1 files changed, 463 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_defer.c b/fs/xfs/libxfs/xfs_defer.c
new file mode 100644
index 000000000000..054a2032fdb3
--- /dev/null
+++ b/fs/xfs/libxfs/xfs_defer.c
@@ -0,0 +1,463 @@
+/*
+ * Copyright (C) 2016 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_log_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_bit.h"
+#include "xfs_sb.h"
+#include "xfs_mount.h"
+#include "xfs_defer.h"
+#include "xfs_trans.h"
+#include "xfs_trace.h"
+
+/*
+ * Deferred Operations in XFS
+ *
+ * Due to the way locking rules work in XFS, certain transactions (block
+ * mapping and unmapping, typically) have permanent reservations so that
+ * we can roll the transaction to adhere to AG locking order rules and
+ * to unlock buffers between metadata updates.  Prior to rmap/reflink,
+ * the mapping code had a mechanism to perform these deferrals for
+ * extents that were going to be freed; this code makes that facility
+ * more generic.
+ *
+ * When adding the reverse mapping and reflink features, it became
+ * necessary to perform complex remapping multi-transactions to comply
+ * with AG locking order rules, and to be able to spread a single
+ * refcount update operation (an operation on an n-block extent can
+ * update as many as n records!) among multiple transactions.  XFS can
+ * roll a transaction to facilitate this, but using this facility
+ * requires us to log "intent" items in case log recovery needs to
+ * redo the operation, and to log "done" items to indicate that redo
+ * is not necessary.
+ *
+ * Deferred work is tracked in xfs_defer_pending items.  Each pending
+ * item tracks one type of deferred work.  Incoming work items (which
+ * have not yet had an intent logged) are attached to a pending item
+ * on the dop_intake list, where they wait for the caller to finish
+ * the deferred operations.
+ *
+ * Finishing a set of deferred operations is an involved process.  To
+ * start, we define "rolling a deferred-op transaction" as follows:
+ *
+ * > For each xfs_defer_pending item on the dop_intake list,
+ *   - Sort the work items in AG order.  XFS locking
+ *     order rules require us to lock buffers in AG order.
+ *   - Create a log intent item for that type.
+ *   - Attach it to the pending item.
+ *   - Move the pending item from the dop_intake list to the
+ *     dop_pending list.
+ * > Roll the transaction.
+ *
+ * NOTE: To avoid exceeding the transaction reservation, we limit the
+ * number of items that we attach to a given xfs_defer_pending.
+ *
+ * The actual finishing process looks like this:
+ *
+ * > For each xfs_defer_pending in the dop_pending list,
+ *   - Roll the deferred-op transaction as above.
+ *   - Create a log done item for that type, and attach it to the
+ *     log intent item.
+ *   - For each work item attached to the log intent item,
+ *     * Perform the described action.
+ *     * Attach the work item to the log done item.
+ *
+ * The key here is that we must log an intent item for all pending
+ * work items every time we roll the transaction, and that we must log
+ * a done item as soon as the work is completed.  With this mechanism
+ * we can perform complex remapping operations, chaining intent items
+ * as needed.
+ *
+ * This is an example of remapping the extent (E, E+B) into file X at
+ * offset A and dealing with the extent (C, C+B) already being mapped
+ * there:
+ * +-------------------------------------------------+
+ * | Unmap file X startblock C offset A length B     | t0
+ * | Intent to reduce refcount for extent (C, B)     |
+ * | Intent to remove rmap (X, C, A, B)              |
+ * | Intent to free extent (D, 1) (bmbt block)       |
+ * | Intent to map (X, A, B) at startblock E         |
+ * +-------------------------------------------------+
+ * | Map file X startblock E offset A length B       | t1
+ * | Done mapping (X, E, A, B)                       |
+ * | Intent to increase refcount for extent (E, B)   |
+ * | Intent to add rmap (X, E, A, B)                 |
