- 根目录:
- fs
- xfs
- xfs_trans_ail.c
/*
* Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
* Copyright (c) 2008 Dave Chinner
* 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_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_trans.h"
#include "xfs_trans_priv.h"
#include "xfs_trace.h"
#include "xfs_error.h"
#include "xfs_log.h"
#ifdef DEBUG
/*
* Check that the list is sorted as it should be.
*/
STATIC void
xfs_ail_check(
struct xfs_ail *ailp,
xfs_log_item_t *lip)
{
xfs_log_item_t *prev_lip;
if (list_empty(&ailp->xa_ail))
return;
/*
* Check the next and previous entries are valid.
*/
ASSERT((lip->li_flags & XFS_LI_IN_AIL) != 0);
prev_lip = list_entry(lip->li_ail.prev, xfs_log_item_t, li_ail);
if (&prev_lip->li_ail != &ailp->xa_ail)
ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) <= 0);
prev_lip = list_entry(lip->li_ail.next, xfs_log_item_t, li_ail);
if (&prev_lip->li_ail != &ailp->xa_ail)
ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) >= 0);
}
#else /* !DEBUG */
#define xfs_ail_check(a,l)
#endif /* DEBUG */
/*
* Return a pointer to the last item in the AIL. If the AIL is empty, then
* return NULL.
*/
static xfs_log_item_t *
xfs_ail_max(
struct xfs_ail *ailp)
{
if (list_empty(&ailp->xa_ail))
return NULL;
return list_entry(ailp->xa_ail.prev, xfs_log_item_t, li_ail);
}
/*
* 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(
struct xfs_ail *ailp,
xfs_log_item_t *lip)
{
if (lip->li_ail.next == &ailp->xa_ail)
return NULL;
return list_first_entry(&lip->li_ail, xfs_log_item_t, li_ail);
}
/*
* 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_ail_min_lsn(
struct xfs_ail *ailp)
{
xfs_lsn_t lsn = 0;
xfs_log_item_t *lip;
spin_lock(&ailp->xa_lock);
lip = xfs_ail_min(ailp);
if (lip)
lsn = lip->li_lsn;
spin_unlock(&ailp->xa_lock);
return lsn;
}
/*
* Return the maximum lsn held in the AIL, or zero if the AIL is empty.
*/
static xfs_lsn_t
xfs_ail_max_lsn(
struct xfs_ail *ailp)
{
xfs_lsn_t lsn = 0;
xfs_log_item_t *lip;
spin_lock(&ailp->xa_lock);
lip = xfs_ail_max(ailp);
if (lip)
lsn = lip->li_lsn;
spin_unlock(&ailp->xa_lock);
return lsn;
}
/*
* The cursor keeps track of where our current traversal is up to by tracking
* the next item in the list for us. However, for this to be safe, removing an
* object from the AIL needs to invalidate any cursor that points to it. hence
* the traversal cursor needs to be linked to the struct xfs_ail so that
* deletion can search all the active cursors for invalidation.
*/
STATIC void
xfs_trans_ail_cursor_init(
struct xfs_ail *ailp,
struct xfs_ail_cursor *cur)
{
cur->item = NULL;
list_add_tail(&cur->list, &ailp->xa_cursors);
}
/*
* Get the next item in the traversal and advance the cursor. If the cursor
* was invalidated (indicated by a lip of 1), restart the traversal.
*/
struct xfs_log_item *
xfs_trans_ail_cursor_next(
struct xfs_ail *ailp,
struct xfs_ail_cursor *cur)
{
struct xfs_log_item *lip = cur->item;
if ((uintptr_t)lip & 1)
lip = xfs_ail_min(ailp);
if (lip)
cur->item = xfs_ail_next(ailp, lip);
return lip;
}
/*
* When the traversal is complete, we need to remove the cursor from the list
* of traversing cursors.
*/
void
xfs_trans_ail_cursor_done(
struct xfs_ail_cursor *cur)
{
cur->item = NULL;
list_del_init(&cur->list);
}
/*
* Invalidate any cursor that is pointing to this item. This is called when an
* item is removed from the AIL. Any cursor pointing to this object is now
* invalid and the traversal needs to be terminated so it doesn't reference a
* freed object. We set the low bit of the cursor item pointer so we can
* distinguish between an invalidation and the end of the list when getting the
* next item from the cursor.
