/*
* Insert the given log item into the AIL.
* We almost always insert at the end of the list, so on inserts
* we search from the end of the list to find where the
* new item belongs.
*/
STATIC void
xfs_ail_insert(
xfs_ail_entry_t *base,
xfs_log_item_t *lip)
/* ARGSUSED */
{
xfs_log_item_t *next_lip;
/*
* If the list is empty, just insert the item.
*/
if (base->ail_back == (xfs_log_item_t*)base) {
base->ail_forw = lip;
base->ail_back = lip;
lip->li_ail.ail_forw = (xfs_log_item_t*)base;
lip->li_ail.ail_back = (xfs_log_item_t*)base;
return;
}
next_lip = base->ail_back;
while ((next_lip != (xfs_log_item_t*)base) &&
(XFS_LSN_CMP(next_lip->li_lsn, lip->li_lsn) > 0)) {
next_lip = next_lip->li_ail.ail_back;
}
ASSERT((next_lip == (xfs_log_item_t*)base) ||
(XFS_LSN_CMP(next_lip->li_lsn, lip->li_lsn) <= 0));
lip->li_ail.ail_forw = next_lip->li_ail.ail_forw;
lip->li_ail.ail_back = next_lip;
next_lip->li_ail.ail_forw = lip;
lip->li_ail.ail_forw->li_ail.ail_back = lip;
xfs_ail_check(base);
return;
}
/*
* xfs_trans_push_ail
*
* This routine is called to move the tail of the AIL forward. It does this by
* trying to flush items in the AIL whose lsns are below the given
* threshold_lsn.
*
* the push is run asynchronously in a separate thread, so we return the tail
* of the log right now instead of the tail after the push. This means we will
* either continue right away, or we will sleep waiting on the async thread to
* do it's work.
*
* We do this unlocked - we only need to know whether there is anything in the
* AIL at the time we are called. We don't need to access the contents of
* any of the objects, so the lock is not needed.
*/
void
xfs_trans_push_ail(
xfs_mount_t *mp,
xfs_lsn_t threshold_lsn)
{
xfs_log_item_t *lip;
lip = xfs_ail_min(&mp->m_ail.xa_ail);
if (lip && !XFS_FORCED_SHUTDOWN(mp)) {
if (XFS_LSN_CMP(threshold_lsn, mp->m_ail.xa_target) > 0)
xfsaild_wakeup(mp, threshold_lsn);
}
}
/*
* Return the item in the AIL with the current lsn.
* Return the current tree generation number for use
* in calls to xfs_trans_next_ail().
*/
STATIC xfs_log_item_t *
xfs_trans_first_push_ail(
xfs_mount_t *mp,
int *gen,
xfs_lsn_t lsn)
{
xfs_log_item_t *lip;
lip = xfs_ail_min(&(mp->m_ail.xa_ail));
*gen = (int)mp->m_ail.xa_gen;
if (lsn == 0)
return lip;
while (lip && (XFS_LSN_CMP(lip->li_lsn, lsn) < 0))
lip = lip->li_ail.ail_forw;
return lip;
}
/*
* Check that the list is sorted as it should be.
*/
STATIC void
xfs_ail_check(
xfs_ail_entry_t *base)
{
xfs_log_item_t *lip;
xfs_log_item_t *prev_lip;
lip = base->ail_forw;
if (lip == (xfs_log_item_t*)base) {
/*
* Make sure the pointers are correct when the list
* is empty.
*/
ASSERT(base->ail_back == (xfs_log_item_t*)base);
return;
}
/*
* Walk the list checking forward and backward pointers,
* lsn ordering, and that every entry has the XFS_LI_IN_AIL
* flag set.
*/
prev_lip = (xfs_log_item_t*)base;
while (lip != (xfs_log_item_t*)base) {
if (prev_lip != (xfs_log_item_t*)base) {
ASSERT(prev_lip->li_ail.ail_forw == lip);
ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) <= 0);
}
ASSERT(lip->li_ail.ail_back == prev_lip);
ASSERT((lip->li_flags & XFS_LI_IN_AIL) != 0);
prev_lip = lip;
lip = lip->li_ail.ail_forw;
}
ASSERT(lip == (xfs_log_item_t*)base);
ASSERT(base->ail_back == prev_lip);
}
/*
* This is called to perform the commit processing for each
* item described by the given chunk.
