1 files changed, 219 insertions, 143 deletions

diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index 1f77c00af566..2d47f10f8bed 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
+ * Copyright (c) 2008 Dave Chinner
  * All Rights Reserved.
  *
  * This program is free software; you can redistribute it and/or
@@ -28,13 +29,13 @@
 #include "xfs_trans_priv.h"
 #include "xfs_error.h"
 
-STATIC void xfs_ail_insert(xfs_ail_t *, xfs_log_item_t *);
-STATIC xfs_log_item_t * xfs_ail_delete(xfs_ail_t *, xfs_log_item_t *);
-STATIC xfs_log_item_t * xfs_ail_min(xfs_ail_t *);
-STATIC xfs_log_item_t * xfs_ail_next(xfs_ail_t *, xfs_log_item_t *);
+STATIC void xfs_ail_insert(struct xfs_ail *, xfs_log_item_t *);
+STATIC xfs_log_item_t * xfs_ail_delete(struct xfs_ail *, xfs_log_item_t *);
+STATIC xfs_log_item_t * xfs_ail_min(struct xfs_ail *);
+STATIC xfs_log_item_t * xfs_ail_next(struct xfs_ail *, xfs_log_item_t *);
 
 #ifdef DEBUG
-STATIC void xfs_ail_check(xfs_ail_t *, xfs_log_item_t *);
+STATIC void xfs_ail_check(struct xfs_ail *, xfs_log_item_t *);
 #else
 #define xfs_ail_check(a,l)
 #endif /* DEBUG */
@@ -50,20 +51,20 @@ STATIC void xfs_ail_check(xfs_ail_t *, xfs_log_item_t *);
  * lsn of the last item in the AIL.
  */
 xfs_lsn_t
-xfs_trans_tail_ail(
-        xfs_mount_t     *mp)
+xfs_trans_ail_tail(
+        struct xfs_ail  *ailp)
 {
         xfs_lsn_t       lsn;
         xfs_log_item_t  *lip;
 
-        spin_lock(&mp->m_ail_lock);
-        lip = xfs_ail_min(&mp->m_ail);
+        spin_lock(&ailp->xa_lock);
+        lip = xfs_ail_min(ailp);
         if (lip == NULL) {
                 lsn = (xfs_lsn_t)0;
         } else {
                 lsn = lip->li_lsn;
         }
-        spin_unlock(&mp->m_ail_lock);
+        spin_unlock(&ailp->xa_lock);
 
