[XFS] Allow xfsbufd flush intervals to take immediate effect after changing...

[XFS] Allow xfsbufd flush intervals to take immediate effect after changing the flush sysctl value.  Fix from Bart Samwel.

SGI Modid: xfs-linux:xfs-kern:170053a

fs/xfs/linux/xfs_buf.c

@@ -1535,7 +1535,7 @@ pagebuf_delwri_queue(
 	}
 
 	list_add_tail(&pb->pb_list, &pbd_delwrite_queue);
-	pb->pb_flushtime = jiffies + xfs_age_buffer;
+	pb->pb_queuetime = jiffies;
 	spin_unlock(&pbd_delwrite_lock);
 
 	if (unlock)
@@ -1605,7 +1605,9 @@ pagebuf_daemon(
 
 			if (!pagebuf_ispin(pb) && !pagebuf_cond_lock(pb)) {
 				if (!force_flush &&
-				    time_before(jiffies, pb->pb_flushtime)) {
+				    time_before(jiffies,
+						pb->pb_queuetime +
+						xfs_age_buffer)) {
 					pagebuf_unlock(pb);
 					break;
 				}

fs/xfs/linux/xfs_buf.h

@@ -135,7 +135,7 @@ typedef int (*page_buf_bdstrat_t)(struct xfs_buf *);
 
 typedef struct xfs_buf {
 	struct semaphore	pb_sema;	/* semaphore for lockables  */
-	unsigned long		pb_flushtime;	/* time to flush pagebuf    */
+	unsigned long		pb_queuetime;	/* time buffer was queued   */
 	atomic_t		pb_pin_count;	/* pin count		    */
 	wait_queue_head_t	pb_waiters;	/* unpin waiters	    */
 	struct list_head	pb_list;