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@@ -1396,8 +1396,9 @@ xfs_alloc_ag_vextent_small(
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if (error)
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goto error0;
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if (fbno != NULLAGBLOCK) {
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- if (xfs_alloc_busy_search(args->mp, args->agno, fbno, 1))
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- xfs_trans_set_sync(args->tp);
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+ xfs_alloc_busy_reuse(args->mp, args->agno, fbno, 1,
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+ args->userdata);
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+
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if (args->userdata) {
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xfs_buf_t *bp;
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@@ -2475,100 +2476,6 @@ error0:
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return error;
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}
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-
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-/*
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- * AG Busy list management
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- * The busy list contains block ranges that have been freed but whose
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- * transactions have not yet hit disk. If any block listed in a busy
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- * list is reused, the transaction that freed it must be forced to disk
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- * before continuing to use the block.
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- *
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- * xfs_alloc_busy_insert - add to the per-ag busy list
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- * xfs_alloc_busy_clear - remove an item from the per-ag busy list
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- * xfs_alloc_busy_search - search for a busy extent
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- */
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-
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-/*
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- * Insert a new extent into the busy tree.
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- *
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- * The busy extent tree is indexed by the start block of the busy extent.
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- * there can be multiple overlapping ranges in the busy extent tree but only
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- * ever one entry at a given start block. The reason for this is that
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- * multi-block extents can be freed, then smaller chunks of that extent
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- * allocated and freed again before the first transaction commit is on disk.
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- * If the exact same start block is freed a second time, we have to wait for
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- * that busy extent to pass out of the tree before the new extent is inserted.
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- * There are two main cases we have to handle here.
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- *
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- * The first case is a transaction that triggers a "free - allocate - free"
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- * cycle. This can occur during btree manipulations as a btree block is freed
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- * to the freelist, then allocated from the free list, then freed again. In
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- * this case, the second extxpnet free is what triggers the duplicate and as
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- * such the transaction IDs should match. Because the extent was allocated in
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- * this transaction, the transaction must be marked as synchronous. This is
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- * true for all cases where the free/alloc/free occurs in the one transaction,
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- * hence the addition of the ASSERT(tp->t_flags & XFS_TRANS_SYNC) to this case.
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- * This serves to catch violations of the second case quite effectively.
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- *
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- * The second case is where the free/alloc/free occur in different
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- * transactions. In this case, the thread freeing the extent the second time
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- * can't mark the extent busy immediately because it is already tracked in a
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- * transaction that may be committing. When the log commit for the existing
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- * busy extent completes, the busy extent will be removed from the tree. If we
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- * allow the second busy insert to continue using that busy extent structure,
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- * it can be freed before this transaction is safely in the log. Hence our
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- * only option in this case is to force the log to remove the existing busy
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- * extent from the list before we insert the new one with the current
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- * transaction ID.
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- *
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- * The problem we are trying to avoid in the free-alloc-free in separate
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- * transactions is most easily described with a timeline:
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- *
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- * Thread 1 Thread 2 Thread 3 xfslogd
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- * xact alloc
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- * free X
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- * mark busy
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- * commit xact
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- * free xact
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- * xact alloc
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- * alloc X
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- * busy search
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- * mark xact sync
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- * commit xact
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- * free xact
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- * force log
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- * checkpoint starts
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- * ....
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- * xact alloc
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- * free X
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- * mark busy
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- * finds match
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- * *** KABOOM! ***
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- * ....
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- * log IO completes
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- * unbusy X
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- * checkpoint completes
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- *
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- * By issuing a log force in thread 3 @ "KABOOM", the thread will block until
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- * the checkpoint completes, and the busy extent it matched will have been
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- * removed from the tree when it is woken. Hence it can then continue safely.
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- *
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- * However, to ensure this matching process is robust, we need to use the
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- * transaction ID for identifying transaction, as delayed logging results in
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- * the busy extent and transaction lifecycles being different. i.e. the busy
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- * extent is active for a lot longer than the transaction. Hence the
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- * transaction structure can be freed and reallocated, then mark the same
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- * extent busy again in the new transaction. In this case the new transaction
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- * will have a different tid but can have the same address, and hence we need
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- * to check against the tid.
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- *
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- * Future: for delayed logging, we could avoid the log force if the extent was
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- * first freed in the current checkpoint sequence. This, however, requires the
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- * ability to pin the current checkpoint in memory until this transaction
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- * commits to ensure that both the original free and the current one combine
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- * logically into the one checkpoint. If the checkpoint sequences are
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- * different, however, we still need to wait on a log force.
