From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Fri, 27 Jun 2008 06:05:45 -0700 (PDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.168.28]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m5RD5auY005420 for ; Fri, 27 Jun 2008 06:05:36 -0700 Received: from verein.lst.de (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id A5B4012CDF83 for ; Fri, 27 Jun 2008 06:06:36 -0700 (PDT) Received: from verein.lst.de (verein.lst.de [213.95.11.210]) by cuda.sgi.com with ESMTP id Cui4naCm1apAWt8I for ; Fri, 27 Jun 2008 06:06:36 -0700 (PDT) Received: from verein.lst.de (localhost [127.0.0.1]) by verein.lst.de (8.12.3/8.12.3/Debian-7.1) with ESMTP id m5RD6RNW023565 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO) for ; Fri, 27 Jun 2008 15:06:27 +0200 Received: (from hch@localhost) by verein.lst.de (8.12.3/8.12.3/Debian-6.6) id m5RD6RIh023563 for xfs@oss.sgi.com; Fri, 27 Jun 2008 15:06:27 +0200 Date: Fri, 27 Jun 2008 15:06:27 +0200 From: Christoph Hellwig Subject: Re: [PATCH 2/2] kill xfs_lock_dir_and_entry Message-ID: <20080627130627.GC23431@lst.de> References: <20080502105803.GC17870@lst.de> <20080520063639.GC8869@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080520063639.GC8869@lst.de> Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: xfs@oss.sgi.com ping^2 On Tue, May 20, 2008 at 08:36:39AM +0200, Christoph Hellwig wrote: > ping? > > On Fri, May 02, 2008 at 12:58:03PM +0200, Christoph Hellwig wrote: > > When multiple inodes are locked in XFS it happens in order of the inode > > number, with the everything but the first inode trylocked if any of > > the previous inodes is in the AIL. > > > > Except for the sorting of the inodes this logic is implemented in > > xfs_lock_inodes, but also partially duplicated in xfs_lock_dir_and_entry > > in a particularly stupid way adds a lock roundtrip if the inode ordering > > is not optimal. > > > > This patch adds a new helper xfs_lock_two_inodes that takes two inodes > > and locks them in the most optimal way according to the above locking > > protocol and uses it for all places that want to lock two inodes. > > > > The only caller of xfs_lock_inodes is xfs_rename which might lock up to > > four inodes. > > > > > > Signed-off-by: Christoph Hellwig > > > > Index: linux-2.6-xfs/fs/xfs/xfs_vnodeops.c > > =================================================================== > > --- linux-2.6-xfs.orig/fs/xfs/xfs_vnodeops.c 2008-05-02 08:30:24.000000000 +0200 > > +++ linux-2.6-xfs/fs/xfs/xfs_vnodeops.c 2008-05-02 08:30:30.000000000 +0200 > > @@ -1897,111 +1897,6 @@ std_return: > > } > > > > #ifdef DEBUG > > -/* > > - * Some counters to see if (and how often) we are hitting some deadlock > > - * prevention code paths. > > - */ > > - > > -int xfs_rm_locks; > > -int xfs_rm_lock_delays; > > -int xfs_rm_attempts; > > -#endif > > - > > -/* > > - * The following routine will lock the inodes associated with the > > - * directory and the named entry in the directory. The locks are > > - * acquired in increasing inode number. > > - * > > - * If the entry is "..", then only the directory is locked. The > > - * vnode ref count will still include that from the .. entry in > > - * this case. > > - * > > - * There is a deadlock we need to worry about. If the locked directory is > > - * in the AIL, it might be