linux/fs/xfs/xfs_trans_ail.c
Peter Zijlstra f5d39b0208 freezer,sched: Rewrite core freezer logic
Rewrite the core freezer to behave better wrt thawing and be simpler
in general.

By replacing PF_FROZEN with TASK_FROZEN, a special block state, it is
ensured frozen tasks stay frozen until thawed and don't randomly wake
up early, as is currently possible.

As such, it does away with PF_FROZEN and PF_FREEZER_SKIP, freeing up
two PF_flags (yay!).

Specifically; the current scheme works a little like:

	freezer_do_not_count();
	schedule();
	freezer_count();

And either the task is blocked, or it lands in try_to_freezer()
through freezer_count(). Now, when it is blocked, the freezer
considers it frozen and continues.

However, on thawing, once pm_freezing is cleared, freezer_count()
stops working, and any random/spurious wakeup will let a task run
before its time.

That is, thawing tries to thaw things in explicit order; kernel
threads and workqueues before doing bringing SMP back before userspace
etc.. However due to the above mentioned races it is entirely possible
for userspace tasks to thaw (by accident) before SMP is back.

This can be a fatal problem in asymmetric ISA architectures (eg ARMv9)
where the userspace task requires a special CPU to run.

As said; replace this with a special task state TASK_FROZEN and add
the following state transitions:

	TASK_FREEZABLE	-> TASK_FROZEN
	__TASK_STOPPED	-> TASK_FROZEN
	__TASK_TRACED	-> TASK_FROZEN

The new TASK_FREEZABLE can be set on any state part of TASK_NORMAL
(IOW. TASK_INTERRUPTIBLE and TASK_UNINTERRUPTIBLE) -- any such state
is already required to deal with spurious wakeups and the freezer
causes one such when thawing the task (since the original state is
lost).

The special __TASK_{STOPPED,TRACED} states *can* be restored since
their canonical state is in ->jobctl.

With this, frozen tasks need an explicit TASK_FROZEN wakeup and are
free of undue (early / spurious) wakeups.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20220822114649.055452969@infradead.org
2022-09-07 21:53:50 +02:00