*/
STATIC void
xfs_trans_ail_cursor_clear(
struct xfs_ail *ailp,
struct xfs_log_item *lip)
{
struct xfs_ail_cursor *cur;
list_for_each_entry(cur, &ailp->xa_cursors, list) {
if (cur->item == lip)
cur->item = (struct xfs_log_item *)
((uintptr_t)cur->item | 1);
}
}
/*
* Find the first item in the AIL with the given @lsn by searching in ascending
* LSN order and initialise the cursor to point to the next item for a
* ascending traversal. Pass a @lsn of zero to initialise the cursor to the
* first item in the AIL. Returns NULL if the list is empty.
*/
xfs_log_item_t *
xfs_trans_ail_cursor_first(
struct xfs_ail *ailp,
struct xfs_ail_cursor *cur,
xfs_lsn_t lsn)
{
xfs_log_item_t *lip;
xfs_trans_ail_cursor_init(ailp, cur);
if (lsn == 0) {
lip = xfs_ail_min(ailp);
goto out;
}
list_for_each_entry(lip, &ailp->xa_ail, li_ail) {
if (XFS_LSN_CMP(lip->li_lsn, lsn) >= 0)
goto out;
}
return NULL;
out:
if (lip)
cur->item = xfs_ail_next(ailp, lip);
return lip;
}
static struct xfs_log_item *
__xfs_trans_ail_cursor_last(
struct xfs_ail *ailp,
xfs_lsn_t lsn)
{
xfs_log_item_t *lip;
list_for_each_entry_reverse(lip, &ailp->xa_ail, li_ail) {
if (XFS_LSN_CMP(lip->li_lsn, lsn) <= 0)
return lip;
}
return NULL;
}
/*
* Find the last item in the AIL with the given @lsn by searching in descending
* LSN order and initialise the cursor to point to that item. If there is no
* item with the value of @lsn, then it sets the cursor to the last item with an
* LSN lower than @lsn. Returns NULL if the list is empty.
*/
struct xfs_log_item *
xfs_trans_ail_cursor_last(
struct xfs_ail *ailp,
struct xfs_ail_cursor *cur,
xfs_lsn_t lsn)
{
xfs_trans_ail_cursor_init(ailp, cur);
cur->item = __xfs_trans_ail_cursor_last(ailp, lsn);
return cur->item;
}
/*
* Splice the log item list into the AIL at the given LSN. We splice to the
* tail of the given LSN to maintain insert order for push traversals. The
* cursor is optional, allowing repeated updates to the same LSN to avoid
* repeated traversals. This should not be called with an empty list.
*/
static void
xfs_ail_splice(
struct xfs_ail *ailp,
struct xfs_ail_cursor *cur,
struct list_head *list,
xfs_lsn_t lsn)
{
struct xfs_log_item *lip;
ASSERT(!list_empty(list));
/*
* Use the cursor to determine the insertion point if one is
* provided. If not, or if the one we got is not valid,
* find the place in the AIL where the items belong.
*/
lip = cur ? cur->item : NULL;
if (!lip || (uintptr_t)lip & 1)
lip = __xfs_trans_ail_cursor_last(ailp, lsn);
/*
* If a cursor is provided, we know we're processing the AIL
* in lsn order, and future items to be spliced in will
* follow the last one being inserted now. Update the
* cursor to point to that last item, now while we have a
* reliable pointer to it.
*/
if (cur)
cur->item = list_entry(list->prev, struct xfs_log_item, li_ail);
/*
* Finally perform the splice. Unless the AIL was empty,
* lip points to the item in the AIL _after_ which the new
* items should go. If lip is null the AIL was empty, so
* the new items go at the head of the AIL.
*/
if (lip)
list_splice(list, &lip->li_ail);
else
list_splice(list, &ailp->xa_ail);
}
/*
* Delete the given item from the AIL. Return a pointer to the item.
*/
static void
xfs_ail_delete(
struct xfs_ail *ailp,
xfs_log_item_t *lip)
{
xfs_ail_check(ailp, lip);
list_del(&lip->li_ail);
xfs_trans_ail_cursor_clear(ailp, lip);
}
static long
xfsaild_push(
struct xfs_ail *ailp)
{
xfs_mount_t *mp = ailp->xa_mount;
struct xfs_ail_cursor cur;
xfs_log_item_t *lip;
xfs_lsn_t lsn;
xfs_lsn_t target;
long tout;
int stuck = 0;
int flushing = 0;
int count = 0;
/*
* If we encountered pinned items or did not finish writing out all
* buffers the last time we ran, force the log first and wait for it
* before pushing again.