+ * +-------------------------------------------------+
+ * | Reduce refcount for extent (C, B)               | t2
+ * | Done reducing refcount for extent (C, B)        |
+ * | Increase refcount for extent (E, B)             |
+ * | Done increasing refcount for extent (E, B)      |
+ * | Intent to free extent (C, B)                    |
+ * | Intent to free extent (F, 1) (refcountbt block) |
+ * | Intent to remove rmap (F, 1, REFC)              |
+ * +-------------------------------------------------+
+ * | Remove rmap (X, C, A, B)                        | t3
+ * | Done removing rmap (X, C, A, B)                 |
+ * | Add rmap (X, E, A, B)                           |
+ * | Done adding rmap (X, E, A, B)                   |
+ * | Remove rmap (F, 1, REFC)                        |
+ * | Done removing rmap (F, 1, REFC)                 |
+ * +-------------------------------------------------+
+ * | Free extent (C, B)                              | t4
+ * | Done freeing extent (C, B)                      |
+ * | Free extent (D, 1)                              |
+ * | Done freeing extent (D, 1)                      |
+ * | Free extent (F, 1)                              |
+ * | Done freeing extent (F, 1)                      |
+ * +-------------------------------------------------+
+ *
+ * If we should crash before t2 commits, log recovery replays
+ * the following intent items:
+ *
+ * - Intent to reduce refcount for extent (C, B)
+ * - Intent to remove rmap (X, C, A, B)
+ * - Intent to free extent (D, 1) (bmbt block)
+ * - Intent to increase refcount for extent (E, B)
+ * - Intent to add rmap (X, E, A, B)
+ *
+ * In the process of recovering, it should also generate and take care
+ * of these intent items:
+ *
+ * - Intent to free extent (C, B)
+ * - Intent to free extent (F, 1) (refcountbt block)
+ * - Intent to remove rmap (F, 1, REFC)
+ */
+
+static const struct xfs_defer_op_type *defer_op_types[XFS_DEFER_OPS_TYPE_MAX];
+
+/*
+ * For each pending item in the intake list, log its intent item and the
+ * associated extents, then add the entire intake list to the end of
+ * the pending list.
+ */
+STATIC void
+xfs_defer_intake_work(
+        struct xfs_trans                *tp,
+        struct xfs_defer_ops            *dop)
+{
+        struct list_head                *li;
+        struct xfs_defer_pending        *dfp;
+
+        list_for_each_entry(dfp, &dop->dop_intake, dfp_list) {
+                trace_xfs_defer_intake_work(tp->t_mountp, dfp);
+                dfp->dfp_intent = dfp->dfp_type->create_intent(tp,
+                                dfp->dfp_count);
+                list_sort(tp->t_mountp, &dfp->dfp_work,
+                                dfp->dfp_type->diff_items);
+                list_for_each(li, &dfp->dfp_work)
+                        dfp->dfp_type->log_item(tp, dfp->dfp_intent, li);
+        }
+
+        list_splice_tail_init(&dop->dop_intake, &dop->dop_pending);
+}
+
+/* Abort all the intents that were committed. */
+STATIC void
+xfs_defer_trans_abort(
+        struct xfs_trans                *tp,
+        struct xfs_defer_ops            *dop,
+        int                             error)
+{
+        struct xfs_defer_pending        *dfp;
+
+        trace_xfs_defer_trans_abort(tp->t_mountp, dop);
+        /*
+         * If the transaction was committed, drop the intent reference
+         * since we're bailing out of here. The other reference is
+         * dropped when the intent hits the AIL.  If the transaction
+         * was not committed, the intent is freed by the intent item
+         * unlock handler on abort.
+         */
+        if (!dop->dop_committed)
+                return;
+
+        /* Abort intent items. */
+        list_for_each_entry(dfp, &dop->dop_pending, dfp_list) {
+                trace_xfs_defer_pending_abort(tp->t_mountp, dfp);
+                if (dfp->dfp_committed)
+                        dfp->dfp_type->abort_intent(dfp->dfp_intent);
+        }
+
+        /* Shut down FS. */
+        xfs_force_shutdown(tp->t_mountp, (error == -EFSCORRUPTED) ?
