v4.19.13 snapshot.
diff --git a/fs/xfs/libxfs/xfs_defer.c b/fs/xfs/libxfs/xfs_defer.c
new file mode 100644
index 0000000..e792b16
--- /dev/null
+++ b/fs/xfs/libxfs/xfs_defer.c
@@ -0,0 +1,549 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2016 Oracle. All Rights Reserved.
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+#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_buf_item.h"
+#include "xfs_inode.h"
+#include "xfs_inode_item.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.
+ * * If the result of doing the work was -EAGAIN, ->finish work
+ * wants a new transaction. See the "Requesting a Fresh
+ * Transaction while Finishing Deferred Work" section below for
+ * details.
+ *
+ * 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.
+ *
+ * Requesting a Fresh Transaction while Finishing Deferred Work
+ *
+ * If ->finish_item decides that it needs a fresh transaction to
+ * finish the work, it must ask its caller (xfs_defer_finish) for a
+ * continuation. The most likely cause of this circumstance are the
+ * refcount adjust functions deciding that they've logged enough items
+ * to be at risk of exceeding the transaction reservation.
+ *
+ * To get a fresh transaction, we want to log the existing log done
+ * item to prevent the log intent item from replaying, immediately log
+ * a new log intent item with the unfinished work items, roll the
+ * transaction, and re-call ->finish_item wherever it left off. The
+ * log done item and the new log intent item must be in the same
+ * transaction or atomicity cannot be guaranteed; defer_finish ensures
+ * that this happens.
+ *
+ * This requires some coordination between ->finish_item and
+ * defer_finish. Upon deciding to request a new transaction,
+ * ->finish_item should update the current work item to reflect the
+ * unfinished work. Next, it should reset the log done item's list
+ * count to the number of items finished, and return -EAGAIN.
+ * defer_finish sees the -EAGAIN, logs the new log intent item
+ * with the remaining work items, and leaves the xfs_defer_pending
+ * item at the head of the dop_work queue. Then it rolls the
+ * transaction and picks up processing where it left off. It is
+ * required that ->finish_item must be careful to leave enough
+ * transaction reservation to fit the new log intent item.
+ *
+ * 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, 9) |
+ * | Intent to reduce refcount for extent (C+9, B-9) |
+ * | (ran out of space after 9 refcount updates) |
+ * +-------------------------------------------------+
+ * | Reduce refcount for extent (C+9, B+9) | t3
+ * | Done reducing refcount for extent (C+9, B-9) |
+ * | 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) | t4
+ * | 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) | t5
+ * | 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)
+ *
+ * Note that the continuation requested between t2 and t3 is likely to
+ * reoccur.
+ */
+
+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_create_intents(
+ struct xfs_trans *tp)
+{
+ struct list_head *li;
+ struct xfs_defer_pending *dfp;
+
+ list_for_each_entry(dfp, &tp->t_dfops, dfp_list) {
+ dfp->dfp_intent = dfp->dfp_type->create_intent(tp,
+ dfp->dfp_count);
+ trace_xfs_defer_create_intent(tp->t_mountp, dfp);
+ 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);
+ }
+}
+
+/* Abort all the intents that were committed. */
+STATIC void
+xfs_defer_trans_abort(
+ struct xfs_trans *tp,
+ struct list_head *dop_pending)
+{
+ struct xfs_defer_pending *dfp;