*
* The commit processing consists of unlocking items which were
* held locked with the SYNC_UNLOCK attribute, calling the committed
* routine of each logged item, updating the item's position in the AIL
* if necessary, and unpinning each item. If the committed routine
* returns -1, then do nothing further with the item because it
* may have been freed.
*
* Since items are unlocked when they are copied to the incore
* log, it is possible for two transactions to be completing
* and manipulating the same item simultaneously. The AIL lock
* will protect the lsn field of each item. The value of this
* field can never go backwards.
*
* We unpin the items after repositioning them in the AIL, because
* otherwise they could be immediately flushed and we'd have to race
* with the flusher trying to pull the item from the AIL as we add it.
*/
STATIC void
xfs_trans_chunk_committed(
xfs_log_item_chunk_t *licp,
xfs_lsn_t lsn,
int aborted)
{
xfs_log_item_desc_t *lidp;
xfs_log_item_t *lip;
xfs_lsn_t item_lsn;
struct xfs_mount *mp;
int i;
SPLDECL(s);
lidp = licp->lic_descs;
for (i = 0; i < licp->lic_unused; i++, lidp++) {
if (XFS_LIC_ISFREE(licp, i)) {
continue;
}
lip = lidp->lid_item;
if (aborted)
lip->li_flags |= XFS_LI_ABORTED;
/*
* Send in the ABORTED flag to the COMMITTED routine
* so that it knows whether the transaction was aborted
* or not.
*/
item_lsn = IOP_COMMITTED(lip, lsn);
/*
* If the committed routine returns -1, make
* no more references to the item.
*/
if (XFS_LSN_CMP(item_lsn, (xfs_lsn_t)-1) == 0) {
continue;
}
/*
* If the returned lsn is greater than what it
* contained before, update the location of the
* item in the AIL. If it is not, then do nothing.
* Items can never move backwards in the AIL.
*
* While the new lsn should usually be greater, it
* is possible that a later transaction completing
* simultaneously with an earlier one using the
* same item could complete first with a higher lsn.
* This would cause the earlier transaction to fail
* the test below.
*/
mp = lip->li_mountp;
AIL_LOCK(mp,s);
if (XFS_LSN_CMP(item_lsn, lip->li_lsn) > 0) {
/*
* This will set the item's lsn to item_lsn
* and update the position of the item in
* the AIL.
*
* xfs_trans_update_ail() drops the AIL lock.
*/
xfs_trans_update_ail(mp, lip, item_lsn, s);
} else {
AIL_UNLOCK(mp, s);
}
/*
* Now that we've repositioned the item in the AIL,
* unpin it so it can be flushed. Pass information
* about buffer stale state down from the log item
* flags, if anyone else stales the buffer we do not
* want to pay any attention to it.
*/
IOP_UNPIN(lip, lidp->lid_flags & XFS_LID_BUF_STALE);
}
}
/*
* xfs_trans_push_ail
*
* This routine is called to move the tail of the AIL
* forward. It does this by trying to flush items in the AIL
* whose lsns are below the given threshold_lsn.
*
* The routine returns the lsn of the tail of the log.
*/
xfs_lsn_t
xfs_trans_push_ail(
xfs_mount_t *mp,
xfs_lsn_t threshold_lsn)
{
xfs_lsn_t lsn;
xfs_log_item_t *lip;
int gen;
int restarts;
int lock_result;
int flush_log;
SPLDECL(s);
#define XFS_TRANS_PUSH_AIL_RESTARTS 10
AIL_LOCK(mp,s);
lip = xfs_trans_first_ail(mp, &gen);
if (lip == NULL || XFS_FORCED_SHUTDOWN(mp)) {
/*
* Just return if the AIL is empty.