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- */
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void
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xfs_alloc_busy_insert(
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struct xfs_trans *tp,
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@@ -2580,9 +2487,7 @@ xfs_alloc_busy_insert(
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struct xfs_busy_extent *busyp;
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struct xfs_perag *pag;
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struct rb_node **rbp;
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- struct rb_node *parent;
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- int match;
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-
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+ struct rb_node *parent = NULL;
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new = kmem_zalloc(sizeof(struct xfs_busy_extent), KM_MAYFAIL);
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if (!new) {
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@@ -2591,7 +2496,7 @@ xfs_alloc_busy_insert(
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* block, make this a synchronous transaction to insure that
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* the block is not reused before this transaction commits.
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*/
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- trace_xfs_alloc_busy(tp, agno, bno, len, 1);
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+ trace_xfs_alloc_busy_enomem(tp->t_mountp, agno, bno, len);
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xfs_trans_set_sync(tp);
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return;
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}
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@@ -2599,66 +2504,28 @@ xfs_alloc_busy_insert(
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new->agno = agno;
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new->bno = bno;
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new->length = len;
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- new->tid = xfs_log_get_trans_ident(tp);
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-
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INIT_LIST_HEAD(&new->list);
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/* trace before insert to be able to see failed inserts */
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- trace_xfs_alloc_busy(tp, agno, bno, len, 0);
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+ trace_xfs_alloc_busy(tp->t_mountp, agno, bno, len);
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pag = xfs_perag_get(tp->t_mountp, new->agno);
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-restart:
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spin_lock(&pag->pagb_lock);
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rbp = &pag->pagb_tree.rb_node;
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- parent = NULL;
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- busyp = NULL;
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- match = 0;
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- while (*rbp && match >= 0) {
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+ while (*rbp) {
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parent = *rbp;
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busyp = rb_entry(parent, struct xfs_busy_extent, rb_node);
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if (new->bno < busyp->bno) {
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- /* may overlap, but exact start block is lower */
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rbp = &(*rbp)->rb_left;
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- if (new->bno + new->length > busyp->bno)
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- match = busyp->tid == new->tid ? 1 : -1;
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+ ASSERT(new->bno + new->length <= busyp->bno);
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} else if (new->bno > busyp->bno) {
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- /* may overlap, but exact start block is higher */
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rbp = &(*rbp)->rb_right;
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- if (bno < busyp->bno + busyp->length)
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- match = busyp->tid == new->tid ? 1 : -1;
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+ ASSERT(bno >= busyp->bno + busyp->length);
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} else {
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- match = busyp->tid == new->tid ? 1 : -1;
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- break;
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+ ASSERT(0);
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}
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}
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- if (match < 0) {
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- /* overlap marked busy in different transaction */
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- spin_unlock(&pag->pagb_lock);
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- xfs_log_force(tp->t_mountp, XFS_LOG_SYNC);
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- goto restart;
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- }
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- if (match > 0) {
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- /*
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- * overlap marked busy in same transaction. Update if exact
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- * start block match, otherwise combine the busy extents into
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- * a single range.
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- */
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- if (busyp->bno == new->bno) {
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- busyp->length = max(busyp->length, new->length);
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- spin_unlock(&pag->pagb_lock);
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- ASSERT(tp->t_flags & XFS_TRANS_SYNC);
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- xfs_perag_put(pag);
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- kmem_free(new);
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- return;
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- }
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- rb_erase(&busyp->rb_node, &pag->pagb_tree);
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- new->length = max(busyp->bno + busyp->length,
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- new->bno + new->length) -
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- min(busyp->bno, new->bno);
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- new->bno = min(busyp->bno, new->bno);
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- } else
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- busyp = NULL;
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rb_link_node(&new->rb_node, parent, rbp);
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rb_insert_color(&new->rb_node, &pag->pagb_tree);
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@@ -2666,7 +2533,6 @@ restart:
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list_add(&new->list, &tp->t_busy);
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spin_unlock(&pag->pagb_lock);
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xfs_perag_put(pag);
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- kmem_free(busyp);
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}
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/*
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@@ -2715,11 +2581,195 @@ xfs_alloc_busy_search(
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}
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}
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spin_unlock(&pag->pagb_lock);
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- trace_xfs_alloc_busysearch(mp, agno, bno, len, !!match);
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xfs_perag_put(pag);
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return match;
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}
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+/*
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+ * The found free extent [fbno, fend] overlaps part or all of the given busy
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+ * extent. If the overlap covers the beginning, the end, or all of the busy
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+ * extent, the overlapping portion can be made unbusy and used for the
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+ * allocation. We can't split a busy extent because we can't modify a
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+ * transaction/CIL context busy list, but we can update an entries block
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+ * number or length.
