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[87.16.96.199]) by smtp.gmail.com with ESMTPSA id o18-20020a5d6852000000b0021552eebde6sm1121807wrw.32.2022.06.16.01.11.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Jun 2022 01:11:56 -0700 (PDT) From: "Fabio M. De Francesco" To: David Sterba Cc: Chris Mason , Josef Bacik , Nick Terrell , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, Ira Weiny , Andrew Morton , Matthew Wilcox , Kees Cook , Sebastian Andrzej Siewior , "James E . J . Bottomley" , Helge Deller , John David Anglin , linux-parisc@vger.kernel.org, "Fabio M. De Francesco" , David Sterba Subject: [PATCH v3 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *" Date: Thu, 16 Jun 2022 10:11:32 +0200 Message-Id: <20220616081133.14144-2-fmdefrancesco@gmail.com> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220616081133.14144-1-fmdefrancesco@gmail.com> References: <20220616081133.14144-1-fmdefrancesco@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" __kunmap_ {local,atomic}() currently take pointers to void. However, this is semantically incorrect, since these functions do not change the memory their arguments point to. Therefore, make this semantics explicit by modifying the __kunmap_{local,atomic}() prototypes to take pointers to const void. As a side effect, compilers will likely produce more efficient code. Cc: Andrew Morton Suggested-by: David Sterba Suggested-by: Ira Weiny Signed-off-by: Fabio M. De Francesco --- v3->v4: Cc Maintainers and lists which had been overlooked when sending v3. v2->v3: Fix compilation errors for ARCH=3Dparisc. Reported-by: kernel test robot v1->v2: Change the commit message to clearly explain why these functions should require pointers to const void. The fundamental argument=20 behind the commit message changes is semantic correctness. Obviously, there are no changes to the code. Many thanks to David Sterba and Ira Weiny for suggestions and reviews. arch/parisc/include/asm/cacheflush.h | 6 +++--- arch/parisc/kernel/cache.c | 2 +- include/linux/highmem-internal.h | 10 +++++----- mm/highmem.c | 2 +- 4 files changed, 10 insertions(+), 10 deletions(-) diff --git a/arch/parisc/include/asm/cacheflush.h b/arch/parisc/include/asm= /cacheflush.h index 8d03b3b26229..0bdee6724132 100644 --- a/arch/parisc/include/asm/cacheflush.h +++ b/arch/parisc/include/asm/cacheflush.h @@ -22,7 +22,7 @@ void flush_kernel_icache_range_asm(unsigned long, unsigne= d long); void flush_user_dcache_range_asm(unsigned long, unsigned long); void flush_kernel_dcache_range_asm(unsigned long, unsigned long); void purge_kernel_dcache_range_asm(unsigned long, unsigned long); -void flush_kernel_dcache_page_asm(void *); +void flush_kernel_dcache_page_asm(const void *addr); void flush_kernel_icache_page(void *); =20 /* Cache flush operations */ @@ -31,7 +31,7 @@ void flush_cache_all_local(void); void flush_cache_all(void); void flush_cache_mm(struct mm_struct *mm); =20 -void flush_kernel_dcache_page_addr(void *addr); +void flush_kernel_dcache_page_addr(const void *addr); =20 #define flush_kernel_dcache_range(start,size) \ flush_kernel_dcache_range_asm((start), (start)+(size)); @@ -75,7 +75,7 @@ void flush_dcache_page_asm(unsigned long phys_addr, unsig= ned long vaddr); void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsign= ed long vmaddr); =20 #define ARCH_HAS_FLUSH_ON_KUNMAP -static inline void kunmap_flush_on_unmap(void *addr) +static inline void kunmap_flush_on_unmap(const