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linux/fs/xfs/xfs_trans_ail.c

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/*
* 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_types.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_trans_priv.h"
#include "xfs_error.h"
STATIC void xfs_ail_insert(struct xfs_ail *, xfs_log_item_t *);
STATIC xfs_log_item_t * xfs_ail_delete(struct xfs_ail *, xfs_log_item_t *);
STATIC xfs_log_item_t * xfs_ail_min(struct xfs_ail *);
STATIC xfs_log_item_t * xfs_ail_next(struct xfs_ail *, xfs_log_item_t *);
#ifdef DEBUG
STATIC void xfs_ail_check(struct xfs_ail *, 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_ail_tail(
struct xfs_ail *ailp)
{
xfs_lsn_t lsn;
xfs_log_item_t *lip;
spin_lock(&ailp->xa_lock);
lip = xfs_ail_min(ailp);
if (lip == NULL) {
lsn = (xfs_lsn_t)0;
} else {
lsn = lip->li_lsn;
}
spin_unlock(&ailp->xa_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 its 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_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)) {
if (XFS_LSN_CMP(threshold_lsn, ailp->xa_target) > 0)
xfsaild_wakeup(ailp, threshold_lsn);
}
}
/*
* AIL traversal cursor initialisation.
*
* The cursor keeps track of where our current traversal is up
* to by tracking the next ƣtem 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.
*
* We don't link the push cursor because it is embedded in the struct
* xfs_ail and hence easily findable.
*/
STATIC void
xfs_trans_ail_cursor_init(
struct xfs_ail *ailp,
struct xfs_ail_cursor *cur)
{
cur->item = NULL;
if (cur == &ailp->xa_cursors)
return;
cur->next = ailp->xa_cursors.next;
ailp->xa_cursors.next = cur;
}
/*
* Set the cursor to the next item, because when we look
* up the cursor the current item may have been freed.
*/
STATIC void
xfs_trans_ail_cursor_set(
struct xfs_ail *ailp,
struct xfs_ail_cursor *cur,
struct xfs_log_item *lip)
{
if (lip)
cur->item = xfs_ail_next(ailp, lip);
}
/*
* Get the next item in the traversal and advance the cursor.
* If the cursor was invalidated (inidicated 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 ((__psint_t)lip & 1)
lip = xfs_ail_min(ailp);
xfs_trans_ail_cursor_set(ailp, cur, lip);
return lip;
}
/*
* Now that the traversal is complete, we need to remove the cursor
* from the list of traversing cursors. Avoid removing the embedded
* push cursor, but use the fact it is always present to make the
* list deletion simple.
*/
void
xfs_trans_ail_cursor_done(
struct xfs_ail *ailp,
struct xfs_ail_cursor *done)
{
struct xfs_ail_cursor *prev = NULL;
struct xfs_ail_cursor *cur;
done->item = NULL;
if (done == &ailp->xa_cursors)
return;
prev = &ailp->xa_cursors;
for (cur = prev->next; cur; prev = cur, cur = prev->next) {
if (cur == done) {
prev->next = cur->next;
break;
}
}
ASSERT(cur);
}
/*
* 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
* cursor item to a value of 1 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;
/* need to search all cursors */
for (cur = &ailp->xa_cursors; cur; cur = cur->next) {
if (cur->item == lip)
cur->item = (struct xfs_log_item *)
((__psint_t)cur->item | 1);
}
}
/*
* 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().
*/
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);
lip = xfs_ail_min(ailp);
if (lsn == 0)
goto out;
list_for_each_entry(lip, &ailp->xa_ail, li_ail) {
if (XFS_LSN_CMP(lip->li_lsn, lsn) >= 0)
goto out;
}
lip = NULL;
out:
xfs_trans_ail_cursor_set(ailp, cur, lip);
return lip;
}
/*
* xfsaild_push does the work of pushing on the AIL. Returning a timeout of
* zero indicates that the caller should sleep until woken.