*/
if (ailp->xa_log_flush && ailp->xa_last_pushed_lsn == 0 &&
(!list_empty_careful(&ailp->xa_buf_list) ||
xfs_ail_min_lsn(ailp))) {
ailp->xa_log_flush = 0;
XFS_STATS_INC(mp, xs_push_ail_flush);
xfs_log_force(mp, XFS_LOG_SYNC);
}
spin_lock(&ailp->xa_lock);
/* barrier matches the xa_target update in xfs_ail_push() */
smp_rmb();
target = ailp->xa_target;
ailp->xa_target_prev = target;
lip = xfs_trans_ail_cursor_first(ailp, &cur, ailp->xa_last_pushed_lsn);
if (!lip) {
/*
* If the AIL is empty or our push has reached the end we are
* done now.
*/
xfs_trans_ail_cursor_done(&cur);
spin_unlock(&ailp->xa_lock);
goto out_done;
}
XFS_STATS_INC(mp, xs_push_ail);
lsn = lip->li_lsn;
while ((XFS_LSN_CMP(lip->li_lsn, target) <= 0)) {
int lock_result;
/*
* Note that iop_push may unlock and reacquire the AIL lock. We
* rely on the AIL cursor implementation to be able to deal with
* the dropped lock.
*/
lock_result = lip->li_ops->iop_push(lip, &ailp->xa_buf_list);
switch (lock_result) {
case XFS_ITEM_SUCCESS:
XFS_STATS_INC(mp, xs_push_ail_success);
trace_xfs_ail_push(lip);
ailp->xa_last_pushed_lsn = lsn;
break;
case XFS_ITEM_FLUSHING:
/*
* The item or its backing buffer is already beeing
* flushed. The typical reason for that is that an
* inode buffer is locked because we already pushed the
* updates to it as part of inode clustering.
*
* We do not want to to stop flushing just because lots
* of items are already beeing flushed, but we need to
* re-try the flushing relatively soon if most of the
* AIL is beeing flushed.
*/
XFS_STATS_INC(mp, xs_push_ail_flushing);
trace_xfs_ail_flushing(lip);
flushing++;
ailp->xa_last_pushed_lsn = lsn;
break;
case XFS_ITEM_PINNED:
XFS_STATS_INC(mp, xs_push_ail_pinned);
trace_xfs_ail_pinned(lip);
stuck++;
ailp->xa_log_flush++;
break;
case XFS_ITEM_LOCKED:
XFS_STATS_INC(mp, xs_push_ail_locked);
trace_xfs_ail_locked(lip);
stuck++;
break;
default:
ASSERT(0);
break;
}
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_ail_cursor_next(ailp, &cur);
if (lip == NULL)
break;
lsn = lip->li_lsn;
}
xfs_trans_ail_cursor_done(&cur);
spin_unlock(&ailp->xa_lock);
if (xfs_buf_delwri_submit_nowait(&ailp->xa_buf_list))
ailp->xa_log_flush++;
if (!count || XFS_LSN_CMP(lsn, target) >= 0) {
out_done:
/*
* We reached the target or the AIL is empty, 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 = 50;
ailp->xa_last_pushed_lsn = 0;
} else if (((stuck + flushing) * 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
* restarting from the start of the AIL. This prevents us from
* spinning on the same items, and if they are pinned will all
* the restart to issue a log force to unpin the stuck items.
*/
tout = 20;
ailp->xa_last_pushed_lsn = 0;
} else {
/*
* Assume we have more work to do in a short while.
*/
tout = 10;
}
return tout;
}
static int
xfsaild(
void *data)
{
struct xfs_ail *ailp = data;
long tout = 0; /* milliseconds */
current->flags |= PF_MEMALLOC;
set_freezable();
while (!kthread_should_stop()) {
if (tout && tout <= 20)
__set_current_state(TASK_KILLABLE);
else
__set_current_state(TASK_INTERRUPTIBLE);
spin_lock(&ailp->xa_lock);
/*
* Idle if the AIL is empty and we are not racing with a target
* update. We check the AIL after we set the task to a sleep
* state to guarantee that we either catch an xa_target update
* or that a wake_up resets the state to TASK_RUNNING.
* Otherwise, we run the risk of sleeping indefinitely.