blocking up the log. The next inode we lock > > - * could be already locked by another thread waiting for log space (e.g > > - * a permanent log reservation with a long running transaction (see > > - * xfs_itruncate_finish)). To solve this, we must check if the directory > > - * is in the ail and use lock_nowait. If we can't lock, we need to > > - * drop the inode lock on the directory and try again. xfs_iunlock will > > - * potentially push the tail if we were holding up the log. > > - */ > > -STATIC int > > -xfs_lock_dir_and_entry( > > - xfs_inode_t *dp, > > - xfs_inode_t *ip) /* inode of entry 'name' */ > > -{ > > - int attempts; > > - xfs_ino_t e_inum; > > - xfs_inode_t *ips[2]; > > - xfs_log_item_t *lp; > > - > > -#ifdef DEBUG > > - xfs_rm_locks++; > > -#endif > > - attempts = 0; > > - > > -again: > > - xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT); > > - > > - e_inum = ip->i_ino; > > - > > - xfs_itrace_ref(ip); > > - > > - /* > > - * We want to lock in increasing inum. Since we've already > > - * acquired the lock on the directory, we may need to release > > - * if if the inum of the entry turns out to be less. > > - */ > > - if (e_inum > dp->i_ino) { > > - /* > > - * We are already in the right order, so just > > - * lock on the inode of the entry. > > - * We need to use nowait if dp is in the AIL. > > - */ > > - > > - lp = (xfs_log_item_t *)dp->i_itemp; > > - if (lp && (lp->li_flags & XFS_LI_IN_AIL)) { > > - if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL)) { > > - attempts++; > > -#ifdef DEBUG > > - xfs_rm_attempts++; > > -#endif > > - > > - /* > > - * Unlock dp and try again. > > - * xfs_iunlock will try to push the tail > > - * if the inode is in the AIL. > > - */ > > - > > - xfs_iunlock(dp, XFS_ILOCK_EXCL); > > - > > - if ((attempts % 5) == 0) { > > - delay(1); /* Don't just spin the CPU */ > > -#ifdef DEBUG > > - xfs_rm_lock_delays++; > > -#endif > > - } > > - goto again; > > - } > > - } else { > > - xfs_ilock(ip, XFS_ILOCK_EXCL); > > - } > > - } else if (e_inum < dp->i_ino) { > > - xfs_iunlock(dp, XFS_ILOCK_EXCL); > > - > > - ips[0] = ip; > > - ips[1] = dp; > > - xfs_lock_inodes(ips, 2, XFS_ILOCK_EXCL); > > - } > > - /* else e_inum == dp->i_ino */ > > - /* This can happen if we're asked to lock /x/.. > > - * the entry is "..", which is also the parent directory. > > - */ > > - > > - return 0; > > -} > > - > > -#ifdef DEBUG > > int xfs_locked_n; > > int xfs_small_retries; > > int xfs_middle_retries; > > @@ -2135,6 +2030,45 @@ again: > > #endif > > } > > > > +void > > +xfs_lock_two_inodes( > > + xfs_inode_t *ip0, > > + xfs_inode_t *ip1, > > + uint lock_mode) > > +{ > > + xfs_inode_t *temp; > > + int attempts = 0; > > + xfs_log_item_t *lp; > > + > > + ASSERT(ip0->i_ino != ip1->i_ino); > > + > > + if (ip0->i_ino > ip1->i_ino) { > > + temp = ip0; > > + ip0 = ip1; > > + ip1 = temp; > > + } > > + > > + again: > > + xfs_ilock(ip0, xfs_lock_inumorder(lock_mode, 0)); > > + > > + /* > > + * If the first lock we have locked is in the AIL, we must TRY to get > > + * the second lock. If we can't get it, we must release the first one > > + * and try again. > > + */ > > + lp = (xfs_log_item_t *)ip0->i_itemp; > > + if (lp && (lp->li_flags & XFS_LI_IN_AIL)) { > > + if (!xfs_ilock_nowait(ip1, xfs_lock_inumorder(lock_mode, 