Re: [PATCH v5 2/9] fs: tracepoints around multigrain timestamp events

Darrick J. Wong
2024-07-11T16:49:51Z

On Thu, Jul 11, 2024 at 07:08:06AM -0400, Jeff Layton wrote:
> Add some tracepoints around various multigrain timestamp events.
>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
> fs/inode.c | 5 ++
> fs/stat.c | 3 ++
> include/trace/events/timestamp.h | 109 +++++++++++++++++++++++++++++++++++++++
> 3 files changed, 117 insertions(+)
>
> diff --git a/fs/inode.c b/fs/inode.c
> index 2b5889ff7b36..81b45e0a95a6 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -22,6 +22,9 @@
> #include <linux/iversion.h>
> #include <linux/rw_hint.h>
> #include <trace/events/writeback.h>
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/timestamp.h>
> +
> #include "internal.h"
>
> /*
> @@ -2571,6 +2574,7 @@ struct timespec64 inode_set_ctime_to_ts(struct inode *inode, struct timespec64 t
> {
> inode->i_ctime_sec = ts.tv_sec;
> inode->i_ctime_nsec = ts.tv_nsec & ~I_CTIME_QUERIED;
> + trace_inode_set_ctime_to_ts(inode, &ts);
> return ts;
> }
> EXPORT_SYMBOL(inode_set_ctime_to_ts);
> @@ -2670,6 +2674,7 @@ struct timespec64 inode_set_ctime_current(struct inode *inode)
> if (try_cmpxchg(&inode->i_ctime_nsec, &cur, now_ts.tv_nsec)) {
> /* If swap occurred, then we're (mostly) done */
> inode->i_ctime_sec = now_ts.tv_sec;
> + trace_ctime_ns_xchg(inode, cns, now_ts.tv_nsec, cur);
> } else {
> /*
> * Was the change due to someone marking the old ctime QUERIED?
> diff --git a/fs/stat.c b/fs/stat.c
> index df7fdd3afed9..552dfd67688b 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -23,6 +23,8 @@
> #include <linux/uaccess.h>
> #include <asm/unistd.h>
>
> +#include <trace/events/timestamp.h>
> +
> #include "internal.h"
> #include "mount.h"
>
> @@ -49,6 +51,7 @@ void fill_mg_cmtime(struct kstat *stat, u32 request_mask, struct inode *inode)
> stat->mtime = inode_get_mtime(inode);
> stat->ctime.tv_sec = inode->i_ctime_sec;
> stat->ctime.tv_nsec = ((u32)atomic_fetch_or(I_CTIME_QUERIED, pcn)) & ~I_CTIME_QUERIED;
> + trace_fill_mg_cmtime(inode, &stat->ctime, &stat->mtime);
> }
> EXPORT_SYMBOL(fill_mg_cmtime);
>
> diff --git a/include/trace/events/timestamp.h b/include/trace/events/timestamp.h
> new file mode 100644
> index 000000000000..3a603190b46c
> --- /dev/null
> +++ b/include/trace/events/timestamp.h
> @@ -0,0 +1,109 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM timestamp
> +
> +#if !defined(_TRACE_TIMESTAMP_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_TIMESTAMP_H
> +
> +#include <linux/tracepoint.h>
> +#include <linux/fs.h>
> +
> +TRACE_EVENT(inode_set_ctime_to_ts,
> + TP_PROTO(struct inode *inode,
> + struct timespec64 *ctime),
> +
> + TP_ARGS(inode, ctime),
> +
> + TP_STRUCT__entry(
> + __field(dev_t, dev)
> + __field(ino_t, ino)
> + __field(time64_t, ctime_s)
> + __field(u32, ctime_ns)
> + __field(u32, gen)
> + ),
> +
> + TP_fast_assign(
> + __entry->dev = inode->i_sb->s_dev;

Odd indenting of the second columns between the struct definition above
and the assignment code here.

> + __entry->ino = inode->i_ino;
> + __entry->gen = inode->i_generation;
> + __entry->ctime_s = ctime->tv_sec;
> + __entry->ctime_ns = ctime->tv_nsec;
> + ),
> +
> + TP_printk("ino=%d:%d:%ld:%u ctime=%lld.%u",
> + MAJOR(__entry->dev), MINOR(__entry->dev), __entry->ino, __entry->gen,
> + __entry->ctime_s, __entry->ctime_ns
> + )
> +);
> +
> +TRACE_EVENT(ctime_ns_xchg,
> + TP_PROTO(struct inode *inode,
> + u32 old,
> + u32 new,
> + u32 cur),
> +
> + TP_ARGS(inode, old, new, cur),
> +
> + TP_STRUCT__entry(
> + __field(dev_t, dev)
> + __field(ino_t, ino)
> + __field(u32, gen)
> + __field(u32, old)
> + __field(u32, new)
> + __field(u32, cur)
> + ),
> +
> + TP_fast_assign(
> + __entry->dev = inode->i_sb->s_dev;
> + __entry->ino = inode->i_ino;
> + __entry->gen = inode->i_generation;
> + __entry->old = old;
> + __entry->new = new;
> + __entry->cur = cur;
> + ),
> +
> + TP_printk("ino=%d:%d:%ld:%u old=%u:%c new=%u cur=%u:%c",
> + MAJOR(__entry->dev), MINOR(__entry->dev), __entry->ino, __entry->gen,
> + __entry->old & ~I_CTIME_QUERIED, __entry->old & I_CTIME_QUERIED ? 'Q' : '-',
> + __entry->new,
> + __entry->cur & ~I_CTIME_QUERIED, __entry->cur & I_CTIME_QUERIED ? 'Q' : '-'

