From patchwork Thu Feb 7 18:24:18 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 10801759 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 82BE1746 for ; Thu, 7 Feb 2019 18:24:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6DB3C2846C for ; Thu, 7 Feb 2019 18:24:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 617832E306; Thu, 7 Feb 2019 18:24:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2132D2846C for ; Thu, 7 Feb 2019 18:24:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726442AbfBGSY0 (ORCPT ); Thu, 7 Feb 2019 13:24:26 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:59332 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726401AbfBGSY0 (ORCPT ); Thu, 7 Feb 2019 13:24:26 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x17IOK7j009592; Thu, 7 Feb 2019 18:24:20 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2018-07-02; bh=JwtwRLbJyDF+DeY5DT1nXeCHsc7d13n5NJ9p7qWoets=; b=2QdBwc8vYYXZyInchAQYbJL0I7r5Jx/4QMmMOC5AQXAAAyoNpVMTmgd3VzLIg8I4fz1S ZsfpC8tglSBRrkUPWNKVDvoyALfZZxnRoHUlEC/xbG48z6Haei2p47HimGspa4HLjAYm eD6EM5A8ej/7TDIZChJgb4wYmnlkBR3StQKzEB1HOiyKG+UgotScbMbd7cTNMCVcR2dB lmRhfv+bagQzDo/BclM1X46cnQ8geWZ/kpsdXUE/cJrEsPTAO+rBgN9jEGCWCLyJeQ2C H/Zh0hx+MoAGG1bSkvOQ88SN/5KDkF7M9cDVJUX4HtR5bRVuko4xpk4CaE8ovgBecxRd lw== Received: from userv0021.oracle.com (userv0021.oracle.com [156.151.31.71]) by userp2120.oracle.com with ESMTP id 2qd98ngmxt-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 07 Feb 2019 18:24:20 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x17IOJvO029690 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 7 Feb 2019 18:24:19 GMT Received: from abhmp0022.oracle.com (abhmp0022.oracle.com [141.146.116.28]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x17IOJvD009616; Thu, 7 Feb 2019 18:24:19 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 07 Feb 2019 18:24:19 +0000 Date: Thu, 7 Feb 2019 10:24:18 -0800 From: "Darrick J. Wong" To: linux-xfs@vger.kernel.org Cc: Brian Foster Subject: [PATCH v2 9/9] xfs: cache unlinked pointers in an rhashtable Message-ID: <20190207182418.GD7991@magnolia> References: <154947207759.22369.11575570374120223292.stgit@magnolia> <154947213625.22369.7330296004413590907.stgit@magnolia> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <154947213625.22369.7330296004413590907.stgit@magnolia> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9160 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=3 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902070138 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Darrick J. Wong Use a rhashtable to cache the unlinked list incore. This should speed up unlinked processing considerably when there are a lot of inodes on the unlinked list because iunlink_remove no longer has to traverse an entire bucket list to find which inode points to the one being removed. The incore list structure records "X.next_unlinked = Y" relations, with the rhashtable using Y to index the records. This makes finding the inode X that points to a inode Y very quick. If our cache fails to find anything we can always fall back on the old method. FWIW this drastically reduces the amount of time it takes to remove inodes from the unlinked list. I wrote a program to open a lot of O_TMPFILE files and then close them in the same order, which takes a very long time if we have to traverse the unlinked lists. With the ptach, I see: + /d/t/tmpfile/tmpfile Opened 193531 files in 6.33s. Closed 193531 files in 5.86s real 0m12.192s user 0m0.064s sys 0m11.619s + cd / + umount /mnt real 0m0.050s user 0m0.004s sys 0m0.030s And without the patch: + /d/t/tmpfile/tmpfile