+                        SHUTDOWN_CORRUPT_INCORE : SHUTDOWN_META_IO_ERROR);
+}
+
+/* Roll a transaction so we can do some deferred op processing. */
+STATIC int
+xfs_defer_trans_roll(
+        struct xfs_trans                **tp,
+        struct xfs_defer_ops            *dop,
+        struct xfs_inode                *ip)
+{
+        int                             i;
+        int                             error;
+
+        /* Log all the joined inodes except the one we passed in. */
+        for (i = 0; i < XFS_DEFER_OPS_NR_INODES && dop->dop_inodes[i]; i++) {
+                if (dop->dop_inodes[i] == ip)
+                        continue;
+                xfs_trans_log_inode(*tp, dop->dop_inodes[i], XFS_ILOG_CORE);
+        }
+
+        trace_xfs_defer_trans_roll((*tp)->t_mountp, dop);
+
+        /* Roll the transaction. */
+        error = xfs_trans_roll(tp, ip);
+        if (error) {
+                trace_xfs_defer_trans_roll_error((*tp)->t_mountp, dop, error);
+                xfs_defer_trans_abort(*tp, dop, error);
+                return error;
+        }
+        dop->dop_committed = true;
+
+        /* Rejoin the joined inodes except the one we passed in. */
+        for (i = 0; i < XFS_DEFER_OPS_NR_INODES && dop->dop_inodes[i]; i++) {
+                if (dop->dop_inodes[i] == ip)
+                        continue;
+                xfs_trans_ijoin(*tp, dop->dop_inodes[i], 0);
+        }
+
+        return error;
+}
+
+/* Do we have any work items to finish? */
+bool
+xfs_defer_has_unfinished_work(
+        struct xfs_defer_ops            *dop)
+{
+        return !list_empty(&dop->dop_pending) || !list_empty(&dop->dop_intake);
+}
+
+/*
+ * Add this inode to the deferred op.  Each joined inode is relogged
+ * each time we roll the transaction, in addition to any inode passed
+ * to xfs_defer_finish().
+ */
+int
+xfs_defer_join(
+        struct xfs_defer_ops            *dop,
+        struct xfs_inode                *ip)
+{
+        int                             i;
+
+        for (i = 0; i < XFS_DEFER_OPS_NR_INODES; i++) {
+                if (dop->dop_inodes[i] == ip)
+                        return 0;
+                else if (dop->dop_inodes[i] == NULL) {
+                        dop->dop_inodes[i] = ip;
+                        return 0;
+                }
+        }
+
+        return -EFSCORRUPTED;
+}
+
+/*
+ * Finish all the pending work.  This involves logging intent items for
+ * any work items that wandered in since the last transaction roll (if
+ * one has even happened), rolling the transaction, and finishing the
+ * work items in the first item on the logged-and-pending list.
+ *
+ * If an inode is provided, relog it to the new transaction.
+ */
+int
+xfs_defer_finish(
+        struct xfs_trans                **tp,
+        struct xfs_defer_ops            *dop,
+        struct xfs_inode                *ip)
+{
+        struct xfs_defer_pending        *dfp;
+        struct list_head                *li;
+        struct list_head                *n;
+        void                            *done_item = NULL;
+        void                            *state;
+        int                             error = 0;
+        void                            (*cleanup_fn)(struct xfs_trans *, void *, int);
+
+        ASSERT((*tp)->t_flags & XFS_TRANS_PERM_LOG_RES);
+
+        trace_xfs_defer_finish((*tp)->t_mountp, dop);
+
+        /* Until we run out of pending work to finish... */
+        while (xfs_defer_has_unfinished_work(dop)) {
+                /* Log intents for work items sitting in the intake. */
+                xfs_defer_intake_work(*tp, dop);
+
+                /* Roll the transaction. */
+                error = xfs_defer_trans_roll(tp, dop, ip);
+                if (error)
+                        goto out;
+
+                /* Mark all pending intents as committed. */
+                list_for_each_entry_reverse(dfp, &dop->dop_pending, dfp_list) {
+                        if (dfp->dfp_committed)
+                                break;
+                        trace_xfs_defer_pending_commit((*tp)->t_mountp, dfp);
+                        dfp->dfp_committed = true;
+                }
+
+                /* Log an intent-done item for the first pending item. */
+                dfp = list_first_entry(&dop->dop_pending,
+                                struct xfs_defer_pending, dfp_list);
+                trace_xfs_defer_pending_finish((*tp)->t_mountp, dfp);
+                done_item = dfp->dfp_type->create_done(*tp, dfp->dfp_intent,
+                                dfp->dfp_count);
+                cleanup_fn = dfp->dfp_type->finish_cleanup;
+
+                /* Finish the work items. */
+                state = NULL;
+                list_for_each_safe(li, n, &dfp->dfp_work) {
+                        list_del(li);
+                        dfp->dfp_count--;
+                        error = dfp->dfp_type->finish_item(*tp, dop, li,
+                                        done_item, &state);
+                        if (error) {
+                                /*
+                                 * Clean up after ourselves and jump out.
+                                 * xfs_defer_cancel will take care of freeing
+                                 * all these lists and stuff.
