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[XFS] Introduce per-filesystem delwri pagebuf flushing to reduce
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contention between filesystems and prevent deadlocks between filesystems
when a flush dependency exists between them.

SGI-PV: 947098
SGI-Modid: xfs-linux-melb:xfs-kern:24844a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>
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David Chinner authored and Nathan Scott committed Jan 11, 2006
1 parent 216d3b2 commit a6867a6
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Showing 2 changed files with 101 additions and 44 deletions.
136 changes: 92 additions & 44 deletions fs/xfs/linux-2.6/xfs_buf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@

STATIC kmem_cache_t *pagebuf_zone;
STATIC kmem_shaker_t pagebuf_shake;
STATIC int xfsbufd(void *);
STATIC int xfsbufd_wakeup(int, gfp_t);
STATIC void pagebuf_delwri_queue(xfs_buf_t *, int);

Expand Down Expand Up @@ -1492,6 +1493,30 @@ xfs_free_bufhash(
btp->bt_hash = NULL;
}

/*
* buftarg list for delwrite queue processing
*/
STATIC LIST_HEAD(xfs_buftarg_list);
STATIC DEFINE_SPINLOCK(xfs_buftarg_lock);

STATIC void
xfs_register_buftarg(
xfs_buftarg_t *btp)
{
spin_lock(&xfs_buftarg_lock);
list_add(&btp->bt_list, &xfs_buftarg_list);
spin_unlock(&xfs_buftarg_lock);
}

STATIC void
xfs_unregister_buftarg(
xfs_buftarg_t *btp)
{
spin_lock(&xfs_buftarg_lock);
list_del(&btp->bt_list);
spin_unlock(&xfs_buftarg_lock);
}

void
xfs_free_buftarg(
xfs_buftarg_t *btp,
Expand All @@ -1502,6 +1527,12 @@ xfs_free_buftarg(
xfs_blkdev_put(btp->pbr_bdev);
xfs_free_bufhash(btp);
iput(btp->pbr_mapping->host);

/* unregister the buftarg first so that we don't get a
* wakeup finding a non-existent task */
xfs_unregister_buftarg(btp);
kthread_stop(btp->bt_task);

kmem_free(btp, sizeof(*btp));
}

Expand Down Expand Up @@ -1591,6 +1622,26 @@ xfs_mapping_buftarg(
return 0;
}

STATIC int
xfs_alloc_delwrite_queue(
xfs_buftarg_t *btp)
{
int error = 0;

INIT_LIST_HEAD(&btp->bt_list);
INIT_LIST_HEAD(&btp->bt_delwrite_queue);
spinlock_init(&btp->bt_delwrite_lock, "delwri_lock");
btp->bt_flags = 0;
btp->bt_task = kthread_run(xfsbufd, btp, "xfsbufd");
if (IS_ERR(btp->bt_task)) {
error = PTR_ERR(btp->bt_task);
goto out_error;
}
xfs_register_buftarg(btp);
out_error:
return error;
}

xfs_buftarg_t *
xfs_alloc_buftarg(
struct block_device *bdev,
Expand All @@ -1606,6 +1657,8 @@ xfs_alloc_buftarg(
goto error;
if (xfs_mapping_buftarg(btp, bdev))
goto error;
if (xfs_alloc_delwrite_queue(btp))
goto error;
xfs_alloc_bufhash(btp, external);
return btp;

Expand All @@ -1618,20 +1671,19 @@ xfs_alloc_buftarg(
/*
* Pagebuf delayed write buffer handling
*/

STATIC LIST_HEAD(pbd_delwrite_queue);
STATIC DEFINE_SPINLOCK(pbd_delwrite_lock);

STATIC void
pagebuf_delwri_queue(
xfs_buf_t *pb,
int unlock)
{
struct list_head *dwq = &pb->pb_target->bt_delwrite_queue;
spinlock_t *dwlk = &pb->pb_target->bt_delwrite_lock;

