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path: root/fs/xfs/libxfs/xfs_defer.c
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diff --git a/fs/xfs/libxfs/xfs_defer.c b/fs/xfs/libxfs/xfs_defer.c
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+/*
+ * 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);
+}
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