1 files changed, 158 insertions, 77 deletions

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 4c5deb6e9e31..92f1f2acc6ab 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -44,12 +44,7 @@
 
 static kmem_zone_t *xfs_buf_zone;
 STATIC int xfsbufd(void *);
-STATIC int xfsbufd_wakeup(struct shrinker *, int, gfp_t);
 STATIC void xfs_buf_delwri_queue(xfs_buf_t *, int);
-static struct shrinker xfs_buf_shake = {
-        .shrink = xfsbufd_wakeup,
-        .seeks = DEFAULT_SEEKS,
-};
 
 static struct workqueue_struct *xfslogd_workqueue;
 struct workqueue_struct *xfsdatad_workqueue;
@@ -168,8 +163,79 @@ test_page_region(
 }
 
 /*
- *      Internal xfs_buf_t object manipulation
+ * xfs_buf_lru_add - add a buffer to the LRU.
+ *
+ * The LRU takes a new reference to the buffer so that it will only be freed
+ * once the shrinker takes the buffer off the LRU.
  */
+STATIC void
+xfs_buf_lru_add(
+        struct xfs_buf  *bp)
+{
+        struct xfs_buftarg *btp = bp->b_target;
+
+        spin_lock(&btp->bt_lru_lock);
+        if (list_empty(&bp->b_lru)) {
+                atomic_inc(&bp->b_hold);
+                list_add_tail(&bp->b_lru, &btp->bt_lru);
+                btp->bt_lru_nr++;
+        }
+        spin_unlock(&btp->bt_lru_lock);
+}
+
+/*
+ * xfs_buf_lru_del - remove a buffer from the LRU
+ *
+ * The unlocked check is safe here because it only occurs when there are not
+ * b_lru_ref counts left on the inode under the pag->pag_buf_lock. it is there
+ * to optimise the shrinker removing the buffer from the LRU and calling
+ * xfs_buf_free(). i.e. it removes an unneccessary round trip on the
+ * bt_lru_lock.
+ */
+STATIC void
+xfs_buf_lru_del(
+        struct xfs_buf  *bp)
+{
+        struct xfs_buftarg *btp = bp->b_target;
+
+        if (list_empty(&bp->b_lru))
+                return;
+
+        spin_lock(&btp->bt_lru_lock);
+        if (!list_empty(&bp->b_lru)) {
+                list_del_init(&bp->b_lru);
+                btp->bt_lru_nr--;
+        }
+        spin_unlock(&btp->bt_lru_lock);
+}
+
+/*
+ * When we mark a buffer stale, we remove the buffer from the LRU and clear the
+ * b_lru_ref count so that the buffer is freed immediately when the buffer
+ * reference count falls to zero. If the buffer is already on the LRU, we need
+ * to remove the reference that LRU holds on the buffer.
+ *
+ * This prevents build-up of stale buffers on the LRU.
+ */
+void
+xfs_buf_stale(
+        struct xfs_buf  *bp)
+{
+        bp->b_flags |= XBF_STALE;
+        atomic_set(&(bp)->b_lru_ref, 0);
+        if (!list_empty(&bp->b_lru)) {
+                struct xfs_buftarg *btp = bp->b_target;
+
+                spin_lock(&btp->bt_lru_lock);
+                if (!list_empty(&bp->b_lru)) {
+                        list_del_init(&bp->b_lru);
+                        btp->bt_lru_nr--;
+                        atomic_dec(&bp->b_hold);
+                }
+                spin_unlock(&btp->bt_lru_lock);
+        }
+        ASSERT(atomic_read(&bp->b_hold) >= 1);
+}
 
 STATIC void
 _xfs_buf_initialize(
@@ -186,7 +252,9 @@ _xfs_buf_initialize(
 
         memset(bp, 0, sizeof(xfs_buf_t));
         atomic_set(&bp->b_hold, 1);
+        atomic_set(&bp->b_lru_ref, 1);
         init_completion(&bp->b_iowait);
+        INIT_LIST_HEAD(&bp->b_lru);
         INIT_LIST_HEAD(&bp->b_list);
         RB_CLEAR_NODE(&bp->b_rbnode);
         sema_init(&bp->b_sema, 0); /* held, no waiters */
@@ -262,6 +330,8 @@ xfs_buf_free(
 {
         trace_xfs_buf_free(bp, _RET_IP_);
 
+        ASSERT(list_empty(&bp->b_lru));
+
         if (bp->b_flags & (_XBF_PAGE_CACHE|_XBF_PAGES)) {
                 uint            i;
 
@@ -337,7 +407,6 @@ _xfs_buf_lookup_pages(
                                         __func__, gfp_mask);
 