void *addr) { flush_kernel_dcache_page_addr(addr); } diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c index c8a11fcecf4c..824064cafd61 100644 --- a/arch/parisc/kernel/cache.c +++ b/arch/parisc/kernel/cache.c @@ -549,7 +549,7 @@ extern void purge_kernel_dcache_page_asm(unsigned long); extern void clear_user_page_asm(void *, unsigned long); extern void copy_user_page_asm(void *, void *, unsigned long); =20 -void flush_kernel_dcache_page_addr(void *addr) +void flush_kernel_dcache_page_addr(const void *addr) { unsigned long flags; =20 diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-inter= nal.h index cddb42ff0473..034b1106d022 100644 --- a/include/linux/highmem-internal.h +++ b/include/linux/highmem-internal.h @@ -8,7 +8,7 @@ #ifdef CONFIG_KMAP_LOCAL void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot); void *__kmap_local_page_prot(struct page *page, pgprot_t prot); -void kunmap_local_indexed(void *vaddr); +void kunmap_local_indexed(const void *vaddr); void kmap_local_fork(struct task_struct *tsk); void __kmap_local_sched_out(void); void __kmap_local_sched_in(void); @@ -89,7 +89,7 @@ static inline void *kmap_local_pfn(unsigned long pfn) return __kmap_local_pfn_prot(pfn, kmap_prot); } =20 -static inline void __kunmap_local(void *vaddr) +static inline void __kunmap_local(const void *vaddr) { kunmap_local_indexed(vaddr); } @@ -121,7 +121,7 @@ static inline void *kmap_atomic_pfn(unsigned long pfn) return __kmap_local_pfn_prot(pfn, kmap_prot); } =20 -static inline void __kunmap_atomic(void *addr) +static inline void __kunmap_atomic(const void *addr) { kunmap_local_indexed(addr); pagefault_enable(); @@ -197,7 +197,7 @@ static inline void *kmap_local_pfn(unsigned long pfn) return kmap_local_page(pfn_to_page(pfn)); } =20 -static inline void __kunmap_local(void *addr) +static inline void __kunmap_local(const void *addr) { #ifdef ARCH_HAS_FLUSH_ON_KUNMAP kunmap_flush_on_unmap(addr); @@ -224,7 +224,7 @@ static inline void *kmap_atomic_pfn(unsigned long pfn) return kmap_atomic(pfn_to_page(pfn)); } =20 -static inline void __kunmap_atomic(void *addr) +static inline void __kunmap_atomic(const void *addr) { #ifdef ARCH_HAS_FLUSH_ON_KUNMAP kunmap_flush_on_unmap(addr); diff --git a/mm/highmem.c b/mm/highmem.c index 1a692997fac4..e32083e4ce0d 100644 --- a/mm/highmem.c +++ b/mm/highmem.c @@ -561,7 +561,7 @@ void *__kmap_local_page_prot(struct page *page, pgprot_= t prot) } EXPORT_SYMBOL(__kmap_local_page_prot); =20 -void kunmap_local_indexed(void *vaddr) +void kunmap_local_indexed(const void *vaddr) { unsigned long addr =3D (unsigned long) vaddr & PAGE_MASK; pte_t *kmap_pte; --=20 2.36.1 From nobody Mon Apr 27 06:25:31 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E80AAC433EF for ; Thu, 16 Jun 2022 08:12:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1359682AbiFPIML (ORCPT ); Thu, 16 Jun 2022 04:12:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59756 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1359662AbiFPIMF (ORCPT ); Thu, 16 Jun 2022 04:12:05 -0400 Received: from mail-wm1-x332.google.com (mail-wm1-x332.google.com [IPv6:2a00:1450:4864:20::332]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2660D5D658; Thu, 16 Jun 2022 01:12:04 -0700 (PDT) Received: by mail-wm1-x332.google.com with SMTP id m32-20020a05600c3b2000b0039756bb41f2so428893wms.3; 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[87.16.96.199]) by smtp.gmail.com with ESMTPSA id o18-20020a5d6852000000b0021552eebde6sm1121807wrw.32.2022.06.16.01.12.