Opened 193588 files in 6.35s. Closed 193588 files in 751.61s real 12m38.853s user 0m0.084s sys 12m34.470s + cd / + umount /mnt real 0m0.086s user 0m0.000s sys 0m0.060s Signed-off-by: Darrick J. Wong Reviewed-by: Brian Foster --- v2: rework comments and factor out hashtable insertion to a helper --- fs/xfs/libxfs/xfs_errortag.h | 4 - fs/xfs/xfs_error.c | 3 fs/xfs/xfs_inode.c | 284 +++++++++++++++++++++++++++++++++++++++++- fs/xfs/xfs_inode.h | 3 fs/xfs/xfs_mount.c | 5 + fs/xfs/xfs_mount.h | 7 + fs/xfs/xfs_trace.h | 1 7 files changed, 300 insertions(+), 7 deletions(-) diff --git a/fs/xfs/libxfs/xfs_errortag.h b/fs/xfs/libxfs/xfs_errortag.h index 66077a105cbb..79e6c4fb1d8a 100644 --- a/fs/xfs/libxfs/xfs_errortag.h +++ b/fs/xfs/libxfs/xfs_errortag.h @@ -54,7 +54,8 @@ #define XFS_ERRTAG_BUF_LRU_REF 31 #define XFS_ERRTAG_FORCE_SCRUB_REPAIR 32 #define XFS_ERRTAG_FORCE_SUMMARY_RECALC 33 -#define XFS_ERRTAG_MAX 34 +#define XFS_ERRTAG_IUNLINK_FALLBACK 34 +#define XFS_ERRTAG_MAX 35 /* * Random factors for above tags, 1 means always, 2 means 1/2 time, etc. @@ -93,5 +94,6 @@ #define XFS_RANDOM_BUF_LRU_REF 2 #define XFS_RANDOM_FORCE_SCRUB_REPAIR 1 #define XFS_RANDOM_FORCE_SUMMARY_RECALC 1 +#define XFS_RANDOM_IUNLINK_FALLBACK (XFS_RANDOM_DEFAULT/10) #endif /* __XFS_ERRORTAG_H_ */ diff --git a/fs/xfs/xfs_error.c b/fs/xfs/xfs_error.c index 9866f542e77b..cc77c11bd0d4 100644 --- a/fs/xfs/xfs_error.c +++ b/fs/xfs/xfs_error.c @@ -51,6 +51,7 @@ static unsigned int xfs_errortag_random_default[] = { XFS_RANDOM_BUF_LRU_REF, XFS_RANDOM_FORCE_SCRUB_REPAIR, XFS_RANDOM_FORCE_SUMMARY_RECALC, + XFS_RANDOM_IUNLINK_FALLBACK, }; struct xfs_errortag_attr { @@ -159,6 +160,7 @@ XFS_ERRORTAG_ATTR_RW(log_item_pin, XFS_ERRTAG_LOG_ITEM_PIN); XFS_ERRORTAG_ATTR_RW(buf_lru_ref, XFS_ERRTAG_BUF_LRU_REF); XFS_ERRORTAG_ATTR_RW(force_repair, XFS_ERRTAG_FORCE_SCRUB_REPAIR); XFS_ERRORTAG_ATTR_RW(bad_summary, XFS_ERRTAG_FORCE_SUMMARY_RECALC); +XFS_ERRORTAG_ATTR_RW(iunlink_fallback, XFS_ERRTAG_IUNLINK_FALLBACK); static struct attribute *xfs_errortag_attrs[] = { XFS_ERRORTAG_ATTR_LIST(noerror), @@ -195,6 +197,7 @@ static struct attribute *xfs_errortag_attrs[] = { XFS_ERRORTAG_ATTR_LIST(buf_lru_ref), XFS_ERRORTAG_ATTR_LIST(force_repair), XFS_ERRORTAG_ATTR_LIST(bad_summary), + XFS_ERRORTAG_ATTR_LIST(iunlink_fallback), NULL, }; diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 206bb004c4f2..9e2e0e9e3473 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -1906,6 +1906,208 @@ xfs_inactive( xfs_qm_dqdetach(ip); } +/* + * In-Core Unlinked List Lookups + * ============================= + * + * Every inode is supposed to be reachable from some other piece of metadata + * with the exception of the root directory. Inodes with a connection to a + * file descriptor but not linked from anywhere in the on-disk directory tree + * are collectively known as unlinked inodes, though the filesystem itself + * maintains links to these inodes so that on-disk metadata are consistent. + * + * XFS implements a per-AG on-disk hash table of unlinked inodes. The AGI + * header contains a number of buckets that point to an inode, and each inode + * record has a pointer to the next inode in the hash chain. This + * singly-linked list causes scaling problems in the iunlink remove function + * because we must walk that list to find the inode that points to the inode + * being removed from the unlinked hash bucket list. + * + * What if we modelled the unlinked list as a collection of records capturing + * "X.next_unlinked = Y" relations? If we indexed those records on Y, we'd + * have a fast way to look up unlinked list predecessors, which avoids