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xfs: exact busy extent tracking

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Update the extent tree in case we have to reuse a busy extent, so that it
always is kept uptodate.  This is done by replacing the busy list searches
with a new xfs_alloc_busy_reuse helper, which updates the busy extent tree
in case of a reuse.  This allows us to allow reusing metadata extents
unconditionally, and thus avoid log forces especially for allocation btree
blocks.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
This commit is contained in:
Christoph Hellwig 2011-04-24 19:06:16 +00:00 committed by Alex Elder
parent e26f0501cf
commit 97d3ac75e5
9 changed files with 237 additions and 248 deletions
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79
fs/xfs/linux-2.6/xfs_trace.h
View File

@ -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,

1
fs/xfs/xfs_ag.h
View File

@ -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 */
};
/*

373
fs/xfs/xfs_alloc.c
View File

@ -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);
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);

4
fs/xfs/xfs_alloc.h
View File

@ -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__ */
/*

15
fs/xfs/xfs_alloc_btree.c
View File

@ -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;

7
fs/xfs/xfs_log.c
View File

@ -3248,13 +3248,6 @@ xfs_log_ticket_get(
return ticket;
}
xlog_tid_t
xfs_log_get_trans_ident(
struct xfs_trans *tp)
{
return tp->t_ticket->t_tid;
}
/*
* Allocate and initialise a new log ticket.
*/

2
fs/xfs/xfs_log.h
View File

@ -189,8 +189,6 @@ void xlog_iodone(struct xfs_buf *);
struct xlog_ticket *xfs_log_ticket_get(struct xlog_ticket *ticket);
void xfs_log_ticket_put(struct xlog_ticket *ticket);
xlog_tid_t xfs_log_get_trans_ident(struct xfs_trans *tp);
void xfs_log_commit_cil(struct xfs_mount *mp, struct xfs_trans *tp,
struct xfs_log_vec *log_vector,
xfs_lsn_t *commit_lsn, int flags);

2
fs/xfs/xfs_log_priv.h
View File

@ -146,6 +146,8 @@ static inline uint xlog_get_client_id(__be32 i)
shutdown */
#define XLOG_TAIL_WARN 0x10 /* log tail verify warning issued */
typedef __uint32_t xlog_tid_t;
#ifdef __KERNEL__
/*
* Below are states for covering allocation transactions.

2
fs/xfs/xfs_types.h
View File

@ -73,8 +73,6 @@ typedef __int32_t xfs_tid_t; /* transaction identifier */
typedef __uint32_t xfs_dablk_t; /* dir/attr block number (in file) */
typedef __uint32_t xfs_dahash_t; /* dir/attr hash value */
typedef __uint32_t xlog_tid_t; /* transaction ID type */
/*
* These types are 64 bits on disk but are either 32 or 64 bits in memory.
* Disk based types: