From 79c62de859f7e854399efb84a2f04ceeb1c13cc9 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 2 Sep 2021 14:56:26 -0700 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 Acked-by: Linus Torvalds Cc: "James E.J. Bottomley" Cc: Russell King Cc: Guo Ren Cc: Thomas Bogendoerfer Cc: Nick Hu Cc: Greentime Hu Cc: Vincent Chen Cc: Helge Deller Cc: Yoshinori Sato Cc: Rich Felker Cc: Geoff Levand Cc: Paul Cercueil Cc: Ulf Hansson Cc: Alex Shi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/mmc/host/jz4740_mmc.c | 4 ---- 1 file changed, 4 deletions(-) (limited to 'drivers/mmc') diff --git a/drivers/mmc/host/jz4740_mmc.c b/drivers/mmc/host/jz4740_mmc.c index cb1a64a5c256..80a2c270d502 100644 --- a/drivers/mmc/host/jz4740_mmc.c +++ b/drivers/mmc/host/jz4740_mmc.c @@ -578,10 +578,6 @@ static bool jz4740_mmc_read_data(struct jz4740_mmc_host *host, } } 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); -- cgit v1.2.3-59-g8ed1b