936 lines
24 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
* Copyright (c) 2008 Dave Chinner
* All Rights Reserved.
*/
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.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_errortag.h"
#include "xfs_error.h"
#include "xfs_log.h"
#include "xfs_log_priv.h"
#ifdef DEBUG
/*
* Check that the list is sorted as it should be.
*
* Called with the ail lock held, but we don't want to assert fail with it
* held otherwise we'll lock everything up and won't be able to debug the
* cause. Hence we sample and check the state under the AIL lock and return if
* everything is fine, otherwise we drop the lock and run the ASSERT checks.
* Asserts may not be fatal, so pick the lock back up and continue onwards.
*/
STATIC void
xfs_ail_check(
struct xfs_ail *ailp,
struct xfs_log_item *lip)
__must_hold(&ailp->ail_lock)
{
struct xfs_log_item *prev_lip;
struct xfs_log_item *next_lip;
xfs_lsn_t prev_lsn = NULLCOMMITLSN;
xfs_lsn_t next_lsn = NULLCOMMITLSN;
xfs_lsn_t lsn;
bool in_ail;
if (list_empty(&ailp->ail_head))
return;
/*
* Sample then check the next and previous entries are valid.
*/
in_ail = test_bit(XFS_LI_IN_AIL, &lip->li_flags);
prev_lip = list_entry(lip->li_ail.prev, struct xfs_log_item, li_ail);
if (&prev_lip->li_ail != &ailp->ail_head)
prev_lsn = prev_lip->li_lsn;
next_lip = list_entry(lip->li_ail.next, struct xfs_log_item, li_ail);
if (&next_lip->li_ail != &ailp->ail_head)
next_lsn = next_lip->li_lsn;
lsn = lip->li_lsn;
if (in_ail &&
(prev_lsn == NULLCOMMITLSN || XFS_LSN_CMP(prev_lsn, lsn) <= 0) &&
(next_lsn == NULLCOMMITLSN || XFS_LSN_CMP(next_lsn, lsn) >= 0))
return;
spin_unlock(&ailp->ail_lock);
ASSERT(in_ail);
ASSERT(prev_lsn == NULLCOMMITLSN || XFS_LSN_CMP(prev_lsn, lsn) <= 0);
ASSERT(next_lsn == NULLCOMMITLSN || XFS_LSN_CMP(next_lsn, lsn) >= 0);
spin_lock(&ailp->ail_lock);
}
#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 struct xfs_log_item *
xfs_ail_max(
struct xfs_ail *ailp)
{
if (list_empty(&ailp->ail_head))
return NULL;
return list_entry(ailp->ail_head.prev, struct xfs_log_item, 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 struct xfs_log_item *
xfs_ail_next(
struct xfs_ail *ailp,
struct xfs_log_item *lip)
{
if (lip->li_ail.next == &ailp->ail_head)
return NULL;
return list_first_entry(&lip->li_ail, struct xfs_log_item, 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.
*/
static xfs_lsn_t
__xfs_ail_min_lsn(
struct xfs_ail *ailp)
{
struct xfs_log_item *lip = xfs_ail_min(ailp);
if (lip)
return lip->li_lsn;
return 0;
}
xfs_lsn_t
xfs_ail_min_lsn(
struct xfs_ail *ailp)
{
xfs_lsn_t lsn;
spin_lock(&ailp->ail_lock);
lsn = __xfs_ail_min_lsn(ailp);
spin_unlock(&ailp->ail_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;
struct xfs_log_item *lip;
spin_lock(&ailp->ail_lock);
lip = xfs_ail_max(ailp);
if (lip)
lsn = lip->li_lsn;
spin_unlock(&ailp->ail_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->ail_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->ail_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.
*/
struct xfs_log_item *
xfs_trans_ail_cursor_first(
struct xfs_ail *ailp,
struct xfs_ail_cursor *cur,
xfs_lsn_t lsn)
{
struct xfs_log_item *lip;
xfs_trans_ail_cursor_init(ailp, cur);
if (lsn == 0) {
lip = xfs_ail_min(ailp);
goto out;
}
list_for_each_entry(lip, &ailp->ail_head, 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)
{
struct xfs_log_item *lip;
list_for_each_entry_reverse(lip, &ailp->ail_head, 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->ail_head);
}
/*
* Delete the given item from the AIL. Return a pointer to the item.
*/
static void
xfs_ail_delete(
struct xfs_ail *ailp,
struct xfs_log_item *lip)
{
xfs_ail_check(ailp, lip);
list_del(&lip->li_ail);
xfs_trans_ail_cursor_clear(ailp, lip);
}
/*
* Requeue a failed buffer for writeback.
*
* We clear the log item failed state here as well, but we have to be careful
* about reference counts because the only active reference counts on the buffer
* may be the failed log items. Hence if we clear the log item failed state
* before queuing the buffer for IO we can release all active references to
* the buffer and free it, leading to use after free problems in
* xfs_buf_delwri_queue. It makes no difference to the buffer or log items which
* order we process them in - the buffer is locked, and we own the buffer list
* so nothing on them is going to change while we are performing this action.
*
* Hence we can safely queue the buffer for IO before we clear the failed log
* item state, therefore always having an active reference to the buffer and
* avoiding the transient zero-reference state that leads to use-after-free.
*/
static inline int
xfsaild_resubmit_item(