         return lsn;
 }
@@ -85,16 +86,125 @@ xfs_trans_tail_ail(
  * any of the objects, so the lock is not needed.
  */
 void
-xfs_trans_push_ail(
-        xfs_mount_t             *mp,
-        xfs_lsn_t               threshold_lsn)
+xfs_trans_ail_push(
+        struct xfs_ail  *ailp,
+        xfs_lsn_t       threshold_lsn)
 {
-        xfs_log_item_t          *lip;
+        xfs_log_item_t  *lip;
+
+        lip = xfs_ail_min(ailp);
+        if (lip && !XFS_FORCED_SHUTDOWN(ailp->xa_mount)) {
+                if (XFS_LSN_CMP(threshold_lsn, ailp->xa_target) > 0)
+                        xfsaild_wakeup(ailp, threshold_lsn);
+        }
+}
+
+/*
+ * AIL traversal cursor initialisation.
+ *
+ * The cursor keeps track of where our current traversal is up
+ * to by tracking the next ƣtem in the list for us. However, for
+ * this to be safe, removing an object from the AIL needs to invalidate
+ * any cursor that points to it. hence the traversal cursor needs to
+ * be linked to the struct xfs_ail so that deletion can search all the
+ * active cursors for invalidation.
+ *
+ * We don't link the push cursor because it is embedded in the struct
+ * xfs_ail and hence easily findable.
+ */
+STATIC void
+xfs_trans_ail_cursor_init(
+        struct xfs_ail          *ailp,
+        struct xfs_ail_cursor   *cur)
+{
+        cur->item = NULL;
+        if (cur == &ailp->xa_cursors)
+                return;
+
+        cur->next = ailp->xa_cursors.next;
+        ailp->xa_cursors.next = cur;
+}
+
+/*
+ * Set the cursor to the next item, because when we look
+ * up the cursor the current item may have been freed.
+ */
+STATIC void
+xfs_trans_ail_cursor_set(
+        struct xfs_ail          *ailp,
+        struct xfs_ail_cursor   *cur,
+        struct xfs_log_item     *lip)
+{
+        if (lip)
+                cur->item = xfs_ail_next(ailp, lip);
+}
+
+/*
+ * Get the next item in the traversal and advance the cursor.
+ * If the cursor was invalidated (inidicated by a lip of 1),
+ * restart the traversal.
+ */
+struct xfs_log_item *
+xfs_trans_ail_cursor_next(
+        struct xfs_ail          *ailp,
+        struct xfs_ail_cursor   *cur)
+{
+        struct xfs_log_item     *lip = cur->item;
+
+        if ((__psint_t)lip & 1)
+                lip = xfs_ail_min(ailp);
+        xfs_trans_ail_cursor_set(ailp, cur, lip);
+        return lip;
+}
+
+/*
+ * Now that the traversal is complete, we need to remove the cursor
+ * from the list of traversing cursors. Avoid removing the embedded
+ * push cursor, but use the fact it is alway present to make the
+ * list deletion simple.
+ */
+void
+xfs_trans_ail_cursor_done(
+        struct xfs_ail          *ailp,
+        struct xfs_ail_cursor   *done)
+{
+        struct xfs_ail_cursor   *prev = NULL;
+        struct xfs_ail_cursor   *cur;
+
+        done->item = NULL;
+        if (done == &ailp->xa_cursors)
+                return;
+        prev = &ailp->xa_cursors;
+        for (cur = prev->next; cur; prev = cur, cur = prev->next) {
+                if (cur == done) {
+                        prev->next = cur->next;
+                        break;
+                }
+        }
+        ASSERT(cur);
+}
+
+/*
+ * Invalidate any cursor that is pointing to this item. This is
+ * called when an item is removed from the AIL. Any cursor pointing
+ * to this object is now invalid and the traversal needs to be
+ * terminated so it doesn't reference a freed object. We set the
+ * cursor item to a value of 1 so we can distinguish between an
+ * invalidation and the end of the list when getting the next item
+ * from the cursor.
+ */
+STATIC void
+xfs_trans_ail_cursor_clear(
+        struct xfs_ail          *ailp,
+        struct xfs_log_item     *lip)
+{
+        struct xfs_ail_cursor   *cur;
 
-        lip = xfs_ail_min(&mp->m_ail);
-        if (lip && !XFS_FORCED_SHUTDOWN(mp)) {
-                if (XFS_LSN_CMP(threshold_lsn, mp->m_ail.xa_target) > 0)
-                        xfsaild_wakeup(mp, threshold_lsn);
+        /* need to search all cursors */
+        for (cur = &ailp->xa_cursors; cur; cur = cur->next) {
+                if (cur->item == lip)
+                        cur->item = (struct xfs_log_item *)
+                                        ((__psint_t)cur->item | 1);
         }
 }
 
@@ -103,25 +213,27 @@ xfs_trans_push_ail(
  * Return the current tree generation number for use
  * in calls to xfs_trans_next_ail().
  */
-STATIC xfs_log_item_t *
-xfs_trans_first_push_ail(
-        xfs_mount_t     *mp,
-        int             *gen,
-        xfs_lsn_t       lsn)
+xfs_log_item_t *
+xfs_trans_ail_cursor_first(
+        struct xfs_ail          *ailp,
+        struct xfs_ail_cursor   *cur,
+        xfs_lsn_t               lsn)
 {
-        xfs_log_item_t  *lip;
+        xfs_log_item_t          *lip;
 