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Jun 2022 01:12:01 -0700 (PDT) From: "Fabio M. De Francesco" To: David Sterba Cc: Chris Mason , Josef Bacik , Nick Terrell , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, Ira Weiny , Andrew Morton , Matthew Wilcox , Kees Cook , Sebastian Andrzej Siewior , "James E . J . Bottomley" , Helge Deller , John David Anglin , linux-parisc@vger.kernel.org, "Fabio M. De Francesco" , Filipe Manana Subject: [PATCH v3 2/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c Date: Thu, 16 Jun 2022 10:11:33 +0200 Message-Id: <20220616081133.14144-3-fmdefrancesco@gmail.com> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220616081133.14144-1-fmdefrancesco@gmail.com> References: <20220616081133.14144-1-fmdefrancesco@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The use of kmap() is being deprecated in favor of kmap_local_page(). With kmap_local_page(), the mapping is per thread, CPU local and not globally visible. Therefore, use kmap_local_page() / kunmap_local() in zstd.c because in this file the mappings are per thread and are not visible in other contexts; meanwhile refactor zstd_compress_pages() to comply with nested local mapping / unmapping ordering rules. Tested with xfstests on QEMU + KVM 32 bits VM with 4GB of RAM and HIGHMEM64G enabled. These changes passed all tests of the "compress" group. Cc: Filipe Manana Suggested-by: Ira Weiny Signed-off-by: Fabio M. De Francesco --- v3->v4: Cc Maintainers and lists that had been overlooked when v3 was sent (mostly regarding patch 1/2). v2->v3: Remove unnecessary casts to arguments of kunmap_local() now that this API can take pointers to const void. v1->v2: No changes. Thanks to Ira Weiny for his invaluable help and persevering support. Thanks also to Filipe Manana for identifying a fundamental detail I had overlooked in RFC: https://lore.kernel.org/lkml/20220611093411.GA3779054@falcondesktop/ fs/btrfs/zstd.c | 42 +++++++++++++++++++++++------------------- 1 file changed, 23 insertions(+), 19 deletions(-) diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c index 0fe31a6f6e68..5d2ab0bac9d2 100644 --- a/fs/btrfs/zstd.c +++ b/fs/btrfs/zstd.c @@ -391,6 +391,8 @@ int zstd_compress_pages(struct list_head *ws, struct ad= dress_space *mapping, *out_pages =3D 0; *total_out =3D 0; *total_in =3D 0; + workspace->in_buf.src =3D NULL; + workspace->out_buf.dst =3D NULL; =20 /* Initialize the stream */ stream =3D zstd_init_cstream(¶ms, len, workspace->mem, @@ -403,7 +405,7 @@ int zstd_compress_pages(struct list_head *ws, struct ad= dress_space *mapping, =20 /* map in the first page of input data */ in_page =3D find_get_page(mapping, start >> PAGE_SHIFT); - workspace->in_buf.src =3D kmap(in_page); + workspace->in_buf.src =3D kmap_local_page(in_page); workspace->in_buf.pos =3D 0; workspace->in_buf.size =3D min_t(size_t, len, PAGE_SIZE); =20 @@ -415,7 +417,7 @@ int zstd_compress_pages(struct list_head *ws, struct ad= dress_space *mapping, goto out; } pages[nr_pages++] =3D out_page; - workspace->out_buf.dst =3D kmap(out_page); + workspace->out_buf.dst =3D kmap_local_page(out_page); workspace->out_buf.pos =3D 0; workspace->out_buf.size =3D min_t(size_t, max_out, PAGE_SIZE); =20 @@ -450,9 +452,9 @@ int zstd_compress_pages(struct list_head *ws, struct ad= dress_space *mapping, if (workspace->out_buf.pos =3D=3D workspace->out_buf.size) { tot_out +=3D PAGE_SIZE; max_out -=3D