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To skip copies when SKB data already resides in the destination buffer we check if (src == dst), and skip the copy when it's true. Signed-off-by: Ben Ben-Ishay Signed-off-by: Boris Pismenny Signed-off-by: Or Gerlitz Signed-off-by: Yoray Zack Signed-off-by: Shai Malin Signed-off-by: Aurelien Aptel Reviewed-by: Chaitanya Kulkarni --- lib/iov_iter.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index b667b1e2f688..1c9b10e1e1c8 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -313,9 +313,15 @@ size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i) return 0; if (user_backed_iter(i)) might_fault(); + /* + * When using direct data placement (DDP) the hardware writes + * data directly to the destination buffer, and constructs + * IOVs such that they point to this data. + * Thus, when the src == dst we skip the memcpy. + */ iterate_and_advance(i, bytes, base, len, off, copyout(base, addr + off, len), - memcpy(base, addr + off, len) + (base != addr + off) && memcpy(base, addr + off, len) ) return bytes; -- 2.34.1