struct xfs_log_item *lip,
struct list_head *buffer_list)
{
struct xfs_buf *bp = lip->li_buf;
if (!xfs_buf_trylock(bp))
return XFS_ITEM_LOCKED;
if (!xfs_buf_delwri_queue(bp, buffer_list)) {
xfs_buf_unlock(bp);
return XFS_ITEM_FLUSHING;
}
/* protected by ail_lock */
list_for_each_entry(lip, &bp->b_li_list, li_bio_list) {
if (bp->b_flags & _XBF_INODES)
clear_bit(XFS_LI_FAILED, &lip->li_flags);
else
xfs_clear_li_failed(lip);
}
xfs_buf_unlock(bp);
return XFS_ITEM_SUCCESS;
}
static inline uint
xfsaild_push_item(
struct xfs_ail *ailp,
struct xfs_log_item *lip)
{
/*
* If log item pinning is enabled, skip the push and track the item as
* pinned. This can help induce head-behind-tail conditions.
*/
if (XFS_TEST_ERROR(false, ailp->ail_log->l_mp, XFS_ERRTAG_LOG_ITEM_PIN))
return XFS_ITEM_PINNED;
/*
* Consider the item pinned if a push callback is not defined so the
* caller will force the log. This should only happen for intent items
* as they are unpinned once the associated done item is committed to
* the on-disk log.
*/
if (!lip->li_ops->iop_push)
return XFS_ITEM_PINNED;
if (test_bit(XFS_LI_FAILED, &lip->li_flags))
return xfsaild_resubmit_item(lip, &ailp->ail_buf_list);
return lip->li_ops->iop_push(lip, &ailp->ail_buf_list);
}
static long
xfsaild_push(
struct xfs_ail *ailp)
{
struct xfs_mount *mp = ailp->ail_log->l_mp;
struct xfs_ail_cursor cur;
struct xfs_log_item *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 a background CIL push to get the
* items unpinned in the near future. We do not wait on the CIL push as
* that could stall us for seconds if there is enough background IO
* load. Stalling for that long when the tail of the log is pinned and
* needs flushing will hard stop the transaction subsystem when log
* space runs out.
*/
if (ailp->ail_log_flush && ailp->ail_last_pushed_lsn == 0 &&
(!list_empty_careful(&ailp->ail_buf_list) ||
xfs_ail_min_lsn(ailp))) {
ailp->ail_log_flush = 0;
XFS_STATS_INC(mp, xs_push_ail_flush);
xlog_cil_flush(ailp->ail_log);
}
spin_lock(&ailp->ail_lock);
/*
* If we have a sync push waiter, we always have to push till the AIL is
* empty. Update the target to point to the end of the AIL so that
* capture updates that occur after the sync push waiter has gone to
* sleep.
*/
if (waitqueue_active(&ailp->ail_empty)) {
lip = xfs_ail_max(ailp);
if (lip)
target = lip->li_lsn;
} else {
/* barrier matches the ail_target update in xfs_ail_push() */
smp_rmb();
target = ailp->ail_target;
ailp->ail_target_prev = target;
}
/* we're done if the AIL is empty or our push has reached the end */
lip = xfs_trans_ail_cursor_first(ailp, &cur, ailp->ail_last_pushed_lsn);
if (!lip)
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 = xfsaild_push_item(ailp, lip);
switch (lock_result) {
case XFS_ITEM_SUCCESS:
XFS_STATS_INC(mp, xs_push_ail_success);
trace_xfs_ail_push(lip);
ailp->ail_last_pushed_lsn = lsn;
break;
case XFS_ITEM_FLUSHING:
/*
* The item or its backing buffer is already being
* 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 stop flushing just because lots
* of items are already being flushed, but we need to
* re-try the flushing relatively soon if most of the
* AIL is being flushed.
*/
XFS_STATS_INC(mp, xs_push_ail_flushing);
trace_xfs_ail_flushing(lip);
flushing++;
ailp->ail_last_pushed_lsn = lsn;
break;
case XFS_ITEM_PINNED:
XFS_STATS_INC(mp, xs_push_ail_pinned);
trace_xfs_ail_pinned(lip);
stuck++;
ailp->ail_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 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;
}
out_done:
xfs_trans_ail_cursor_done(&cur);
spin_unlock(&ailp->ail_lock);
if (xfs_buf_delwri_submit_nowait(&ailp->ail_buf_list))
ailp->ail_log_flush++;
if (!count || XFS_LSN_CMP(lsn, target) >= 0) {
/*
* 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->ail_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->ail_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 */
unsigned int noreclaim_flag;
noreclaim_flag = memalloc_noreclaim_save();
set_freezable();
while (1) {
if (tout && tout <= 20)
set_current_state(TASK_KILLABLE|TASK_FREEZABLE);
else
set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
/*
* Check kthread_should_stop() after we set the task state to
* guarantee that we either see the stop bit and exit or the
* task state is reset to runnable such that it's not scheduled
* out indefinitely and detects the stop bit at next iteration.
* A memory barrier is included in above task state set to
* serialize again kthread_stop().
*/
if (kthread_should_stop()) {
__set_current_state(TASK_RUNNING);
/*
* The caller forces out the AIL before stopping the
* thread in the common case, which means the delwri
* queue is drained. In the shutdown case, the queue may
