Re: [PATCH 11/12] fuse_trace: constrain iomap mapping cache size

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Apr 29, 2026 at 07:38:17AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> Add tracepoints for the previous patch.
> 
> Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
> ---
>  fs/fuse/fuse_trace.h       |   31 +++++++++++++++++++++++++++++--
>  fs/fuse/fuse_iomap_cache.c |    4 +++-
>  2 files changed, 32 insertions(+), 3 deletions(-)
> 
> 
> diff --git a/fs/fuse/fuse_trace.h b/fs/fuse/fuse_trace.h
> index 09da9bce61b98c..aa2d5ca88c9d40 100644
> --- a/fs/fuse/fuse_trace.h
> +++ b/fs/fuse/fuse_trace.h
> @@ -320,6 +320,7 @@ struct iomap_ioend;
>  struct iomap;
>  struct fuse_iext_cursor;
>  struct fuse_iomap_lookup;
> +struct fuse_iext_root;
>  
>  /* tracepoint boilerplate so we don't have to keep doing this */
>  #define FUSE_IOMAP_OPFLAGS_FIELD \
> @@ -1157,6 +1158,8 @@ TRACE_EVENT(fuse_iomap_config,
>  		__field(int64_t,		time_max)
>  		__field(int64_t,		maxbytes)
>  		__field(uint8_t,		uuid_len)
> +
> +		__field(uint32_t,		cache_maxbytes)
>  	),
>  
>  	TP_fast_assign(
> @@ -1170,14 +1173,15 @@ TRACE_EVENT(fuse_iomap_config,
>  		__entry->time_max	=	outarg->s_time_max;
>  		__entry->maxbytes	=	outarg->s_maxbytes;
>  		__entry->uuid_len	=	outarg->s_uuid_len;
> +		__entry->cache_maxbytes	=	outarg->cache_maxbytes;
>  	),
>  
> -	TP_printk("connection %u root_ino 0x%llx flags (%s) blocksize 0x%x max_links %u time_gran %u time_min %lld time_max %lld maxbytes 0x%llx uuid_len %u",
> +	TP_printk("connection %u root_ino 0x%llx flags (%s) blocksize 0x%x max_links %u time_gran %u time_min %lld time_max %lld maxbytes 0x%llx uuid_len %u cache_maxbytes %u",
>  		  __entry->connection, __entry->root_nodeid,
>  		  __print_flags(__entry->flags, "|", FUSE_IOMAP_CONFIG_STRINGS),
>  		  __entry->blocksize, __entry->max_links, __entry->time_gran,
>  		  __entry->time_min, __entry->time_max, __entry->maxbytes,
> -		  __entry->uuid_len)
> +		  __entry->uuid_len, __entry->cache_maxbytes)
>  );
>  
>  TRACE_EVENT(fuse_iomap_dev_inval,
> @@ -1395,6 +1399,29 @@ DEFINE_IEXT_ALT_UPDATE_EVENT(fuse_iext_del_mapping_got);
>  DEFINE_IEXT_ALT_UPDATE_EVENT(fuse_iext_add_mapping_left);
>  DEFINE_IEXT_ALT_UPDATE_EVENT(fuse_iext_add_mapping_right);
>  
> +TRACE_EVENT(fuse_iomap_cache_cleanup,
> +	TP_PROTO(const struct inode *inode, unsigned int iodir,
> +		 struct fuse_iext_root *ir),
> +	TP_ARGS(inode, iodir, ir),
> +
> +	TP_STRUCT__entry(
> +		FUSE_IO_RANGE_FIELDS()

There's no file range here, so let's shrink the tracepoint data by only
recording the inode fields instead of just reporting zeroes.

--D

> +		FUSE_IOMAP_IODIR_FIELD
> +		__field(unsigned long long,	bytes)
> +	),
> +
> +	TP_fast_assign(
> +		FUSE_INODE_ASSIGN(inode, fi, fm);
> +		__entry->iodir		=	iodir;
> +		__entry->bytes		=	ir->ir_bytes;
> +	),
> +
> +	TP_printk(FUSE_IO_RANGE_FMT() FUSE_IOMAP_IODIR_FMT " bytes 0x%llx",
> +		  FUSE_IO_RANGE_PRINTK_ARGS(),
> +		  FUSE_IOMAP_IODIR_PRINTK_ARGS,
> +		  __entry->bytes)
> +);
> +
>  TRACE_EVENT(fuse_iomap_cache_remove,
>  	TP_PROTO(const struct inode *inode, unsigned int iodir,
>  		 loff_t offset, uint64_t length, unsigned long caller_ip),
> diff --git a/fs/fuse/fuse_iomap_cache.c b/fs/fuse/fuse_iomap_cache.c
> index a8e16302ce4405..66739ec59e9c8b 100644
> --- a/fs/fuse/fuse_iomap_cache.c
> +++ b/fs/fuse/fuse_iomap_cache.c
> @@ -1672,8 +1672,10 @@ fuse_iomap_cache_cleanup(
>  	struct fuse_mount	*fm = get_fuse_mount(inode);
>  	struct fuse_iext_root	*ir = fuse_iext_root_ptr(fi->cache, iodir);
>  
> -	if (ir && ir->ir_bytes > fm->fc->iomap_conn.cache_maxbytes)
> +	if (ir && ir->ir_bytes > fm->fc->iomap_conn.cache_maxbytes) {
> +		trace_fuse_iomap_cache_cleanup(inode, iodir, ir);
>  		fuse_iext_destroy(ir);
> +	}
>  }
>  
>  int
> 
>