_t swap_index;
12885cbe88ddf6 Baolin Wang 2024-08-12 2166
12885cbe88ddf6 Baolin Wang 2024-08-12 2167 xas_lock_irq(&xas);
12885cbe88ddf6 Baolin Wang 2024-08-12 2168 old = xas_load(&xas);
12885cbe88ddf6 Baolin Wang 2024-08-12 2169 if (!xa_is_value(old) || swp_to_radix_entry(swap) != old) {
12885cbe88ddf6 Baolin Wang 2024-08-12 2170 xas_set_err(&xas, -EEXIST);
12885cbe88ddf6 Baolin Wang 2024-08-12 2171 goto unlock;
Imagine we hit this goto on the first iteration
12885cbe88ddf6 Baolin Wang 2024-08-12 2172 }
12885cbe88ddf6 Baolin Wang 2024-08-12 2173
d53c78fffe7ad3 Zi Yan 2025-03-14 2174 entry_order = xas_get_order(&xas);
12885cbe88ddf6 Baolin Wang 2024-08-12 2175
d53c78fffe7ad3 Zi Yan 2025-03-14 2176 if (!entry_order)
d53c78fffe7ad3 Zi Yan 2025-03-14 2177 goto unlock;
12885cbe88ddf6 Baolin Wang 2024-08-12 2178
12885cbe88ddf6 Baolin Wang 2024-08-12 2179 /* Try to split large swap entry in pagecache */
d53c78fffe7ad3 Zi Yan 2025-03-14 2180 cur_order = entry_order;
d53c78fffe7ad3 Zi Yan 2025-03-14 2181 swap_index = round_down(index, 1 << entry_order);
d53c78fffe7ad3 Zi Yan 2025-03-14 2182
d53c78fffe7ad3 Zi Yan 2025-03-14 2183 split_order = xas_try_split_min_order(cur_order);
d53c78fffe7ad3 Zi Yan 2025-03-14 2184
d53c78fffe7ad3 Zi Yan 2025-03-14 2185 while (cur_order > 0) {
d53c78fffe7ad3 Zi Yan 2025-03-14 2186 pgoff_t aligned_index =
d53c78fffe7ad3 Zi Yan 2025-03-14 2187 round_down(index, 1 << cur_order);
d53c78fffe7ad3 Zi Yan 2025-03-14 2188 pgoff_t swap_offset = aligned_index - swap_index;
d53c78fffe7ad3 Zi Yan 2025-03-14 2189
d53c78fffe7ad3 Zi Yan 2025-03-14 2190 xas_set_order(&xas, index, split_order);
d53c78fffe7ad3 Zi Yan 2025-03-14 2191 xas_try_split(&xas, old, cur_order);
d53c78fffe7ad3 Zi Yan 2025-03-14 2192 if (xas_error(&xas))
12885cbe88ddf6 Baolin Wang 2024-08-12 2193 goto unlock;
12885cbe88ddf6 Baolin Wang 2024-08-12 2194
12885cbe88ddf6 Baolin Wang 2024-08-12 2195 /*
12885cbe88ddf6 Baolin Wang 2024-08-12 2196 * Re-set the swap entry after splitting, and the swap
12885cbe88ddf6 Baolin Wang 2024-08-12 2197 * offset of the original large entry must be continuous.
12885cbe88ddf6 Baolin Wang 2024-08-12 2198 */
d53c78fffe7ad3 Zi Yan 2025-03-14 2199 for (i = 0; i < 1 << cur_order;
d53c78fffe7ad3 Zi Yan 2025-03-14 2200 i += (1 << split_order)) {
12885cbe88ddf6 Baolin Wang 2024-08-12 2201 swp_entry_t tmp;
12885cbe88ddf6 Baolin Wang 2024-08-12 2202
d53c78fffe7ad3 Zi Yan 2025-03-14 2203 tmp = swp_entry(swp_type(swap),
d53c78fffe7ad3 Zi Yan 2025-03-14 2204 swp_offset(swap) + swap_offset +
d53c78fffe7ad3 Zi Yan 2025-03-14 2205 i);
12885cbe88ddf6 Baolin Wang 2024-08-12 2206 __xa_store(&mapping->i_pages, aligned_index + i,
12885cbe88ddf6 Baolin Wang 2024-08-12 2207 swp_to_radix_entry(tmp), 0);
12885cbe88ddf6 Baolin Wang 2024-08-12 2208 }
d53c78fffe7ad3 Zi Yan 2025-03-14 2209 cur_order = split_order;
d53c78fffe7ad3 Zi Yan 2025-03-14 2210 split_order = xas_try_split_min_order(split_order);
12885cbe88ddf6 Baolin Wang 2024-08-12 2211 }
12885cbe88ddf6 Baolin Wang 2024-08-12 2212
12885cbe88ddf6 Baolin Wang 2024-08-12 2213 unlock:
12885cbe88ddf6 Baolin Wang 2024-08-12 2214 xas_unlock_irq(&xas);
12885cbe88ddf6 Baolin Wang 2024-08-12 2215
12885cbe88ddf6 Baolin Wang 2024-08-12 2216 if (!xas_nomem(&xas, gfp))
12885cbe88ddf6 Baolin Wang 2024-08-12 2217 break;
And we hit this break.