*/
long
xfsaild_push(
struct xfs_ail *ailp,
xfs_lsn_t *last_lsn)
{
long tout = 0;
xfs_lsn_t last_pushed_lsn = *last_lsn;
xfs_lsn_t target = ailp->xa_target;
xfs_lsn_t lsn;
xfs_log_item_t *lip;
int flush_log, count, stuck;
xfs_mount_t *mp = ailp->xa_mount;
struct xfs_ail_cursor *cur = &ailp->xa_cursors;
int push_xfsbufd = 0;
spin_lock(&ailp->xa_lock);
xfs_trans_ail_cursor_init(ailp, cur);
lip = xfs_trans_ail_cursor_first(ailp, cur, *last_lsn);
if (!lip || XFS_FORCED_SHUTDOWN(mp)) {
/*
* AIL is empty or our push has reached the end.
*/
xfs_trans_ail_cursor_done(ailp, cur);
spin_unlock(&ailp->xa_lock);
*last_lsn = 0;
return tout;
}
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.
*/
lsn = lip->li_lsn;
flush_log = stuck = count = 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(&ailp->xa_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;
push_xfsbufd = 1;
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;
default:
ASSERT(0);
break;
}
spin_lock(&ailp->xa_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_ail_cursor_next(ailp, cur);
if (lip == NULL)
break;
lsn = lip->li_lsn;
}
xfs_trans_ail_cursor_done(ailp, cur);
spin_unlock(&ailp->xa_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, 0);
}
if (push_xfsbufd) {
/* we've got delayed write buffers to flush */
wake_up_process(mp->m_ddev_targp->bt_task);
}
if (!count) {
/* We're past our target or empty, so idle */
last_pushed_lsn = 0;
} 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 = 50;
last_pushed_lsn = 0;
} else if ((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 = 20;
} else {
/* more to do, but wait a short while before continuing */
tout = 10;
}
*last_lsn = last_pushed_lsn;
return tout;
}
/*
* 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(
struct xfs_ail *ailp,
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(ailp->xa_mount)) {
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(ailp);
if (min_lip == lip)
xfs_log_move_tail(ailp->xa_mount, 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.
*
* This function must be called with the AIL lock held. The lock
* is dropped before returning.
*/
void
xfs_trans_ail_update(
struct xfs_ail *ailp,
xfs_log_item_t *lip,
xfs_lsn_t lsn) __releases(ailp->xa_lock)
{
xfs_log_item_t *dlip = NULL;
xfs_log_item_t *mlip; /* ptr to minimum lip */
xfs_lsn_t tail_lsn;
mlip = xfs_ail_min(ailp);
if (lip->li_flags & XFS_LI_IN_AIL) {
dlip = xfs_ail_delete(ailp, lip);
ASSERT(dlip == lip);
xfs_trans_ail_cursor_clear(ailp, dlip);
} else {
lip->li_flags |= XFS_LI_IN_AIL;
}
lip->li_lsn = lsn;
xfs_ail_insert(ailp, lip);
if (mlip == dlip) {
mlip = xfs_ail_min(ailp);
/*
* It is not safe to access mlip after the AIL lock is
* dropped, so we must get a copy of li_lsn before we do
* so. This is especially important on 32-bit platforms
* where accessing and updating 64-bit values like li_lsn
* is not atomic.
*/
tail_lsn = mlip->li_lsn;
spin_unlock(&ailp->xa_lock);
xfs_log_move_tail(ailp->xa_mount, tail_lsn);
} else {
spin_unlock(&ailp->xa_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_ail_delete(
struct xfs_ail *ailp,
xfs_log_item_t *lip) __releases(ailp->xa_lock)
{
xfs_log_item_t *dlip;
xfs_log_item_t *mlip;
xfs_lsn_t tail_lsn;
if (lip->li_flags & XFS_LI_IN_AIL) {
mlip = xfs_ail_min(ailp);
dlip = xfs_ail_delete(ailp, lip);
ASSERT(dlip == lip);
xfs_trans_ail_cursor_clear(ailp, dlip);
lip->li_flags &= ~XFS_LI_IN_AIL;
lip->li_lsn = 0;
if (mlip == dlip) {
mlip = xfs_ail_min(ailp);
/*
* It is not safe to access mlip after the AIL lock
* is dropped, so we must get a copy of li_lsn
* before we do so. This is especially important
* on 32-bit platforms where accessing and updating
* 64-bit values like li_lsn is not atomic.