                         XFS_STATS_INC(xb_page_retries);
-                        xfsbufd_wakeup(NULL, 0, gfp_mask);
                         congestion_wait(BLK_RW_ASYNC, HZ/50);
                         goto retry;
                 }
@@ -828,6 +897,7 @@ xfs_buf_rele(
 
         if (!pag) {
                 ASSERT(!bp->b_relse);
+                ASSERT(list_empty(&bp->b_lru));
                 ASSERT(RB_EMPTY_NODE(&bp->b_rbnode));
                 if (atomic_dec_and_test(&bp->b_hold))
                         xfs_buf_free(bp);
@@ -835,13 +905,19 @@ xfs_buf_rele(
         }
 
         ASSERT(!RB_EMPTY_NODE(&bp->b_rbnode));
+
         ASSERT(atomic_read(&bp->b_hold) > 0);
         if (atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock)) {
                 if (bp->b_relse) {
                         atomic_inc(&bp->b_hold);
                         spin_unlock(&pag->pag_buf_lock);
                         bp->b_relse(bp);
+                } else if (!(bp->b_flags & XBF_STALE) &&
+                           atomic_read(&bp->b_lru_ref)) {
+                        xfs_buf_lru_add(bp);
+                        spin_unlock(&pag->pag_buf_lock);
                 } else {
+                        xfs_buf_lru_del(bp);
                         ASSERT(!(bp->b_flags & (XBF_DELWRI|_XBF_DELWRI_Q)));
                         rb_erase(&bp->b_rbnode, &pag->pag_buf_tree);
                         spin_unlock(&pag->pag_buf_lock);
@@ -1438,51 +1514,84 @@ xfs_buf_iomove(
  */
 
 /*
- *      Wait for any bufs with callbacks that have been submitted but
- *      have not yet returned... walk the hash list for the target.
+ * Wait for any bufs with callbacks that have been submitted but have not yet
+ * returned. These buffers will have an elevated hold count, so wait on those
+ * while freeing all the buffers only held by the LRU.
  */
 void
 xfs_wait_buftarg(
         struct xfs_buftarg      *btp)
 {
-        struct xfs_perag        *pag;
-        uint                    i;
+        struct xfs_buf          *bp;
 
-        for (i = 0; i < btp->bt_mount->m_sb.sb_agcount; i++) {
-                pag = xfs_perag_get(btp->bt_mount, i);
-                spin_lock(&pag->pag_buf_lock);
-                while (rb_first(&pag->pag_buf_tree)) {
-                        spin_unlock(&pag->pag_buf_lock);
+restart:
+        spin_lock(&btp->bt_lru_lock);
+        while (!list_empty(&btp->bt_lru)) {
+                bp = list_first_entry(&btp->bt_lru, struct xfs_buf, b_lru);
+                if (atomic_read(&bp->b_hold) > 1) {
+                        spin_unlock(&btp->bt_lru_lock);
                         delay(100);
-                        spin_lock(&pag->pag_buf_lock);
+                        goto restart;
                 }
-                spin_unlock(&pag->pag_buf_lock);
-                xfs_perag_put(pag);
+                /*
+                 * clear the LRU reference count so the bufer doesn't get
+                 * ignored in xfs_buf_rele().
+                 */
+                atomic_set(&bp->b_lru_ref, 0);
+                spin_unlock(&btp->bt_lru_lock);
+                xfs_buf_rele(bp);
+                spin_lock(&btp->bt_lru_lock);
         }
+        spin_unlock(&btp->bt_lru_lock);
 }
 
-/*
- *      buftarg list for delwrite queue processing
- */
-static LIST_HEAD(xfs_buftarg_list);
-static DEFINE_SPINLOCK(xfs_buftarg_lock);
-
-STATIC void
-xfs_register_buftarg(
-        xfs_buftarg_t           *btp)
+int
+xfs_buftarg_shrink(
+        struct shrinker         *shrink,
+        int                     nr_to_scan,
+        gfp_t                   mask)
 {
-        spin_lock(&xfs_buftarg_lock);
-        list_add(&btp->bt_list, &xfs_buftarg_list);
-        spin_unlock(&xfs_buftarg_lock);
-}
+        struct xfs_buftarg      *btp = container_of(shrink,
+                                        struct xfs_buftarg, bt_shrinker);
+        struct xfs_buf          *bp;
+        LIST_HEAD(dispose);
 
