From fd5670f22fce247754243cf2ed41941e5762d990 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Fri, 6 May 2011 02:54:07 +0000 Subject: xfs: make AIL target updates and compares 32bit safe. The recent conversion of the xfsaild functionality to a work queue introduced a hard-to-hit log space grant hang. One of the problems noticed was that updates of the push target are not 32 bit safe as the target is a 64 bit value. We cannot copy a 64 bit LSN without the possibility of corrupting the result when racing with another updating thread. We have function to do this update safely without needing to care about 32/64 bit issues - xfs_trans_ail_copy_lsn() - so use that when updating the AIL push target. Also move the reading of the target in the push work inside the AIL lock, and use XFS_LSN_CMP() for the unlocked comparison during work termination to close read holes as well. Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig Reviewed-by: Alex Elder --- fs/xfs/xfs_trans_ail.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'fs/xfs') diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c index 9f427c2597bb..d7eebbf71362 100644 --- a/fs/xfs/xfs_trans_ail.c +++ b/fs/xfs/xfs_trans_ail.c @@ -354,7 +354,7 @@ xfs_ail_worker( struct xfs_ail_cursor *cur = &ailp->xa_cursors; xfs_log_item_t *lip; xfs_lsn_t lsn; - xfs_lsn_t target = ailp->xa_target; + xfs_lsn_t target; long tout = 10; int flush_log = 0; int stuck = 0; @@ -362,6 +362,7 @@ xfs_ail_worker( int push_xfsbufd = 0; spin_lock(&ailp->xa_lock); + target = ailp->xa_target; xfs_trans_ail_cursor_init(ailp, cur); lip = xfs_trans_ail_cursor_first(ailp, cur, ailp->xa_last_pushed_lsn); if (!lip || XFS_FORCED_SHUTDOWN(mp)) { @@ -491,7 +492,7 @@ out_done: * work to do. Wait a bit longer before starting that work. */ smp_rmb(); - if (ailp->xa_target == target) { + if (XFS_LSN_CMP(ailp->xa_target, target) == 0) { clear_bit(XFS_AIL_PUSHING_BIT, &ailp->xa_flags); return; } @@ -553,7 +554,7 @@ xfs_ail_push( * the XFS_AIL_PUSHING_BIT. */ smp_wmb(); - ailp->xa_target = threshold_lsn; + xfs_trans_ail_copy_lsn(ailp, &ailp->xa_target, &threshold_lsn); if (!test_and_set_bit(XFS_AIL_PUSHING_BIT, &ailp->xa_flags)) queue_delayed_work(xfs_syncd_wq, &ailp->xa_work, 0); } -- cgit v1.2.3