On Fri, 30 Nov 2007, Kostik Belousov wrote:

Something like that seems to be right. The folowing hack in ufs_inactive() seems to fix the problem with sift updates, as does unsetting MNT_RDONLY for the whole VOP_SYNC() in ffs_mount().

% Index: ufs_inode.c % =================================================================== % RCS file: /home/ncvs/src/sys/ufs/ufs/ufs_inode.c,v % retrieving revision 1.53 % diff -u -2 -r1.53 ufs_inode.c % --- ufs_inode.c 7 Apr 2004 03:47:20 -0000 1.53 % +++ ufs_inode.c 30 Nov 2007 12:58:39 -0000 % @@ -59,4 +59,6 @@ % #endif % % +#include <ufs/ffs/fs.h> % + % /* % * Last reference to an inode. If necessary, write or delete it. % @@ -118,6 +120,15 @@ % ip->i_flag &= ~IN_ACCESS; % } else { % + int wasro = 0; % + % (void) vn_write_suspend_wait(vp, NULL, V_WAIT); % + if (vp->v_mount->mnt_flag & MNT_RDONLY && % + ip->i_fs->fs_ronly == 0) { % + vp->v_mount->mnt_flag &= ~MNT_RDONLY; % + wasro = 1; % + } % UFS_UPDATE(vp, 0); % + if (wasro) % + vp->v_mount->mnt_flag |= MNT_RDONLY; % } % }

I didn't bother with correct locking here (only tested under UP).

With this change, the VOP_SYNC() in ffs_mount() for MNT_UPDATE seems to flush everything in simple cases (with no open files), just like the VOP_SYNC() in unmount() flushes everything before ffs_unmount() is reached. OTOH, without a forced flush, soft updates takes a long time to flush things -- more like 3 syncer periods than 1 for non-waitfor syncs. With soft updates, the above is called from deep in VOP_SYNC(). It's strange that the above non-waitfor UFS_UPDATE() is used inside of waitfor syncs. It apparently works because the waitfor syncs wait for it later, but only if it is non-null.

BTW, *_mount() has lots of bogusness related to string options. In particular, ffs_mount() for update from r/w to r/o checks the "ro" string option and sets MNT_RDONLY later, but MNT_RDONLY is already set and other things depend on it being set early.