From nobody Mon Feb 9 12:15:42 2026 Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F02493D669E; Tue, 20 Jan 2026 11:27:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.112 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768908442; cv=pass; b=qlKMrWWxtuwXO6aWQLpZ7+yXc0MltNl2FDFumNS7/Pct1Ye7lUZRIruvofwnt0W8941hxC0mdldD5woeaAsARD1gGb6OuWqP8fIKIhLTbj6UG4+YT/F4wlkt/G1vrryqT1GgSm8bZ5JnBOLRJZpWGi2c03B5dGS8+mpyXe3TlqA= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768908442; c=relaxed/simple; bh=oWKDxPIb2khKjpqFB1hods/FuIUqRj7VoWuJWLh4il8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eSCrZxiegAWvbfmnOCgYy9DYLRV021iloKuYOfC17N2YQ6QI+LuOuCuFU50z+RtqyhZ+10EBIsLh/qC5EBAPFJfNiwkKJHgXwbWI8pqupeIamjBO6pkPimmddCcwfyruxGW7DkREsp7ANH443ynRzq48v1Xi477A1GE4fr30KpI= ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux.beauty; spf=pass smtp.mailfrom=linux.beauty; dkim=pass (1024-bit key) header.d=linux.beauty header.i=me@linux.beauty header.b=TeTrNHKd; arc=pass smtp.client-ip=136.143.188.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux.beauty Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.beauty Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.beauty header.i=me@linux.beauty header.b="TeTrNHKd" ARC-Seal: i=1; a=rsa-sha256; t=1768908382; cv=none; d=zohomail.com; s=zohoarc; b=l0RVpk0vdYCLCYZ+zCLfPI4m/RKFtCg50/oWJRkyakCEvV19qWbPcAneajFaxU+AEUD8tZy1XbV0UiDGJtj208KrBZoiN3GihklDbsjsNpt8vuwv3XfyF3oeA9LvOwYXHClanU6bGWzBgGU+/8HP8mpiesXb9WH6BaE6fDe8FOs= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1768908382; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=LvhCWF3FvvL6YDco3Bdp7x5v4DKlqw5hZmCYaXOmJc8=; b=T4+hERsmlLh10kJBRyD3vUmUZn7iFNw4YV48jcdEQ0KfIgXVaGDsUAO09vnahzLkJlWMRmm2NorcKWNo9v4NCgBe1VuFpXao7yVtG18st6s44P6qUSmD0i7ID2p3Z+rxzRkbQJW0iC0EK/9XhEriIM6st6+W5ots9DLmTn0JUJ8= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=linux.beauty; spf=pass smtp.mailfrom=me@linux.beauty; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1768908382; s=zmail; d=linux.beauty; i=me@linux.beauty; h=From:From:To:To:Cc:Cc:Subject:Subject:Date:Date:Message-ID:In-Reply-To:References:MIME-Version:Content-Transfer-Encoding:Message-Id:Reply-To; bh=LvhCWF3FvvL6YDco3Bdp7x5v4DKlqw5hZmCYaXOmJc8=; b=TeTrNHKdgZXlYhCnYF7hQ7JvtKVyghjg7aiv1WXMmp2Xz9QhMYlwAW29e9KzAzzA Kg+WRNvC1UQmpX262Wq/irl2dra50dH2eVig+0prlvv1c7gRp1UHr+HIpzkE4+LU+Yv HlTmZvTRbVzfa5KAyz5bPABIu/N8HODXTg5fBV88= Received: by mx.zohomail.com with SMTPS id 1768908380099737.3273924208657; Tue, 20 Jan 2026 03:26:20 -0800 (PST) From: Li Chen To: Zhang Yi , "Theodore Ts'o" , Andreas Dilger , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Li Chen Subject: [RFC v4 6/7] ext4: fast commit: add lock_updates tracepoint Date: Tue, 20 Jan 2026 19:25:35 +0800 Message-ID: <20260120112538.132774-7-me@linux.beauty> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260120112538.132774-1-me@linux.beauty> References: <20260120112538.132774-1-me@linux.beauty> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMailClient: External Content-Type: text/plain; charset="utf-8" Commit-time fast commit snapshots run under