xfs: exact busy extent tracking (97d3ac75) · Commits · 戴 / test

fs/xfs/linux-2.6/xfs_trace.h

+11 −68

Original line number	Diff line number	Diff line
		@@ -1151,44 +1151,7 @@ TRACE_EVENT(xfs_bunmap,

		);

		#define XFS_BUSY_SYNC \
		{ 0, "async" }, \
		{ 1, "sync" }

		TRACE_EVENT(xfs_alloc_busy,
		TP_PROTO(struct xfs_trans *trans, xfs_agnumber_t agno,
		xfs_agblock_t agbno, xfs_extlen_t len, int sync),
		TP_ARGS(trans, agno, agbno, len, sync),
		TP_STRUCT__entry(
		__field(dev_t, dev)
		__field(struct xfs_trans *, tp)
		__field(int, tid)
		__field(xfs_agnumber_t, agno)
		__field(xfs_agblock_t, agbno)
		__field(xfs_extlen_t, len)
		__field(int, sync)
		),
		TP_fast_assign(
		__entry->dev = trans->t_mountp->m_super->s_dev;
		__entry->tp = trans;
		__entry->tid = trans->t_ticket->t_tid;
		__entry->agno = agno;
		__entry->agbno = agbno;
		__entry->len = len;
		__entry->sync = sync;
		),
		TP_printk("dev %d:%d trans 0x%p tid 0x%x agno %u agbno %u len %u %s",
		MAJOR(__entry->dev), MINOR(__entry->dev),
		__entry->tp,
		__entry->tid,
		__entry->agno,
		__entry->agbno,
		__entry->len,
		__print_symbolic(__entry->sync, XFS_BUSY_SYNC))

		);

		TRACE_EVENT(xfs_alloc_unbusy,
		DECLARE_EVENT_CLASS(xfs_busy_class,
		TP_PROTO(struct xfs_mount *mp, xfs_agnumber_t agno,
		xfs_agblock_t agbno, xfs_extlen_t len),
		TP_ARGS(mp, agno, agbno, len),
		@@ -1210,36 +1173,16 @@ TRACE_EVENT(xfs_alloc_unbusy,
		__entry->agbno,
		__entry->len)
		);

		#define XFS_BUSY_STATES \
		{ 0, "missing" }, \
		{ 1, "found" }

		TRACE_EVENT(xfs_alloc_busysearch,
		TP_PROTO(struct xfs_mount *mp, xfs_agnumber_t agno,
		xfs_agblock_t agbno, xfs_extlen_t len, int found),
		TP_ARGS(mp, agno, agbno, len, found),
		TP_STRUCT__entry(
		__field(dev_t, dev)
		__field(xfs_agnumber_t, agno)
		__field(xfs_agblock_t, agbno)
		__field(xfs_extlen_t, len)
		__field(int, found)
		),
		TP_fast_assign(
		__entry->dev = mp->m_super->s_dev;
		__entry->agno = agno;
		__entry->agbno = agbno;
		__entry->len = len;
		__entry->found = found;
		),
		TP_printk("dev %d:%d agno %u agbno %u len %u %s",
		MAJOR(__entry->dev), MINOR(__entry->dev),
		__entry->agno,
		__entry->agbno,
		__entry->len,
		__print_symbolic(__entry->found, XFS_BUSY_STATES))
		);
		#define DEFINE_BUSY_EVENT(name) \
		DEFINE_EVENT(xfs_busy_class, name, \
		TP_PROTO(struct xfs_mount *mp, xfs_agnumber_t agno, \
		xfs_agblock_t agbno, xfs_extlen_t len), \
		TP_ARGS(mp, agno, agbno, len))
		DEFINE_BUSY_EVENT(xfs_alloc_busy);
		DEFINE_BUSY_EVENT(xfs_alloc_busy_enomem);
		DEFINE_BUSY_EVENT(xfs_alloc_busy_force);
		DEFINE_BUSY_EVENT(xfs_alloc_busy_reuse);
		DEFINE_BUSY_EVENT(xfs_alloc_busy_clear);

