File remove problem

[Bruce Evans]

On Fri, 30 Nov 2007, Kostik Belousov wrote:

> On Fri, Nov 30, 2007 at 03:58:55PM +1100, Bruce Evans wrote:
>> On Fri, 30 Nov 2007, David Cecil wrote:
>...
>>> One more point to address Julian's question, the partition is not mounted
>>> with soft updates.
>>
>> Interesting.  I saw no sign of the problem without soft updates except a
>> panic later after enabling soft updates.  I was running fsck a lot but
>> may have forgotten one since no error was detected.  The problem should
>> be easier to understand if it affects non-soft-updates.
>
> As a speculation, it might be that ufs_inactive() should conditionalize on
> fs_ronly instead of MNT_RDONLY. Then, VOP_INACTIVE() would set up the
> IN_CHANGE|IN_UPDATE and finally call the ffs_update() ?

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.

Bruce