jbd2_journal_lock_updates(), so it is useful to quantify the time spent with updates locked and to understand why snapshotting can fail. Add a new tracepoint, ext4_fc_lock_updates, reporting the time spent in the updates-locked window along with the number of snapshotted inodes and ranges. Record the first snapshot failure reason in a stable snap_err field for tooling. Signed-off-by: Li Chen --- fs/ext4/fast_commit.c | 86 ++++++++++++++++++++++++++++++------- include/trace/events/ext4.h | 33 ++++++++++++++ 2 files changed, 104 insertions(+), 15 deletions(-) diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c index d1eefee60912..d266eb2a4219 100644 --- a/fs/ext4/fast_commit.c +++ b/fs/ext4/fast_commit.c @@ -193,6 +193,27 @@ static struct kmem_cache *ext4_fc_range_cachep; #define EXT4_FC_SNAPSHOT_MAX_INODES 1024 #define EXT4_FC_SNAPSHOT_MAX_RANGES 2048 =20 +/* + * Snapshot failure reasons for ext4_fc_lock_updates tracepoint. + * Keep these stable for tooling. + */ +enum ext4_fc_snap_err { + EXT4_FC_SNAP_ERR_NONE =3D 0, + EXT4_FC_SNAP_ERR_ES_MISS, + EXT4_FC_SNAP_ERR_ES_DELAYED, + EXT4_FC_SNAP_ERR_ES_OTHER, + EXT4_FC_SNAP_ERR_INODES_CAP, + EXT4_FC_SNAP_ERR_RANGES_CAP, + EXT4_FC_SNAP_ERR_NOMEM, + EXT4_FC_SNAP_ERR_INODE_LOC, +}; + +static inline void ext4_fc_set_snap_err(int *snap_err, int err) +{ + if (snap_err && *snap_err =3D=3D EXT4_FC_SNAP_ERR_NONE) + *snap_err =3D err; +} + static void ext4_end_buffer_io_sync(struct buffer_head *bh, int uptodate) { BUFFER_TRACE(bh, ""); @@ -983,11 +1004,12 @@ static void ext4_fc_free_inode_snap(struct inode *in= ode) static int ext4_fc_snapshot_inode_data(struct inode *inode, struct list_head *ranges, unsigned int nr_ranges_total, - unsigned int *nr_rangesp) + unsigned int *nr_rangesp, + int *snap_err) { struct ext4_inode_info *ei =3D EXT4_I(inode); - unsigned int nr_ranges =3D 0; ext4_lblk_t start_lblk, end_lblk, cur_lblk; + unsigned int nr_ranges =3D 0; =20 spin_lock(&ei->i_fc_lock); if (ei->i_fc_lblk_len =3D=3D 0) { @@ -1010,11 +1032,16 @@ static int ext4_fc_snapshot_inode_data(struct inode= *inode, struct ext4_fc_range *range; ext4_lblk_t len; =20 - if (!ext4_es_lookup_extent(inode, cur_lblk, NULL, &es, NULL)) + if (!ext4_es_lookup_extent(inode, cur_lblk, NULL, &es, NULL)) { + ext4_fc_set_snap_err(snap_err, EXT4_FC_SNAP_ERR_ES_MISS); return -EAGAIN; + } =20 - if (ext4_es_is_delayed(&es)) + if (ext4_es_is_delayed(&es)) { + ext4_fc_set_snap_err(snap_err, + EXT4_FC_SNAP_ERR_ES_DELAYED); return -EAGAIN; + } =20 len =3D es.es_len - (cur_lblk - es.es_lblk); if (len > end_lblk - cur_lblk + 1) @@ -1024,12 +1051,17 @@ static int ext4_fc_snapshot_inode_data(struct inode= *inode, continue; } =20 - if (nr_ranges_total + nr_ranges >=3D EXT4_FC_SNAPSHOT_MAX_RANGES) + if (nr_ranges_total + nr_ranges >=3D EXT4_FC_SNAPSHOT_MAX_RANGES) { + ext4_fc_set_snap_err(snap_err, + EXT4_FC_SNAP_ERR_RANGES_CAP); return -E2BIG; + } =20 range =3D kmem_cache_alloc(ext4_fc_range_cachep, GFP_NOFS); - if (!range) + if (!range) { + ext4_fc_set_snap_err(snap_err, EXT4_FC_SNAP_ERR_NOMEM); return -ENOMEM; + } nr_ranges++; =20 range->lblk =3D cur_lblk; @@ -1054,6 +1086,7 @@ static