-        lip = xfs_ail_min(&mp->m_ail);
-        *gen = (int)mp->m_ail.xa_gen;
+        xfs_trans_ail_cursor_init(ailp, cur);
+        lip = xfs_ail_min(ailp);
         if (lsn == 0)
-                return lip;
+                goto out;
 
-        list_for_each_entry(lip, &mp->m_ail.xa_ail, li_ail) {
+        list_for_each_entry(lip, &ailp->xa_ail, li_ail) {
                 if (XFS_LSN_CMP(lip->li_lsn, lsn) >= 0)
-                        return lip;
+                        goto out;
         }
-
-        return NULL;
+        lip = NULL;
+out:
+        xfs_trans_ail_cursor_set(ailp, cur, lip);
+        return lip;
 }
 
 /*
@@ -129,29 +241,29 @@ xfs_trans_first_push_ail(
  */
 long
 xfsaild_push(
-        xfs_mount_t     *mp,
+        struct xfs_ail  *ailp,
         xfs_lsn_t       *last_lsn)
 {
         long            tout = 1000; /* milliseconds */
         xfs_lsn_t       last_pushed_lsn = *last_lsn;
-        xfs_lsn_t       target =  mp->m_ail.xa_target;
+        xfs_lsn_t       target =  ailp->xa_target;
         xfs_lsn_t       lsn;
         xfs_log_item_t  *lip;
-        int             gen;
-        int             restarts;
         int             flush_log, count, stuck;
+        xfs_mount_t     *mp = ailp->xa_mount;
+        struct xfs_ail_cursor   *cur = &ailp->xa_cursors;
 
-#define XFS_TRANS_PUSH_AIL_RESTARTS     10
-
-        spin_lock(&mp->m_ail_lock);
-        lip = xfs_trans_first_push_ail(mp, &gen, *last_lsn);
+        spin_lock(&ailp->xa_lock);
+        xfs_trans_ail_cursor_init(ailp, cur);
+        lip = xfs_trans_ail_cursor_first(ailp, cur, *last_lsn);
         if (!lip || XFS_FORCED_SHUTDOWN(mp)) {
                 /*
                  * AIL is empty or our push has reached the end.
                  */
-                spin_unlock(&mp->m_ail_lock);
+                xfs_trans_ail_cursor_done(ailp, cur);
+                spin_unlock(&ailp->xa_lock);
                 last_pushed_lsn = 0;
-                goto out;
+                return tout;
         }
 
         XFS_STATS_INC(xs_push_ail);
@@ -169,7 +281,7 @@ xfsaild_push(
          */
         tout = 10;
         lsn = lip->li_lsn;
-        flush_log = stuck = count = restarts = 0;
+        flush_log = stuck = count = 0;
         while ((XFS_LSN_CMP(lip->li_lsn, target) < 0)) {
                 int     lock_result;
                 /*
@@ -184,7 +296,7 @@ xfsaild_push(
                  * skip to the next item in the list.
                  */
                 lock_result = IOP_TRYLOCK(lip);
-                spin_unlock(&mp->m_ail_lock);
+                spin_unlock(&ailp->xa_lock);
                 switch (lock_result) {
                 case XFS_ITEM_SUCCESS:
                         XFS_STATS_INC(xs_push_ail_success);
@@ -221,7 +333,7 @@ xfsaild_push(
                         break;
                 }
 
-                spin_lock(&mp->m_ail_lock);
+                spin_lock(&ailp->xa_lock);
                 /* should we bother continuing? */
                 if (XFS_FORCED_SHUTDOWN(mp))
                         break;
@@ -244,14 +356,13 @@ xfsaild_push(
                 if (stuck > 100)
                         break;
 