12885cbe88ddf6 Baolin Wang 2024-08-12 2218 }
12885cbe88ddf6 Baolin Wang 2024-08-12 2219
12885cbe88ddf6 Baolin Wang 2024-08-12 2220 if (xas_error(&xas))
12885cbe88ddf6 Baolin Wang 2024-08-12 2221 return xas_error(&xas);
12885cbe88ddf6 Baolin Wang 2024-08-12 2222
d53c78fffe7ad3 Zi Yan 2025-03-14 @2223 return entry_order;
6cec2b95dadf77 Miaohe Lin 2022-05-19 2224 }
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: mm/shmem.c:2223 shmem_split_large_entry() error: uninitialized symbol 'entry_order'.
2025-06-18 17:42 mm/shmem.c:2223 shmem_split_large_entry() error: uninitialized symbol 'entry_order' Dan Carpenter
@ 2025-06-18 17:47 ` Matthew Wilcox
2025-06-18 17:53 ` Zi Yan
0 siblings, 1 reply; 3+ messages in thread
From: Matthew Wilcox @ 2025-06-18 17:47 UTC (permalink / raw)
To: Dan Carpenter
Cc: oe-kbuild, Zi Yan, lkp, oe-kbuild-all, linux-kernel,
Andrew Morton, Linux Memory Management List, Baolin Wang
On Wed, Jun 18, 2025 at 08:42:17PM +0300, Dan Carpenter wrote:
> smatch warnings:
> mm/shmem.c:2223 shmem_split_large_entry() error: uninitialized symbol 'entry_order'.
...
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2169 if (!xa_is_value(old) || swp_to_radix_entry(swap) != old) {
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2170 xas_set_err(&xas, -EEXIST);
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2171 goto unlock;
>
> Imagine we hit this goto on the first iteration
That can happen (but if it does, we set -EEXIST in the xa_state).
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2213 unlock:
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2214 xas_unlock_irq(&xas);
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2215
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2216 if (!xas_nomem(&xas, gfp))
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2217 break;
>
> And we hit this break.
That's guaranteed. If there's an errno in the xa_state that isn't
-ENOMEM, xas_nomem() will fail.
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2218 }
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2219
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2220 if (xas_error(&xas))
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2221 return xas_error(&xas);
> 12885cbe88ddf6 Baolin Wang 2024-08-12 2222
> d53c78fffe7ad3 Zi Yan 2025-03-14 @2223 return entry_order;
but if this does happen, then xas_error() will be true and we'll return
-EEXIST here instead of returning entry_order.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: mm/shmem.c:2223 shmem_split_large_entry() error: uninitialized symbol 'entry_order'.
2025-06-18 17:47 ` Matthew Wilcox
@ 2025-06-18 17:53 ` Zi Yan
0 siblings, 0 replies; 3+ messages in thread
From: Zi Yan @ 2025-06-18 17:53 UTC (permalink / raw)
To: Matthew Wilcox, Dan Carpenter
Cc: oe-kbuild, lkp, oe-kbuild-all, linux-kernel, Andrew Morton,
Linux Memory Management List, Baolin Wang
On 18 Jun 2025, at 13:47, Matthew Wilcox wrote:
> On Wed, Jun 18, 2025 at 08:42:17PM +0300, Dan Carpenter wrote:
>> smatch warnings:
>> mm/shmem.c:2223 shmem_split_large_entry() error: uninitialized symbol 'entry_order'.
>
> ...
>
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2169 if (!xa_is_value(old) || swp_to_radix_entry(swap) != old) {
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2170 xas_set_err(&xas, -EEXIST);
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2171 goto unlock;
>>
>> Imagine we hit this goto on the first iteration
>
> That can happen (but if it does, we set -EEXIST in the xa_state).
>
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2213 unlock:
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2214 xas_unlock_irq(&xas);
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2215
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2216 if (!xas_nomem(&xas, gfp))
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2217 break;
>>
>> And we hit this break.
>
> That's guaranteed. If there's an errno in the xa_state that isn't
> -ENOMEM, xas_nomem() will fail.
>
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2218 }
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2219
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2220 if (xas_error(&xas))
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2221 return xas_error(&xas);
>> 12885cbe88ddf6 Baolin Wang 2024-08-12 2222
>> d53c78fffe7ad3 Zi Yan 2025-03-14 @2223 return entry_order;
>
> but if this does happen, then xas_error() will be true and we'll return
> -EEXIST here instead of returning entry_order.
Hi Matthew,
Thank you for the explanation.
Hi Dan,
I got a similar report 3 months ago and explained it already.
See https://lore.kernel.org/linux-mm/B024C29C-96D4-4F92-B2EF-F01CB06B27DF@nvidia.com/
Best Regards,
Yan, Zi
^ permalink raw reply [flat|nested] 3+ messages in thread
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2025-06-18 17:42 mm/shmem.c:2223 shmem_split_large_entry() error: uninitialized symbol 'entry_order' Dan Carpenter
2025-06-18 17:47 ` Matthew Wilcox
2025-06-18 17:53 ` Zi Yan
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