Re: [PATCH 1/6] nfs: "open code" the NFS direct write rescheduler

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Andrew Morton wrote:
Chuck Lever <[email protected]> wrote:
+	 * Prevent I/O completion while we're still rescheduling
+	 */
+	dreq->outstanding++;
+

No locking.

 	dreq->count = 0;
+	list_for_each(pos, &dreq->rewrite_list) {
+		struct nfs_write_data *data =
+			list_entry(dreq->rewrite_list.next, struct nfs_write_data, pages);
+
+		spin_lock(&dreq->lock);
+		dreq->outstanding++;
+		spin_unlock(&dreq->lock);

Locking.

Deliberate?

Yes. At the top of the loop, there is no outstanding I/O, so no locking is needed while updating "outstanding." Inside the loop, we've dispatched some I/O against "dreq" so locking is needed to ensure outstanding is updated properly.

--
corporate:	cel at netapp dot com
personal:	chucklever at bigfoot dot com
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