Date: Tue, 2 Sep 2003 21:37:31 +0200 From: Pawel Jakub Dawidek <nick@garage.freebsd.pl> To: Jeff Roberson <jeff@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/sys buf.h src/sys/kern vfs_bio.c vfs_cluster.c src/sys/ufs/ffs ffs_softdep.c Message-ID: <20030902193731.GV47959@garage.freebsd.pl> In-Reply-To: <200308280655.h7S6tJTS064892@repoman.freebsd.org> References: <200308280655.h7S6tJTS064892@repoman.freebsd.org>
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On Wed, Aug 27, 2003 at 11:55:19PM -0700, Jeff Roberson wrote:
+> Commiter: Jeff Roberson <jeff@FreeBSD.org>
+> Branch: HEAD
+>=20
+> Files:
+> 1.398 src/sys/kern/vfs_bio.c =20
+> 1.143 src/sys/kern/vfs_cluster.c =20
+> 1.155 src/sys/sys/buf.h =20
+> 1.140 src/sys/ufs/ffs/ffs_softdep.c =20
+>=20
+> Log:
+> - Move BX_BKGRDWAIT and BX_BKGRDINPROG to BV_ and the b_vflags field.
+> - Surround all accesses of the BKGRD{WAIT,INPROG} flags with the vnode
+> interlock.
+> - Don't use the B_LOCKED flag and QUEUE_LOCKED for background write
+> buffers. Check for the BKGRDINPROG flag before recycling or throwi=
ng
+> away a buffer. We do this instead because it is not safe for us to=
move
+> the original buffer to a new queue from the callback on the backgro=
und
+> write buffer.
+> - Remove the B_LOCKED flag and the locked buffer queue. They are no =
longer
+> used.
+> - The vnode interlock is used around checks for BKGRDINPROG where it =
may
+> not be strictly necessary. If we hold the buf lock the a back-grou=
nd
+> write will not be started without our knowledge, one may only be
+> completed while we're not looking. Rather than remove the code, Do=
cument
+> two of the places where this extra locking is done. A pass should =
be
+> done to verify and minimize the locking later.
[...]
+> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
+> RCS file: /usr/local/www/cvsroot/FreeBSD/src/sys/ufs/ffs/ffs_softdep.c,v
+> retrieving revision 1.139
+> retrieving revision 1.140
+> diff -u -p -r1.139 -r1.140
+> --- src/sys/ufs/ffs/ffs_softdep.c 2003/03/18 08:45:24 1.139
+> +++ src/sys/ufs/ffs/ffs_softdep.c 2003/08/28 06:55:18 1.140
[...]
+> @@ -5803,21 +5801,31 @@ getdirtybuf(bpp, waitfor)
+> struct buf *bp;
+> int error;
+> =20
+> + /*
+> + * XXX This code and the code that calls it need to be reviewed to
+> + * verify its use of the vnode interlock.
+> + */
+> +
+> for (;;) {
+> if ((bp =3D *bpp) =3D=3D NULL)
+> return (0);
+> - /* XXX Probably needs interlock */
+> + VI_LOCK(bp->b_vp);
+> if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL) =3D=3D 0) {
+> - if ((bp->b_xflags & BX_BKGRDINPROG) =3D=3D 0)
+> + if ((bp->b_vflags & BV_BKGRDINPROG) =3D=3D 0) {
+> + VI_UNLOCK(bp->b_vp);
+> break;
+> + }
+> BUF_UNLOCK(bp);
+> - if (waitfor !=3D MNT_WAIT)
+> + if (waitfor !=3D MNT_WAIT) {
+> + VI_UNLOCK(bp->b_vp);
+> return (0);
+> - bp->b_xflags |=3D BX_BKGRDWAIT;
+> - interlocked_sleep(&lk, SLEEP, &bp->b_xflags, NULL,
+> - PRIBIO, "getbuf", 0);
+> + }
+> + bp->b_vflags |=3D BV_BKGRDWAIT;
+> + interlocked_sleep(&lk, SLEEP, &bp->b_xflags,
+> + VI_MTX(bp->b_vp), PRIBIO|PDROP, "getbuf", 0);
+> continue;
+> }
+> + VI_UNLOCK(bp->b_vp);
+> if (waitfor !=3D MNT_WAIT)
+> return (0);
+> error =3D interlocked_sleep(&lk, LOCKBUF, bp, NULL,=20
I'm afraid that something is wrong with this change.
I get panics:
_mtx_lock_flags()
getdirtybuf()
[...]
I'll provide more info when I'll reproduce it.
--=20
Pawel Jakub Dawidek pawel@dawidek.net
UNIX Systems Programmer/Administrator http://garage.freebsd.pl
Am I Evil? Yes, I Am! http://cerber.sourceforge.net
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