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+ *
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+ * Returns true if the extent can safely be reused, or false if the search
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+ * needs to be restarted.
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+ */
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+STATIC bool
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+xfs_alloc_busy_update_extent(
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+ struct xfs_mount *mp,
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+ struct xfs_perag *pag,
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+ struct xfs_busy_extent *busyp,
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+ xfs_agblock_t fbno,
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+ xfs_extlen_t flen,
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+ bool userdata)
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+{
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+ xfs_agblock_t fend = fbno + flen;
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+ xfs_agblock_t bbno = busyp->bno;
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+ xfs_agblock_t bend = bbno + busyp->length;
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+
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+ /*
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+ * If there is a busy extent overlapping a user allocation, we have
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+ * no choice but to force the log and retry the search.
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+ *
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+ * Fortunately this does not happen during normal operation, but
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+ * only if the filesystem is very low on space and has to dip into
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+ * the AGFL for normal allocations.
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+ */
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+ if (userdata)
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+ goto out_force_log;
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+
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+ if (bbno < fbno && bend > fend) {
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+ /*
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+ * Case 1:
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+ * bbno bend
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+ * +BBBBBBBBBBBBBBBBB+
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+ * +---------+
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+ * fbno fend
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+ */
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+
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+ /*
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+ * We would have to split the busy extent to be able to track
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+ * it correct, which we cannot do because we would have to
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+ * modify the list of busy extents attached to the transaction
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+ * or CIL context, which is immutable.
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+ *
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+ * Force out the log to clear the busy extent and retry the
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+ * search.
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+ */
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+ goto out_force_log;
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+ } else if (bbno >= fbno && bend <= fend) {
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+ /*
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+ * Case 2:
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+ * bbno bend
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+ * +BBBBBBBBBBBBBBBBB+
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+ * +-----------------+
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+ * fbno fend
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+ *
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+ * Case 3:
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+ * bbno bend
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+ * +BBBBBBBBBBBBBBBBB+
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+ * +--------------------------+
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+ * fbno fend
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+ *
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+ * Case 4:
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+ * bbno bend
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+ * +BBBBBBBBBBBBBBBBB+
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+ * +--------------------------+
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+ * fbno fend
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+ *
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+ * Case 5:
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+ * bbno bend
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+ * +BBBBBBBBBBBBBBBBB+
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+ * +-----------------------------------+
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+ * fbno fend
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+ *
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+ */
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+
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+ /*
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+ * The busy extent is fully covered by the extent we are
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+ * allocating, and can simply be removed from the rbtree.
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+ * However we cannot remove it from the immutable list
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+ * tracking busy extents in the transaction or CIL context,
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+ * so set the length to zero to mark it invalid.
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+ *
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+ * We also need to restart the busy extent search from the
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+ * tree root, because erasing the node can rearrange the
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+ * tree topology.
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+ */
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+ rb_erase(&busyp->rb_node, &pag->pagb_tree);
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+ busyp->length = 0;
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+ return false;
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+ } else if (fend < bend) {
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+ /*
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+ * Case 6:
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+ * bbno bend
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+ * +BBBBBBBBBBBBBBBBB+
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+ * +---------+
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+ * fbno fend
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+ *
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+ * Case 7:
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+ * bbno bend
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+ * +BBBBBBBBBBBBBBBBB+
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+ * +------------------+
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+ * fbno fend
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+ *
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+ */
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+ busyp->bno = fend;
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+ } else if (bbno < fbno) {
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+ /*
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+ * Case 8:
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+ * bbno bend
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+ * +BBBBBBBBBBBBBBBBB+
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+ * +-------------+
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+ * fbno fend
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+ *
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+ * Case 9:
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+ * bbno bend
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+ * +BBBBBBBBBBBBBBBBB+
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+ * +----------------------+
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+ * fbno fend
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+ */
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+ busyp->length = fbno - busyp->bno;
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+ } else {
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+ ASSERT(0);
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+ }
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+
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+ trace_xfs_alloc_busy_reuse(mp, pag->pag_agno, fbno, flen);
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+ return true;
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+
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+out_force_log:
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+ spin_unlock(&pag->pagb_lock);
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+ xfs_log_force(mp, XFS_LOG_SYNC);
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+ trace_xfs_alloc_busy_force(mp, pag->pag_agno, fbno, flen);
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+ spin_lock(&pag->pagb_lock);
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+ return false;
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+}
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+
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+
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+/*
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+ * For a given extent [fbno, flen], make sure we can reuse it safely.