+
+ trace_xfs_defer_trans_abort(tp, _RET_IP_);
+
+ /* Abort intent items that don't have a done item. */
+ list_for_each_entry(dfp, dop_pending, dfp_list) {
+ trace_xfs_defer_pending_abort(tp->t_mountp, dfp);
+ if (dfp->dfp_intent && !dfp->dfp_done) {
+ dfp->dfp_type->abort_intent(dfp->dfp_intent);
+ dfp->dfp_intent = NULL;
+ }
+ }
+}
+
+/* Roll a transaction so we can do some deferred op processing. */
+STATIC int
+xfs_defer_trans_roll(
+ struct xfs_trans **tpp)
+{
+ struct xfs_trans *tp = *tpp;
+ struct xfs_buf_log_item *bli;
+ struct xfs_inode_log_item *ili;
+ struct xfs_log_item *lip;
+ struct xfs_buf *bplist[XFS_DEFER_OPS_NR_BUFS];
+ struct xfs_inode *iplist[XFS_DEFER_OPS_NR_INODES];
+ int bpcount = 0, ipcount = 0;
+ int i;
+ int error;
+
+ list_for_each_entry(lip, &tp->t_items, li_trans) {
+ switch (lip->li_type) {
+ case XFS_LI_BUF:
+ bli = container_of(lip, struct xfs_buf_log_item,
+ bli_item);
+ if (bli->bli_flags & XFS_BLI_HOLD) {
+ if (bpcount >= XFS_DEFER_OPS_NR_BUFS) {
+ ASSERT(0);
+ return -EFSCORRUPTED;
+ }
+ xfs_trans_dirty_buf(tp, bli->bli_buf);
+ bplist[bpcount++] = bli->bli_buf;
+ }
+ break;
+ case XFS_LI_INODE:
+ ili = container_of(lip, struct xfs_inode_log_item,
+ ili_item);
+ if (ili->ili_lock_flags == 0) {
+ if (ipcount >= XFS_DEFER_OPS_NR_INODES) {
+ ASSERT(0);
+ return -EFSCORRUPTED;
+ }
+ xfs_trans_log_inode(tp, ili->ili_inode,
+ XFS_ILOG_CORE);
+ iplist[ipcount++] = ili->ili_inode;
+ }
+ break;
+ default:
+ break;
+ }
+ }
+
+ trace_xfs_defer_trans_roll(tp, _RET_IP_);
+
+ /* Roll the transaction. */
+ error = xfs_trans_roll(tpp);
+ tp = *tpp;
+ if (error) {
+ trace_xfs_defer_trans_roll_error(tp, error);
+ return error;
+ }
+
+ /* Rejoin the joined inodes. */
+ for (i = 0; i < ipcount; i++)
+ xfs_trans_ijoin(tp, iplist[i], 0);
+
+ /* Rejoin the buffers and dirty them so the log moves forward. */
+ for (i = 0; i < bpcount; i++) {
+ xfs_trans_bjoin(tp, bplist[i]);
+ xfs_trans_bhold(tp, bplist[i]);
+ }
+
+ return error;
+}
+
+/*
+ * Reset an already used dfops after finish.
+ */
+static void
+xfs_defer_reset(
+ struct xfs_trans *tp)
+{
+ ASSERT(list_empty(&tp->t_dfops));
+
+ /*
+ * Low mode state transfers across transaction rolls to mirror dfops
+ * lifetime. Clear it now that dfops is reset.
+ */
+ tp->t_flags &= ~XFS_TRANS_LOWMODE;
+}
+
+/*
+ * Free up any items left in the list.
+ */
+static void
+xfs_defer_cancel_list(
+ struct xfs_mount *mp,
+ struct list_head *dop_list)
+{
+ struct xfs_defer_pending *dfp;
+ struct xfs_defer_pending *pli;
+ struct list_head *pwi;
+ struct list_head *n;
+
+ /*
+ * Free the pending items. Caller should already have arranged
+ * for the intent items to be released.
+ */
+ list_for_each_entry_safe(dfp, pli, dop_list, dfp_list) {
+ trace_xfs_defer_cancel_list(mp, 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);
+ }
+}
+
+/*
+ * 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_noroll(
+ struct xfs_trans **tp)
+{
+ struct xfs_defer_pending *dfp;
+ struct list_head *li;
+ struct list_head *n;
+ void *state;
+ int error = 0;
+ void (*cleanup_fn)(struct xfs_trans *, void *, int);
+ LIST_HEAD(dop_pending);
+
+ ASSERT((*tp)->t_flags & XFS_TRANS_PERM_LOG_RES);
+
+ trace_xfs_defer_finish(*tp, _RET_IP_);
+
+ /* Until we run out of pending work to finish... */
+ while (!list_empty(&dop_pending) || !list_empty(&(*tp)->t_dfops)) {
+ /* log intents and pull in intake items */
+ xfs_defer_create_intents(*tp);
+ list_splice_tail_init(&(*tp)->t_dfops, &dop_pending);
+
+ /*
+ * Roll the transaction.