*/
AIL_UNLOCK(mp, s);
return (xfs_lsn_t)0;
}
XFS_STATS_INC(xs_push_ail);
/*
* While the item we are looking at is below the given threshold
* try to flush it out. Make sure to limit the number of times
* we allow xfs_trans_next_ail() to restart scanning from the
* beginning of the list. We'd like not to stop until we've at least
* tried to push on everything in the AIL with an LSN less than
* the given threshold. However, we may give up before that if
* we realize that we've been holding the AIL_LOCK for 'too long',
* blocking interrupts. Currently, too long is < 500us roughly.
*/
flush_log = 0;
restarts = 0;
while (((restarts < XFS_TRANS_PUSH_AIL_RESTARTS) &&
(XFS_LSN_CMP(lip->li_lsn, threshold_lsn) < 0))) {
/*
* If we can lock the item without sleeping, unlock
* the AIL lock and flush the item. Then re-grab the
* AIL lock so we can look for the next item on the
* AIL. Since we unlock the AIL while we flush the
* item, the next routine may start over again at the
* the beginning of the list if anything has changed.
* That is what the generation count is for.
*
* If we can't lock the item, either its holder will flush
* it or it is already being flushed or it is being relogged.
* In any of these case it is being taken care of and we
* can just skip to the next item in the list.
*/
lock_result = IOP_TRYLOCK(lip);
switch (lock_result) {
case XFS_ITEM_SUCCESS:
AIL_UNLOCK(mp, s);
XFS_STATS_INC(xs_push_ail_success);
IOP_PUSH(lip);
AIL_LOCK(mp,s);
break;
case XFS_ITEM_PUSHBUF:
AIL_UNLOCK(mp, s);
XFS_STATS_INC(xs_push_ail_pushbuf);
#ifdef XFSRACEDEBUG
delay_for_intr();
delay(300);
#endif
ASSERT(lip->li_ops->iop_pushbuf);
ASSERT(lip);
IOP_PUSHBUF(lip);
AIL_LOCK(mp,s);
break;
case XFS_ITEM_PINNED:
XFS_STATS_INC(xs_push_ail_pinned);
flush_log = 1;
break;
case XFS_ITEM_LOCKED:
XFS_STATS_INC(xs_push_ail_locked);
break;
case XFS_ITEM_FLUSHING:
XFS_STATS_INC(xs_push_ail_flushing);
break;
default:
ASSERT(0);
break;
}
lip = xfs_trans_next_ail(mp, lip, &gen, &restarts);
if (lip == NULL) {
break;
}
if (XFS_FORCED_SHUTDOWN(mp)) {
/*
* Just return if we shut down during the last try.
*/
AIL_UNLOCK(mp, s);
return (xfs_lsn_t)0;
}
}
if (flush_log) {
/*
* If something we need to push out was pinned, then
* push out the log so it will become unpinned and
* move forward in the AIL.
*/
AIL_UNLOCK(mp, s);
XFS_STATS_INC(xs_push_ail_flush);
xfs_log_force(mp, (xfs_lsn_t)0, XFS_LOG_FORCE);
AIL_LOCK(mp, s);
}
lip = xfs_ail_min(&(mp->m_ail));
if (lip == NULL) {
lsn = (xfs_lsn_t)0;
} else {
lsn = lip->li_lsn;
}
AIL_UNLOCK(mp, s);
return lsn;
} /* xfs_trans_push_ail */
/*
* Function that does the work of pushing on the AIL
*/
long
xfsaild_push(
xfs_mount_t *mp,
xfs_lsn_t *last_lsn)
{
long tout = 1000; /* milliseconds */
xfs_lsn_t last_pushed_lsn = *last_lsn;
xfs_lsn_t target = mp->m_ail.xa_target;
xfs_lsn_t lsn;
xfs_log_item_t *lip;
int gen;
int restarts;
int flush_log, count, stuck;
#define XFS_TRANS_PUSH_AIL_RESTARTS 10
spin_lock(&mp->m_ail_lock);
lip = xfs_trans_first_push_ail(mp, &gen, *last_lsn);
if (!lip || XFS_FORCED_SHUTDOWN(mp)) {
/*
* AIL is empty or our push has reached the end.
