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linux/fs/xfs/xfs_trans_ail.c

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/*
* Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
* All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_trans_priv.h"
#include "xfs_error.h"
STATIC void xfs_ail_insert(xfs_ail_entry_t *, xfs_log_item_t *);
STATIC xfs_log_item_t * xfs_ail_delete(xfs_ail_entry_t *, xfs_log_item_t *);
STATIC xfs_log_item_t * xfs_ail_min(xfs_ail_entry_t *);
STATIC xfs_log_item_t * xfs_ail_next(xfs_ail_entry_t *, xfs_log_item_t *);
#ifdef DEBUG
STATIC void xfs_ail_check(xfs_ail_entry_t *, xfs_log_item_t *);
#else
#define xfs_ail_check(a,l)
#endif /* DEBUG */
/*
* This is called by the log manager code to determine the LSN
* of the tail of the log. This is exactly the LSN of the first
* item in the AIL. If the AIL is empty, then this function
* returns 0.
*
* We need the AIL lock in order to get a coherent read of the
* lsn of the last item in the AIL.
*/
xfs_lsn_t
xfs_trans_tail_ail(
xfs_mount_t *mp)
{
xfs_lsn_t lsn;
xfs_log_item_t *lip;
spin_lock(&mp->m_ail_lock);
lip = xfs_ail_min(&(mp->m_ail.xa_ail));
if (lip == NULL) {
lsn = (xfs_lsn_t)0;
} else {
lsn = lip->li_lsn;
}
spin_unlock(&mp->m_ail_lock);
return lsn;
}
/*
* 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;
}
/*
* 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 */
/*
* This is to be called when an item is unlocked that may have
* been in the AIL. It will wake up the first member of the AIL
* wait list if this item's unlocking might allow it to progress.
* If the item is in the AIL, then we need to get the AIL lock
* while doing our checking so we don't race with someone going
* to sleep waiting for this event in xfs_trans_push_ail().
*/
void
xfs_trans_unlocked_item(
xfs_mount_t *mp,
xfs_log_item_t *lip)
{
xfs_log_item_t *min_lip;
/*
* If we're forcibly shutting down, we may have
* unlocked log items arbitrarily. The last thing
* we want to do is to move the tail of the log
* over some potentially valid data.
*/
if (!(lip->li_flags & XFS_LI_IN_AIL) ||
XFS_FORCED_SHUTDOWN(mp)) {
return;
}
/*
* This is the one case where we can call into xfs_ail_min()
* without holding the AIL lock because we only care about the
* case where we are at the tail of the AIL. If the object isn't
* at the tail, it doesn't matter what result we get back. This
* is slightly racy because since we were just unlocked, we could
* go to sleep between the call to xfs_ail_min and the call to
* xfs_log_move_tail, have someone else lock us, commit to us disk,
* move us out of the tail of the AIL, and then we wake up. However,
* the call to xfs_log_move_tail() doesn't do anything if there's
* not enough free space to wake people up so we're safe calling it.
*/
min_lip = xfs_ail_min(&mp->m_ail.xa_ail);
if (min_lip == lip)
xfs_log_move_tail(mp, 1);
} /* xfs_trans_unlocked_item */
/*
* Update the position of the item in the AIL with the new
* lsn. If it is not yet in the AIL, add it. Otherwise, move
* it to its new position by removing it and re-adding it.
*
* Wakeup anyone with an lsn less than the item's lsn. If the item
* we move in the AIL is the minimum one, update the tail lsn in the
* log manager.
*
* Increment the AIL's generation count to indicate that the tree
* has changed.
*
* This function must be called with the AIL lock held. The lock
* is dropped before returning.
*/
void
xfs_trans_update_ail(
xfs_mount_t *mp,
xfs_log_item_t *lip,
xfs_lsn_t lsn) __releases(mp->m_ail_lock)
{
xfs_ail_entry_t *ailp;
xfs_log_item_t *dlip=NULL;
xfs_log_item_t *mlip; /* ptr to minimum lip */
ailp = &(mp->m_ail.xa_ail);
mlip = xfs_ail_min(ailp);
if (lip->li_flags & XFS_LI_IN_AIL) {
dlip = xfs_ail_delete(ailp, lip);
ASSERT(dlip == lip);
} else {
lip->li_flags |= XFS_LI_IN_AIL;
}
lip->li_lsn = lsn;
xfs_ail_insert(ailp, lip);
mp->m_ail.xa_gen++;
if (mlip == dlip) {
mlip = xfs_ail_min(&(mp->m_ail.xa_ail));
spin_unlock(&mp->m_ail_lock);
xfs_log_move_tail(mp, mlip->li_lsn);
} else {
spin_unlock(&mp->m_ail_lock);
}
} /* xfs_trans_update_ail */
/*
* Delete the given item from the AIL. It must already be in
* the AIL.
*
* Wakeup anyone with an lsn less than item's lsn. If the item
* we delete in the AIL is the minimum one, update the tail lsn in the
* log manager.
*
* Clear the IN_AIL flag from the item, reset its lsn to 0, and
* bump the AIL's generation count to indicate that the tree
* has changed.
*
* This function must be called with the AIL lock held. The lock
* is dropped before returning.
