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Date:   Thu, 13 Apr 2023 07:42:32 -0700
From:   "Darrick J. Wong" <djwong@kernel.org>
To:     "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
        Jan Kara <jack@suse.cz>, Christoph Hellwig <hch@infradead.org>,
        Ojaswin Mujoo <ojaswin@linux.ibm.com>,
        Disha Goel <disgoel@linux.ibm.com>
Subject: Re: [RFCv3 10/10] iomap: Add trace points for DIO path
Message-ID: <20230413144232.GD360877@frogsfrogsfrogs>
References: <cover.1681365596.git.ritesh.list@gmail.com>
 <93ab8386c4620395c5e674a7930506895fc758ef.1681365596.git.ritesh.list@gmail.com>
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On Thu, Apr 13, 2023 at 02:10:32PM +0530, Ritesh Harjani (IBM) wrote:
> This patch adds trace point events for iomap DIO path.
> 
> <e.g. iomap dio trace>
>      xfs_io-8815  [000]   526.790418: iomap_dio_rw_begin:   dev 7:7 ino 0xc isize 0x0 pos 0x0 count 4096 flags DIRECT dio_flags DIO_FORCE_WAIT done_before 0 aio 0 ret 0
>      xfs_io-8815  [000]   526.790978: iomap_dio_complete:   dev 7:7 ino 0xc isize 0x1000 pos 0x1000 flags DIRECT aio 0 error 0 ret 4096
>      xfs_io-8815  [000]   526.790988: iomap_dio_rw_end:     dev 7:7 ino 0xc isize 0x1000 pos 0x1000 count 0 flags DIRECT dio_flags DIO_FORCE_WAIT done_before 0 aio 0 ret 4096
>         fsx-8827  [005]   526.939345: iomap_dio_rw_begin:   dev 7:7 ino 0xc isize 0x922f8 pos 0x4f000 count 61440 flags NOWAIT|DIRECT|ALLOC_CACHE dio_flags  done_before 0 aio 1 ret 0
>         fsx-8827  [005]   526.939459: iomap_dio_rw_end:     dev 7:7 ino 0xc isize 0x922f8 pos 0x4f000 count 0 flags NOWAIT|DIRECT|ALLOC_CACHE dio_flags  done_before 0 aio 1 ret -529
> ksoftirqd/5-41    [005]   526.939564: iomap_dio_complete:   dev 7:7 ino 0xc isize 0x922f8 pos 0x5e000 flags NOWAIT|DIRECT|ALLOC_CACHE aio 1 error 0 ret 61440
> 
> Tested-by: Disha Goel <disgoel@linux.ibm.com>
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> ---
>  fs/iomap/direct-io.c |  3 ++
>  fs/iomap/trace.c     |  1 +
>  fs/iomap/trace.h     | 90 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 94 insertions(+)
> 
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 5871956ee880..bb7a6dfbc8b3 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -130,6 +130,7 @@ ssize_t iomap_dio_complete(struct iomap_dio *dio)
>  	if (ret > 0)
>  		ret += dio->done_before;
>  
> +	trace_iomap_dio_complete(iocb, dio->error, ret);
>  	kfree(dio);
>  
>  	return ret;
> @@ -681,6 +682,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  	struct iomap_dio *dio;
>  	ssize_t ret = 0;
>  
> +	trace_iomap_dio_rw_begin(iocb, iter, dio_flags, done_before, ret);
>  	dio = __iomap_dio_rw(iocb, iter, ops, dops, dio_flags, private,
>  			     done_before);
>  	if (IS_ERR_OR_NULL(dio)) {
> @@ -689,6 +691,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  	}
>  	ret = iomap_dio_complete(dio);
>  out:
> +	trace_iomap_dio_rw_end(iocb, iter, dio_flags, done_before, ret);
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(iomap_dio_rw);
> diff --git a/fs/iomap/trace.c b/fs/iomap/trace.c
> index da217246b1a9..728d5443daf5 100644
> --- a/fs/iomap/trace.c
> +++ b/fs/iomap/trace.c
> @@ -3,6 +3,7 @@
>   * Copyright (c) 2019 Christoph Hellwig
>   */
>  #include <linux/iomap.h>
> +#include <linux/uio.h>
>  
>  /*
>   * We include this last to have the helpers above available for the trace
> diff --git a/fs/iomap/trace.h b/fs/iomap/trace.h
> index f6ea9540d082..dcb4dd4db5fb 100644
> --- a/fs/iomap/trace.h
> +++ b/fs/iomap/trace.h
> @@ -183,6 +183,96 @@ TRACE_EVENT(iomap_iter,
>  		   (void *)__entry->caller)
>  );
>  
> +#define TRACE_IOMAP_DIO_STRINGS \
> +	{IOMAP_DIO_FORCE_WAIT, "DIO_FORCE_WAIT" }, \
> +	{IOMAP_DIO_OVERWRITE_ONLY, "DIO_OVERWRITE_ONLY" }, \
> +	{IOMAP_DIO_PARTIAL, "DIO_PARTIAL" }

Can you make the strings line up too, please?

