Date: Mon, 19 Nov 2012 22:08:53 +0100 From: Davide Italiano <davide@freebsd.org> To: attilio@freebsd.org Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r243307 - head/sys/kern Message-ID: <CACYV=-HvFp7mExNosna3ZvPvOfB%2BJ9c8rV8FdikMzofWPgU6VQ@mail.gmail.com> In-Reply-To: <CAJ-FndBUNezKNFPQCqw8j%2B47fOcvqR6nVEy%2BUUxnbqQg7LoY7A@mail.gmail.com> References: <201211192043.qAJKhJ9i038016@svn.freebsd.org> <CACYV=-Hya1-V_RNToWHDD_LFqxEcJYovUjnp0P9b-Q8Hzm3t_w@mail.gmail.com> <CAJ-FndBUNezKNFPQCqw8j%2B47fOcvqR6nVEy%2BUUxnbqQg7LoY7A@mail.gmail.com>
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On Mon, Nov 19, 2012 at 9:55 PM, Attilio Rao <attilio@freebsd.org> wrote: > On Mon, Nov 19, 2012 at 8:53 PM, Davide Italiano <davide@freebsd.org> wrote: >> On Mon, Nov 19, 2012 at 9:43 PM, Attilio Rao <attilio@freebsd.org> wrote: >>> Author: attilio >>> Date: Mon Nov 19 20:43:19 2012 >>> New Revision: 243307 >>> URL: http://svnweb.freebsd.org/changeset/base/243307 >>> >>> Log: >>> insmntque() is always called with the lock held in exclusive mode, >>> then: >>> - assume the lock is held in exclusive mode and remove a moot check >>> about the lock acquisition. >>> - in the destructor remove !MPSAFE specific chunk. >>> >>> Reviewed by: kib >>> MFC after: 2 weeks >>> >>> Modified: >>> head/sys/kern/vfs_subr.c >>> >>> Modified: head/sys/kern/vfs_subr.c >>> ============================================================================== >>> --- head/sys/kern/vfs_subr.c Mon Nov 19 19:31:55 2012 (r243306) >>> +++ head/sys/kern/vfs_subr.c Mon Nov 19 20:43:19 2012 (r243307) >>> @@ -1111,10 +1111,6 @@ insmntque_stddtr(struct vnode *vp, void >>> >>> vp->v_data = NULL; >>> vp->v_op = &dead_vnodeops; >>> - /* XXX non mp-safe fs may still call insmntque with vnode >>> - unlocked */ >>> - if (!VOP_ISLOCKED(vp)) >>> - vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); >>> vgone(vp); >>> vput(vp); >>> } >>> @@ -1126,7 +1122,6 @@ int >>> insmntque1(struct vnode *vp, struct mount *mp, >>> void (*dtr)(struct vnode *, void *), void *dtr_arg) >>> { >>> - int locked; >>> >>> KASSERT(vp->v_mount == NULL, >>> ("insmntque: vnode already on per mount vnode list")); >>> @@ -1144,18 +1139,15 @@ insmntque1(struct vnode *vp, struct moun >>> */ >>> MNT_ILOCK(mp); >>> VI_LOCK(vp); >>> - if ((mp->mnt_kern_flag & MNTK_NOINSMNTQ) != 0 && >>> + if (((mp->mnt_kern_flag & MNTK_NOINSMNTQ) != 0 && >>> ((mp->mnt_kern_flag & MNTK_UNMOUNTF) != 0 || >>> - mp->mnt_nvnodelistsize == 0)) { >>> - locked = VOP_ISLOCKED(vp); >>> - if (!locked || (locked == LK_EXCLUSIVE && >>> - (vp->v_vflag & VV_FORCEINSMQ) == 0)) { >>> - VI_UNLOCK(vp); >>> - MNT_IUNLOCK(mp); >>> - if (dtr != NULL) >>> - dtr(vp, dtr_arg); >>> - return (EBUSY); >>> - } >>> + mp->mnt_nvnodelistsize == 0)) && >>> + (vp->v_vflag & VV_FORCEINSMQ) == 0) { >>> + VI_UNLOCK(vp);s >>> + MNT_IUNLOCK(mp); >>> + if (dtr != NULL) >>> + dtr(vp, dtr_arg); >>> + return (EBUSY); >>> } >>> vp->v_mount = mp; >>> MNT_REF(mp); >> >> Thanks for doing this. >> Attilio, I don't know if this really could help, but what do you think >> about adding an assertion to check if the vnode is locked? >> This could help in some cases, e.g. it might be useful to discover the >> violation of this assumption for a developer which wants to port a new >> fs into the source tree. > > Exactly where? insmntque1() already has this. > > Attilio > > > -- > Peace can only be achieved by understanding - A. Einstein I was talking about the destructor code, instead of the vn_lock() call which you removed. I was in doubt so I asked, but now after closely looking at the code I see the destructor function is called only within insmntque1 and the check I suggest is probably redundant/useless. Thanks
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