the + * slow list walk. That's exactly what we do here (in-core) with a per-AG + * rhashtable. + * + * Because this is a backref cache, we ignore operational failures since the + * iunlink code can fall back to the slow bucket walk. The only errors that + * should bubble out are for obviously incorrect situations. + * + * All users of the backref cache MUST hold the AGI buffer lock to serialize + * access or have otherwise provided for concurrency control. + */ + +/* Capture a "X.next_unlinked = Y" relationship. */ +struct xfs_iunlink { + struct rhash_head iu_rhash_head; + xfs_agino_t iu_agino; /* X */ + xfs_agino_t iu_next_unlinked; /* Y */ +}; + +/* Unlinked list predecessor lookup hashtable construction */ +static int +xfs_iunlink_obj_cmpfn( + struct rhashtable_compare_arg *arg, + const void *obj) +{ + const xfs_agino_t *key = arg->key; + const struct xfs_iunlink *iu = obj; + + if (iu->iu_next_unlinked != *key) + return 1; + return 0; +} + +static const struct rhashtable_params xfs_iunlink_hash_params = { + .min_size = XFS_AGI_UNLINKED_BUCKETS, + .key_len = sizeof(xfs_agino_t), + .key_offset = offsetof(struct xfs_iunlink, + iu_next_unlinked), + .head_offset = offsetof(struct xfs_iunlink, iu_rhash_head), + .automatic_shrinking = true, + .obj_cmpfn = xfs_iunlink_obj_cmpfn, +}; + +/* + * Return X, where X.next_unlinked == @agino. Returns NULLAGINO if no such + * relation is found. + */ +static xfs_agino_t +xfs_iunlink_lookup_backref( + struct xfs_perag *pag, + xfs_agino_t agino) +{ + struct xfs_iunlink *iu; + + iu = rhashtable_lookup_fast(&pag->pagi_unlinked_hash, &agino, + xfs_iunlink_hash_params); + return iu ? iu->iu_agino : NULLAGINO; +} + +/* + * Take ownership of an iunlink cache entry and insert it into the hash table. + * If successful, the entry will be owned by the cache; if not it is freed. + * Either way the caller must not use @iu after this call. + */ +static int +xfs_iunlink_insert_backref( + struct xfs_perag *pag, + struct xfs_iunlink *iu) +{ + int error; + + error = rhashtable_insert_fast(&pag->pagi_unlinked_hash, + &iu->iu_rhash_head, xfs_iunlink_hash_params); + /* + * Fail loudly if there already was an entry because that's a sign of + * corruption of in-memory data. Absorb any other runtime errors + * because this is a cache and we can always fall back to bucket list + * scanning. + */ + if (error) + kmem_free(iu); + if (error != 0 && error != -EEXIST) + error = 0; + return error; +} + +/* Remember that @prev_agino.next_unlinked = @this_agino. */ +static int +xfs_iunlink_add_backref( + struct xfs_perag *pag, + xfs_agino_t prev_agino, + xfs_agino_t this_agino) +{ + struct xfs_iunlink *iu; + + if (XFS_TEST_ERROR(false, pag->pag_mount, XFS_ERRTAG_IUNLINK_FALLBACK)) + return 0; + + iu = kmem_zalloc(sizeof(*iu), KM_SLEEP | KM_NOFS); + iu->iu_agino = prev_agino; + iu->iu_next_unlinked = this_agino; + + return xfs_iunlink_insert_backref(pag, iu); +} + +/* + * Replace X.next_unlinked = @agino with X.next_unlinked = @next_unlinked. + * If @next_unlinked is NULLAGINO, we drop the backref and exit. If there + * wasn't any such entry then we don't bother. + */ +static int +xfs_iunlink_change_backref( + struct xfs_perag *pag, + xfs_agino_t agino, + xfs_agino_t next_unlinked) +{ + struct xfs_iunlink *iu; + int error; + + /* Look up the old entry; if there wasn't one then exit. */ + iu = rhashtable_lookup_fast(&pag->pagi_unlinked_hash, &agino, + xfs_iunlink_hash_params); + if (!iu) + return 0; + + /* + * Remove the entry. This shouldn't ever return an error, but if we + * couldn't remove the old entry we don't want to add it again to the + * hash table, and if the