int ext4_fc_snapshot_inode_data(struct inode *= inode, range->len =3D max; } else { kmem_cache_free(ext4_fc_range_cachep, range); + ext4_fc_set_snap_err(snap_err, EXT4_FC_SNAP_ERR_ES_OTHER); return -EAGAIN; } =20 @@ -1070,7 +1103,7 @@ static int ext4_fc_snapshot_inode_data(struct inode *= inode, =20 static int ext4_fc_snapshot_inode(struct inode *inode, unsigned int nr_ranges_total, - unsigned int *nr_rangesp) + unsigned int *nr_rangesp, int *snap_err) { struct ext4_inode_info *ei =3D EXT4_I(inode); struct ext4_fc_inode_snap *snap; @@ -1082,8 +1115,10 @@ static int ext4_fc_snapshot_inode(struct inode *inod= e, int alloc_ctx; =20 ret =3D ext4_get_inode_loc_noio(inode, &iloc); - if (ret) + if (ret) { + ext4_fc_set_snap_err(snap_err, EXT4_FC_SNAP_ERR_INODE_LOC); return ret; + } =20 if (ext4_test_inode_flag(inode, EXT4_INODE_INLINE_DATA)) inode_len =3D EXT4_INODE_SIZE(inode->i_sb); @@ -1092,6 +1127,7 @@ static int ext4_fc_snapshot_inode(struct inode *inode, =20 snap =3D kmalloc(struct_size(snap, inode_buf, inode_len), GFP_NOFS); if (!snap) { + ext4_fc_set_snap_err(snap_err, EXT4_FC_SNAP_ERR_NOMEM); brelse(iloc.bh); return -ENOMEM; } @@ -1102,7 +1138,7 @@ static int ext4_fc_snapshot_inode(struct inode *inode, brelse(iloc.bh); =20 ret =3D ext4_fc_snapshot_inode_data(inode, &ranges, nr_ranges_total, - &nr_ranges); + &nr_ranges, snap_err); if (ret) { kfree(snap); ext4_fc_free_ranges(&ranges); @@ -1203,7 +1239,10 @@ static int ext4_fc_alloc_snapshot_inodes(struct supe= r_block *sb, unsigned int *nr_inodesp); =20 static int ext4_fc_snapshot_inodes(journal_t *journal, struct inode **inod= es, - unsigned int inodes_size) + unsigned int inodes_size, + unsigned int *nr_inodesp, + unsigned int *nr_rangesp, + int *snap_err) { struct super_block *sb =3D journal->j_private; struct ext4_sb_info *sbi =3D EXT4_SB(sb); @@ -1221,6 +1260,8 @@ static int ext4_fc_snapshot_inodes(journal_t *journal= , struct inode **inodes, alloc_ctx =3D ext4_fc_lock(sb); list_for_each_entry(iter, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) { if (i >=3D inodes_size) { + ext4_fc_set_snap_err(snap_err, + EXT4_FC_SNAP_ERR_INODES_CAP); ret =3D -E2BIG; goto unlock; } @@ -1244,6 +1285,8 @@ static int ext4_fc_snapshot_inodes(journal_t *journal= , struct inode **inodes, continue; =20 if (i >=3D inodes_size) { + ext4_fc_set_snap_err(snap_err, + EXT4_FC_SNAP_ERR_INODES_CAP); ret =3D -E2BIG; goto unlock; } @@ -1268,16 +1311,20 @@ static int ext4_fc_snapshot_inodes(journal_t *journ= al, struct inode **inodes, unsigned int inode_ranges =3D 0; =20 ret =3D ext4_fc_snapshot_inode(inodes[idx], nr_ranges, - &inode_ranges); + &inode_ranges, snap_err); if (ret) break; nr_ranges +=3D inode_ranges; } =20 + if (nr_inodesp) + *nr_inodesp =3D i; + if (nr_rangesp) + *nr_rangesp =3D nr_ranges; return ret; } =20 -static int ext4_fc_perform_commit(journal_t *journal) +static int ext4_fc_perform_commit(journal_t *journal, tid_t commit_tid) { struct super_block *sb =3D journal->j_private; struct ext4_sb_info *sbi =3D EXT4_SB(sb); @@ -1286,10 +1333,15 @@ static int ext4_fc_perform_commit(journal_t *journa= l) struct inode *inode; struct