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Commit 1877e1a7 authored by Zach Brown's avatar Zach Brown Committed by Chris Mason
Browse files

btrfs: remove move_pages() 



move_pages() has an inefficient backwards byte copy of regions of two
different pages.  They're different pages so the regions won't overlap
and it could use memcpy().

At that point, though, move_pages() would be a slightly dimmer
re-implementation of copy_pages() that lacked the test for overlapping
page regions.

So remove move_pages() and just call copy_pages().

Signed-off-by: default avatarZach Brown <zab@redhat.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent 4546bcae

fs/btrfs/extent_io.c

+1 −18
Original line number Diff line number Diff line
@@ -5082,23 +5082,6 @@ void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src, 
	}

}



static void move_pages(struct page *dst_page, struct page *src_page,

		       unsigned long dst_off, unsigned long src_off,

		       unsigned long len)

{

	char *dst_kaddr = page_address(dst_page);

	if (dst_page == src_page) {

		memmove(dst_kaddr + dst_off, dst_kaddr + src_off, len);

	} else {

		char *src_kaddr = page_address(src_page);

		char *p = dst_kaddr + dst_off + len;

		char *s = src_kaddr + src_off + len;



		while (len--)

			*--p = *--s;

	}

}



static inline bool areas_overlap(unsigned long src, unsigned long dst, unsigned long len)

{

	unsigned long distance = (src > dst) ? src - dst : dst - src;
@@ -5209,7 +5192,7 @@ void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset, 


		cur = min_t(unsigned long, len, src_off_in_page + 1);

		cur = min(cur, dst_off_in_page + 1);

		move_pages(extent_buffer_page(dst, dst_i),

		copy_pages(extent_buffer_page(dst, dst_i),

			   extent_buffer_page(dst, src_i),

			   dst_off_in_page - cur + 1,

			   src_off_in_page - cur + 1, cur);