From 9a57fa8ee7c29e11c2a29ce058573ba99157eda7 Mon Sep 17 00:00:00 2001 From: Mark Tinguely Date: Tue, 24 Jul 2012 10:59:19 -0500 Subject: [PATCH] xfs: wait for the write the superblock on unmount v2: Add the xfs_buf_lock to xfs_quiesce_attr(). Add explaination why xfs_buf_lock() is used to wait for write. xfs_wait_buftarg() does not wait for the completion of the write of the uncached superblock. This write can race with the shutdown of the log and causes a panic if the write does not win the race. During the log write, xfsaild_push() will lock the buffer and set the XBF_ASYNC flag. Because the XBF_FLAG is set, complete() is not performed on the buffer's iowait entry, we cannot call xfs_buf_iowait() to wait for the write to complete. The buffer's lock is held until the write is complete, so we can block on a xfs_buf_lock() request to be notified that the write is complete. Signed-off-by: Mark Tinguely Reviewed-by: Christoph Hellwig Signed-off-by: Ben Myers --- fs/xfs/xfs_mount.c | 9 +++++++++ fs/xfs/xfs_sync.c | 9 +++++++++ 2 files changed, 18 insertions(+) diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c index 9536fd1..711ca51 100644 --- a/fs/xfs/xfs_mount.c +++ b/fs/xfs/xfs_mount.c @@ -1529,6 +1529,15 @@ xfs_unmountfs( xfs_ail_push_all_sync(mp->m_ail); xfs_wait_buftarg(mp->m_ddev_targp); + /* + * The superblock buffer is uncached and xfsaild_push() will lock and + * set the XBF_ASYNC flag on the buffer. We cannot do xfs_buf_iowait() + * here but a lock on the superblock buffer will block until iodone() + * has completed. + */ + xfs_buf_lock(mp->m_sb_bp); + xfs_buf_unlock(mp->m_sb_bp); + xfs_log_unmount_write(mp); xfs_log_unmount(mp); xfs_uuid_unmount(mp); diff --git a/fs/xfs/xfs_sync.c b/fs/xfs/xfs_sync.c index e61fc151..97304f1 100644 --- a/fs/xfs/xfs_sync.c +++ b/fs/xfs/xfs_sync.c @@ -359,6 +359,15 @@ xfs_quiesce_attr( * added an item to the AIL, thus flush it again. */ xfs_ail_push_all_sync(mp->m_ail); + + /* + * The superblock buffer is uncached and xfsaild_push() will lock and + * set the XBF_ASYNC flag on the buffer. We cannot do xfs_buf_iowait() + * here but a lock on the superblock buffer will block until iodone() + * has completed. + */ + xfs_buf_lock(mp->m_sb_bp); + xfs_buf_unlock(mp->m_sb_bp); } static void -- 2.7.4