*/
tail_lsn = mlip ? mlip->li_lsn : 0;
spin_unlock(&ailp->xa_lock);
xfs_log_move_tail(ailp->xa_mount, tail_lsn);
} else {
spin_unlock(&ailp->xa_lock);
}
}
else {
/*
* If the file system is not being shutdown, we are in
* serious trouble if we get to this stage.
*/
struct xfs_mount *mp = ailp->xa_mount;
spin_unlock(&ailp->xa_lock);
if (!XFS_FORCED_SHUTDOWN(mp)) {
xfs_cmn_err(XFS_PTAG_AILDELETE, CE_ALERT, mp,
"%s: attempting to delete a log item that is not in the AIL",
__func__);
xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
}
}
}
/*
* 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)
{
struct xfs_ail *ailp;
int error;
ailp = kmem_zalloc(sizeof(struct xfs_ail), KM_MAYFAIL);
if (!ailp)
return ENOMEM;
ailp->xa_mount = mp;
INIT_LIST_HEAD(&ailp->xa_ail);
spin_lock_init(&ailp->xa_lock);
error = xfsaild_start(ailp);
if (error)
goto out_free_ailp;
mp->m_ail = ailp;
return 0;
out_free_ailp:
kmem_free(ailp);
return error;
}
void
xfs_trans_ail_destroy(
xfs_mount_t *mp)
{
struct xfs_ail *ailp = mp->m_ail;
xfsaild_stop(ailp);
kmem_free(ailp);
}
/*
* 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(
struct xfs_ail *ailp,
xfs_log_item_t *lip)
/* ARGSUSED */
{
xfs_log_item_t *next_lip;
/*
* If the list is empty, just insert the item.
*/
if (list_empty(&ailp->xa_ail)) {
list_add(&lip->li_ail, &ailp->xa_ail);
return;
}
list_for_each_entry_reverse(next_lip, &ailp->xa_ail, li_ail) {
if (XFS_LSN_CMP(next_lip->li_lsn, lip->li_lsn) <= 0)
break;
}
ASSERT((&next_lip->li_ail == &ailp->xa_ail) ||
(XFS_LSN_CMP(next_lip->li_lsn, lip->li_lsn) <= 0));
list_add(&lip->li_ail, &next_lip->li_ail);
xfs_ail_check(ailp, lip);
return;
}
/*
* Delete the given item from the AIL. Return a pointer to the item.
*/
/*ARGSUSED*/
STATIC xfs_log_item_t *
xfs_ail_delete(
struct xfs_ail *ailp,
xfs_log_item_t *lip)
/* ARGSUSED */
{
xfs_ail_check(ailp, lip);
list_del(&lip->li_ail);
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(
struct xfs_ail *ailp)
/* ARGSUSED */
{
if (list_empty(&ailp->xa_ail))
return NULL;
return list_first_entry(&ailp->xa_ail, 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)
/* ARGSUSED */
{
if (lip->li_ail.next == &ailp->xa_ail)
return NULL;
return list_first_entry(&lip->li_ail, xfs_log_item_t, li_ail);
}
#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);
#ifdef XFS_TRANS_DEBUG
/*
* Walk the list checking 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 = list_entry(&ailp->xa_ail, xfs_log_item_t, li_ail);
list_for_each_entry(lip, &ailp->xa_ail, li_ail) {
if (&prev_lip->li_ail != &ailp->xa_ail)
ASSERT(XFS_LSN_CMP(prev_lip->li_lsn, lip->li_lsn) <= 0);
ASSERT((lip->li_flags & XFS_LI_IN_AIL) != 0);
prev_lip = lip;
}
#endif /* XFS_TRANS_DEBUG */
}
#endif /* DEBUG */
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