-                lip = xfs_trans_next_ail(mp, lip, &gen, &restarts);
+                lip = xfs_trans_ail_cursor_next(ailp, cur);
                 if (lip == NULL)
                         break;
-                if (restarts > XFS_TRANS_PUSH_AIL_RESTARTS)
-                        break;
                 lsn = lip->li_lsn;
         }
-        spin_unlock(&mp->m_ail_lock);
+        xfs_trans_ail_cursor_done(ailp, cur);
+        spin_unlock(&ailp->xa_lock);
 
         if (flush_log) {
                 /*
@@ -274,8 +385,7 @@ xfsaild_push(
                  */
                 tout += 20;
                 last_pushed_lsn = 0;
-        } else if ((restarts > XFS_TRANS_PUSH_AIL_RESTARTS) ||
-                   ((stuck * 100) / count > 90)) {
+        } else if ((stuck * 100) / count > 90) {
                 /*
                  * Either there is a lot of contention on the AIL or we
                  * are stuck due to operations in progress. "Stuck" in this
@@ -287,7 +397,6 @@ xfsaild_push(
                  */
                 tout += 10;
         }
-out:
         *last_lsn = last_pushed_lsn;
         return tout;
 }       /* xfsaild_push */
@@ -303,7 +412,7 @@ out:
  */
 void
 xfs_trans_unlocked_item(
-        xfs_mount_t     *mp,
+        struct xfs_ail  *ailp,
         xfs_log_item_t  *lip)
 {
         xfs_log_item_t  *min_lip;
@@ -315,7 +424,7 @@ xfs_trans_unlocked_item(
          * over some potentially valid data.
          */
         if (!(lip->li_flags & XFS_LI_IN_AIL) ||
-            XFS_FORCED_SHUTDOWN(mp)) {
+            XFS_FORCED_SHUTDOWN(ailp->xa_mount)) {
                 return;
         }
 
@@ -331,10 +440,10 @@ xfs_trans_unlocked_item(
          * the call to xfs_log_move_tail() doesn't do anything if there's
          * not enough free space to wake people up so we're safe calling it.
          */
-        min_lip = xfs_ail_min(&mp->m_ail);
+        min_lip = xfs_ail_min(ailp);
 
         if (min_lip == lip)
-                xfs_log_move_tail(mp, 1);
+                xfs_log_move_tail(ailp->xa_mount, 1);
 }       /* xfs_trans_unlocked_item */
 
 
@@ -347,41 +456,37 @@ xfs_trans_unlocked_item(
  * we move in the AIL is the minimum one, update the tail lsn in the
  * log manager.
  *
- * Increment the AIL's generation count to indicate that the tree
- * has changed.
- *
  * This function must be called with the AIL lock held.  The lock
  * is dropped before returning.
  */
 void
-xfs_trans_update_ail(
-        xfs_mount_t     *mp,
+xfs_trans_ail_update(
+        struct xfs_ail  *ailp,
         xfs_log_item_t  *lip,
-        xfs_lsn_t       lsn) __releases(mp->m_ail_lock)
+        xfs_lsn_t       lsn) __releases(ailp->xa_lock)
 {
-        xfs_log_item_t          *dlip=NULL;
+        xfs_log_item_t          *dlip = NULL;
         xfs_log_item_t          *mlip;  /* ptr to minimum lip */
 