		TRACE_EVENT(xfs_alloc_busy_trim,
		TP_PROTO(struct xfs_mount *mp, xfs_agnumber_t agno,

fs/xfs/xfs_ag.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -187,7 +187,6 @@ struct xfs_busy_extent {
		xfs_agnumber_t agno;
		xfs_agblock_t bno;
		xfs_extlen_t length;
		xlog_tid_t tid; /* transaction that created this */
		};

		/*

fs/xfs/xfs_alloc.c

+218 −155

Original line number	Diff line number	Diff line
		@@ -1396,8 +1396,9 @@ xfs_alloc_ag_vextent_small(
		if (error)
		goto error0;
		if (fbno != NULLAGBLOCK) {
		if (xfs_alloc_busy_search(args->mp, args->agno, fbno, 1))
		xfs_trans_set_sync(args->tp);
		xfs_alloc_busy_reuse(args->mp, args->agno, fbno, 1,
		args->userdata);

		if (args->userdata) {
		xfs_buf_t *bp;

		@@ -2475,100 +2476,6 @@ error0:
		return error;
		}


		/*
		* AG Busy list management
		* The busy list contains block ranges that have been freed but whose
		* transactions have not yet hit disk. If any block listed in a busy
		* list is reused, the transaction that freed it must be forced to disk
		* before continuing to use the block.
		*
		* xfs_alloc_busy_insert - add to the per-ag busy list
		* xfs_alloc_busy_clear - remove an item from the per-ag busy list
		* xfs_alloc_busy_search - search for a busy extent
		*/

		/*
		* Insert a new extent into the busy tree.
		*
		* The busy extent tree is indexed by the start block of the busy extent.
		* there can be multiple overlapping ranges in the busy extent tree but only
		* ever one entry at a given start block. The reason for this is that
		* multi-block extents can be freed, then smaller chunks of that extent
		* allocated and freed again before the first transaction commit is on disk.
		* If the exact same start block is freed a second time, we have to wait for
		* that busy extent to pass out of the tree before the new extent is inserted.
		* There are two main cases we have to handle here.
		*
		* The first case is a transaction that triggers a "free - allocate - free"
		* cycle. This can occur during btree manipulations as a btree block is freed
		* to the freelist, then allocated from the free list, then freed again. In
		* this case, the second extxpnet free is what triggers the duplicate and as
		* such the transaction IDs should match. Because the extent was allocated in
		* this transaction, the transaction must be marked as synchronous. This is
		* true for all cases where the free/alloc/free occurs in the one transaction,
		* hence the addition of the ASSERT(tp->t_flags & XFS_TRANS_SYNC) to this case.
		* This serves to catch violations of the second case quite effectively.
		*
		* The second case is where the free/alloc/free occur in different
		* transactions. In this case, the thread freeing the extent the second time
		* can't mark the extent busy immediately because it is already tracked in a
		* transaction that may be committing. When the log commit for the existing
		* busy extent completes, the busy extent will be removed from the tree. If we
		* allow the second busy insert to continue using that busy extent structure,
		* it can be freed before this transaction is safely in the log. Hence our
		* only option in this case is to force the log to remove the existing busy
		* extent from the list before we insert the new one with the current
		* transaction ID.
		*
		* The problem we are trying to avoid in the free-alloc-free in separate
		* transactions is most easily described with a timeline:
		*
		* Thread 1 Thread 2 Thread 3 xfslogd
		* xact alloc
		* free X
		* mark busy
		* commit xact
		* free xact
		* xact alloc
		* alloc X
		* busy search
		* mark xact sync
		* commit xact
		* free xact
		* force log
		* checkpoint starts
		* ....
		* xact alloc
		* free X
		* mark busy
		* finds match
		* * KABOOM! *
		* ....
		* log IO completes
		* unbusy X
		* checkpoint completes
		*
		* By issuing a log force in thread 3 @ "KABOOM", the thread will block until
		* the checkpoint completes, and the busy extent it matched will have been
		* removed from the tree when it is woken. Hence it can then continue safely.
		*
		* However, to ensure this matching process is robust, we need to use the
		* transaction ID for identifying transaction, as delayed logging results in
		* the busy extent and transaction lifecycles being different. i.e. the busy
		* extent is active for a lot longer than the transaction. Hence the
		* transaction structure can be freed and reallocated, then mark the same
		* extent busy again in the new transaction. In this case the new transaction
		* will have a different tid but can have the same address, and hence we need
		* to check against the tid.
		*
		* Future: for delayed logging, we could avoid the log force if the extent was
		* first freed in the current checkpoint sequence. This, however, requires the
		* ability to pin the current checkpoint in memory until this transaction
		* commits to ensure that both the original free and the current one combine
		* logically into the one checkpoint. If the checkpoint sequences are
		* different, however, we still need to wait on a log force.
		*/
		void
		xfs_alloc_busy_insert(
		struct xfs_trans *tp,
		@@ -2580,9 +2487,7 @@ xfs_alloc_busy_insert(
		struct xfs_busy_extent *busyp;
		struct xfs_perag *pag;
		struct rb_node **rbp;
		struct rb_node *parent;
		int match;