1))) { > > + xfs_iunlock(ip0, lock_mode); > > + if ((++attempts % 5) == 0) > > + delay(1); /* Don't just spin the CPU */ > > + goto again; > > + } > > + } else { > > + xfs_ilock(ip1, xfs_lock_inumorder(lock_mode, 1)); > > + } > > +} > > + > > int > > xfs_remove( > > xfs_inode_t *dp, > > @@ -2210,9 +2144,7 @@ xfs_remove( > > goto out_trans_cancel; > > } > > > > - error = xfs_lock_dir_and_entry(dp, ip); > > - if (error) > > - goto out_trans_cancel; > > + xfs_lock_two_inodes(dp, ip, XFS_ILOCK_EXCL); > > > > /* > > * At this point, we've gotten both the directory and the entry > > @@ -2239,9 +2171,6 @@ xfs_remove( > > } > > } > > > > - /* > > - * Entry must exist since we did a lookup in xfs_lock_dir_and_entry. > > - */ > > XFS_BMAP_INIT(&free_list, &first_block); > > error = xfs_dir_removename(tp, dp, name, ip->i_ino, > > &first_block, &free_list, resblks); > > @@ -2347,7 +2276,6 @@ xfs_link( > > { > > xfs_mount_t *mp = tdp->i_mount; > > xfs_trans_t *tp; > > - xfs_inode_t *ips[2]; > > int error; > > xfs_bmap_free_t free_list; > > xfs_fsblock_t first_block; > > @@ -2395,15 +2323,7 @@ xfs_link( > > goto error_return; > > } > > > > - if (sip->i_ino < tdp->i_ino) { > > - ips[0] = sip; > > - ips[1] = tdp; > > - } else { > > - ips[0] = tdp; > > - ips[1] = sip; > > - } > > - > > - xfs_lock_inodes(ips, 2, XFS_ILOCK_EXCL); > > + xfs_lock_two_inodes(sip, tdp, XFS_ILOCK_EXCL); > > > > /* > > * Increment vnode ref counts since xfs_trans_commit & > > Index: linux-2.6-xfs/fs/xfs/xfs_dfrag.c > > =================================================================== > > --- linux-2.6-xfs.orig/fs/xfs/xfs_dfrag.c 2008-04-26 17:43:14.000000000 +0200 > > +++ linux-2.6-xfs/fs/xfs/xfs_dfrag.c 2008-05-02 08:30:30.000000000 +0200 > > @@ -128,7 +128,6 @@ xfs_swap_extents( > > xfs_swapext_t *sxp) > > { > > xfs_mount_t *mp; > > - xfs_inode_t *ips[2]; > > xfs_trans_t *tp; > > xfs_bstat_t *sbp = &sxp->sx_stat; > > bhv_vnode_t *vp, *tvp; > > @@ -153,16 +152,7 @@ xfs_swap_extents( > > vp = XFS_ITOV(ip); > > tvp = XFS_ITOV(tip); > > > > - /* Lock in i_ino order */ > > - if (ip->i_ino < tip->i_ino) { > > - ips[0] = ip; > > - ips[1] = tip; > > - } else { > > - ips[0] = tip; > > - ips[1] = ip; > > - } > > - > > - xfs_lock_inodes(ips, 2, lock_flags); > > + xfs_lock_two_inodes(ip, tip, lock_flags); > > locked = 1; > > > > /* Verify that both files have the same format */ > > @@ -265,7 +255,7 @@ xfs_swap_extents( > > locked = 0; > > goto error0; > > } > > - xfs_lock_inodes(ips, 2, XFS_ILOCK_EXCL); > > + xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL); > > > > /* > > * Count the number of extended attribute blocks > > Index: linux-2.6-xfs/fs/xfs/xfs_inode.h > > =================================================================== > > --- linux-2.6-xfs.orig/fs/xfs/xfs_inode.h 2008-05-01 22:56:57.000000000 +0200 > > +++ linux-2.6-xfs/fs/xfs/xfs_inode.h 2008-05-02 08:30:30.000000000 +0200 > > @@ -522,6 +522,7 @@ void xfs_iflush_all(struct xfs_mount *) > > void xfs_ichgtime(xfs_inode_t *, int); > > xfs_fsize_t xfs_file_last_byte(xfs_inode_t *); > > void xfs_lock_inodes(xfs_inode_t **, int, uint); > > +void xfs_lock_two_inodes(xfs_inode_t *, xfs_inode_t *, uint); > > > > void xfs_synchronize_atime(xfs_inode_t *); > > void xfs_mark_inode_dirty_sync(xfs_inode_t *); > ---end quoted text--- ---end quoted text---