*/
void
xfs_trans_delete_ail(
xfs_mount_t *mp,
xfs_log_item_t *lip) __releases(mp->m_ail_lock)
{
xfs_ail_entry_t *ailp;
xfs_log_item_t *dlip;
xfs_log_item_t *mlip;
if (lip->li_flags & XFS_LI_IN_AIL) {
ailp = &(mp->m_ail.xa_ail);
mlip = xfs_ail_min(ailp);
dlip = xfs_ail_delete(ailp, lip);
ASSERT(dlip == lip);
lip->li_flags &= ~XFS_LI_IN_AIL;
lip->li_lsn = 0;
mp->m_ail.xa_gen++;
if (mlip == dlip) {
mlip = xfs_ail_min(&(mp->m_ail.xa_ail));
spin_unlock(&mp->m_ail_lock);
xfs_log_move_tail(mp, (mlip ? mlip->li_lsn : 0));
} else {
spin_unlock(&mp->m_ail_lock);
}
}
else {
/*
* If the file system is not being shutdown, we are in
* serious trouble if we get to this stage.
*/
if (XFS_FORCED_SHUTDOWN(mp))
spin_unlock(&mp->m_ail_lock);
else {
xfs_cmn_err(XFS_PTAG_AILDELETE, CE_ALERT, mp,
"%s: attempting to delete a log item that is not in the AIL",
__FUNCTION__);
spin_unlock(&mp->m_ail_lock);
xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
}
}
}
/*
* Return the item in the AIL with the smallest lsn.
* Return the current tree generation number for use
* in calls to xfs_trans_next_ail().
*/
xfs_log_item_t *
xfs_trans_first_ail(
xfs_mount_t *mp,
int *gen)
{
xfs_log_item_t *lip;
lip = xfs_ail_min(&(mp->m_ail.xa_ail));
*gen = (int)mp->m_ail.xa_gen;
return lip;
}
/*
* If the generation count of the tree has not changed since the
* caller last took something from the AIL, then return the elmt
* in the tree which follows the one given. If the count has changed,
* then return the minimum elmt of the AIL and bump the restarts counter
* if one is given.
*/
xfs_log_item_t *
xfs_trans_next_ail(
xfs_mount_t *mp,
xfs_log_item_t *lip,
int *gen,
int *restarts)
{
xfs_log_item_t *nlip;
ASSERT(mp && lip && gen);
if (mp->m_ail.xa_gen == *gen) {
nlip = xfs_ail_next(&(mp->m_ail.xa_ail), lip);
} else {
nlip = xfs_ail_min(&(mp->m_ail).xa_ail);
*gen = (int)mp->m_ail.xa_gen;
if (restarts != NULL) {
XFS_STATS_INC(xs_push_ail_restarts);
(*restarts)++;
}
}
return (nlip);
}
/*
* The active item list (AIL) is a doubly linked list of log
* items sorted by ascending lsn. The base of the list is
* a forw/back pointer pair embedded in the xfs mount structure.
* The base is initialized with both pointers pointing to the
* base. This case always needs to be distinguished, because
* the base has no lsn to look at. 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.
*/
/*
* Initialize the doubly linked list to point only to itself.
*/
int
xfs_trans_ail_init(
xfs_mount_t *mp)
{
mp->m_ail.xa_ail.ail_forw = (xfs_log_item_t*)&mp->m_ail.xa_ail;
mp->m_ail.xa_ail.ail_back = (xfs_log_item_t*)&mp->m_ail.xa_ail;
return xfsaild_start(mp);
}
void
xfs_trans_ail_destroy(
xfs_mount_t *mp)
{
xfsaild_stop(mp);
}
/*
* 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, lip);
return;
}
/*
* Delete the given item from the AIL. Return a pointer to the item.
*/
/*ARGSUSED*/
STATIC xfs_log_item_t *
xfs_ail_delete(
xfs_ail_entry_t *base,
xfs_log_item_t *lip)
/* ARGSUSED */
{
xfs_ail_check(base, lip);
lip->li_ail.ail_forw->li_ail.ail_back = lip->li_ail.ail_back;
lip->li_ail.ail_back->li_ail.ail_forw = lip->li_ail.ail_forw;
lip->li_ail.ail_forw = NULL;
lip->li_ail.ail_back = NULL;
return lip;
}
/*
* Return a pointer to the first item in the AIL.
* If the AIL is empty, then return NULL.
*/
STATIC xfs_log_item_t *
xfs_ail_min(
xfs_ail_entry_t *base)
/* ARGSUSED */
{
register xfs_log_item_t *forw = base->ail_forw;
if (forw == (xfs_log_item_t*)base) {
return NULL;
}
return forw;
}
/*
* Return a pointer to the item which follows
* the given item in the AIL. If the given item
* is the last item in the list, then return NULL.
*/
STATIC xfs_log_item_t *
xfs_ail_next(
xfs_ail_entry_t *base,
xfs_log_item_t *lip)
/* ARGSUSED */
{
if (lip->li_ail.ail_forw == (xfs_log_item_t*)base) {
return NULL;
}
return lip->li_ail.ail_forw;
}
#ifdef DEBUG
/*
* 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;
prev_lip = base->ail_forw;
if (prev_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;
}
/*
* Check the next and previous entries are valid.
*/
ASSERT((lip->li_flags & XFS_LI_IN_AIL) != 0);
prev_lip = lip->li_ail.ail_back;
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);
}
prev_lip = lip->li_ail.ail_forw;
if (prev_lip != (xfs_log_item_t*)base) {
ASSERT(prev_lip->li_ail.ail_back == lip);
ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) >= 0);
}
#ifdef XFS_TRANS_DEBUG
/*
* Walk the list checking forward and backward pointers,
* lsn ordering, and that every entry has the XFS_LI_IN_AIL
* flag set. This is really expensive, so only do it when
* specifically debugging the transaction subsystem.
*/
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);
#endif /* XFS_TRANS_DEBUG */
}
#endif /* DEBUG */
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