Portions of upstream commit a4055888629b ("mm/memcg: warning on !memcg after readahead page charged") were backported as commit cfe575954ddd ("mm: add VM_WARN_ON_ONCE_PAGE() macro"). Unfortunately, the backport did not account for the lack of commit 33def8498fdd ("treewide: Convert macro and uses of __section(foo) to __section("foo")") in kernels prior to 5.10, resulting in the following orphan section warnings on PowerPC clang builds with CONFIG_DEBUG_VM=y:
powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"' powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"' powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"'
This is a difference between how clang and gcc handle macro stringification, which was resolved for the kernel by not stringifying the argument to the __section() macro. Since that change was deemed not suitable for the stable kernels by commit 59f89518f510 ("once: fix section mismatch on clang builds"), do that same thing as that change and remove the quotes from the argument to __section().
Fixes: cfe575954ddd ("mm: add VM_WARN_ON_ONCE_PAGE() macro") Signed-off-by: Nathan Chancellor nathan@kernel.org ---
As far as I can tell, this should be applied to 5.4 and earlier. It should apply cleanly but let me know if not.
include/linux/mmdebug.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h index 5d0767cb424a..4ed52879ce55 100644 --- a/include/linux/mmdebug.h +++ b/include/linux/mmdebug.h @@ -38,7 +38,7 @@ void dump_mm(const struct mm_struct *mm); } \ } while (0) #define VM_WARN_ON_ONCE_PAGE(cond, page) ({ \ - static bool __section(".data.once") __warned; \ + static bool __section(.data.once) __warned; \ int __ret_warn_once = !!(cond); \ \ if (unlikely(__ret_warn_once && !__warned)) { \
base-commit: 4d2a309b5c28a2edc0900542d22fec3a5a22243b
On Mon, 28 Nov 2022, Nathan Chancellor wrote:
Portions of upstream commit a4055888629b ("mm/memcg: warning on !memcg after readahead page charged") were backported as commit cfe575954ddd ("mm: add VM_WARN_ON_ONCE_PAGE() macro"). Unfortunately, the backport did not account for the lack of commit 33def8498fdd ("treewide: Convert macro and uses of __section(foo) to __section("foo")") in kernels prior to 5.10, resulting in the following orphan section warnings on PowerPC clang builds with CONFIG_DEBUG_VM=y:
powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"' powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"' powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"'
This is a difference between how clang and gcc handle macro stringification, which was resolved for the kernel by not stringifying the argument to the __section() macro. Since that change was deemed not suitable for the stable kernels by commit 59f89518f510 ("once: fix section mismatch on clang builds"), do that same thing as that change and remove the quotes from the argument to __section().
Fixes: cfe575954ddd ("mm: add VM_WARN_ON_ONCE_PAGE() macro") Signed-off-by: Nathan Chancellor nathan@kernel.org
Yes indeed: thanks Nathan, sorry about that.
Acked-by: Hugh Dickins hughd@google.com
As far as I can tell, this should be applied to 5.4 and earlier. It should apply cleanly but let me know if not.
I think it should be good for 4.19 also, but I don't know what happens or would happen in 4.14 and 4.9 trees, since those have no other example of .data.once or ".data.once" (and I've lost what little I ever knew of that linker script stuff).
Since we're not hearing complaints about those (or are you?), perhaps those trees are not clang-ready in other ways, and for gcc it all works out by itself: I'd be inclined to just leave them as is myself, if there are no reports of breakage; but you may know better, and prefer to remove the ' __section(".data.once")' from the 4.14 and 4.9 versions.
include/linux/mmdebug.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h index 5d0767cb424a..4ed52879ce55 100644 --- a/include/linux/mmdebug.h +++ b/include/linux/mmdebug.h @@ -38,7 +38,7 @@ void dump_mm(const struct mm_struct *mm); } \ } while (0) #define VM_WARN_ON_ONCE_PAGE(cond, page) ({ \
- static bool __section(".data.once") __warned; \
- static bool __section(.data.once) __warned; \ int __ret_warn_once = !!(cond); \ \ if (unlikely(__ret_warn_once && !__warned)) { \
base-commit: 4d2a309b5c28a2edc0900542d22fec3a5a22243b
2.38.1
On Tue, Nov 29, 2022 at 10:28:33PM -0800, Hugh Dickins wrote:
On Mon, 28 Nov 2022, Nathan Chancellor wrote:
Portions of upstream commit a4055888629b ("mm/memcg: warning on !memcg after readahead page charged") were backported as commit cfe575954ddd ("mm: add VM_WARN_ON_ONCE_PAGE() macro"). Unfortunately, the backport did not account for the lack of commit 33def8498fdd ("treewide: Convert macro and uses of __section(foo) to __section("foo")") in kernels prior to 5.10, resulting in the following orphan section warnings on PowerPC clang builds with CONFIG_DEBUG_VM=y:
powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"' powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"' powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"'
This is a difference between how clang and gcc handle macro stringification, which was resolved for the kernel by not stringifying the argument to the __section() macro. Since that change was deemed not suitable for the stable kernels by commit 59f89518f510 ("once: fix section mismatch on clang builds"), do that same thing as that change and remove the quotes from the argument to __section().
Fixes: cfe575954ddd ("mm: add VM_WARN_ON_ONCE_PAGE() macro") Signed-off-by: Nathan Chancellor nathan@kernel.org
Yes indeed: thanks Nathan, sorry about that.