PB_TRACE(pb, "delwri_q", (long)unlock);
ASSERT((pb->pb_flags & (PBF_DELWRI|PBF_ASYNC)) ==
(PBF_DELWRI|PBF_ASYNC));

spin_lock(&pbd_delwrite_lock);
spin_lock(dwlk);
/* If already in the queue, dequeue and place at tail */
if (!list_empty(&pb->pb_list)) {
ASSERT(pb->pb_flags & _PBF_DELWRI_Q);
Expand All @@ -1642,9 +1694,9 @@ pagebuf_delwri_queue(
}

pb->pb_flags |= _PBF_DELWRI_Q;
list_add_tail(&pb->pb_list, &pbd_delwrite_queue);
list_add_tail(&pb->pb_list, dwq);
pb->pb_queuetime = jiffies;
spin_unlock(&pbd_delwrite_lock);
spin_unlock(dwlk);

if (unlock)
pagebuf_unlock(pb);
Expand All @@ -1654,16 +1706,17 @@ void
pagebuf_delwri_dequeue(
xfs_buf_t *pb)
{
spinlock_t *dwlk = &pb->pb_target->bt_delwrite_lock;
int dequeued = 0;

spin_lock(&pbd_delwrite_lock);
spin_lock(dwlk);
if ((pb->pb_flags & PBF_DELWRI) && !list_empty(&pb->pb_list)) {
ASSERT(pb->pb_flags & _PBF_DELWRI_Q);
list_del_init(&pb->pb_list);
dequeued = 1;
}
pb->pb_flags &= ~(PBF_DELWRI|_PBF_DELWRI_Q);
spin_unlock(&pbd_delwrite_lock);
spin_unlock(dwlk);

if (dequeued)
pagebuf_rele(pb);
Expand All @@ -1678,21 +1731,22 @@ pagebuf_runall_queues(
flush_workqueue(queue);
}

/* Defines for pagebuf daemon */
STATIC struct task_struct *xfsbufd_task;
STATIC int xfsbufd_force_flush;
STATIC int xfsbufd_force_sleep;

STATIC int
xfsbufd_wakeup(
int priority,
gfp_t mask)
{
if (xfsbufd_force_sleep)
return 0;
xfsbufd_force_flush = 1;
barrier();
wake_up_process(xfsbufd_task);
xfs_buftarg_t *btp, *n;

spin_lock(&xfs_buftarg_lock);
list_for_each_entry_safe(btp, n, &xfs_buftarg_list, bt_list) {
if (test_bit(BT_FORCE_SLEEP, &btp->bt_flags))
continue;
set_bit(BT_FORCE_FLUSH, &btp->bt_flags);
barrier();
wake_up_process(btp->bt_task);
}
spin_unlock(&xfs_buftarg_lock);
return 0;
}

Expand All @@ -1702,31 +1756,34 @@ xfsbufd(
{
struct list_head tmp;
unsigned long age;
xfs_buftarg_t *target;
xfs_buftarg_t *target = (xfs_buftarg_t *)data;
xfs_buf_t *pb, *n;
struct list_head *dwq = &target->bt_delwrite_queue;
spinlock_t *dwlk = &target->bt_delwrite_lock;

current->flags |= PF_MEMALLOC;

INIT_LIST_HEAD(&tmp);
do {
if (unlikely(freezing(current))) {
xfsbufd_force_sleep = 1;
set_bit(BT_FORCE_SLEEP, &target->bt_flags);
refrigerator();
} else {
xfsbufd_force_sleep = 0;
clear_bit(BT_FORCE_SLEEP, &target->bt_flags);
}

schedule_timeout_interruptible(
xfs_buf_timer_centisecs * msecs_to_jiffies(10));

age = xfs_buf_age_centisecs * msecs_to_jiffies(10);
spin_lock(&pbd_delwrite_lock);
list_for_each_entry_safe(pb, n, &pbd_delwrite_queue, pb_list) {
spin_lock(dwlk);
list_for_each_entry_safe(pb, n, dwq, pb_list) {
PB_TRACE(pb, "walkq1", (long)pagebuf_ispin(pb));
ASSERT(pb->pb_flags & PBF_DELWRI);

