From 1a387d3be2b30c90f20d49a3497a8fc0693a9d18 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Tue, 24 Aug 2010 11:46:31 +1000 Subject: [PATCH] xfs: dummy transactions should not dirty VFS state When we need to cover the log, we issue dummy transactions to ensure the current log tail is on disk. Unfortunately we currently use the root inode in the dummy transaction, and the act of committing the transaction dirties the inode at the VFS level. As a result, the VFS writeback of the dirty inode will prevent the filesystem from idling long enough for the log covering state machine to complete. The state machine gets stuck in a loop issuing new dummy transactions to cover the log and never makes progress. To avoid this problem, the dummy transactions should not cause externally visible state changes. To ensure this occurs, make sure that dummy transactions log an unchanging field in the superblock as it's state is never propagated outside the filesystem. This allows the log covering state machine to complete successfully and the filesystem now correctly enters a fully idle state about 90s after the last modification was made. Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig --- fs/xfs/linux-2.6/xfs_super.c | 2 +- fs/xfs/linux-2.6/xfs_sync.c | 42 ++++++------------------------------ fs/xfs/xfs_fsops.c | 31 +++++++++++++++----------- fs/xfs/xfs_fsops.h | 2 +- 4 files changed, 26 insertions(+), 51 deletions(-) diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c index c6b24e7c308a..a4e07974955b 100644 --- a/fs/xfs/linux-2.6/xfs_super.c +++ b/fs/xfs/linux-2.6/xfs_super.c @@ -1407,7 +1407,7 @@ xfs_fs_freeze( xfs_save_resvblks(mp); xfs_quiesce_attr(mp); - return -xfs_fs_log_dummy(mp); + return -xfs_fs_log_dummy(mp, SYNC_WAIT); } STATIC int diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c index dfcbd98d1599..d59c4a65d492 100644 --- a/fs/xfs/linux-2.6/xfs_sync.c +++ b/fs/xfs/linux-2.6/xfs_sync.c @@ -34,6 +34,7 @@ #include "xfs_inode_item.h" #include "xfs_quota.h" #include "xfs_trace.h" +#include "xfs_fsops.h" #include #include @@ -340,38 +341,6 @@ xfs_sync_attr( XFS_ICI_NO_TAG, 0, NULL); } -STATIC int -xfs_commit_dummy_trans( - struct xfs_mount *mp, - uint flags) -{ - struct xfs_inode *ip = mp->m_rootip; - struct xfs_trans *tp; - int error; - - /* - * Put a dummy transaction in the log to tell recovery - * that all others are OK. - */ - tp = xfs_trans_alloc(mp, XFS_TRANS_DUMMY1); - error = xfs_trans_reserve(tp, 0, XFS_ICHANGE_LOG_RES(mp), 0, 0, 0); - if (error) { - xfs_trans_cancel(tp, 0); - return error; - } - - xfs_ilock(ip, XFS_ILOCK_EXCL); - - xfs_trans_ijoin(tp, ip); - xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE); - error = xfs_trans_commit(tp, 0); - xfs_iunlock(ip, XFS_ILOCK_EXCL); - - /* the log force ensures this transaction is pushed to disk */ - xfs_log_force(mp, (flags & SYNC_WAIT) ? XFS_LOG_SYNC : 0); - return error; -} - STATIC int xfs_sync_fsdata( struct xfs_mount *mp) @@ -432,7 +401,7 @@ xfs_quiesce_data( /* mark the log as covered if needed */ if (xfs_log_need_covered(mp)) - error2 = xfs_commit_dummy_trans(mp, SYNC_WAIT); + error2 = xfs_fs_log_dummy(mp, SYNC_WAIT); /* flush data-only devices */ if (mp->m_rtdev_targp) @@ -563,7 +532,7 @@ xfs_flush_inodes( /* * Every sync period we need to unpin all items, reclaim inodes and sync * disk quotas. We might need to cover the log to indicate that the - * filesystem is idle. + * filesystem is idle and not frozen. */ STATIC void xfs_sync_worker( @@ -577,8 +546,9 @@ xfs_sync_worker( xfs_reclaim_inodes(mp, 0); /* dgc: errors ignored here */ error = xfs_qm_sync(mp, SYNC_TRYLOCK); - if (xfs_log_need_covered(mp)) - error = xfs_commit_dummy_trans(mp, 0); + if (mp->m_super->s_frozen == SB_UNFROZEN && + xfs_log_need_covered(mp)) + error = xfs_fs_log_dummy(mp, 0); } mp->m_sync_seq++; wake_up(&mp->m_wait_single_sync_task); diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c index dbca5f5c37ba..43b1d5699335 100644 --- a/fs/xfs/xfs_fsops.c +++ b/fs/xfs/xfs_fsops.c @@ -604,31 +604,36 @@ out: return 0; } +/* + * Dump a transaction into the log that contains no real change. This is needed + * to be able to make the log dirty or stamp the current tail LSN into the log + * during the covering operation. + * + * We cannot use an inode here for this - that will push dirty state back up + * into the VFS and then periodic inode flushing will prevent log covering from + * making progress. Hence we log a field in the superblock instead. + */ int xfs_fs_log_dummy( - xfs_mount_t *mp) + xfs_mount_t *mp, + int flags) { xfs_trans_t *tp; - xfs_inode_t *ip; int error; tp = _xfs_trans_alloc(mp, XFS_TRANS_DUMMY1, KM_SLEEP); - error = xfs_trans_reserve(tp, 0, XFS_ICHANGE_LOG_RES(mp), 0, 0, 0); + error = xfs_trans_reserve(tp, 0, mp->m_sb.sb_sectsize + 128, 0, 0, + XFS_DEFAULT_LOG_COUNT); if (error) { xfs_trans_cancel(tp, 0); return error; } - ip = mp->m_rootip; - xfs_ilock(ip, XFS_ILOCK_EXCL); - - xfs_trans_ijoin(tp, ip); - xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE); - xfs_trans_set_sync(tp); - error = xfs_trans_commit(tp, 0); - - xfs_iunlock(ip, XFS_ILOCK_EXCL); - return error; + /* log the UUID because it is an unchanging field */ + xfs_mod_sb(tp, XFS_SB_UUID); + if (flags & SYNC_WAIT) + xfs_trans_set_sync(tp); + return xfs_trans_commit(tp, 0); } int diff --git a/fs/xfs/xfs_fsops.h b/fs/xfs/xfs_fsops.h index 88435e0a77c9..a786c5212c1e 100644 --- a/fs/xfs/xfs_fsops.h +++ b/fs/xfs/xfs_fsops.h @@ -25,6 +25,6 @@ extern int xfs_fs_counts(xfs_mount_t *mp, xfs_fsop_counts_t *cnt); extern int xfs_reserve_blocks(xfs_mount_t *mp, __uint64_t *inval, xfs_fsop_resblks_t *outval); extern int xfs_fs_goingdown(xfs_mount_t *mp, __uint32_t inflags); -extern int xfs_fs_log_dummy(xfs_mount_t *mp); +extern int xfs_fs_log_dummy(xfs_mount_t *mp, int flags); #endif /* __XFS_FSOPS_H__ */ -- 2.30.2