Acked-by: Hugh Dickins hughd@google.com
No worries, it is a really subtle problem that I would not expect someone doing normal backports to catch. Thanks for taking a look!
As far as I can tell, this should be applied to 5.4 and earlier. It should apply cleanly but let me know if not.
I think it should be good for 4.19 also, but I don't know what happens or would happen in 4.14 and 4.9 trees, since those have no other example of .data.once or ".data.once" (and I've lost what little I ever knew of that linker script stuff).
Since we're not hearing complaints about those (or are you?), perhaps those trees are not clang-ready in other ways, and for gcc it all works out by itself: I'd be inclined to just leave them as is myself, if there are no reports of breakage; but you may know better, and prefer to remove the ' __section(".data.once")' from the 4.14 and 4.9 versions.
Those trees have very rudimentary clang support, they are far from warning and issue clean in all configurations (even mainline has known issues for some architectures, including powerpc). Since this specifically requires CONFIG_DEBUG_VM to see, I am perfectly fine with just applying it to 4.19 and 5.4.
Cheers, Nathan
include/linux/mmdebug.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h index 5d0767cb424a..4ed52879ce55 100644 --- a/include/linux/mmdebug.h +++ b/include/linux/mmdebug.h @@ -38,7 +38,7 @@ void dump_mm(const struct mm_struct *mm); } \ } while (0) #define VM_WARN_ON_ONCE_PAGE(cond, page) ({ \
- static bool __section(".data.once") __warned; \
- static bool __section(.data.once) __warned; \ int __ret_warn_once = !!(cond); \ \ if (unlikely(__ret_warn_once && !__warned)) { \
base-commit: 4d2a309b5c28a2edc0900542d22fec3a5a22243b
2.38.1
On Mon, Nov 28, 2022 at 03:53:46PM -0700, Nathan Chancellor wrote:
Portions of upstream commit a4055888629b ("mm/memcg: warning on !memcg after readahead page charged") were backported as commit cfe575954ddd ("mm: add VM_WARN_ON_ONCE_PAGE() macro"). Unfortunately, the backport did not account for the lack of commit 33def8498fdd ("treewide: Convert macro and uses of __section(foo) to __section("foo")") in kernels prior to 5.10, resulting in the following orphan section warnings on PowerPC clang builds with CONFIG_DEBUG_VM=y:
powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"' powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"' powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"'
This is a difference between how clang and gcc handle macro stringification, which was resolved for the kernel by not stringifying the argument to the __section() macro. Since that change was deemed not suitable for the stable kernels by commit 59f89518f510 ("once: fix section mismatch on clang builds"), do that same thing as that change and remove the quotes from the argument to __section().
Fixes: cfe575954ddd ("mm: add VM_WARN_ON_ONCE_PAGE() macro") Signed-off-by: Nathan Chancellor nathan@kernel.org
As far as I can tell, this should be applied to 5.4 and earlier. It should apply cleanly but let me know if not.
Queued up everywhere, thanks.
greg k-h
On Sat, 3 Dec 2022, Greg Kroah-Hartman wrote:
On Mon, Nov 28, 2022 at 03:53:46PM -0700, Nathan Chancellor wrote:
As far as I can tell, this should be applied to 5.4 and earlier. It should apply cleanly but let me know if not.
Queued up everywhere, thanks.
Thanks for queueing them up, Greg, but please read through the thread: I have doubts on the 4.14 and 4.9 ones, which would want a different patch if we're going to make any change; but thought we could just leave those trees without the patch, and Nathan agreed.
Thanks, Hugh
On Sat, Dec 03, 2022 at 09:41:34AM -0800, Hugh Dickins wrote:
On Sat, 3 Dec 2022, Greg Kroah-Hartman wrote:
On Mon, Nov 28, 2022 at 03:53:46PM -0700, Nathan Chancellor wrote:
As far as I can tell, this should be applied to 5.4 and earlier. It should apply cleanly but let me know if not.
Queued up everywhere, thanks.
Thanks for queueing them up, Greg, but please read through the thread: I have doubts on the 4.14 and 4.9 ones, which would want a different patch if we're going to make any change; but thought we could just leave those trees without the patch, and Nathan agreed.
Oops, sorry, now dropped from 4.14 and 4.9 and I left the 4.19 one as that one was ok to keep, right?
thanks,
greg k-h
On Sun, 4 Dec 2022, Greg Kroah-Hartman wrote:
On Sat, Dec 03, 2022 at 09:41:34AM -0800, Hugh Dickins wrote:
On Sat, 3 Dec 2022, Greg Kroah-Hartman wrote:
On Mon, Nov 28, 2022 at 03:53:46PM -0700, Nathan Chancellor wrote:
As far as I can tell, this should be applied to 5.4 and earlier. It should apply cleanly but let me know if not.
Queued up everywhere, thanks.
Thanks for queueing them up, Greg, but please read through the thread: I have doubts on the 4.14 and 4.9 ones, which would want a different patch if we're going to make any change; but thought we could just leave those trees without the patch, and Nathan agreed.
Oops, sorry, now dropped from 4.14 and 4.9 and I left the 4.19 one as that one was ok to keep, right?
That's right, the 5.4 and the 4.19 ones are straightforward. It was just the 4.14 and 4.9 ones which were questionable (because of other related infrastructure missing), so better dropped.
Thanks, Hugh
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