if (!pagebuf_ispin(pb) && !pagebuf_cond_lock(pb)) {
if (!xfsbufd_force_flush &&
if (!test_bit(BT_FORCE_FLUSH,
&target->bt_flags) &&
time_before(jiffies,
pb->pb_queuetime + age)) {
pagebuf_unlock(pb);
Expand All @@ -1738,11 +1795,11 @@ xfsbufd(
list_move(&pb->pb_list, &tmp);
}
}
spin_unlock(&pbd_delwrite_lock);
spin_unlock(dwlk);

while (!list_empty(&tmp)) {
pb = list_entry(tmp.next, xfs_buf_t, pb_list);
target = pb->pb_target;
ASSERT(target == pb->pb_target);

list_del_init(&pb->pb_list);
pagebuf_iostrategy(pb);
Expand All @@ -1753,7 +1810,7 @@ xfsbufd(
if (as_list_len > 0)
purge_addresses();

xfsbufd_force_flush = 0;
clear_bit(BT_FORCE_FLUSH, &target->bt_flags);
} while (!kthread_should_stop());

return 0;
Expand All @@ -1772,17 +1829,17 @@ xfs_flush_buftarg(
struct list_head tmp;
xfs_buf_t *pb, *n;
int pincount = 0;
struct list_head *dwq = &target->bt_delwrite_queue;
spinlock_t *dwlk = &target->bt_delwrite_lock;

pagebuf_runall_queues(xfsdatad_workqueue);
pagebuf_runall_queues(xfslogd_workqueue);

INIT_LIST_HEAD(&tmp);
spin_lock(&pbd_delwrite_lock);
list_for_each_entry_safe(pb, n, &pbd_delwrite_queue, pb_list) {

if (pb->pb_target != target)
continue;
spin_lock(dwlk);
list_for_each_entry_safe(pb, n, dwq, pb_list) {

ASSERT(pb->pb_target == target);
ASSERT(pb->pb_flags & (PBF_DELWRI|_PBF_DELWRI_Q));
PB_TRACE(pb, "walkq2", (long)pagebuf_ispin(pb));
if (pagebuf_ispin(pb)) {
Expand All @@ -1792,7 +1849,7 @@ xfs_flush_buftarg(

list_move(&pb->pb_list, &tmp);
}
spin_unlock(&pbd_delwrite_lock);
spin_unlock(dwlk);

/*
* Dropped the delayed write list lock, now walk the temporary list
Expand Down Expand Up @@ -1847,20 +1904,12 @@ pagebuf_init(void)
if (!xfsdatad_workqueue)
goto out_destroy_xfslogd_workqueue;

xfsbufd_task = kthread_run(xfsbufd, NULL, "xfsbufd");
if (IS_ERR(xfsbufd_task)) {
error = PTR_ERR(xfsbufd_task);
goto out_destroy_xfsdatad_workqueue;
}

pagebuf_shake = kmem_shake_register(xfsbufd_wakeup);
if (!pagebuf_shake)
goto out_stop_xfsbufd;
goto out_destroy_xfsdatad_workqueue;

return 0;

out_stop_xfsbufd:
kthread_stop(xfsbufd_task);
out_destroy_xfsdatad_workqueue:
destroy_workqueue(xfsdatad_workqueue);
out_destroy_xfslogd_workqueue:
Expand All @@ -1878,7 +1927,6 @@ void
pagebuf_terminate(void)
{
kmem_shake_deregister(pagebuf_shake);
kthread_stop(xfsbufd_task);
destroy_workqueue(xfsdatad_workqueue);
destroy_workqueue(xfslogd_workqueue);
kmem_zone_destroy(pagebuf_zone);
Expand Down
9 changes: 9 additions & 0 deletions fs/xfs/linux-2.6/xfs_buf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,15 @@ typedef struct xfs_buftarg {
uint bt_hashmask;
uint bt_hashshift;
xfs_bufhash_t *bt_hash;

/* per device delwri queue */
struct task_struct *bt_task;
struct list_head bt_list;
struct list_head bt_delwrite_queue;
spinlock_t bt_delwrite_lock;
uint bt_flags;
#define BT_FORCE_SLEEP 1
#define BT_FORCE_FLUSH 2
} xfs_buftarg_t;

/*
Expand Down

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