| Message ID | 44312f4a-8b9c-49ce-9277-5873a94ca1bb@oracle.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC] mm/slab: Avoid build bug for calls to kmalloc with a large constant | expand |
On 01/11/2024 20:16, Dave Kleikamp wrote: > When boot-time page size is enabled, the test against KMALLOC_MAX_CACHE_SIZE > is no longer optimized out with a constant size, so a build bug may > occur on a path that won't be reached. > > Found compiling drivers/net/ethernet/qlogic/qed/qed_sriov.c > > Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com> > --- > > Ryan, > > Please consider incorporating this fix or something similar into your > mm patch in the boot-time pages size patches. > > include/linux/slab.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/include/linux/slab.h b/include/linux/slab.h > index 9848296ca6ba..a4c7507ab8ec 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -685,7 +685,8 @@ static __always_inline unsigned int __kmalloc_index(size_t > size, > if (size <= 1024 * 1024) return 20; > if (size <= 2 * 1024 * 1024) return 21; > > - if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant) > + if (!IS_ENABLED(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE) && Thanks for the patch! I think this may be better as: if (PAGE_SHIFT_MIN == PAGE_SHIFT_MAX && Since that is independent of the architecture. Your approach wouldn't work if another arch wanted to enable boot time page size, or if arm64 dropped the Kconfig because it decided only boot time page size will be supported in future. Thanks, Ryan > + !IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant) > BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()"); > else > BUG();
On 11/6/24 5:44AM, Ryan Roberts wrote: > On 01/11/2024 20:16, Dave Kleikamp wrote: >> When boot-time page size is enabled, the test against KMALLOC_MAX_CACHE_SIZE >> is no longer optimized out with a constant size, so a build bug may >> occur on a path that won't be reached. >> >> Found compiling drivers/net/ethernet/qlogic/qed/qed_sriov.c >> >> Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com> >> --- >> >> Ryan, >> >> Please consider incorporating this fix or something similar into your >> mm patch in the boot-time pages size patches. >> >> include/linux/slab.h | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/include/linux/slab.h b/include/linux/slab.h >> index 9848296ca6ba..a4c7507ab8ec 100644 >> --- a/include/linux/slab.h >> +++ b/include/linux/slab.h >> @@ -685,7 +685,8 @@ static __always_inline unsigned int __kmalloc_index(size_t >> size, >> if (size <= 1024 * 1024) return 20; >> if (size <= 2 * 1024 * 1024) return 21; >> >> - if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant) >> + if (!IS_ENABLED(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE) && > > Thanks for the patch! I think this may be better as: > > if (PAGE_SHIFT_MIN == PAGE_SHIFT_MAX && > > Since that is independent of the architecture. Your approach wouldn't work if > another arch wanted to enable boot time page size, or if arm64 dropped the > Kconfig because it decided only boot time page size will be supported in future. Absolutely. I may be sending some more. I haven't gotten to JFS yet, but that one is my responsibility. Thanks, Shaggy > > Thanks, > Ryan > >> + !IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant) >> BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()"); >> else >> BUG(); >
On 11/1/24 21:16, Dave Kleikamp wrote: > When boot-time page size is enabled, the test against KMALLOC_MAX_CACHE_SIZE > is no longer optimized out with a constant size, so a build bug may > occur on a path that won't be reached. That's rather unfortunate, the __builtin_constant_p(size) part of kmalloc_noprof() really expects things to resolve at compile time and it would be better to keep it that way. I think it would be better if we based KMALLOC_MAX_CACHE_SIZE itself on PAGE_SHIFT_MAX and kept it constant, instead of introducing KMALLOC_SHIFT_HIGH_MAX only for some sanity checks. So if the kernel was built to support 4k to 64k, but booted as 4k, it would still create and use kmalloc caches up to 128k. SLUB should handle that fine (if not, please report it :) Maybe we could also stop adding + 1 to PAGE_SHIFT_MAX if it's >=64k, so the cache size is max 64k and not 128k but that should be probably evaluated separately from this series. Vlastimil > Found compiling drivers/net/ethernet/qlogic/qed/qed_sriov.c > > Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com> > --- > > Ryan, > > Please consider incorporating this fix or something similar into your > mm patch in the boot-time pages size patches. > > include/linux/slab.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/include/linux/slab.h b/include/linux/slab.h > index 9848296ca6ba..a4c7507ab8ec 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -685,7 +685,8 @@ static __always_inline unsigned int __kmalloc_index(size_t size, > if (size <= 1024 * 1024) return 20; > if (size <= 2 * 1024 * 1024) return 21; > > - if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant) > + if (!IS_ENABLED(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE) && > + !IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant) > BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()"); > else > BUG();
diff --git a/include/linux/slab.h b/include/linux/slab.h index 9848296ca6ba..a4c7507ab8ec 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -685,7 +685,8 @@ static __always_inline unsigned int __kmalloc_index(size_t size, if (size <= 1024 * 1024) return 20; if (size <= 2 * 1024 * 1024) return 21; - if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant) + if (!IS_ENABLED(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE) && + !IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant) BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()"); else BUG();
When boot-time page size is enabled, the test against KMALLOC_MAX_CACHE_SIZE is no longer optimized out with a constant size, so a build bug may occur on a path that won't be reached. Found compiling drivers/net/ethernet/qlogic/qed/qed_sriov.c Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com> --- Ryan, Please consider incorporating this fix or something similar into your mm patch in the boot-time pages size patches. include/linux/slab.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)