Date: Thu, 05 Nov 1998 00:57:47 -0800 From: Mike Smith <mike@smith.net.au> To: Peter Jeremy <peter.jeremy@auss2.alcatel.com.au> Cc: peter@netplex.com.au, hackers@FreeBSD.ORG Subject: Re: MMAP and sync writes (Re: sync writes with softupdates enabled) Message-ID: <199811050857.AAA01153@dingo.cdrom.com> In-Reply-To: Your message of "Wed, 04 Nov 1998 21:05:16 %2B1100." <98Nov4.210449est.40336@border.alcanet.com.au>
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Any followthrough on this one? Particularly, any test results?
> Peter Wemm <peter@netplex.com.au> wrote:
> >> Note that there is a similar bug in 2.2.x. The fix is similar, but
> >> needs some thought since there appears to be a problem with the
> >> parameters to vm_object_page_clean(). In particular, `syncio' is
> >> defined as boolean_t, as passed as the `waitfor' argument to
> >> VOP_FSYNC() - which is MNT_ASYNC or MNT_SYNC elsewhere. I haven't
> >> had the time to work out the correct definitions.
> >
> >Use TRUE and FALSE instead of OBJPC_SYNC and 0.
>
> I don't think it's that simple. The following is from 2.2.7-RELEASE:
>
> Looking at vm_object_page_clean(), all the existing calls use TRUE or
> FALSE (or 1 or 0, which is equivalent, if less clear). This matches
> the definition 'boolean_t syncio'.
>
> Within vm_object_page_clean(), syncio is only used as:
> VOP_FSYNC(vp, NULL, syncio, curproc);
>
> The problem is that everywhere else, VOP_FSYNC() is called with the
> third parameter as one of the following:
> a) MNT_WAIT or MNT_NOWAIT explicitly specified.
> b) (struct vop_fsync_args).a_waitfor
> c) the 2nd argument of {fstype}_sync, invoked via VFS_SYNC() and
> explicitly defined as MNT_WAIT or MNT_NOWAIT in <sys/mount.h>
>
> a_waitfor is only assigned from VOP_FSYNC() and is compared against
> MNT_WAIT/MNT_NOWAIT everywhere except:
> ffs_inode.c:ffs_update()
> if (ap->a_waitfor && (ap->a_vp->v_mount->mnt_flag & MNT_ASYNC) == 0)
> return (bwrite(bp));
>
> lfs_inode.c:lfs_update()
> error = (ap->a_waitfor & LFS_SYNC ? lfs_vflush(vp) : 0);
> if(ap->a_waitfor & LFS_SYNC && vp->v_dirtyblkhd.lh_first != NULL)
>
> VFS_SYNC() is invoked with the second parameter as one of the following:
> a) MNT_WAIT or MNT_NOWAIT explicitly specified.
> b) 1 in lfs_vfsops.c:lfs_unmount()
>
> Based on the above, I believe the 4th argument to vm_object_page_clean()
> should really be an int and all calls should be updated to pass
> MNT_WAIT or MNT_NOWAIT.
>
> These discrepancies would be far more obvious if more of the kernel
> magic numbers were enum's instead of #defines - the compiler would
> have some hope of pointing out the inconsistencies.
>
> Peter
> --
> Peter Jeremy (VK2PJ) peter.jeremy@alcatel.com.au
> Alcatel Australia Limited
> 41 Mandible St Phone: +61 2 9690 5019
> ALEXANDRIA NSW 2015 Fax: +61 2 9690 5247
>
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--
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\\ sometimes you're behind. \\ mike@smith.net.au
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