* still hold relogged buffers that haven't been
* submitted because they were pinned since added to the
* queue.
*
* Log I/O error processing stales the underlying buffer
* and clears the delwri state, expecting the buf to be
* removed on the next submission attempt. That won't
* happen if we're shutting down, so this is the last
* opportunity to release such buffers from the queue.
*/
ASSERT(list_empty(&ailp->ail_buf_list) ||
xlog_is_shutdown(ailp->ail_log));
xfs_buf_delwri_cancel(&ailp->ail_buf_list);
break;
}
spin_lock(&ailp->ail_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 ail_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 ail_target update in xfs_ail_push().
*/
smp_rmb();
if (!xfs_ail_min(ailp) &&
ailp->ail_target == ailp->ail_target_prev &&
list_empty(&ailp->ail_buf_list)) {
spin_unlock(&ailp->ail_lock);
schedule();
tout = 0;
continue;
}
spin_unlock(&ailp->ail_lock);
if (tout)
schedule_timeout(msecs_to_jiffies(tout));
__set_current_state(TASK_RUNNING);
try_to_freeze();
tout = xfsaild_push(ailp);
}
memalloc_noreclaim_restore(noreclaim_flag);
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 appropriately.
*
* 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)
{
struct xfs_log_item *lip;
lip = xfs_ail_min(ailp);
if (!lip || xlog_is_shutdown(ailp->ail_log) ||
XFS_LSN_CMP(threshold_lsn, ailp->ail_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->ail_target, &threshold_lsn);
smp_wmb();
wake_up_process(ailp->ail_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->ail_lock);
while ((lip = xfs_ail_max(ailp)) != NULL) {
prepare_to_wait(&ailp->ail_empty, &wait, TASK_UNINTERRUPTIBLE);
wake_up_process(ailp->ail_task);
spin_unlock(&ailp->ail_lock);
schedule();
spin_lock(&ailp->ail_lock);
}
spin_unlock(&ailp->ail_lock);
finish_wait(&ailp->ail_empty, &wait);
}
void
xfs_ail_update_finish(
struct xfs_ail *ailp,
xfs_lsn_t old_lsn) __releases(ailp->ail_lock)
{
struct xlog *log = ailp->ail_log;
/* if the tail lsn hasn't changed, don't do updates or wakeups. */
if (!old_lsn || old_lsn == __xfs_ail_min_lsn(ailp)) {
spin_unlock(&ailp->ail_lock);
return;
}
if (!xlog_is_shutdown(log))
xlog_assign_tail_lsn_locked(log->l_mp);
if (list_empty(&ailp->ail_head))
wake_up_all(&ailp->ail_empty);
spin_unlock(&ailp->ail_lock);
xfs_log_space_wake(log->l_mp);
}
/*
* 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->ail_lock)
{
struct xfs_log_item *mlip;
xfs_lsn_t tail_lsn = 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 (test_and_set_bit(XFS_LI_IN_AIL, &lip->li_flags)) {
/* 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);
if (mlip == lip && !tail_lsn)
tail_lsn = lip->li_lsn;
xfs_ail_delete(ailp, lip);
} else {
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);
xfs_ail_update_finish(ailp, tail_lsn);
}
/* Insert a log item into the AIL. */
void
xfs_trans_ail_insert(
struct xfs_ail *ailp,
struct xfs_log_item *lip,
xfs_lsn_t lsn)
{
spin_lock(&ailp->ail_lock);
xfs_trans_ail_update_bulk(ailp, NULL, &lip, 1, lsn);
}
/*
* Delete one log item from the AIL.
*
* If this item was at the tail of the AIL, return the LSN of the log item so
* that we can use it to check if the LSN of the tail of the log has moved
* when finishing up the AIL delete process in xfs_ail_update_finish().
*/
xfs_lsn_t
xfs_ail_delete_one(
struct xfs_ail *ailp,
struct xfs_log_item *lip)
{
struct xfs_log_item *mlip = xfs_ail_min(ailp);
xfs_lsn_t lsn = lip->li_lsn;
trace_xfs_ail_delete(lip, mlip->li_lsn, lip->li_lsn);
xfs_ail_delete(ailp, lip);
clear_bit(XFS_LI_IN_AIL, &lip->li_flags);
lip->li_lsn = 0;
if (mlip == lip)
return lsn;
return 0;
}
void
xfs_trans_ail_delete(
struct xfs_log_item *lip,
int shutdown_type)
{
struct xfs_ail *ailp = lip->li_ailp;
struct xlog *log = ailp->ail_log;
xfs_lsn_t tail_lsn;
spin_lock(&ailp->ail_lock);
if (!test_bit(XFS_LI_IN_AIL, &lip->li_flags)) {
spin_unlock(&ailp->ail_lock);
if (shutdown_type && !xlog_is_shutdown(log)) {
xfs_alert_tag(log->l_mp, XFS_PTAG_AILDELETE,
"%s: attempting to delete a log item that is not in the AIL",
__func__);
xlog_force_shutdown(log, shutdown_type);
}
return;
}
/* xfs_ail_update_finish() drops the AIL lock */
xfs_clear_li_failed(lip);
tail_lsn = xfs_ail_delete_one(ailp, lip);
xfs_ail_update_finish(ailp, tail_lsn);
}
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->ail_log = mp->m_log;
INIT_LIST_HEAD(&ailp->ail_head);
INIT_LIST_HEAD(&ailp->ail_cursors);
spin_lock_init(&ailp->ail_lock);
INIT_LIST_HEAD(&ailp->ail_buf_list);
init_waitqueue_head(&ailp->ail_empty);
ailp->ail_task = kthread_run(xfsaild, ailp, "xfsaild/%s",
mp->m_super->s_id);
if (IS_ERR(ailp->ail_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->ail_task);
kmem_free(ailp);
}