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

[Jeff Layton <jlayton@kernel.org>]

On Thu, 2024-07-11 at 09:49 -0700, Darrick J. Wong wrote:
> 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. :)
> 

That seems reasonable. I hadn't looked at the unrolled format
monstrosity, but making it more compact is good. I'll make that change
and see how it looks.

Thanks for the reviews so far!

> > +	)
> > +);
> > +
> > +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
> > 
> > 

-- 
Jeff Layton <jlayton@kernel.org>