*/
spin_unlock(&mp->m_ail_lock);
last_pushed_lsn = 0;
goto out;
}
XFS_STATS_INC(xs_push_ail);
/*
* While the item we are looking at is below the given threshold
* try to flush it out. We'd like not to stop until we've at least
* tried to push on everything in the AIL with an LSN less than
* the given threshold.
*
* However, we will stop after a certain number of pushes and wait
* for a reduced timeout to fire before pushing further. This
* prevents use from spinning when we can't do anything or there is
* lots of contention on the AIL lists.
*/
tout = 10;
lsn = lip->li_lsn;
flush_log = stuck = count = restarts = 0;
while ((XFS_LSN_CMP(lip->li_lsn, target) < 0)) {
int lock_result;
/*
* If we can lock the item without sleeping, unlock the AIL
* lock and flush the item. Then re-grab the AIL lock so we
* can look for the next item on the AIL. List changes are
* handled by the AIL lookup functions internally
*
* If we can't lock the item, either its holder will flush it
* or it is already being flushed or it is being relogged. In
* any of these case it is being taken care of and we can just
* skip to the next item in the list.
*/
lock_result = IOP_TRYLOCK(lip);
spin_unlock(&mp->m_ail_lock);
switch (lock_result) {
case XFS_ITEM_SUCCESS:
XFS_STATS_INC(xs_push_ail_success);
IOP_PUSH(lip);
last_pushed_lsn = lsn;
break;
case XFS_ITEM_PUSHBUF:
XFS_STATS_INC(xs_push_ail_pushbuf);
IOP_PUSHBUF(lip);
last_pushed_lsn = lsn;
break;
case XFS_ITEM_PINNED:
XFS_STATS_INC(xs_push_ail_pinned);
stuck++;
flush_log = 1;
break;
case XFS_ITEM_LOCKED:
XFS_STATS_INC(xs_push_ail_locked);
last_pushed_lsn = lsn;
stuck++;
break;
case XFS_ITEM_FLUSHING:
XFS_STATS_INC(xs_push_ail_flushing);
last_pushed_lsn = lsn;
stuck++;
break;
default:
ASSERT(0);
break;
}
spin_lock(&mp->m_ail_lock);
/* should we bother continuing? */
if (XFS_FORCED_SHUTDOWN(mp))
break;
ASSERT(mp->m_log);
count++;
/*
* Are there too many items we can't do anything with?
* If we we are skipping too many items because we can't flush
* them or they are already being flushed, we back off and
* given them time to complete whatever operation is being
* done. i.e. remove pressure from the AIL while we can't make
* progress so traversals don't slow down further inserts and
* removals to/from the AIL.
*
* The value of 100 is an arbitrary magic number based on
* observation.
*/
if (stuck > 100)
break;
lip = xfs_trans_next_ail(mp, lip, &gen, &restarts);
if (lip == NULL)
break;
if (restarts > XFS_TRANS_PUSH_AIL_RESTARTS)
break;
lsn = lip->li_lsn;
}
spin_unlock(&mp->m_ail_lock);
if (flush_log) {
/*
* If something we need to push out was pinned, then
* push out the log so it will become unpinned and
* move forward in the AIL.
*/
XFS_STATS_INC(xs_push_ail_flush);
xfs_log_force(mp, (xfs_lsn_t)0, XFS_LOG_FORCE);
}
if (!count) {
/* We're past our target or empty, so idle */
tout = 1000;
} else if (XFS_LSN_CMP(lsn, target) >= 0) {
/*
* We reached the target so wait a bit longer for I/O to
* complete and remove pushed items from the AIL before we
* start the next scan from the start of the AIL.
*/
tout += 20;
last_pushed_lsn = 0;
} else if ((restarts > XFS_TRANS_PUSH_AIL_RESTARTS) ||
((stuck * 100) / count > 90)) {
/*
* Either there is a lot of contention on the AIL or we
* are stuck due to operations in progress. "Stuck" in this
* case is defined as >90% of the items we tried to push
* were stuck.
*
* Backoff a bit more to allow some I/O to complete before
* continuing from where we were.
*/
tout += 10;
}
out:
*last_lsn = last_pushed_lsn;
return tout;
} /* xfsaild_push */