-STATIC void
-xfs_unregister_buftarg(
-        xfs_buftarg_t           *btp)
-{
-        spin_lock(&xfs_buftarg_lock);
-        list_del(&btp->bt_list);
-        spin_unlock(&xfs_buftarg_lock);
+        if (!nr_to_scan)
+                return btp->bt_lru_nr;
+
+        spin_lock(&btp->bt_lru_lock);
+        while (!list_empty(&btp->bt_lru)) {
+                if (nr_to_scan-- <= 0)
+                        break;
+
+                bp = list_first_entry(&btp->bt_lru, struct xfs_buf, b_lru);
+
+                /*
+                 * Decrement the b_lru_ref count unless the value is already
+                 * zero. If the value is already zero, we need to reclaim the
+                 * buffer, otherwise it gets another trip through the LRU.
+                 */
+                if (!atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
+                        list_move_tail(&bp->b_lru, &btp->bt_lru);
+                        continue;
+                }
+
+                /*
+                 * remove the buffer from the LRU now to avoid needing another
+                 * lock round trip inside xfs_buf_rele().
+                 */
+                list_move(&bp->b_lru, &dispose);
+                btp->bt_lru_nr--;
+        }
+        spin_unlock(&btp->bt_lru_lock);
+
+        while (!list_empty(&dispose)) {
+                bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
+                list_del_init(&bp->b_lru);
+                xfs_buf_rele(bp);
+        }
+
+        return btp->bt_lru_nr;
 }
 
 void
@@ -1490,17 +1599,14 @@ xfs_free_buftarg(
         struct xfs_mount        *mp,
         struct xfs_buftarg      *btp)
 {
+        unregister_shrinker(&btp->bt_shrinker);
+
         xfs_flush_buftarg(btp, 1);
         if (mp->m_flags & XFS_MOUNT_BARRIER)
                 xfs_blkdev_issue_flush(btp);
         iput(btp->bt_mapping->host);
 
-        /* Unregister the buftarg first so that we don't get a
-         * wakeup finding a non-existent task
-         */
-        xfs_unregister_buftarg(btp);
         kthread_stop(btp->bt_task);
-
         kmem_free(btp);
 }
 
@@ -1597,20 +1703,13 @@ xfs_alloc_delwrite_queue(
         xfs_buftarg_t           *btp,
         const char              *fsname)
 {
-        int     error = 0;
-
-        INIT_LIST_HEAD(&btp->bt_list);
         INIT_LIST_HEAD(&btp->bt_delwrite_queue);
         spin_lock_init(&btp->bt_delwrite_lock);
         btp->bt_flags = 0;
         btp->bt_task = kthread_run(xfsbufd, btp, "xfsbufd/%s", fsname);
-        if (IS_ERR(btp->bt_task)) {
-                error = PTR_ERR(btp->bt_task);
-                goto out_error;
-        }
-        xfs_register_buftarg(btp);
-out_error:
-        return error;
+        if (IS_ERR(btp->bt_task))
+                return PTR_ERR(btp->bt_task);
+        return 0;
 }
 
 xfs_buftarg_t *
@@ -1627,12 +1726,17 @@ xfs_alloc_buftarg(
         btp->bt_mount = mp;
         btp->bt_dev =  bdev->bd_dev;
         btp->bt_bdev = bdev;
+        INIT_LIST_HEAD(&btp->bt_lru);
+        spin_lock_init(&btp->bt_lru_lock);
         if (xfs_setsize_buftarg_early(btp, bdev))
                 goto error;
         if (xfs_mapping_buftarg(btp, bdev))
                 goto error;
         if (xfs_alloc_delwrite_queue(btp, fsname))
                 goto error;
+        btp->bt_shrinker.shrink = xfs_buftarg_shrink;
+        btp->bt_shrinker.seeks = DEFAULT_SEEKS;
+        register_shrinker(&btp->bt_shrinker);
         return btp;
 
 error:
@@ -1737,27 +1841,6 @@ xfs_buf_runall_queues(
         flush_workqueue(queue);
 }
 
-STATIC int
-xfsbufd_wakeup(
-        struct shrinker         *shrink,
-        int                     priority,
-        gfp_t                   mask)
-{
-        xfs_buftarg_t           *btp;
-
-        spin_lock(&xfs_buftarg_lock);
-        list_for_each_entry(btp, &xfs_buftarg_list, bt_list) {
-                if (test_bit(XBT_FORCE_SLEEP, &btp->bt_flags))
-                        continue;
-                if (list_empty(&btp->bt_delwrite_queue))
-                        continue;
-                set_bit(XBT_FORCE_FLUSH, &btp->bt_flags);
-                wake_up_process(btp->bt_task);
-        }
-        spin_unlock(&xfs_buftarg_lock);
-        return 0;
-}
-
 /*
  * Move as many buffers as specified to the supplied list
  * idicating if we skipped any buffers to prevent deadlocks.
@@ -1952,7 +2035,6 @@ xfs_buf_init(void)
         if (!xfsconvertd_workqueue)
                 goto out_destroy_xfsdatad_workqueue;
 
-        register_shrinker(&xfs_buf_shake);
         return 0;
 
  out_destroy_xfsdatad_workqueue:
@@ -1968,7 +2050,6 @@ xfs_buf_init(void)
 void
 xfs_buf_terminate(void)
 {
-        unregister_shrinker(&xfs_buf_shake);
         destroy_workqueue(xfsconvertd_workqueue);
         destroy_workqueue(xfsdatad_workqueue);
         destroy_workqueue(xfslogd_workqueue);