-        mlip = xfs_ail_min(&mp->m_ail);
+        mlip = xfs_ail_min(ailp);
 
         if (lip->li_flags & XFS_LI_IN_AIL) {
-                dlip = xfs_ail_delete(&mp->m_ail, lip);
+                dlip = xfs_ail_delete(ailp, lip);
                 ASSERT(dlip == lip);
+                xfs_trans_ail_cursor_clear(ailp, dlip);
         } else {
                 lip->li_flags |= XFS_LI_IN_AIL;
         }
 
         lip->li_lsn = lsn;
-
-        xfs_ail_insert(&mp->m_ail, lip);
-        mp->m_ail.xa_gen++;
+        xfs_ail_insert(ailp, lip);
 
         if (mlip == dlip) {
-                mlip = xfs_ail_min(&mp->m_ail);
-                spin_unlock(&mp->m_ail_lock);
-                xfs_log_move_tail(mp, mlip->li_lsn);
+                mlip = xfs_ail_min(ailp);
+                spin_unlock(&ailp->xa_lock);
+                xfs_log_move_tail(ailp->xa_mount, mlip->li_lsn);
         } else {
-                spin_unlock(&mp->m_ail_lock);
+                spin_unlock(&ailp->xa_lock);
         }
 
 
@@ -403,29 +508,30 @@ xfs_trans_update_ail(
  * is dropped before returning.
  */
 void
-xfs_trans_delete_ail(
-        xfs_mount_t     *mp,
-        xfs_log_item_t  *lip) __releases(mp->m_ail_lock)
+xfs_trans_ail_delete(
+        struct xfs_ail  *ailp,
+        xfs_log_item_t  *lip) __releases(ailp->xa_lock)
 {
         xfs_log_item_t          *dlip;
         xfs_log_item_t          *mlip;
 
         if (lip->li_flags & XFS_LI_IN_AIL) {
-                mlip = xfs_ail_min(&mp->m_ail);
-                dlip = xfs_ail_delete(&mp->m_ail, lip);
+                mlip = xfs_ail_min(ailp);
+                dlip = xfs_ail_delete(ailp, lip);
                 ASSERT(dlip == lip);
+                xfs_trans_ail_cursor_clear(ailp, dlip);
 
 
                 lip->li_flags &= ~XFS_LI_IN_AIL;
                 lip->li_lsn = 0;
-                mp->m_ail.xa_gen++;
 
                 if (mlip == dlip) {
-                        mlip = xfs_ail_min(&mp->m_ail);
-                        spin_unlock(&mp->m_ail_lock);
-                        xfs_log_move_tail(mp, (mlip ? mlip->li_lsn : 0));
+                        mlip = xfs_ail_min(ailp);
+                        spin_unlock(&ailp->xa_lock);
+                        xfs_log_move_tail(ailp->xa_mount,
+                                                (mlip ? mlip->li_lsn : 0));
                 } else {
-                        spin_unlock(&mp->m_ail_lock);
+                        spin_unlock(&ailp->xa_lock);
                 }
         }
         else {
@@ -433,13 +539,13 @@ xfs_trans_delete_ail(
                  * If the file system is not being shutdown, we are in
                  * serious trouble if we get to this stage.
                  */
-                if (XFS_FORCED_SHUTDOWN(mp))
-                        spin_unlock(&mp->m_ail_lock);
-                else {
+                struct xfs_mount        *mp = ailp->xa_mount;
+
+                spin_unlock(&ailp->xa_lock);
+                if (!XFS_FORCED_SHUTDOWN(mp)) {
                         xfs_cmn_err(XFS_PTAG_AILDELETE, CE_ALERT, mp,
                 "%s: attempting to delete a log item that is not in the AIL",
                                         __func__);
-                        spin_unlock(&mp->m_ail_lock);
                         xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
                 }
         }
@@ -448,56 +554,6 @@ xfs_trans_delete_ail(
 