		struct rb_node *parent = NULL;

		new = kmem_zalloc(sizeof(struct xfs_busy_extent), KM_MAYFAIL);
		if (!new) {
		@@ -2591,7 +2496,7 @@ xfs_alloc_busy_insert(
		* block, make this a synchronous transaction to insure that
		* the block is not reused before this transaction commits.
		*/
		trace_xfs_alloc_busy(tp, agno, bno, len, 1);
		trace_xfs_alloc_busy_enomem(tp->t_mountp, agno, bno, len);
		xfs_trans_set_sync(tp);
		return;
		}
		@@ -2599,66 +2504,28 @@ xfs_alloc_busy_insert(
		new->agno = agno;
		new->bno = bno;
		new->length = len;
		new->tid = xfs_log_get_trans_ident(tp);

		INIT_LIST_HEAD(&new->list);

		/* trace before insert to be able to see failed inserts */
		trace_xfs_alloc_busy(tp, agno, bno, len, 0);
		trace_xfs_alloc_busy(tp->t_mountp, agno, bno, len);

		pag = xfs_perag_get(tp->t_mountp, new->agno);
		restart:
		spin_lock(&pag->pagb_lock);
		rbp = &pag->pagb_tree.rb_node;
		parent = NULL;
		busyp = NULL;
		match = 0;
		while (*rbp && match >= 0) {
		while (*rbp) {
		parent = *rbp;
		busyp = rb_entry(parent, struct xfs_busy_extent, rb_node);

		if (new->bno < busyp->bno) {
		/* may overlap, but exact start block is lower */
		rbp = &(*rbp)->rb_left;
		if (new->bno + new->length > busyp->bno)
		match = busyp->tid == new->tid ? 1 : -1;
		ASSERT(new->bno + new->length <= busyp->bno);
		} else if (new->bno > busyp->bno) {
		/* may overlap, but exact start block is higher */
		rbp = &(*rbp)->rb_right;
		if (bno < busyp->bno + busyp->length)
		match = busyp->tid == new->tid ? 1 : -1;
		ASSERT(bno >= busyp->bno + busyp->length);
		} else {
		match = busyp->tid == new->tid ? 1 : -1;
		break;
		}
		ASSERT(0);
		}
		if (match < 0) {
		/* overlap marked busy in different transaction */
		spin_unlock(&pag->pagb_lock);
		xfs_log_force(tp->t_mountp, XFS_LOG_SYNC);
		goto restart;
		}
		if (match > 0) {
		/*
		* overlap marked busy in same transaction. Update if exact
		* start block match, otherwise combine the busy extents into
		* a single range.
		*/
		if (busyp->bno == new->bno) {
		busyp->length = max(busyp->length, new->length);
		spin_unlock(&pag->pagb_lock);
		ASSERT(tp->t_flags & XFS_TRANS_SYNC);
		xfs_perag_put(pag);
		kmem_free(new);
		return;
		}
		rb_erase(&busyp->rb_node, &pag->pagb_tree);
		new->length = max(busyp->bno + busyp->length,
		new->bno + new->length) -
		min(busyp->bno, new->bno);
		new->bno = min(busyp->bno, new->bno);
		} else
		busyp = NULL;

		rb_link_node(&new->rb_node, parent, rbp);
		rb_insert_color(&new->rb_node, &pag->pagb_tree);
		@@ -2666,7 +2533,6 @@ restart:
		list_add(&new->list, &tp->t_busy);
		spin_unlock(&pag->pagb_lock);
		xfs_perag_put(pag);
		kmem_free(busyp);
		}