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+ */
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+void
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+xfs_alloc_busy_reuse(
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+ struct xfs_mount *mp,
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+ xfs_agnumber_t agno,
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+ xfs_agblock_t fbno,
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+ xfs_extlen_t flen,
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+ bool userdata)
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+{
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+ struct xfs_perag *pag;
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+ struct rb_node *rbp;
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+
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+ ASSERT(flen > 0);
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+
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+ pag = xfs_perag_get(mp, agno);
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+ spin_lock(&pag->pagb_lock);
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+restart:
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+ rbp = pag->pagb_tree.rb_node;
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+ while (rbp) {
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+ struct xfs_busy_extent *busyp =
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+ rb_entry(rbp, struct xfs_busy_extent, rb_node);
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+ xfs_agblock_t bbno = busyp->bno;
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+ xfs_agblock_t bend = bbno + busyp->length;
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+
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+ if (fbno + flen <= bbno) {
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+ rbp = rbp->rb_left;
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+ continue;
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+ } else if (fbno >= bend) {
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+ rbp = rbp->rb_right;
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+ continue;
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+ }
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+
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+ if (!xfs_alloc_busy_update_extent(mp, pag, busyp, fbno, flen,
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+ userdata))
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+ goto restart;
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+ }
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+ spin_unlock(&pag->pagb_lock);
|
|
|
+ xfs_perag_put(pag);
|
|
|
+}
|
|
|
+
|
|
|
/*
|
|
|
* For a given extent [fbno, flen], search the busy extent list to find a
|
|
|
* subset of the extent that is not busy. If *rlen is smaller than
|
|
@@ -2734,13 +2784,16 @@ xfs_alloc_busy_trim(
|
|
|
xfs_agblock_t *rbno,
|
|
|
xfs_extlen_t *rlen)
|
|
|
{
|
|
|
- xfs_agblock_t fbno = bno;
|
|
|
- xfs_extlen_t flen = len;
|
|
|
+ xfs_agblock_t fbno;
|
|
|
+ xfs_extlen_t flen;
|
|
|
struct rb_node *rbp;
|
|
|
|
|
|
- ASSERT(flen > 0);
|
|
|
+ ASSERT(len > 0);
|
|
|
|
|
|
spin_lock(&args->pag->pagb_lock);
|
|
|
+restart:
|
|
|
+ fbno = bno;
|
|
|
+ flen = len;
|
|
|
rbp = args->pag->pagb_tree.rb_node;
|
|
|
while (rbp && flen >= args->minlen) {
|
|
|
struct xfs_busy_extent *busyp =
|
|
@@ -2757,6 +2810,18 @@ xfs_alloc_busy_trim(
|
|
|
continue;
|
|
|
}
|
|
|
|
|
|
+ /*
|
|
|
+ * If this is a metadata allocation, try to reuse the busy
|
|
|
+ * extent instead of trimming the allocation.
|
|
|
+ */
|
|
|
+ if (!args->userdata) {
|
|
|
+ if (!xfs_alloc_busy_update_extent(args->mp, args->pag,
|
|
|
+ busyp, fbno, flen,
|
|
|
+ false))
|
|
|
+ goto restart;
|
|
|
+ continue;
|
|
|
+ }
|
|
|
+
|
|
|
if (bbno <= fbno) {
|
|
|
/* start overlap */
|
|
|
|
|
@@ -2906,17 +2971,15 @@ xfs_alloc_busy_clear(
|
|
|
{
|
|
|
struct xfs_perag *pag;
|
|
|
|
|
|
- trace_xfs_alloc_unbusy(mp, busyp->agno, busyp->bno,
|
|
|
- busyp->length);
|
|
|
-
|
|
|
- ASSERT(xfs_alloc_busy_search(mp, busyp->agno, busyp->bno,
|
|
|
- busyp->length) == 1);
|
|
|
-
|
|
|
list_del_init(&busyp->list);
|
|
|
|
|
|
pag = xfs_perag_get(mp, busyp->agno);
|
|
|
spin_lock(&pag->pagb_lock);
|
|
|
- rb_erase(&busyp->rb_node, &pag->pagb_tree);
|
|
|
+ if (busyp->length) {
|
|
|
+ trace_xfs_alloc_busy_clear(mp, busyp->agno, busyp->bno,
|
|
|
+ busyp->length);
|
|
|
+ rb_erase(&busyp->rb_node, &pag->pagb_tree);
|
|
|
+ }
|
|
|
spin_unlock(&pag->pagb_lock);
|
|
|
xfs_perag_put(pag);
|
|
|
|