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 <[email protected]> --- 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 +/* + * Snapshot failure reasons for ext4_fc_lock_updates tracepoint. + * Keep these stable for tooling. + */ +enum ext4_fc_snap_err { + EXT4_FC_SNAP_ERR_NONE = 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 == EXT4_FC_SNAP_ERR_NONE) + *snap_err = 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 *inode) 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 = EXT4_I(inode); - unsigned int nr_ranges = 0; ext4_lblk_t start_lblk, end_lblk, cur_lblk; + unsigned int nr_ranges = 0; spin_lock(&ei->i_fc_lock); if (ei->i_fc_lblk_len == 0) { @@ -1010,11 +1032,16 @@ static int ext4_fc_snapshot_inode_data(struct inode *inode, struct ext4_fc_range *range; ext4_lblk_t len; - 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; + } - 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; + } len = 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; } - if (nr_ranges_total + nr_ranges >= EXT4_FC_SNAPSHOT_MAX_RANGES) + if (nr_ranges_total + nr_ranges >= EXT4_FC_SNAPSHOT_MAX_RANGES) { + ext4_fc_set_snap_err(snap_err, + EXT4_FC_SNAP_ERR_RANGES_CAP); return -E2BIG; + } range = 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++; range->lblk = cur_lblk; @@ -1054,6 +1086,7 @@ static int ext4_fc_snapshot_inode_data(struct inode *inode, range->len = 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; } @@ -1070,7 +1103,7 @@ static int ext4_fc_snapshot_inode_data(struct inode *inode, 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 = EXT4_I(inode); struct ext4_fc_inode_snap *snap; @@ -1082,8 +1115,10 @@ static int ext4_fc_snapshot_inode(struct inode *inode, int alloc_ctx; ret = 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; + } if (ext4_test_inode_flag(inode, EXT4_INODE_INLINE_DATA)) inode_len = EXT4_INODE_SIZE(inode->i_sb); @@ -1092,6 +1127,7 @@ static int ext4_fc_snapshot_inode(struct inode *inode, snap = 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); ret = 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 super_block *sb, unsigned int *nr_inodesp); static int ext4_fc_snapshot_inodes(journal_t *journal, struct inode **inodes, - unsigned int inodes_size) + unsigned int inodes_size, + unsigned int *nr_inodesp, + unsigned int *nr_rangesp, + int *snap_err) { struct super_block *sb = journal->j_private; struct ext4_sb_info *sbi = EXT4_SB(sb); @@ -1221,6 +1260,8 @@ static int ext4_fc_snapshot_inodes(journal_t *journal, struct inode **inodes, alloc_ctx = ext4_fc_lock(sb); list_for_each_entry(iter, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) { if (i >= inodes_size) { + ext4_fc_set_snap_err(snap_err, + EXT4_FC_SNAP_ERR_INODES_CAP); ret = -E2BIG; goto unlock; } @@ -1244,6 +1285,8 @@ static int ext4_fc_snapshot_inodes(journal_t *journal, struct inode **inodes, continue; if (i >= inodes_size) { + ext4_fc_set_snap_err(snap_err, + EXT4_FC_SNAP_ERR_INODES_CAP); ret = -E2BIG; goto unlock; } @@ -1268,16 +1311,20 @@ static int ext4_fc_snapshot_inodes(journal_t *journal, struct inode **inodes, unsigned int inode_ranges = 0; ret = ext4_fc_snapshot_inode(inodes[idx], nr_ranges, - &inode_ranges); + &inode_ranges, snap_err); if (ret) break; nr_ranges += inode_ranges; } + if (nr_inodesp) + *nr_inodesp = i; + if (nr_rangesp) + *nr_rangesp = nr_ranges; return ret; } -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 = journal->j_private; struct ext4_sb_info *sbi = EXT4_SB(sb); @@ -1286,10 +1333,15 @@ static int ext4_fc_perform_commit(journal_t *journal) struct inode *inode; struct inode **inodes; unsigned int inodes_size; + unsigned int snap_inodes = 0; + unsigned int snap_ranges = 0; + int snap_err = EXT4_FC_SNAP_ERR_NONE; struct blk_plug plug; int ret = 0; u32 crc = 0; int alloc_ctx; + ktime_t lock_start; + u64 locked_ns; /* * Step 1: Mark all inodes on s_fc_q[MAIN] with @@ -1337,13 +1389,13 @@ static int ext4_fc_perform_commit(journal_t *journal) if (ret) return ret; - ret = ext4_fc_alloc_snapshot_inodes(sb, &inodes, &inodes_size); if (ret) return ret; /* Step 4: Mark all inodes as being committed. */ jbd2_journal_lock_updates(journal); + lock_start = 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); - ret = ext4_fc_snapshot_inodes(journal, inodes, inodes_size); + ret = ext4_fc_snapshot_inodes(journal, inodes, inodes_size, + &snap_inodes, &snap_ranges, &snap_err); jbd2_journal_unlock_updates(journal); + locked_ns = 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_tid) journal_ioprio = EXT4_DEF_JOURNAL_IOPRIO; set_task_ioprio(current, journal_ioprio); fc_bufs_before = (sbi->s_fc_bytes + bsize - 1) / bsize; - ret = ext4_fc_perform_commit(journal); + ret = ext4_fc_perform_commit(journal, commit_tid); if (ret < 0) { if (ret == -EAGAIN || ret == -E2BIG || ret == -ECANCELED) status = 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) ); +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 = sb->s_dev; + __entry->tid = commit_tid; + __entry->locked_ns = locked_ns; + __entry->nr_inodes = nr_inodes; + __entry->nr_ranges = nr_ranges; + __entry->err = err; + __entry->snap_err = 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] -- 2.52.0
