From: Christoph Hellwig <hch@lst.de> To: Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com> Cc: Russell King <linux@armlinux.org.uk>, Guo Ren <guoren@kernel.org>, Thomas Bogendoerfer <tsbogend@alpha.franken.de>, Nick Hu <nickhu@andestech.com>, Greentime Hu <green.hu@gmail.com>, Vincent Chen <deanbo422@gmail.com>, Helge Deller <deller@gmx.de>, Yoshinori Sato <ysato@users.sourceforge.jp>, Rich Felker <dalias@libc.org>, Geoff Levand <geoff@infradead.org>, Paul Cercueil <paul@crapouillou.net>, Ulf Hansson <ulf.hansson@linaro.org>, Alex Shi <alexs@kernel.org>, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org, linux-mmc@vger.kernel.org, linux-scsi@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Subject: flush_kernel_dcache_page fixes and removal Date: Mon, 12 Jul 2021 08:09:22 +0200 [thread overview] Message-ID: <20210712060928.4161649-1-hch@lst.de> (raw) Hi all, while looking to convert the block layer away from kmap_atomic towards kmap_local_page and prefeably the helpers that abstract it away I noticed that a few block drivers directly or implicitly call flush_kernel_dcache_page before kunmapping a page that has been written to. flush_kernel_dcache_page is documented to to be used in such cases, but flush_dcache_page is actually required when the page could be in the page cache and mapped to userspace, which is pretty much always the case when kmapping an arbitrary page. Unfortunately the documentation doesn't exactly make that clear, which lead to this misused. And it turns out that only the copy_strings / copy_string_kernel in the exec code were actually correct users of flush_kernel_dcache_page, which is why I think we should just remove it and eat the very minor overhead in exec rather than confusing poor driver writers. Diffstat: Documentation/core-api/cachetlb.rst | 86 +++++++---------- Documentation/translations/zh_CN/core-api/cachetlb.rst | 9 - arch/arm/include/asm/cacheflush.h | 4 arch/arm/mm/flush.c | 33 ------ arch/arm/mm/nommu.c | 6 - arch/csky/abiv1/cacheflush.c | 11 -- arch/csky/abiv1/inc/abi/cacheflush.h | 4 arch/mips/include/asm/cacheflush.h | 8 - arch/nds32/include/asm/cacheflush.h | 3 arch/nds32/mm/cacheflush.c | 9 - arch/parisc/include/asm/cacheflush.h | 8 - arch/parisc/kernel/cache.c | 3 arch/sh/include/asm/cacheflush.h | 8 - block/blk-map.c | 2 drivers/block/ps3disk.c | 2 drivers/mmc/host/jz4740_mmc.c | 4 drivers/mmc/host/mmc_spi.c | 2 drivers/scsi/aacraid/aachba.c | 1 fs/exec.c | 6 - include/linux/highmem.h | 5 lib/scatterlist.c | 5 tools/testing/scatterlist/linux/mm.h | 1 22 files changed, 55 insertions(+), 165 deletions(-)
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de> To: Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com> Cc: Russell King <linux@armlinux.org.uk>, Guo Ren <guoren@kernel.org>, Thomas Bogendoerfer <tsbogend@alpha.franken.de>, Nick Hu <nickhu@andestech.com>, Greentime Hu <green.hu@gmail.com>, Vincent Chen <deanbo422@gmail.com>, Helge Deller <deller@gmx.de>, Yoshinori Sato <ysato@users.sourceforge.jp>, Rich Felker <dalias@libc.org>, Geoff Levand <geoff@infradead.org>, Paul Cercueil <paul@crapouillou.net>, Ulf Hansson <ulf.hansson@linaro.org>, Alex Shi <alexs@kernel.org>, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org, linux-mmc@vger.kernel.org, linux-scsi@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Subject: flush_kernel_dcache_page fixes and removal Date: Mon, 12 Jul 2021 08:09:22 +0200 [thread overview] Message-ID: <20210712060928.4161649-1-hch@lst.de> (raw) Hi all, while looking to convert the block layer away from kmap_atomic towards kmap_local_page and prefeably the helpers that abstract it away I noticed