This /might/ be overkill for a single flag, but anything you put in the
TP_printk seems to end up in the format file:

# cat /sys/kernel/debug/tracing/events/xfs/xfbtree_create_root_buf/format
name: xfbtree_create_root_buf
ID: 1644
format:
field:unsigned short common_type; offset:0; size:2; signed:0;
field:unsigned char common_flags; offset:2; size:1; signed:0;
field:unsigned char common_preempt_count; offset:3; size:1; signed:0;
field:int common_pid; offset:4; size:4; signed:1;

field:unsigned long xfino; offset:8; size:8; signed:0;
field:xfs_daddr_t bno; offset:16; size:8; signed:1;
field:int nblks; offset:24; size:4; signed:1;
field:int hold; offset:28; size:4; signed:1;
field:int pincount; offset:32; size:4; signed:1;
field:unsigned int lockval; offset:36; size:4; signed:0;
field:unsigned int flags; offset:40; size:4; signed:0;

print fmt: "xfino 0x%lx daddr 0x%llx bbcount 0x%x hold %d pincount %d lock %d flags %s", REC->xfino, (unsigned long long)REC->bno, REC->nblks, REC->hold, REC->pincount, REC->lockval, __print_flags(REC->flags, "|", { (1u << 0), "READ" }, { (1u << 1), "WRITE" }, { (1u << 2), "READ_AHEAD" }, { (1u << 3), "NO_IOACCT" }, { (1u << 4), "ASYNC" }, { (1u << 5), "DONE" }, { (1u << 6), "STALE" }, { (1u << 7), "WRITE_FAIL" }, { (1u << 16), "INODES" }, { (1u << 17), "DQUOTS" }, { (1u << 18), "LOG_RECOVERY" }, { (1u << 20), "PAGES" }, { (1u << 21), "KMEM" }, { (1u << 22), "DELWRI_Q" }, { (1u << 28), "LIVESCAN" }, { (1u << 29), "INCORE" }, { (1u << 30), "TRYLOCK" }, { (1u << 31), "UNMAPPED" })

I /think/ all that code gets compiled (interpreted?) as if it were C
code, but a more compact format might be:

#define CTIME_QUERIED_FLAGS \
{ I_CTIME_QUERIED, "queried" }

TP_printk("ino=%d:%d:%ld:%u old=%u:%s new=%u cur=%u:%c",
MAJOR(__entry->dev), MINOR(__entry->dev), __entry->ino, __entry->gen,
__entry->old & ~I_CTIME_QUERIED,
__print_flags(__entry->old & I_CTIME_QUERIED, "|",
CTIME_QUERIED_FLAGS),
...

But, again, that could be overkill for a single flag. Aside from my
minor bikeshedding, this all looks good, and I like that we can now
monitor what's going on wrt ctime. :)

--D

> + )
> +);
> +
> +TRACE_EVENT(fill_mg_cmtime,
> + TP_PROTO(struct inode *inode,
> + struct timespec64 *ctime,
> + struct timespec64 *mtime),
> +
> + TP_ARGS(inode, ctime, mtime),
> +
> + TP_STRUCT__entry(
> + __field(dev_t, dev)
> + __field(ino_t, ino)
> + __field(time64_t, ctime_s)
> + __field(time64_t, mtime_s)
> + __field(u32, ctime_ns)
> + __field(u32, mtime_ns)
> + __field(u32, gen)
> + ),
> +
> + TP_fast_assign(
> + __entry->dev = inode->i_sb->s_dev;
> + __entry->ino = inode->i_ino;
> + __entry->gen = inode->i_generation;
> + __entry->ctime_s = ctime->tv_sec;
> + __entry->mtime_s = mtime->tv_sec;
> + __entry->ctime_ns = ctime->tv_nsec;
> + __entry->mtime_ns = mtime->tv_nsec;
> + ),
> +
> + TP_printk("ino=%d:%d:%ld:%u ctime=%lld.%u mtime=%lld.%u",
> + MAJOR(__entry->dev), MINOR(__entry->dev), __entry->ino, __entry->gen,
> + __entry->ctime_s, __entry->ctime_ns,
> + __entry->mtime_s, __entry->mtime_ns
> + )
> +);
> +#endif /* _TRACE_TIMESTAMP_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
>
> --
> 2.45.2
>
>