*
* The barrier matches the xa_target update in xfs_ail_push().
*/
smp_rmb();
if (!xfs_ail_min(ailp) &&
ailp->xa_target == ailp->xa_target_prev) {
spin_unlock(&ailp->xa_lock);
schedule();
tout = 0;
continue;
}
spin_unlock(&ailp->xa_lock);
if (tout)
schedule_timeout(msecs_to_jiffies(tout));
__set_current_state(TASK_RUNNING);
try_to_freeze();
tout = xfsaild_push(ailp);
}
return 0;
}
/*
* 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 workqueue, which means the caller needs
* to handle waiting on the async flush for space to become available.
* We don't want to interrupt any push that is in progress, hence we only queue
* work if we set the pushing bit approriately.
*
* 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_ail_push(
struct xfs_ail *ailp,
xfs_lsn_t threshold_lsn)
{
xfs_log_item_t *lip;
lip = xfs_ail_min(ailp);
if (!lip || XFS_FORCED_SHUTDOWN(ailp->xa_mount) ||
XFS_LSN_CMP(threshold_lsn, ailp->xa_target) <= 0)
return;
/*
* Ensure that the new target is noticed in push code before it clears
* the XFS_AIL_PUSHING_BIT.
*/
smp_wmb();
xfs_trans_ail_copy_lsn(ailp, &ailp->xa_target, &threshold_lsn);
smp_wmb();
wake_up_process(ailp->xa_task);
}
/*
* Push out all items in the AIL immediately
*/
void
xfs_ail_push_all(
struct xfs_ail *ailp)
{
xfs_lsn_t threshold_lsn = xfs_ail_max_lsn(ailp);
if (threshold_lsn)
xfs_ail_push(ailp, threshold_lsn);
}
/*
* Push out all items in the AIL immediately and wait until the AIL is empty.
*/
void
xfs_ail_push_all_sync(
struct xfs_ail *ailp)
{
struct xfs_log_item *lip;
DEFINE_WAIT(wait);
spin_lock(&ailp->xa_lock);
while ((lip = xfs_ail_max(ailp)) != NULL) {
prepare_to_wait(&ailp->xa_empty, &wait, TASK_UNINTERRUPTIBLE);
ailp->xa_target = lip->li_lsn;
wake_up_process(ailp->xa_task);
spin_unlock(&ailp->xa_lock);
schedule();
spin_lock(&ailp->xa_lock);
}
spin_unlock(&ailp->xa_lock);
finish_wait(&ailp->xa_empty, &wait);
}
/*
* xfs_trans_ail_update - bulk AIL insertion operation.
*
* @xfs_trans_ail_update takes an array of log items that all need to be
* positioned at the same LSN in the AIL. If an item is not in the AIL, it will
* be added. Otherwise, it will be repositioned by removing it and re-adding
* it to the AIL. If we move the first item in the AIL, update the log tail to
* match the new minimum LSN in the AIL.
*
* This function takes the AIL lock once to execute the update operations on
* all the items in the array, and as such should not be called with the AIL
* lock held. As a result, once we have the AIL lock, we need to check each log
* item LSN to confirm it needs to be moved forward in the AIL.
*
* To optimise the insert operation, we delete all the items from the AIL in
* the first pass, moving them into a temporary list, then splice the temporary
* list into the correct position in the AIL. This avoids needing to do an
* insert operation on every item.
*
* This function must be called with the AIL lock held. The lock is dropped
* before returning.
