From a7b76b76e17881d47ffd2715135b3512e07d0fbf Mon Sep 17 00:00:00 2001 From: kib Date: Tue, 9 Jul 2013 20:49:32 +0000 Subject: There are several code sequences like vfs_busy(mp); vfs_write_suspend(mp); which are problematic if other thread starts unmount between two calls. The unmount starts a write, while vfs_write_suspend() drain writers. On the other hand, unmount drains busy references, causing the deadlock. Add a flag argument to vfs_write_suspend and require the callers of it to specify VS_SKIP_UNMOUNT flag, when the call is performed not in the mount path, i.e. the covered vnode is not locked. The suspension is not attempted if VS_SKIP_UNMOUNT is specified and unmount is in progress. Reported and tested by: Andreas Longwitz Sponsored by: The FreeBSD Foundation MFC after: 3 weeks --- sys/ufs/ffs/ffs_snapshot.c | 2 +- sys/ufs/ffs/ffs_suspend.c | 2 +- sys/ufs/ffs/ffs_vfsops.c | 4 ++-- 3 files changed, 4 insertions(+), 4 deletions(-) (limited to 'sys/ufs/ffs') diff --git a/sys/ufs/ffs/ffs_snapshot.c b/sys/ufs/ffs/ffs_snapshot.c index 9a9c88a..ad157aa 100644 --- a/sys/ufs/ffs/ffs_snapshot.c +++ b/sys/ufs/ffs/ffs_snapshot.c @@ -423,7 +423,7 @@ restart: */ for (;;) { vn_finished_write(wrtmp); - if ((error = vfs_write_suspend(vp->v_mount)) != 0) { + if ((error = vfs_write_suspend(vp->v_mount, 0)) != 0) { vn_start_write(NULL, &wrtmp, V_WAIT); vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); goto out; diff --git a/sys/ufs/ffs/ffs_suspend.c b/sys/ufs/ffs/ffs_suspend.c index 3198c1a..a8c4578 100644 --- a/sys/ufs/ffs/ffs_suspend.c +++ b/sys/ufs/ffs/ffs_suspend.c @@ -206,7 +206,7 @@ ffs_susp_suspend(struct mount *mp) return (EPERM); #endif - if ((error = vfs_write_suspend(mp)) != 0) + if ((error = vfs_write_suspend(mp, VS_SKIP_UNMOUNT)) != 0) return (error); ump->um_writesuspended = 1; diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c index 57f092c..a87fdfa 100644 --- a/sys/ufs/ffs/ffs_vfsops.c +++ b/sys/ufs/ffs/ffs_vfsops.c @@ -257,7 +257,7 @@ ffs_mount(struct mount *mp) return (error); for (;;) { vn_finished_write(mp); - if ((error = vfs_write_suspend(mp)) != 0) + if ((error = vfs_write_suspend(mp, 0)) != 0) return (error); MNT_ILOCK(mp); if (mp->mnt_kern_flag & MNTK_SUSPENDED) { @@ -1255,7 +1255,7 @@ ffs_unmount(mp, mntflags) */ for (;;) { vn_finished_write(mp); - if ((error = vfs_write_suspend(mp)) != 0) + if ((error = vfs_write_suspend(mp, 0)) != 0) return (error); MNT_ILOCK(mp); if (mp->mnt_kern_flag & MNTK_SUSPENDED) { -- cgit v1.1