PAGE_SIZE; - kunmap(out_page); + kunmap_local(workspace->out_buf.dst); if (nr_pages =3D=3D nr_dest_pages) { - out_page =3D NULL; + workspace->out_buf.dst =3D NULL; ret =3D -E2BIG; goto out; } @@ -462,7 +464,7 @@ int zstd_compress_pages(struct list_head *ws, struct ad= dress_space *mapping, goto out; } pages[nr_pages++] =3D out_page; - workspace->out_buf.dst =3D kmap(out_page); + workspace->out_buf.dst =3D kmap_local_page(out_page); workspace->out_buf.pos =3D 0; workspace->out_buf.size =3D min_t(size_t, max_out, PAGE_SIZE); @@ -477,15 +479,16 @@ int zstd_compress_pages(struct list_head *ws, struct = address_space *mapping, /* Check if we need more input */ if (workspace->in_buf.pos =3D=3D workspace->in_buf.size) { tot_in +=3D PAGE_SIZE; - kunmap(in_page); + kunmap_local(workspace->out_buf.dst); + kunmap_local(workspace->in_buf.src); put_page(in_page); - start +=3D PAGE_SIZE; len -=3D PAGE_SIZE; in_page =3D find_get_page(mapping, start >> PAGE_SHIFT); - workspace->in_buf.src =3D kmap(in_page); + workspace->in_buf.src =3D kmap_local_page(in_page); workspace->in_buf.pos =3D 0; workspace->in_buf.size =3D min_t(size_t, len, PAGE_SIZE); + workspace->out_buf.dst =3D kmap_local_page(out_page); } } while (1) { @@ -510,9 +513,9 @@ int zstd_compress_pages(struct list_head *ws, struct ad= dress_space *mapping, =20 tot_out +=3D PAGE_SIZE; max_out -=3D PAGE_SIZE; - kunmap(out_page); + kunmap_local(workspace->out_buf.dst); if (nr_pages =3D=3D nr_dest_pages) { - out_page =3D NULL; + workspace->out_buf.dst =3D NULL; ret =3D -E2BIG; goto out; } @@ -522,7 +525,7 @@ int zstd_compress_pages(struct list_head *ws, struct ad= dress_space *mapping, goto out; } pages[nr_pages++] =3D out_page; - workspace->out_buf.dst =3D kmap(out_page); + workspace->out_buf.dst =3D kmap_local_page(out_page); workspace->out_buf.pos =3D 0; workspace->out_buf.size =3D min_t(size_t, max_out, PAGE_SIZE); } @@ -538,12 +541,12 @@ int zstd_compress_pages(struct list_head *ws, struct = address_space *mapping, out: *out_pages =3D nr_pages; /* Cleanup */ - if (in_page) { - kunmap(in_page); + if (workspace->out_buf.dst) + kunmap_local(workspace->out_buf.dst); + if (workspace->in_buf.src) { + kunmap_local(workspace->in_buf.src); put_page(in_page); } - if (out_page) - kunmap(out_page); return ret; } =20 @@ -567,7 +570,7 @@ int zstd_decompress_bio(struct list_head *ws, struct co= mpressed_bio *cb) goto done; } =20 - workspace->in_buf.src =3D kmap(pages_in[page_in_index]); + workspace->in_buf.src =3D kmap_local_page(pages_in[page_in_index]); workspace->in_buf.pos =3D 0; workspace->in_buf.size =3D min_t(size_t, srclen, PAGE_SIZE); =20 @@ -603,14 +606,15 @@ int zstd_decompress_bio(struct list_head *ws, struct = compressed_bio *cb) break; =20 if (workspace->in_buf.pos =3D=3D workspace->in_buf.size) { - kunmap(pages_in[page_in_index++]); + kunmap_local(workspace->in_buf.src); + page_in_index++; if (page_in_index >=3D total_pages_in) { workspace->in_buf.src =3D NULL; ret =3D -EIO; goto done; } srclen -=3D PAGE_SIZE; - workspace->in_buf.src =3D kmap(pages_in[page_in_index]); + workspace->in_buf.src =3D kmap_local_page(pages_in[page_in_index]); workspace->in_buf.pos =3D 0; workspace->in_buf.size =3D min_t(size_t, srclen, PAGE_SIZE); } @@ -619,7 +623,7 @@ int zstd_decompress_bio(struct list_head *ws, struct co= mpressed_bio *cb) zero_fill_bio(cb->orig_bio); done: if (workspace->in_buf.src) - kunmap(pages_in[page_in_index]); + kunmap_local(workspace->in_buf.src); return ret; } =20 --=20 2.36.1