+ mmc-jz4740-remove-the-flush_kernel_dcache_page-call-in-jz4740_mmc_read_data.patch added to -mm tree

+ mmc-jz4740-remove-the-flush_kernel_dcache_page-call-in-jz4740_mmc_read_data.patch added to -mm tree

[akpm]

The patch titled
     Subject: mmc: JZ4740: remove the flush_kernel_dcache_page call in jz4740_mmc_read_data
has been added to the -mm tree.  Its filename is
     mmc-jz4740-remove-the-flush_kernel_dcache_page-call-in-jz4740_mmc_read_data.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mmc-jz4740-remove-the-flush_kernel_dcache_page-call-in-jz4740_mmc_read_data.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mmc-jz4740-remove-the-flush_kernel_dcache_page-call-in-jz4740_mmc_read_data.patch

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------------------------------------------------------
From: Christoph Hellwig <hch@lst.de>
Subject: mmc: JZ4740: remove the flush_kernel_dcache_page call in jz4740_mmc_read_data

Patch series "_kernel_dcache_page fixes and removal".

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.


This patch (of 6):

MIPS now implements flush_kernel_dcache_page (as an alias to
flush_dcache_page).

Link: https://lkml.kernel.org/r/20210712060928.4161649-1-hch@lst.de
Link: https://lkml.kernel.org/r/20210712060928.4161649-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Guo Ren <guoren@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Yoshinori Sato <ysato@users.osdn.me>
Cc: Rich Felker <dalias@libc.org>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Paul Cercueil <paul@crapouillou.net>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Alex Shi <alexs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/mmc/host/jz4740_mmc.c |    4 ----
 1 file changed, 4 deletions(-)

--- a/drivers/mmc/host/jz4740_mmc.c~mmc-jz4740-remove-the-flush_kernel_dcache_page-call-in-jz4740_mmc_read_data
+++ a/drivers/mmc/host/jz4740_mmc.c
@@ -578,10 +578,6 @@ static bool jz4740_mmc_read_data(struct
 			}
 		}
 		data->bytes_xfered += miter->length;
-
-		/* This can go away once MIPS implements
-		 * flush_kernel_dcache_page */
-		flush_dcache_page(miter->page);
 	}
 	sg_miter_stop(miter);
 
_

Patches currently in -mm which might be from hch@lst.de are

mm-fix-the-try_to_unmap-prototype-for-config_mmu.patch
mm-call-flush_dcache_page-in-memcpy_to_page-and-memzero_page.patch
mm-use-kmap_local_page-in-memzero_page.patch
mmc-jz4740-remove-the-flush_kernel_dcache_page-call-in-jz4740_mmc_read_data.patch
mmc-mmc_spi-replace-flush_kernel_dcache_page-with-flush_dcache_page.patch
ps3disk-replace-flush_kernel_dcache_page-with-flush_dcache_page.patch
scatterlist-replace-flush_kernel_dcache_page-with-flush_dcache_page.patch
aacraid-remove-an-unused-include.patch
mm-remove-flush_kernel_dcache_page.patch