27d8d5fe0e
To replace the current generation number ensuring sanity of the AIL traversal, replace it with an external cursor that is linked to the AIL. Basically, we store the next item in the cursor whenever we want to drop the AIL lock to do something to the current item. When we regain the lock. the current item may already be free, so we can't reference it, but the next item in the traversal is already held in the cursor. When we move or delete an object, we search all the active cursors and if there is an item match we clear the cursor(s) that point to the object. This forces the traversal to restart transparently. We don't invalidate the cursor on insert because the cursor still points to a valid item. If the intem is inserted between the current item and the cursor it does not matter; the traversal is considered to be past the insertion point so it will be picked up in the next traversal. Hence traversal restarts pretty much disappear altogether with this method of traversal, which should substantially reduce the overhead of pushing on a busy AIL. Version 2 o add restart logic o comment cursor interface o minor cleanups SGI-PV: 988143 SGI-Modid: xfs-linux-melb:xfs-kern:32347a Signed-off-by: David Chinner <david@fromorbit.com> Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: Christoph Hellwig <hch@infradead.org>
109 lines
3.7 KiB
C
109 lines
3.7 KiB
C
/*
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* Copyright (c) 2000,2002,2005 Silicon Graphics, Inc.
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* All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it would be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef __XFS_TRANS_PRIV_H__
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#define __XFS_TRANS_PRIV_H__
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struct xfs_log_item;
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struct xfs_log_item_desc;
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struct xfs_mount;
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struct xfs_trans;
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/*
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* From xfs_trans_item.c
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*/
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struct xfs_log_item_desc *xfs_trans_add_item(struct xfs_trans *,
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struct xfs_log_item *);
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void xfs_trans_free_item(struct xfs_trans *,
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struct xfs_log_item_desc *);
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struct xfs_log_item_desc *xfs_trans_find_item(struct xfs_trans *,
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struct xfs_log_item *);
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struct xfs_log_item_desc *xfs_trans_first_item(struct xfs_trans *);
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struct xfs_log_item_desc *xfs_trans_next_item(struct xfs_trans *,
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struct xfs_log_item_desc *);
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void xfs_trans_free_items(struct xfs_trans *, int);
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void xfs_trans_unlock_items(struct xfs_trans *,
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xfs_lsn_t);
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void xfs_trans_free_busy(xfs_trans_t *tp);
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xfs_log_busy_slot_t *xfs_trans_add_busy(xfs_trans_t *tp,
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xfs_agnumber_t ag,
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xfs_extlen_t idx);
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/*
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* AIL traversal cursor.
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*
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* Rather than using a generation number for detecting changes in the ail, use
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* a cursor that is protected by the ail lock. The aild cursor exists in the
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* struct xfs_ail, but other traversals can declare it on the stack and link it
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* to the ail list.
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*
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* When an object is deleted from or moved int the AIL, the cursor list is
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* searched to see if the object is a designated cursor item. If it is, it is
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* deleted from the cursor so that the next time the cursor is used traversal
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* will return to the start.
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*
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* This means a traversal colliding with a removal will cause a restart of the
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* list scan, rather than any insertion or deletion anywhere in the list. The
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* low bit of the item pointer is set if the cursor has been invalidated so
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* that we can tell the difference between invalidation and reaching the end
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* of the list to trigger traversal restarts.
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*/
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struct xfs_ail_cursor {
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struct xfs_ail_cursor *next;
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struct xfs_log_item *item;
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};
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/*
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* Private AIL structures.
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*
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* Eventually we need to drive the locking in here as well.
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*/
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struct xfs_ail {
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struct xfs_mount *xa_mount;
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struct list_head xa_ail;
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uint xa_gen;
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struct task_struct *xa_task;
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xfs_lsn_t xa_target;
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struct xfs_ail_cursor xa_cursors;
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};
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/*
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* From xfs_trans_ail.c
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*/
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void xfs_trans_update_ail(struct xfs_mount *mp,
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struct xfs_log_item *lip, xfs_lsn_t lsn)
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__releases(mp->m_ail_lock);
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void xfs_trans_delete_ail(struct xfs_mount *mp,
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struct xfs_log_item *lip)
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__releases(mp->m_ail_lock);
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struct xfs_log_item *xfs_trans_first_ail(struct xfs_mount *mp,
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struct xfs_ail_cursor *cur);
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struct xfs_log_item *xfs_trans_next_ail(struct xfs_mount *mp,
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struct xfs_ail_cursor *cur);
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void xfs_trans_ail_cursor_init(struct xfs_ail *ailp,
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struct xfs_ail_cursor *cur);
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void xfs_trans_ail_cursor_done(struct xfs_ail *ailp,
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struct xfs_ail_cursor *cur);
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long xfsaild_push(struct xfs_ail *, xfs_lsn_t *);
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void xfsaild_wakeup(struct xfs_ail *, xfs_lsn_t);
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int xfsaild_start(struct xfs_ail *);
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void xfsaild_stop(struct xfs_ail *);
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#endif /* __XFS_TRANS_PRIV_H__ */
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