From 918533eddff9853f00b23ac94ff0786166d39827 Mon Sep 17 00:00:00 2001 From: Shengqi Chen Date: Thu, 7 Dec 2023 04:37:50 +0800 Subject: [PATCH] compact: workaround for GPL-only symbols on riscv from Linux 6.2 Since Linux 6.2, the implementation of flush_dcache_page on riscv references GPL-only symbol `PageHuge`, breaking the build of zfs. This patch uses existing mechanism to override flush_dcache_page, removing the call to `PageHuge`. According to comments in kernel, it is only used to do some check against HugeTLB pages, which only exist in userspace. ZFS uses flush_dcache_page only on kernel pages, thus this patch will not introduce any behaviour change. See also: torvalds/linux@d33deda, openzfs/zfs@589f59b Reviewed-by: Brian Behlendorf Signed-off-by: Shengqi Chen Closes #14974 Closes #15627 --- config/kernel-flush_dcache_page.m4 | 5 +++-- config/kernel.m4 | 6 ++++++ include/os/linux/kernel/linux/dcache_compat.h | 15 +++++++++++++-- 3 files changed, 22 insertions(+), 4 deletions(-) diff --git a/config/kernel-flush_dcache_page.m4 b/config/kernel-flush_dcache_page.m4 index 2340c386ef57..aa916c87d531 100644 --- a/config/kernel-flush_dcache_page.m4 +++ b/config/kernel-flush_dcache_page.m4 @@ -1,7 +1,8 @@ dnl # dnl # Starting from Linux 5.13, flush_dcache_page() becomes an inline -dnl # function and may indirectly referencing GPL-only cpu_feature_keys on -dnl # powerpc +dnl # function and may indirectly referencing GPL-only symbols: +dnl # on powerpc: cpu_feature_keys +dnl # on riscv: PageHuge (added from 6.2) dnl # dnl # diff --git a/config/kernel.m4 b/config/kernel.m4 index 056517a841f2..d25b65994f6f 100644 --- a/config/kernel.m4 +++ b/config/kernel.m4 @@ -168,6 +168,9 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [ ZFS_AC_KERNEL_SRC_CPU_HAS_FEATURE ZFS_AC_KERNEL_SRC_FLUSH_DCACHE_PAGE ;; + riscv*) + ZFS_AC_KERNEL_SRC_FLUSH_DCACHE_PAGE + ;; esac AC_MSG_CHECKING([for available kernel interfaces]) @@ -310,6 +313,9 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [ ZFS_AC_KERNEL_CPU_HAS_FEATURE ZFS_AC_KERNEL_FLUSH_DCACHE_PAGE ;; + riscv*) + ZFS_AC_KERNEL_FLUSH_DCACHE_PAGE + ;; esac ]) diff --git a/include/os/linux/kernel/linux/dcache_compat.h b/include/os/linux/kernel/linux/dcache_compat.h index 1e35204932d1..ab1711b99f3f 100644 --- a/include/os/linux/kernel/linux/dcache_compat.h +++ b/include/os/linux/kernel/linux/dcache_compat.h @@ -42,8 +42,8 @@ /* * Starting from Linux 5.13, flush_dcache_page() becomes an inline function * and under some configurations, may indirectly referencing GPL-only - * cpu_feature_keys on powerpc. Override this function when it is detected - * being GPL-only. + * symbols, e.g., cpu_feature_keys on powerpc and PageHuge on riscv. + * Override this function when it is detected being GPL-only. */ #if defined __powerpc__ && defined HAVE_FLUSH_DCACHE_PAGE_GPL_ONLY #include @@ -53,6 +53,17 @@ clear_bit(PG_dcache_clean, &(page)->flags); \ } while (0) #endif +/* + * For riscv implementation, the use of PageHuge can be safely removed. + * Because it handles pages allocated by HugeTLB, while flush_dcache_page + * in zfs module is only called on kernel pages. + */ +#if defined __riscv && defined HAVE_FLUSH_DCACHE_PAGE_GPL_ONLY +#define flush_dcache_page(page) do { \ + if (test_bit(PG_dcache_clean, &(page)->flags)) \ + clear_bit(PG_dcache_clean, &(page)->flags); \ + } while (0) +#endif /* * 2.6.30 API change,