From: Christoph Hellwig hch@lst.de Subject: mm: call flush_dcache_page() in memcpy_to_page() and memzero_page()

memcpy_to_page and memzero_page can write to arbitrary pages, which could be in the page cache or in high memory, so call flush_kernel_dcache_pages to flush the dcache.

This is a problem when using these helpers on dcache challeneged architectures. Right now there are just a few users, chances are no one used the PC floppy dr\u0456ver, the aha1542 driver for an ISA SCSI HBA, and a few advanced and optional btrfs and ext4 features on those platforms yet since the conversion.

Link: https://lkml.kernel.org/r/20210713055231.137602-2-hch@lst.de Fixes: bb90d4bc7b6a ("mm/highmem: Lift memcpy_[to|from]_page to core") Fixes: 28961998f858 ("iov_iter: lift memzero_page() to highmem.h") Signed-off-by: Christoph Hellwig hch@lst.de Reviewed-by: Ira Weiny ira.weiny@intel.com Cc: Chaitanya Kulkarni chaitanya.kulkarni@wdc.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

include/linux/highmem.h | 2 ++ 1 file changed, 2 insertions(+)

--- a/include/linux/highmem.h~mm-call-flush_dcache_page-in-memcpy_to_page-and-memzero_page +++ a/include/linux/highmem.h @@ -318,6 +318,7 @@ static inline void memcpy_to_page(struct

VM_BUG_ON(offset + len > PAGE_SIZE); memcpy(to + offset, from, len); + flush_dcache_page(page); kunmap_local(to); }

@@ -325,6 +326,7 @@ static inline void memzero_page(struct p { char *addr = kmap_atomic(page); memset(addr + offset, 0, len); + flush_dcache_page(page); kunmap_atomic(addr); }

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