entry disappeared on us then someone's + * violated the locking rules and we need to fail loudly. Either way + * we cannot remove the inode because internal state is or would have + * been corrupt. + */ + error = rhashtable_remove_fast(&pag->pagi_unlinked_hash, + &iu->iu_rhash_head, xfs_iunlink_hash_params); + if (error) + return error; + + /* If there is no new next entry just free our item and return. */ + if (next_unlinked == NULLAGINO) { + kmem_free(iu); + return 0; + } + + /* Update the entry and re-add it to the hash table. */ + iu->iu_next_unlinked = next_unlinked; + return xfs_iunlink_insert_backref(pag, iu); +} + +/* Set up the in-core predecessor structures. */ +int +xfs_iunlink_init( + struct xfs_perag *pag) +{ + return rhashtable_init(&pag->pagi_unlinked_hash, + &xfs_iunlink_hash_params); +} + +/* Free the in-core predecessor structures. */ +static void +xfs_iunlink_free_item( + void *ptr, + void *arg) +{ + struct xfs_iunlink *iu = ptr; + bool *freed_anything = arg; + + *freed_anything = true; + kmem_free(iu); +} + +void +xfs_iunlink_destroy( + struct xfs_perag *pag) +{ + bool freed_anything = false; + + rhashtable_free_and_destroy(&pag->pagi_unlinked_hash, + xfs_iunlink_free_item, &freed_anything); + + ASSERT(freed_anything == false || XFS_FORCED_SHUTDOWN(pag->pag_mount)); +} + /* * Point the AGI unlinked bucket at an inode and log the results. The caller * is responsible for validating the old value. @@ -2066,7 +2268,8 @@ xfs_iunlink( return -EFSCORRUPTED; if (next_agino != NULLAGINO) { - xfs_agino_t old_agino; + struct xfs_perag *pag; + xfs_agino_t old_agino; /* * There is already another inode in the bucket, so point this @@ -2077,6 +2280,16 @@ xfs_iunlink( if (error) return error; ASSERT(old_agino == NULLAGINO); + + /* + * agino has been unlinked, add a backref from the next inode + * back to agino. + */ + pag = xfs_perag_get(mp, agno); + error = xfs_iunlink_add_backref(pag, agino, next_agino); + xfs_perag_put(pag); + if (error) + return error; } /* Point the head of the list to point to this inode. */ @@ -2133,7 +2346,8 @@ xfs_iunlink_map_prev( xfs_agino_t *agino, struct xfs_imap *imap, struct xfs_dinode **dipp, - struct xfs_buf **bpp) + struct xfs_buf **bpp, + struct xfs_perag *pag) { struct xfs_mount *mp = tp->t_mountp; xfs_agino_t next_agino; @@ -2142,6 +2356,28 @@ xfs_iunlink_map_prev( ASSERT(head_agino != target_agino); *bpp = NULL; + /* See if our backref cache can find it faster. */ + *agino = xfs_iunlink_lookup_backref(pag, target_agino); + if (*agino != NULLAGINO) { + error = xfs_iunlink_map_ino(tp, agno, *agino, imap, dipp, bpp); + if (error) + return error; + + if (be32_to_cpu((*dipp)->di_next_unlinked) == target_agino) + return 0; + + /* + * If we get here the cache contents were corrupt, so drop the + * buffer and fall back to walking the bucket list. + */ + xfs_trans_brelse(tp, *bpp); + *bpp = NULL; + WARN_ON_ONCE(1); + } + + trace_xfs_iunlink_map_prev_fallback(mp, agno); + + /* Otherwise, walk the entire bucket until we find it. */ next_agino = head_agino; while (next_agino != target_agino) { xfs_agino_t unlinked_agino; @@ -2187,6 +2423,7 @@ xfs_iunlink_remove( struct xfs_buf *agibp; struct xfs_buf *last_ibp; struct xfs_dinode *last_dip = NULL; + struct xfs_perag *pag = NULL; xfs_agnumber_t agno = XFS_INO_TO_AGNO(mp, ip->i_ino); xfs_agino_t agino = XFS_INO_TO_AGINO(mp, ip->i_ino); xfs_agino_t next_agino; @@ -2222,27 +2459,62 @@ xfs_iunlink_remove( if (error) return error; + /* + * If there was a backref pointing from the next inode back to this + * one, remove it because we've removed this inode from the list. + * + * Later, if this inode