+ */
+ error = xfs_defer_trans_roll(tp);
+ if (error)
+ goto out;
+
+ /* Log an intent-done item for the first pending item. */
+ dfp = list_first_entry(&dop_pending, struct xfs_defer_pending,
+ dfp_list);
+ trace_xfs_defer_pending_finish((*tp)->t_mountp, dfp);
+ dfp->dfp_done = 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, li,
+ dfp->dfp_done, &state);
+ if (error == -EAGAIN) {
+ /*
+ * Caller wants a fresh transaction;
+ * put the work item back on the list
+ * and jump out.
+ */
+ list_add(li, &dfp->dfp_work);
+ dfp->dfp_count++;
+ break;
+ } else 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);
+ goto out;
+ }
+ }
+ if (error == -EAGAIN) {
+ /*
+ * Caller wants a fresh transaction, so log a
+ * new log intent item to replace the old one
+ * and roll the transaction. See "Requesting
+ * a Fresh Transaction while Finishing
+ * Deferred Work" above.
+ */
+ dfp->dfp_intent = dfp->dfp_type->create_intent(*tp,
+ dfp->dfp_count);
+ dfp->dfp_done = NULL;
+ list_for_each(li, &dfp->dfp_work)
+ dfp->dfp_type->log_item(*tp, dfp->dfp_intent,
+ li);
+ } else {
+ /* 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) {
+ xfs_defer_trans_abort(*tp, &dop_pending);
+ xfs_force_shutdown((*tp)->t_mountp, SHUTDOWN_CORRUPT_INCORE);
+ trace_xfs_defer_finish_error(*tp, error);
+ xfs_defer_cancel_list((*tp)->t_mountp, &dop_pending);
+ xfs_defer_cancel(*tp);
+ return error;
+ }
+
+ trace_xfs_defer_finish_done(*tp, _RET_IP_);
+ return 0;
+}
+
+int
+xfs_defer_finish(
+ struct xfs_trans **tp)
+{
+ int error;
+
+ /*
+ * Finish and roll the transaction once more to avoid returning to the
+ * caller with a dirty transaction.
+ */
+ error = xfs_defer_finish_noroll(tp);
+ if (error)
+ return error;
+ if ((*tp)->t_flags & XFS_TRANS_DIRTY) {
+ error = xfs_defer_trans_roll(tp);
+ if (error) {
+ xfs_force_shutdown((*tp)->t_mountp,
+ SHUTDOWN_CORRUPT_INCORE);
+ return error;
+ }
+ }
+ xfs_defer_reset(*tp);
+ return 0;
+}
+
+void
+xfs_defer_cancel(
+ struct xfs_trans *tp)
+{
+ struct xfs_mount *mp = tp->t_mountp;
+
+ trace_xfs_defer_cancel(tp, _RET_IP_);
+ xfs_defer_cancel_list(mp, &tp->t_dfops);
+}
+
+/* Add an item for later deferred processing. */
+void
+xfs_defer_add(
+ struct xfs_trans *tp,
+ enum xfs_defer_ops_type type,
+ struct list_head *li)
+{
+ struct xfs_defer_pending *dfp = NULL;
+
+ ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES);
+
+ /*
+ * 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(&tp->t_dfops)) {
+ dfp = list_last_entry(&tp->t_dfops,
+ 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_intent = NULL;
+ dfp->dfp_done = NULL;
+ dfp->dfp_count = 0;
+ INIT_LIST_HEAD(&dfp->dfp_work);
+ list_add_tail(&dfp->dfp_list, &tp->t_dfops);
+ }
+
+ 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;
+}
+
+/*
+ * Move deferred ops from one transaction to another and reset the source to
+ * initial state. This is primarily used to carry state forward across
+ * transaction rolls with pending dfops.
+ */
+void
+xfs_defer_move(
+ struct xfs_trans *dtp,
+ struct xfs_trans *stp)
+{
+ list_splice_init(&stp->t_dfops, &dtp->t_dfops);
+
+ /*
+ * Low free space mode was historically controlled by a dfops field.
+ * This meant that low mode state potentially carried across multiple
+ * transaction rolls. Transfer low mode on a dfops move to preserve
+ * that behavior.
+ */
+ dtp->t_flags |= (stp->t_flags & XFS_TRANS_LOWMODE);
+
+ xfs_defer_reset(stp);
+}