On Fri, Nov 27, 2020 at 03:06:24PM +0200, Joonas Lahtinen wrote: > Quoting ira.weiny@xxxxxxxxx (2020-11-24 08:07:39) > > From: Ira Weiny <ira.weiny@xxxxxxxxx> > > > > Working through a conversion to a call such as kmap_thread() 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] > > > > 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. Some headers like > > mm.h or string.h seem ok but don't really portray the functionality > > well. 'pagemap.h', on the other hand, makes sense and is already > > included in many of the places we want to convert. > > > > 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. > > > > Lift memcpy_to_page(), memcpy_from_page(), and memzero_page() to > > pagemap.h. > > > > Also, add a memcpy_page(), memmove_page, and memset_page() to cover more > > kmap/mem*/kunmap. patterns. > > > > [1] https://lore.kernel.org/lkml/20201013200149.GI3576660@xxxxxxxxxxxxxxxxxx/ > > https://lore.kernel.org/lkml/20201013112544.GA5249@xxxxxxxxxxxxx/ > > > > Cc: Dave Hansen <dave.hansen@xxxxxxxxx> > > Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> > > Suggested-by: Christoph Hellwig <hch@xxxxxxxxxxxxx> > > Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx> > > Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > > Suggested-by: Eric Biggers <ebiggers@xxxxxxxxxx> > > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> > > <SNIP> > > > +static inline void memset_page(struct page *page, int val, size_t offset, size_t len) > > +{ > > + char *addr = kmap_atomic(page); > > + memset(addr + offset, val, len); > > + kunmap_atomic(addr); > > +} > > Other functions have (page, offset) pair. Insertion of 'val' in the middle here required > to take a double look during review. Let's be explicit here. Your suggested order is: (page, offset, val, len) right? I think I would prefer that to (page, val, offset, len).