 
 /*
- * Return the item in the AIL with the smallest lsn.
- * Return the current tree generation number for use
- * in calls to xfs_trans_next_ail().
- */
-xfs_log_item_t *
-xfs_trans_first_ail(
-        xfs_mount_t     *mp,
-        int             *gen)
-{
-        xfs_log_item_t  *lip;
-
-        lip = xfs_ail_min(&mp->m_ail);
-        *gen = (int)mp->m_ail.xa_gen;
-
-        return lip;
-}
-
-/*
- * If the generation count of the tree has not changed since the
- * caller last took something from the AIL, then return the elmt
- * in the tree which follows the one given.  If the count has changed,
- * then return the minimum elmt of the AIL and bump the restarts counter
- * if one is given.
- */
-xfs_log_item_t *
-xfs_trans_next_ail(
-        xfs_mount_t     *mp,
-        xfs_log_item_t  *lip,
-        int             *gen,
-        int             *restarts)
-{
-        xfs_log_item_t  *nlip;
-
-        ASSERT(mp && lip && gen);
-        if (mp->m_ail.xa_gen == *gen) {
-                nlip = xfs_ail_next(&mp->m_ail, lip);
-        } else {
-                nlip = xfs_ail_min(&mp->m_ail);
-                *gen = (int)mp->m_ail.xa_gen;
-                if (restarts != NULL) {
-                        XFS_STATS_INC(xs_push_ail_restarts);
-                        (*restarts)++;
-                }
-        }
-
-        return (nlip);
-}
-
-
-/*
  * The active item list (AIL) is a doubly linked list of log
  * items sorted by ascending lsn.  The base of the list is
  * a forw/back pointer pair embedded in the xfs mount structure.
@@ -515,15 +571,35 @@ int
 xfs_trans_ail_init(
         xfs_mount_t     *mp)
 {
-        INIT_LIST_HEAD(&mp->m_ail.xa_ail);
-        return xfsaild_start(mp);
+        struct xfs_ail  *ailp;
+        int             error;
+
+        ailp = kmem_zalloc(sizeof(struct xfs_ail), KM_MAYFAIL);
+        if (!ailp)
+                return ENOMEM;
+
+        ailp->xa_mount = mp;
+        INIT_LIST_HEAD(&ailp->xa_ail);
+        spin_lock_init(&ailp->xa_lock);
+        error = xfsaild_start(ailp);
+        if (error)
+                goto out_free_ailp;
+        mp->m_ail = ailp;
+        return 0;
+
+out_free_ailp:
+        kmem_free(ailp);
+        return error;
 }
 
 void
 xfs_trans_ail_destroy(
         xfs_mount_t     *mp)
 {
-        xfsaild_stop(mp);
+        struct xfs_ail  *ailp = mp->m_ail;
+
+        xfsaild_stop(ailp);
+        kmem_free(ailp);
 }
 
 /*
@@ -534,7 +610,7 @@ xfs_trans_ail_destroy(
  */
 STATIC void
 xfs_ail_insert(
-        xfs_ail_t       *ailp,
+        struct xfs_ail  *ailp,
         xfs_log_item_t  *lip)
 /* ARGSUSED */
 {
@@ -568,7 +644,7 @@ xfs_ail_insert(
 /*ARGSUSED*/
 STATIC xfs_log_item_t *
 xfs_ail_delete(
-        xfs_ail_t       *ailp,
+        struct xfs_ail  *ailp,
         xfs_log_item_t  *lip)
 /* ARGSUSED */
 {
@@ -585,7 +661,7 @@ xfs_ail_delete(
  */
 STATIC xfs_log_item_t *
 xfs_ail_min(
-        xfs_ail_t       *ailp)
+        struct xfs_ail  *ailp)
 /* ARGSUSED */
 {
         if (list_empty(&ailp->xa_ail))
@@ -601,7 +677,7 @@ xfs_ail_min(
  */
 STATIC xfs_log_item_t *
 xfs_ail_next(
-        xfs_ail_t       *ailp,
+        struct xfs_ail  *ailp,
         xfs_log_item_t  *lip)
 /* ARGSUSED */
 {
@@ -617,7 +693,7 @@ xfs_ail_next(
  */
 STATIC void
 xfs_ail_check(
-        xfs_ail_t       *ailp,
+        struct xfs_ail  *ailp,
         xfs_log_item_t  *lip)
 {
         xfs_log_item_t  *prev_lip;