that a few block drivers directly or implicitly call flush_kernel_dcache_page before kunmapping a page that has been written to. flush_kernel_dcache_page is documented to to be used in such cases, but flush_dcache_page is actually required when the page could be in the page cache and mapped to userspace, which is pretty much always the case when kmapping an arbitrary page. Unfortunately the documentation doesn't exactly make that clear, which lead to this misused. And it turns out that only the copy_strings / copy_string_kernel in the exec code were actually correct users of flush_kernel_dcache_page, which is why I think we should just remove it and eat the very minor overhead in exec rather than confusing poor driver writers. Diffstat: Documentation/core-api/cachetlb.rst | 86 +++++++---------- Documentation/translations/zh_CN/core-api/cachetlb.rst | 9 - arch/arm/include/asm/cacheflush.h | 4 arch/arm/mm/flush.c | 33 ------ arch/arm/mm/nommu.c | 6 - arch/csky/abiv1/cacheflush.c | 11 -- arch/csky/abiv1/inc/abi/cacheflush.h | 4 arch/mips/include/asm/cacheflush.h | 8 - arch/nds32/include/asm/cacheflush.h | 3 arch/nds32/mm/cacheflush.c | 9 - arch/parisc/include/asm/cacheflush.h | 8 - arch/parisc/kernel/cache.c | 3 arch/sh/include/asm/cacheflush.h | 8 - block/blk-map.c | 2 drivers/block/ps3disk.c | 2 drivers/mmc/host/jz4740_mmc.c | 4 drivers/mmc/host/mmc_spi.c | 2 drivers/scsi/aacraid/aachba.c | 1 fs/exec.c | 6 - include/linux/highmem.h | 5 lib/scatterlist.c | 5 tools/testing/scatterlist/linux/mm.h | 1 22 files changed, 55 insertions(+), 165 deletions(-) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2021-07-12 6:11 UTC|newest] Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-12 6:09 Christoph Hellwig [this message] 2021-07-12 6:09 ` flush_kernel_dcache_page fixes and removal Christoph Hellwig 2021-07-12 6:09 ` [PATCH 1/6] mmc: JZ4740: remove the flush_kernel_dcache_page call in jz4740_mmc_read_data Christoph Hellwig 2021-07-12 6:09 ` Christoph Hellwig 2021-07-19 8:15 ` Paul Cercueil 2021-07-19 8:15 ` Paul Cercueil 2021-08-04 11:12 ` Ulf Hansson 2021-08-04 11:12 ` Ulf Hansson 2021-08-04 11:12 ` Ulf Hansson 2021-07-12 6:09 ` [PATCH 2/6] mmc: mmc_spi: replace flush_kernel_dcache_page with flush_dcache_page Christoph Hellwig 2021-07-12 6:09 ` Christoph Hellwig 2021-08-04 11:12 ` Ulf Hansson 2021-08-04 11:12 ` Ulf Hansson 2021-08-04 11:12 ` Ulf Hansson 2021-07-12 6:09 ` [PATCH 3/6] ps3disk: " Christoph Hellwig 2021-07-12 6:09 ` Christoph Hellwig 2021-07-19 3:07 ` Geoff Levand 2021-07-19 3:07 ` Geoff Levand 2021-07-12 6:09 ` [PATCH 4/6] scatterlist: " Christoph Hellwig 2021-07-12 6:09 ` Christoph Hellwig 2021-07-12 6:09 ` [PATCH 5/6] aacraid: remove an unused include Christoph Hellwig 2021-07-12 6:09 ` Christoph Hellwig 2021-07-19 1:50 ` Martin K. Petersen 2021-07-19 1:50 ` Martin K. Petersen 2021-07-12 6:09 ` [PATCH 6/6] mm: remove flush_kernel_dcache_page Christoph Hellwig 2021-07-12 6:09 ` Christoph Hellwig 2021-07-12 23:56 ` Ira Weiny 2021-07-12 23:56 ` Ira Weiny 2021-07-12 19:24 ` flush_kernel_dcache_page fixes and removal Linus Torvalds 2021-07-12 19:24 ` Linus Torvalds 2021-07-12 19:24 ` Linus Torvalds 2021-07-13 5:46 ` Christoph Hellwig 2021-07-13 5:46 ` Christoph Hellwig 2021-07-13 8:46 ` Russell King (Oracle) 2021-07-13 8:46 ` Russell King (Oracle) 2021-07-13 9:11 ` Christoph Hellwig 2021-07-13 9:11 ` Christoph Hellwig 2021-07-19 5:38 ` Herbert Xu 2021-07-19 5:38 ` Herbert Xu 2021-07-19 15:42 ` Russell King (Oracle) 2021-07-19 15:42 ` Russell King (Oracle) 2021-07-14 3:13 ` Guo Ren 2021-07-14 3:13 ` Guo Ren 2021-07-14 3:13 ` Guo Ren
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