Re: [RFC v11][PATCH 03/13] General infrastructure for checkpoint restart

Oren Laadan wrote:

+/*
+ * Helpers to write(read) from(to) kernel space to(from) the checkpoint
+ * image file descriptor (similar to how a core-dump is performed).
+ *
+ *   cr_kwrite() - write a kernel-space buffer to the checkpoint image
+ *   cr_kread() - read from the checkpoint image to a kernel-space buffer
+ */
+
+int cr_kwrite(struct cr_ctx *ctx, void *addr, int count)
+{
+	struct file *file = ctx->file;
+	mm_segment_t fs;
+	ssize_t nwrite;
+	int nleft;
+
+	fs = get_fs();
+	set_fs(KERNEL_DS);
+	for (nleft = count; nleft; nleft -= nwrite) {
+		nwrite = file->f_op->write(file, addr, nleft, &file->f_pos);
+		if (nwrite < 0) {
+			if (nwrite == -EAGAIN)
+				nwrite = 0;
+			else

set_fs(fs) here

+				return nwrite;
+		}
+		addr += nwrite;
+	}
+	set_fs(fs);
+	ctx->total += count;
+	return 0;
+}
+
+int cr_kread(struct cr_ctx *ctx, void *addr, int count)
+{
+	struct file *file = ctx->file;
+	mm_segment_t fs;
+	ssize_t nread;
+	int nleft;
+
+	fs = get_fs();
+	set_fs(KERNEL_DS);
+	for (nleft = count; nleft; nleft -= nread) {
+		nread = file->f_op->read(file, addr, nleft, &file->f_pos);
+		if (nread <= 0) {
+			if (nread == -EAGAIN) {
+				nread = 0;
+				continue;
+			} else if (nread == 0)
+				nread = -EPIPE;		/* unexecpted EOF */

set_fs(fs) here as well

+			return nread;
+		}
+		addr += nread;
+	}
+	set_fs(fs);
+	ctx->total += count;
+	return 0;
+}
+

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