> +
> +DECLARE_EVENT_CLASS(iomap_dio_class,
> +	TP_PROTO(struct kiocb *iocb, struct iov_iter *iter,
> +		 unsigned int dio_flags, u64 done_before, int ret),

We're passing in ssize_t values for @ret, shouldn't the types match?

> +	TP_ARGS(iocb, iter, dio_flags, done_before, ret),
> +	TP_STRUCT__entry(
> +		__field(dev_t,	dev)
> +		__field(ino_t,	ino)
> +		__field(loff_t, isize)
> +		__field(loff_t, pos)
> +		__field(u64,	count)

What's the difference between "length" as used in the other tracepoints
and "count" here?

> +		__field(u64,	done_before)
> +		__field(int,	ki_flags)
> +		__field(unsigned int,	dio_flags)
> +		__field(bool,	aio)
> +		__field(int, ret)
> +	),
> +	TP_fast_assign(
> +		__entry->dev = file_inode(iocb->ki_filp)->i_sb->s_dev;
> +		__entry->ino = file_inode(iocb->ki_filp)->i_ino;
> +		__entry->isize = file_inode(iocb->ki_filp)->i_size;
> +		__entry->pos = iocb->ki_pos;
> +		__entry->count = iov_iter_count(iter);
> +		__entry->done_before = done_before;
> +		__entry->dio_flags = dio_flags;
> +		__entry->ki_flags = iocb->ki_flags;
> +		__entry->aio = !is_sync_kiocb(iocb);
> +		__entry->ret = ret;
> +	),
> +	TP_printk("dev %d:%d ino 0x%lx isize 0x%llx pos 0x%llx count %llu "

count and done_before are lengths of file operations, in bytes, right?

Everywhere else we use 0x%llx for that.

> +		  "flags %s dio_flags %s done_before %llu aio %d ret %d",
> +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> +		  __entry->ino,
> +		  __entry->isize,
> +		  __entry->pos,
> +		  __entry->count,
> +		  __print_flags(__entry->ki_flags, "|", TRACE_IOCB_STRINGS),
> +		  __print_flags(__entry->dio_flags, "|", TRACE_IOMAP_DIO_STRINGS),
> +		  __entry->done_before,
> +		  __entry->aio,
> +		  __entry->ret)
> +)
> +
> +#define DEFINE_DIO_RW_EVENT(name)					\
> +DEFINE_EVENT(iomap_dio_class, name,					\
> +	TP_PROTO(struct kiocb *iocb, struct iov_iter *iter,		\
> +		 unsigned int dio_flags, u64 done_before,		\
> +		 int ret),						\
> +	TP_ARGS(iocb, iter, dio_flags, done_before, ret))
> +DEFINE_DIO_RW_EVENT(iomap_dio_rw_begin);
> +DEFINE_DIO_RW_EVENT(iomap_dio_rw_end);
> +
> +TRACE_EVENT(iomap_dio_complete,
> +	TP_PROTO(struct kiocb *iocb, int error, int ret),
> +	TP_ARGS(iocb, error, ret),
> +	TP_STRUCT__entry(
> +		__field(dev_t,	dev)
> +		__field(ino_t,	ino)
> +		__field(loff_t, isize)
> +		__field(loff_t, pos)
> +		__field(int,	ki_flags)
> +		__field(bool,	aio)
> +		__field(int,	error)
> +		__field(int,	ret)

Same comment about @ret and ssize_t here.

--D

> +	),
> +	TP_fast_assign(
> +		__entry->dev = file_inode(iocb->ki_filp)->i_sb->s_dev;
> +		__entry->ino = file_inode(iocb->ki_filp)->i_ino;
> +		__entry->isize = file_inode(iocb->ki_filp)->i_size;
> +		__entry->pos = iocb->ki_pos;
> +		__entry->ki_flags = iocb->ki_flags;
> +		__entry->aio = !is_sync_kiocb(iocb);
> +		__entry->error = error;
> +		__entry->ret = ret;
> +	),
> +	TP_printk("dev %d:%d ino 0x%lx isize 0x%llx pos 0x%llx flags %s aio %d error %d ret %d",
> +		  MAJOR(__entry->dev), MINOR(__entry->dev),
> +		  __entry->ino,
> +		  __entry->isize,
> +		  __entry->pos,
> +		  __print_flags(__entry->ki_flags, "|", TRACE_IOCB_STRINGS),
> +		  __entry->aio,
> +		  __entry->error,
> +		  __entry->ret)
> +);
> +
>  #endif /* _IOMAP_TRACE_H */
>  
>  #undef TRACE_INCLUDE_PATH
> -- 
> 2.39.2
>