was in the middle of the list we'll update + * this inode's backref to point from the next inode. + */ + if (next_agino != NULLAGINO) { + pag = xfs_perag_get(mp, agno); + error = xfs_iunlink_change_backref(pag, next_agino, + NULLAGINO); + if (error) + goto out; + } + if (head_agino == agino) { /* Point the head of the list to the next unlinked inode. */ error = xfs_iunlink_update_bucket(tp, agno, agibp, bucket_index, next_agino); if (error) - return error; + goto out; } else { struct xfs_imap imap; xfs_agino_t prev_agino; + if (!pag) + pag = xfs_perag_get(mp, agno); + /* We need to search the list for the inode being freed. */ error = xfs_iunlink_map_prev(tp, agno, head_agino, agino, - &prev_agino, &imap, &last_dip, &last_ibp); + &prev_agino, &imap, &last_dip, &last_ibp, + pag); if (error) - return error; + goto out; /* Point the previous inode on the list to the next inode. */ xfs_iunlink_update_dinode(tp, agno, prev_agino, last_ibp, last_dip, &imap, next_agino); + + /* + * Now we deal with the backref for this inode. If this inode + * pointed at a real inode, change the backref that pointed to + * us to point to our old next. If this inode was the end of + * the list, delete the backref that pointed to us. Note that + * change_backref takes care of deleting the backref if + * next_agino is NULLAGINO. + */ + error = xfs_iunlink_change_backref(pag, agino, next_agino); + if (error) + goto out; } - return 0; + +out: + if (pag) + xfs_perag_put(pag); + return error; } /* diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h index be2014520155..e62074a5257c 100644 --- a/fs/xfs/xfs_inode.h +++ b/fs/xfs/xfs_inode.h @@ -500,4 +500,7 @@ extern struct kmem_zone *xfs_inode_zone; bool xfs_inode_verify_forks(struct xfs_inode *ip); +int xfs_iunlink_init(struct xfs_perag *pag); +void xfs_iunlink_destroy(struct xfs_perag *pag); + #endif /* __XFS_INODE_H__ */ diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c index b4d8c318be3c..fd63b0b1307c 100644 --- a/fs/xfs/xfs_mount.c +++ b/fs/xfs/xfs_mount.c @@ -149,6 +149,7 @@ xfs_free_perag( spin_unlock(&mp->m_perag_lock); ASSERT(pag); ASSERT(atomic_read(&pag->pag_ref) == 0); + xfs_iunlink_destroy(pag); xfs_buf_hash_destroy(pag); mutex_destroy(&pag->pag_ici_reclaim_lock); call_rcu(&pag->rcu_head, __xfs_free_perag); @@ -227,6 +228,9 @@ xfs_initialize_perag( /* first new pag is fully initialized */ if (first_initialised == NULLAGNUMBER) first_initialised = index; + error = xfs_iunlink_init(pag); + if (error) + goto out_hash_destroy; } index = xfs_set_inode_alloc(mp, agcount); @@ -249,6 +253,7 @@ xfs_initialize_perag( if (!pag) break; xfs_buf_hash_destroy(pag); + xfs_iunlink_destroy(pag); mutex_destroy(&pag->pag_ici_reclaim_lock); kmem_free(pag); } diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h index 7daafe064af8..a33f45077867 100644 --- a/fs/xfs/xfs_mount.h +++ b/fs/xfs/xfs_mount.h @@ -396,6 +396,13 @@ typedef struct xfs_perag { /* reference count */ uint8_t pagf_refcount_level; + + /* + * Unlinked inode information. This incore information reflects + * data stored in the AGI, so callers must hold the AGI buffer lock + * or have some other means to control concurrency. + */ + struct rhashtable pagi_unlinked_hash; } xfs_perag_t; static inline struct xfs_ag_resv * diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h index a6e384a642b1..c83ce022a355 100644 --- a/fs/xfs/xfs_trace.h +++ b/fs/xfs/xfs_trace.h @@ -3447,6 +3447,7 @@ DEFINE_EVENT(xfs_ag_inode_class, name, \ TP_ARGS(ip)) DEFINE_AGINODE_EVENT(xfs_iunlink); DEFINE_AGINODE_EVENT(xfs_iunlink_remove); +DEFINE_AG_EVENT(xfs_iunlink_map_prev_fallback); #endif /* _TRACE_XFS_H */