		/*
		@@ -2715,11 +2581,195 @@ xfs_alloc_busy_search(
		}
		}
		spin_unlock(&pag->pagb_lock);
		trace_xfs_alloc_busysearch(mp, agno, bno, len, !!match);
		xfs_perag_put(pag);
		return match;
		}

		/*
		* The found free extent [fbno, fend] overlaps part or all of the given busy
		* extent. If the overlap covers the beginning, the end, or all of the busy
		* extent, the overlapping portion can be made unbusy and used for the
		* allocation. We can't split a busy extent because we can't modify a
		* transaction/CIL context busy list, but we can update an entries block
		* number or length.
		*
		* Returns true if the extent can safely be reused, or false if the search
		* needs to be restarted.
		*/
		STATIC bool
		xfs_alloc_busy_update_extent(
		struct xfs_mount *mp,
		struct xfs_perag *pag,
		struct xfs_busy_extent *busyp,
		xfs_agblock_t fbno,
		xfs_extlen_t flen,
		bool userdata)
		{
		xfs_agblock_t fend = fbno + flen;
		xfs_agblock_t bbno = busyp->bno;
		xfs_agblock_t bend = bbno + busyp->length;

		/*
		* If there is a busy extent overlapping a user allocation, we have
		* no choice but to force the log and retry the search.
		*
		* Fortunately this does not happen during normal operation, but
		* only if the filesystem is very low on space and has to dip into
		* the AGFL for normal allocations.
		*/
		if (userdata)
		goto out_force_log;

		if (bbno < fbno && bend > fend) {
		/*
		* Case 1:
		* bbno bend
		* +BBBBBBBBBBBBBBBBB+
		* +---------+
		* fbno fend
		*/

		/*
		* We would have to split the busy extent to be able to track
		* it correct, which we cannot do because we would have to
		* modify the list of busy extents attached to the transaction
		* or CIL context, which is immutable.
		*
		* Force out the log to clear the busy extent and retry the
		* search.
		*/
		goto out_force_log;
		} else if (bbno >= fbno && bend <= fend) {
		/*
		* Case 2:
		* bbno bend
		* +BBBBBBBBBBBBBBBBB+
		* +-----------------+
		* fbno fend
		*
		* Case 3:
		* bbno bend
		* +BBBBBBBBBBBBBBBBB+
		* +--------------------------+
		* fbno fend
		*
		* Case 4:
		* bbno bend
		* +BBBBBBBBBBBBBBBBB+
		* +--------------------------+
		* fbno fend
		*
		* Case 5:
		* bbno bend
		* +BBBBBBBBBBBBBBBBB+
		* +-----------------------------------+
		* fbno fend
		*
		*/

		/*
		* The busy extent is fully covered by the extent we are
		* allocating, and can simply be removed from the rbtree.
		* However we cannot remove it from the immutable list
		* tracking busy extents in the transaction or CIL context,
		* so set the length to zero to mark it invalid.
		*
		* We also need to restart the busy extent search from the
		* tree root, because erasing the node can rearrange the
		* tree topology.
		*/
		rb_erase(&busyp->rb_node, &pag->pagb_tree);
		busyp->length = 0;
		return false;
		} else if (fend < bend) {
		/*
		* Case 6:
		* bbno bend
		* +BBBBBBBBBBBBBBBBB+
		* +---------+
		* fbno fend
		*
		* Case 7:
		* bbno bend
		* +BBBBBBBBBBBBBBBBB+
		* +------------------+
		* fbno fend
		*
		*/
		busyp->bno = fend;
		} else if (bbno < fbno) {
		/*
		* Case 8:
		* bbno bend
		* +BBBBBBBBBBBBBBBBB+
		* +-------------+
		* fbno fend
		*
		* Case 9:
		* bbno bend
		* +BBBBBBBBBBBBBBBBB+
		* +----------------------+
		* fbno fend
		*/
		busyp->length = fbno - busyp->bno;
		} else {
		ASSERT(0);
		}

