Re: [PATCH 4/8] xfs: pass a CIL context to xlog_write()

+	/*
+	 * If we have a CIL context, record the LSN of the iclog we were just
+	 * granted space to start writing into. If the context doesn't have
+	 * a start_lsn recorded, then this iclog will contain the start record
+	 * for the checkpoint. Otherwise this write contains the commit record
+	 * for the checkpoint.
+	 */
+	if (ctx) {
+		spin_lock(&ctx->cil->xc_push_lock);
+		if (!ctx->start_lsn)
+			ctx->start_lsn = be64_to_cpu(iclog->ic_header.h_lsn);
+		else
+			ctx->commit_lsn = be64_to_cpu(iclog->ic_header.h_lsn);
+		spin_unlock(&ctx->cil->xc_push_lock);
+	}

I have to say that having this cil_ctx specific logic that somehow
reverse eingeer what the callers is doing here seems pretty awkware.
To me the logical interface would be to pass a function pointer and
private data except for the performance penalty of indirect calls.

But to make this somewhat bearable I think you should start with the
above block as a helper implemented in xfs_log_cil.c.