From b2344ab5ff99165442501d320f8cede2b44c1b75 Mon Sep 17 00:00:00 2001 From: Konstantin Belousov Date: Tue, 9 Dec 2014 10:00:47 +0000 Subject: [PATCH] Do not call VFS_SYNC() before VFS_UNMOUNT() for forced unmount. Since VFS does not/cannot stop writes, sync might run indefinitely, or be a wrong thing to do at all. E. g. NFS ignores VFS_SYNC() for forced unmounts, since non-responding server does not allow sync to finish. On the other hand, filesystems can and do stop writes using fs-specific facilities, and should already fully flush caches in VFS_UNMOUNT() due to the race. Adjust msdosfs tp sync in unmount for forced call, to accomodate the new behaviour. Note that it is still racy, since writes are not stopped. Discussed with: avg, bjk, mckusick Reported and tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 3 weeks --- sys/fs/msdosfs/msdosfs_vfsops.c | 10 +++++++--- sys/kern/vfs_mount.c | 4 ++-- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/sys/fs/msdosfs/msdosfs_vfsops.c b/sys/fs/msdosfs/msdosfs_vfsops.c index 213dd00f2d1..d14cdef51a7 100644 --- a/sys/fs/msdosfs/msdosfs_vfsops.c +++ b/sys/fs/msdosfs/msdosfs_vfsops.c @@ -797,11 +797,15 @@ msdosfs_unmount(struct mount *mp, int mntflags) int error, flags; flags = 0; - if (mntflags & MNT_FORCE) + error = msdosfs_sync(mp, MNT_WAIT); + if ((mntflags & MNT_FORCE) != 0) { flags |= FORCECLOSE; + } else if (error != 0) { + return (error); + } error = vflush(mp, 0, flags, curthread); - if (error && error != ENXIO) - return error; + if (error != 0 && error != ENXIO) + return (error); pmp = VFSTOMSDOSFS(mp); if ((pmp->pm_flags & MSDOSFSMNT_RONLY) == 0) { error = markvoldirty(pmp, 0); diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c index c407699d2ca..b2b4969975c 100644 --- a/sys/kern/vfs_mount.c +++ b/sys/kern/vfs_mount.c @@ -1305,8 +1305,8 @@ dounmount(mp, flags, td) } vput(fsrootvp); } - if (((mp->mnt_flag & MNT_RDONLY) || - (error = VFS_SYNC(mp, MNT_WAIT)) == 0) || (flags & MNT_FORCE) != 0) + if ((mp->mnt_flag & MNT_RDONLY) != 0 || (flags & MNT_FORCE) != 0 || + (error = VFS_SYNC(mp, MNT_WAIT)) == 0) error = VFS_UNMOUNT(mp, flags); vn_finished_write(mp); /*