*/
void
xfs_trans_ail_update_bulk(
struct xfs_ail *ailp,
struct xfs_ail_cursor *cur,
struct xfs_log_item **log_items,
int nr_items,
xfs_lsn_t lsn) __releases(ailp->xa_lock)
{
xfs_log_item_t *mlip;
int mlip_changed = 0;
int i;
LIST_HEAD(tmp);
ASSERT(nr_items > 0); /* Not required, but true. */
mlip = xfs_ail_min(ailp);
for (i = 0; i < nr_items; i++) {
struct xfs_log_item *lip = log_items[i];
if (lip->li_flags & XFS_LI_IN_AIL) {
/* check if we really need to move the item */
if (XFS_LSN_CMP(lsn, lip->li_lsn) <= 0)
continue;
trace_xfs_ail_move(lip, lip->li_lsn, lsn);
xfs_ail_delete(ailp, lip);
if (mlip == lip)
mlip_changed = 1;
} else {
lip->li_flags |= XFS_LI_IN_AIL;
trace_xfs_ail_insert(lip, 0, lsn);
}
lip->li_lsn = lsn;
list_add(&lip->li_ail, &tmp);
}
if (!list_empty(&tmp))
xfs_ail_splice(ailp, cur, &tmp, lsn);
if (mlip_changed) {
if (!XFS_FORCED_SHUTDOWN(ailp->xa_mount))
xlog_assign_tail_lsn_locked(ailp->xa_mount);
spin_unlock(&ailp->xa_lock);
xfs_log_space_wake(ailp->xa_mount);
} else {
spin_unlock(&ailp->xa_lock);
}
}
/*
* xfs_trans_ail_delete_bulk - remove multiple log items from the AIL
*
* @xfs_trans_ail_delete_bulk takes an array of log items that all need to
* removed from the AIL. The caller is already holding the AIL lock, and done
* all the checks necessary to ensure the items passed in via @log_items are
* ready for deletion. This includes checking that the items are in the AIL.
*
* For each log item to be removed, unlink it from the AIL, clear the IN_AIL
* flag from the item and reset the item's lsn to 0. If we remove the first
* item in the AIL, update the log tail to match the new minimum LSN in the
* AIL.
*
* This function will not drop the AIL lock until all items are removed from
* the AIL to minimise the amount of lock traffic on the AIL. This does not
* greatly increase the AIL hold time, but does significantly reduce the amount
* of traffic on the lock, especially during IO completion.
*
* This function must be called with the AIL lock held. The lock is dropped
* before returning.
*/
void
xfs_trans_ail_delete_bulk(
struct xfs_ail *ailp,
struct xfs_log_item **log_items,
int nr_items,
int shutdown_type) __releases(ailp->xa_lock)
{
xfs_log_item_t *mlip;
int mlip_changed = 0;
int i;
mlip = xfs_ail_min(ailp);
for (i = 0; i < nr_items; i++) {
struct xfs_log_item *lip = log_items[i];
if (!(lip->li_flags & XFS_LI_IN_AIL)) {
struct xfs_mount *mp = ailp->xa_mount;
spin_unlock(&ailp->xa_lock);
if (!XFS_FORCED_SHUTDOWN(mp)) {
xfs_alert_tag(mp, XFS_PTAG_AILDELETE,
"%s: attempting to delete a log item that is not in the AIL",
__func__);
xfs_force_shutdown(mp, shutdown_type);
}
return;
}
trace_xfs_ail_delete(lip, mlip->li_lsn, lip->li_lsn);
xfs_ail_delete(ailp, lip);
lip->li_flags &= ~XFS_LI_IN_AIL;
lip->li_lsn = 0;
if (mlip == lip)
mlip_changed = 1;
}
if (mlip_changed) {
if (!XFS_FORCED_SHUTDOWN(ailp->xa_mount))
xlog_assign_tail_lsn_locked(ailp->xa_mount);
if (list_empty(&ailp->xa_ail))
wake_up_all(&ailp->xa_empty);
spin_unlock(&ailp->xa_lock);
xfs_log_space_wake(ailp->xa_mount);
} else {
spin_unlock(&ailp->xa_lock);
}
}
int
xfs_trans_ail_init(
xfs_mount_t *mp)
{
struct xfs_ail *ailp;
ailp = kmem_zalloc(sizeof(struct xfs_ail), KM_MAYFAIL);
if (!ailp)
return -ENOMEM;
ailp->xa_mount = mp;
INIT_LIST_HEAD(&ailp->xa_ail);
INIT_LIST_HEAD(&ailp->xa_cursors);
spin_lock_init(&ailp->xa_lock);
INIT_LIST_HEAD(&ailp->xa_buf_list);
init_waitqueue_head(&ailp->xa_empty);
ailp->xa_task = kthread_run(xfsaild, ailp, "xfsaild/%s",
ailp->xa_mount->m_fsname);
if (IS_ERR(ailp->xa_task))
goto out_free_ailp;
mp->m_ail = ailp;
return 0;
out_free_ailp:
kmem_free(ailp);
return -ENOMEM;
}
void
xfs_trans_ail_destroy(
xfs_mount_t *mp)
{
struct xfs_ail *ailp = mp->m_ail;
kthread_stop(ailp->xa_task);
kmem_free(ailp);
}