		trace_xfs_alloc_busy_reuse(mp, pag->pag_agno, fbno, flen);
		return true;

		out_force_log:
		spin_unlock(&pag->pagb_lock);
		xfs_log_force(mp, XFS_LOG_SYNC);
		trace_xfs_alloc_busy_force(mp, pag->pag_agno, fbno, flen);
		spin_lock(&pag->pagb_lock);
		return false;
		}


		/*
		* For a given extent [fbno, flen], make sure we can reuse it safely.
		*/
		void
		xfs_alloc_busy_reuse(
		struct xfs_mount *mp,
		xfs_agnumber_t agno,
		xfs_agblock_t fbno,
		xfs_extlen_t flen,
		bool userdata)
		{
		struct xfs_perag *pag;
		struct rb_node *rbp;

		ASSERT(flen > 0);

		pag = xfs_perag_get(mp, agno);
		spin_lock(&pag->pagb_lock);
		restart:
		rbp = pag->pagb_tree.rb_node;
		while (rbp) {
		struct xfs_busy_extent *busyp =
		rb_entry(rbp, struct xfs_busy_extent, rb_node);
		xfs_agblock_t bbno = busyp->bno;
		xfs_agblock_t bend = bbno + busyp->length;

		if (fbno + flen <= bbno) {
		rbp = rbp->rb_left;
		continue;
		} else if (fbno >= bend) {
		rbp = rbp->rb_right;
		continue;
		}

		if (!xfs_alloc_busy_update_extent(mp, pag, busyp, fbno, flen,
		userdata))
		goto restart;
		}
		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);
		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);

fs/xfs/xfs_alloc.h

+4 −0

Original line number	Diff line number	Diff line
		@@ -145,6 +145,10 @@ xfs_alloc_busy_clear(struct xfs_mount mp, struct xfs_busy_extent busyp);
		int
		xfs_alloc_busy_search(struct xfs_mount *mp, xfs_agnumber_t agno,
		xfs_agblock_t bno, xfs_extlen_t len);

		void
		xfs_alloc_busy_reuse(struct xfs_mount *mp, xfs_agnumber_t agno,
		xfs_agblock_t fbno, xfs_extlen_t flen, bool userdata);
		#endif /* __KERNEL__ */

		/*

fs/xfs/xfs_alloc_btree.c

+2 −13

Original line number	Diff line number	Diff line
		@@ -94,8 +94,8 @@ xfs_allocbt_alloc_block(
		*stat = 0;
		return 0;
		}
		if (xfs_alloc_busy_search(cur->bc_mp, cur->bc_private.a.agno, bno, 1))
		xfs_trans_set_sync(cur->bc_tp);

		xfs_alloc_busy_reuse(cur->bc_mp, cur->bc_private.a.agno, bno, 1, false);

		xfs_trans_agbtree_delta(cur->bc_tp, 1);
		new->s = cpu_to_be32(bno);
		@@ -120,17 +120,6 @@ xfs_allocbt_free_block(
		if (error)
		return error;

		/*
		* Since blocks move to the free list without the coordination used in
		* xfs_bmap_finish, we can't allow block to be available for
		* reallocation and non-transaction writing (user data) until we know
		* that the transaction that moved it to the free list is permanently
		* on disk. We track the blocks by declaring these blocks as "busy";
		* the busy list is maintained on a per-ag basis and each transaction
		* records which entries should be removed when the iclog commits to
		* disk. If a busy block is allocated, the iclog is pushed up to the
		* LSN that freed the block.
		*/
		xfs_alloc_busy_insert(cur->bc_tp, be32_to_cpu(agf->agf_seqno), bno, 1);
		xfs_trans_agbtree_delta(cur->bc_tp, -1);
		return 0;

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