inode **inodes; unsigned int inodes_size; + unsigned int snap_inodes =3D 0; + unsigned int snap_ranges =3D 0; + int snap_err =3D EXT4_FC_SNAP_ERR_NONE; struct blk_plug plug; int ret =3D 0; u32 crc =3D 0; int alloc_ctx; + ktime_t lock_start; + u64 locked_ns; =20 /* * Step 1: Mark all inodes on s_fc_q[MAIN] with @@ -1337,13 +1389,13 @@ static int ext4_fc_perform_commit(journal_t *journa= l) if (ret) return ret; =20 - ret =3D ext4_fc_alloc_snapshot_inodes(sb, &inodes, &inodes_size); if (ret) return ret; =20 /* Step 4: Mark all inodes as being committed. */ jbd2_journal_lock_updates(journal); + lock_start =3D ktime_get(); /* * The journal is now locked. No more handles can start and all the * previous handles are now drained. Snapshotting happens in this @@ -1357,8 +1409,12 @@ static int ext4_fc_perform_commit(journal_t *journal) } ext4_fc_unlock(sb, alloc_ctx); =20 - ret =3D ext4_fc_snapshot_inodes(journal, inodes, inodes_size); + ret =3D ext4_fc_snapshot_inodes(journal, inodes, inodes_size, + &snap_inodes, &snap_ranges, &snap_err); jbd2_journal_unlock_updates(journal); + locked_ns =3D ktime_to_ns(ktime_sub(ktime_get(), lock_start)); + trace_ext4_fc_lock_updates(sb, commit_tid, locked_ns, snap_inodes, + snap_ranges, ret, snap_err); kvfree(inodes); if (ret) return ret; @@ -1563,7 +1619,7 @@ int ext4_fc_commit(journal_t *journal, tid_t commit_t= id) journal_ioprio =3D EXT4_DEF_JOURNAL_IOPRIO; set_task_ioprio(current, journal_ioprio); fc_bufs_before =3D (sbi->s_fc_bytes + bsize - 1) / bsize; - ret =3D ext4_fc_perform_commit(journal); + ret =3D ext4_fc_perform_commit(journal, commit_tid); if (ret < 0) { if (ret =3D=3D -EAGAIN || ret =3D=3D -E2BIG || ret =3D=3D -ECANCELED) status =3D EXT4_FC_STATUS_INELIGIBLE; diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h index fd76d14c2776..a1493971821d 100644 --- a/include/trace/events/ext4.h +++ b/include/trace/events/ext4.h @@ -2812,6 +2812,39 @@ TRACE_EVENT(ext4_fc_commit_stop, __entry->num_fc_ineligible, __entry->nblks_agg, __entry->tid) ); =20 +TRACE_EVENT(ext4_fc_lock_updates, + TP_PROTO(struct super_block *sb, tid_t commit_tid, u64 locked_ns, + unsigned int nr_inodes, unsigned int nr_ranges, int err, + int snap_err), + + TP_ARGS(sb, commit_tid, locked_ns, nr_inodes, nr_ranges, err, snap_err), + + TP_STRUCT__entry(/* entry */ + __field(dev_t, dev) + __field(tid_t, tid) + __field(u64, locked_ns) + __field(unsigned int, nr_inodes) + __field(unsigned int, nr_ranges) + __field(int, err) + __field(int, snap_err) + ), + + TP_fast_assign(/* assign */ + __entry->dev =3D sb->s_dev; + __entry->tid =3D commit_tid; + __entry->locked_ns =3D locked_ns; + __entry->nr_inodes =3D nr_inodes; + __entry->nr_ranges =3D nr_ranges; + __entry->err =3D err; + __entry->snap_err =3D snap_err; + ), + + TP_printk("dev %d,%d tid %u locked_ns %llu nr_inodes %u nr_ranges %u err = %d snap_err %d", + MAJOR(__entry->dev), MINOR(__entry->dev), __entry->tid, + __entry->locked_ns, __entry->nr_inodes, __entry->nr_ranges, + __entry->err, __entry->snap_err) +); + #define FC_REASON_NAME_STAT(reason) \ show_fc_reason(reason), \ __entry->fc_ineligible_rc[reason] --=20 2.52.0