From: Ira Weiny ira.weiny@intel.com
[ Upstream commit bb90d4bc7b6a536b2e4db45f4763e467c2008251 ]
Working through a conversion to a call kmap_local_page() instead of kmap() revealed many places where the pattern kmap/memcpy/kunmap occurred.
Eric Biggers, Matthew Wilcox, Christoph Hellwig, Dan Williams, and Al Viro all suggested putting this code into helper functions. Al Viro further pointed out that these functions already existed in the iov_iter code.[1]
Various locations for the lifted functions were considered.
Headers like mm.h or string.h seem ok but don't really portray the functionality well. pagemap.h made some sense but is for page cache functionality.[2]
Another alternative would be to create a new header for the promoted memcpy functions, but it masks the fact that these are designed to copy to/from pages using the kernel direct mappings and complicates matters with a new header.
Placing these functions in 'highmem.h' is suboptimal especially with the changes being proposed in the functionality of kmap. From a caller perspective including/using 'highmem.h' implies that the functions defined in that header are only required when highmem is in use which is increasingly not the case with modern processors. However, highmem.h is where all the current functions like this reside (zero_user(), clear_highpage(), clear_user_highpage(), copy_user_highpage(), and copy_highpage()). So it makes the most sense even though it is distasteful for some.[3]
Lift memcpy_to_page() and memcpy_from_page() to pagemap.h.
[1] https://lore.kernel.org/lkml/20201013200149.GI3576660@ZenIV.linux.org.uk/ https://lore.kernel.org/lkml/20201013112544.GA5249@infradead.org/
[2] https://lore.kernel.org/lkml/20201208122316.GH7338@casper.infradead.org/
[3] https://lore.kernel.org/lkml/20201013200149.GI3576660@ZenIV.linux.org.uk/#t https://lore.kernel.org/lkml/20201208163814.GN1563847@iweiny-DESK2.sc.intel....
Cc: Boris Pismenny borisp@mellanox.com Cc: Or Gerlitz gerlitz.or@gmail.com Cc: Dave Hansen dave.hansen@intel.com Suggested-by: Matthew Wilcox willy@infradead.org Suggested-by: Christoph Hellwig hch@infradead.org Suggested-by: Dan Williams dan.j.williams@intel.com Suggested-by: Al Viro viro@zeniv.linux.org.uk Suggested-by: Eric Biggers ebiggers@kernel.org Reviewed-by: Chaitanya Kulkarni chaitanya.kulkarni@wdc.com Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Ira Weiny ira.weiny@intel.com Signed-off-by: David Sterba dsterba@suse.com Stable-dep-of: 956510c0c743 ("fs: ext4: initialize fsdata in pagecache_write()") Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/highmem.h | 18 ++++++++++++++++++ lib/iov_iter.c | 14 -------------- 2 files changed, 18 insertions(+), 14 deletions(-)
diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 14e6202ce47f..b25df1f8d48d 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -345,4 +345,22 @@ static inline void copy_highpage(struct page *to, struct page *from)
#endif
+static inline void memcpy_from_page(char *to, struct page *page, + size_t offset, size_t len) +{ + char *from = kmap_atomic(page); + + memcpy(to, from + offset, len); + kunmap_atomic(from); +} + +static inline void memcpy_to_page(struct page *page, size_t offset, + const char *from, size_t len) +{ + char *to = kmap_atomic(page); + + memcpy(to + offset, from, len); + kunmap_atomic(to); +} + #endif /* _LINUX_HIGHMEM_H */ diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 650554964f18..6e30113303ba 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -467,20 +467,6 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction, } EXPORT_SYMBOL(iov_iter_init);
-static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len) -{ - char *from = kmap_atomic(page); - memcpy(to, from + offset, len); - kunmap_atomic(from); -} - -static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len) -{ - char *to = kmap_atomic(page); - memcpy(to + offset, from, len); - kunmap_atomic(to); -} - static void memzero_page(struct page *page, size_t offset, size_t len) { char *addr = kmap_atomic(page);