+                                 */
+                                if (cleanup_fn)
+                                        cleanup_fn(*tp, state, error);
+                                xfs_defer_trans_abort(*tp, dop, error);
+                                goto out;
+                        }
+                }
+                /* Done with the dfp, free it. */
+                list_del(&dfp->dfp_list);
+                kmem_free(dfp);
+
+                if (cleanup_fn)
+                        cleanup_fn(*tp, state, error);
+        }
+
+out:
+        if (error)
+                trace_xfs_defer_finish_error((*tp)->t_mountp, dop, error);
+        else
+                trace_xfs_defer_finish_done((*tp)->t_mountp, dop);
+        return error;
+}
+
+/*
+ * Free up any items left in the list.
+ */
+void
+xfs_defer_cancel(
+        struct xfs_defer_ops            *dop)
+{
+        struct xfs_defer_pending        *dfp;
+        struct xfs_defer_pending        *pli;
+        struct list_head                *pwi;
+        struct list_head                *n;
+
+        trace_xfs_defer_cancel(NULL, dop);
+
+        /*
+         * Free the pending items.  Caller should already have arranged
+         * for the intent items to be released.
+         */
+        list_for_each_entry_safe(dfp, pli, &dop->dop_intake, dfp_list) {
+                trace_xfs_defer_intake_cancel(NULL, dfp);
+                list_del(&dfp->dfp_list);
+                list_for_each_safe(pwi, n, &dfp->dfp_work) {
+                        list_del(pwi);
+                        dfp->dfp_count--;
+                        dfp->dfp_type->cancel_item(pwi);
+                }
+                ASSERT(dfp->dfp_count == 0);
+                kmem_free(dfp);
+        }
+        list_for_each_entry_safe(dfp, pli, &dop->dop_pending, dfp_list) {
+                trace_xfs_defer_pending_cancel(NULL, dfp);
+                list_del(&dfp->dfp_list);
+                list_for_each_safe(pwi, n, &dfp->dfp_work) {
+                        list_del(pwi);
+                        dfp->dfp_count--;
+                        dfp->dfp_type->cancel_item(pwi);
+                }
+                ASSERT(dfp->dfp_count == 0);
+                kmem_free(dfp);
+        }
+}
+
+/* Add an item for later deferred processing. */
+void
+xfs_defer_add(
+        struct xfs_defer_ops            *dop,
+        enum xfs_defer_ops_type         type,
+        struct list_head                *li)
+{
+        struct xfs_defer_pending        *dfp = NULL;
+
+        /*
+         * Add the item to a pending item at the end of the intake list.
+         * If the last pending item has the same type, reuse it.  Else,
+         * create a new pending item at the end of the intake list.
+         */
+        if (!list_empty(&dop->dop_intake)) {
+                dfp = list_last_entry(&dop->dop_intake,
+                                struct xfs_defer_pending, dfp_list);
+                if (dfp->dfp_type->type != type ||
+                    (dfp->dfp_type->max_items &&
+                     dfp->dfp_count >= dfp->dfp_type->max_items))
+                        dfp = NULL;
+        }
+        if (!dfp) {
+                dfp = kmem_alloc(sizeof(struct xfs_defer_pending),
+                                KM_SLEEP | KM_NOFS);
+                dfp->dfp_type = defer_op_types[type];
+                dfp->dfp_committed = false;
+                dfp->dfp_intent = NULL;
+                dfp->dfp_count = 0;
+                INIT_LIST_HEAD(&dfp->dfp_work);
+                list_add_tail(&dfp->dfp_list, &dop->dop_intake);
+        }
+
+        list_add_tail(li, &dfp->dfp_work);
+        dfp->dfp_count++;
+}
+
+/* Initialize a deferred operation list. */
+void
+xfs_defer_init_op_type(
+        const struct xfs_defer_op_type  *type)
+{
+        defer_op_types[type->type] = type;
+}
+
+/* Initialize a deferred operation. */
+void
+xfs_defer_init(
+        struct xfs_defer_ops            *dop,
+        xfs_fsblock_t                   *fbp)
+{
+        dop->dop_committed = false;
+        dop->dop_low = false;
+        memset(&dop->dop_inodes, 0, sizeof(dop->dop_inodes));
+        *fbp = NULLFSBLOCK;
+        INIT_LIST_HEAD(&dop->dop_intake);
+        INIT_LIST_HEAD(&dop->dop_pending);
+        trace_xfs_defer_init(NULL, dop);
+}