iov_iter.c: iterate_and_advance (7ce2a91e) · Commits · 戴 / test

mm/iov_iter.c

+28 −76

Original line number	Diff line number	Diff line
		@@ -70,6 +70,33 @@
		} \
		}

		#define iterate_and_advance(i, n, v, I, B) { \
		size_t skip = i->iov_offset; \
		if (unlikely(i->type & ITER_BVEC)) { \
		const struct bio_vec *bvec; \
		struct bio_vec v; \
		iterate_bvec(i, n, v, bvec, skip, (B)) \
		if (skip == bvec->bv_len) { \
		bvec++; \
		skip = 0; \
		} \
		i->nr_segs -= bvec - i->bvec; \
		i->bvec = bvec; \
		} else { \
		const struct iovec *iov; \
		struct iovec v; \
		iterate_iovec(i, n, v, iov, skip, (I)) \
		if (skip == iov->iov_len) { \
		iov++; \
		skip = 0; \
		} \
		i->nr_segs -= iov - i->iov; \
		i->iov = iov; \
		} \
		i->count -= n; \
		i->iov_offset = skip; \
		}

		static size_t copy_to_iter_iovec(void from, size_t bytes, struct iov_iter i)
		{
		size_t skip, copy, left, wanted;
		@@ -366,42 +393,6 @@ static size_t zero_iovec(size_t bytes, struct iov_iter *i)
		return wanted - bytes;
		}

		static void advance_iovec(struct iov_iter *i, size_t bytes)
		{
		BUG_ON(i->count < bytes);

		if (likely(i->nr_segs == 1)) {
		i->iov_offset += bytes;
		i->count -= bytes;
		} else {
		const struct iovec *iov = i->iov;
		size_t base = i->iov_offset;
		unsigned long nr_segs = i->nr_segs;

		/*
		* The !iov->iov_len check ensures we skip over unlikely
		* zero-length segments (without overruning the iovec).
		*/
		while (bytes \|\| unlikely(i->count && !iov->iov_len)) {
		int copy;

		copy = min(bytes, iov->iov_len - base);
		BUG_ON(!i->count \|\| i->count < copy);
		i->count -= copy;
		bytes -= copy;
		base += copy;
		if (iov->iov_len == base) {
		iov++;
		nr_segs--;
		base = 0;
		}
		}
		i->iov = iov;
		i->iov_offset = base;
		i->nr_segs = nr_segs;
		}
		}

		/*
		* Fault in the first iovec of the given iov_iter, to a maximum length
		* of bytes. Returns 0 on success, or non-zero if the memory could not be
		@@ -685,42 +676,6 @@ static size_t zero_bvec(size_t bytes, struct iov_iter *i)
		return wanted - bytes;
		}

		static void advance_bvec(struct iov_iter *i, size_t bytes)
		{
		BUG_ON(i->count < bytes);

		if (likely(i->nr_segs == 1)) {
		i->iov_offset += bytes;
		i->count -= bytes;
		} else {
		const struct bio_vec *bvec = i->bvec;
		size_t base = i->iov_offset;
		unsigned long nr_segs = i->nr_segs;

		/*
		* The !iov->iov_len check ensures we skip over unlikely
		* zero-length segments (without overruning the iovec).
		*/
		while (bytes \|\| unlikely(i->count && !bvec->bv_len)) {
		int copy;

		copy = min(bytes, bvec->bv_len - base);
		BUG_ON(!i->count \|\| i->count < copy);
		i->count -= copy;
		bytes -= copy;
		base += copy;
		if (bvec->bv_len == base) {
		bvec++;
		nr_segs--;
		base = 0;
		}
		}
		i->bvec = bvec;
		i->iov_offset = base;
		i->nr_segs = nr_segs;
		}
		}

		static ssize_t get_pages_bvec(struct iov_iter *i,
		struct page **pages, size_t maxsize, unsigned maxpages,
		size_t *start)
		@@ -849,10 +804,7 @@ EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);

		void iov_iter_advance(struct iov_iter *i, size_t size)
		{
		if (i->type & ITER_BVEC)
		advance_bvec(i, size);
		else
		advance_iovec(i, size);
		iterate_and_advance(i, size, v, 0, 0)
		}
		EXPORT_SYMBOL(iov_iter_advance);

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