Linux 6.17: fuse: add tracepoints for i_size changes, writeback ranges and READ replies

fs/fuse/file.c

@@ -8,6 +8,7 @@
 
 #include "fuse_i.h"
 #include "fuse_dlm_cache.h"
+#include "fuse_trace.h"
 
 #include <linux/pagemap.h>
 #include <linux/slab.h>
@@ -1069,6 +1070,7 @@ static int fuse_do_readfolio(struct file *file, struct folio *folio,
 
 	fuse_read_args_fill(&ia, file, pos, desc.length, FUSE_READ);
 	res = fuse_simple_request(fm, &ia.ap.args);
+	trace_fuse_readfolio_reply(inode, pos, desc.length, res);
 	if (res < 0) {
 		/*
 		 * Please refer to Documentation/filesystems/fuse/fuse-AOP_TRUNCATED_PAGE-reason.txt
@@ -2529,6 +2531,8 @@ static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
 			orig_size = i_size_read(inode);
 			if (end > orig_size) {
 				i_size_write(inode, end);
+				trace_fuse_isize_change(inode, orig_size, end,
+							FUSE_ISIZE_WRITE_CLAIM);
 				extended = true;
 			}
 			spin_unlock(&fi->lock);
@@ -2553,8 +2557,11 @@ static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
 
 			if (reached < end) {
 				spin_lock(&fi->lock);
-				if (i_size_read(inode) == end)
+				if (i_size_read(inode) == end) {
 					i_size_write(inode, reached);
+					trace_fuse_isize_change(inode, end, reached,
+								FUSE_ISIZE_WRITE_RETRACT);
+				}
 				spin_unlock(&fi->lock);
 			}
 		}
@@ -3320,6 +3327,8 @@ static ssize_t fuse_iomap_writeback_range(struct iomap_writepage_ctx *wpc,
 	if (pos + len > end_pos)
 		send_len = end_pos - pos;
 
+	trace_fuse_writeback_range(inode, pos, len, end_pos, send_len);
+
 	if (!data->ff) {
 		data->ff = fuse_write_file_get(fi);
 		if (!data->ff)

fs/fuse/fuse_i.h

@@ -1230,6 +1230,12 @@ static inline struct fuse_mount *get_fuse_mount(struct inode *inode)
 	return get_fuse_mount_super(inode->i_sb);
 }
 
+enum fuse_isize_reason {
+	FUSE_ISIZE_WRITE_CLAIM,
+	FUSE_ISIZE_WRITE_RETRACT,
+	FUSE_ISIZE_ATTR,
+};
+
 static inline struct fuse_conn *get_fuse_conn(struct inode *inode)
 {
 	return get_fuse_mount_super(inode->i_sb)->fc;

fs/fuse/fuse_trace.h

@@ -150,6 +150,114 @@ TRACE_EVENT(fuse_request_end,
 		  __entry->unique, __entry->len, __entry->error)
 );
 
+#define FUSE_ISIZE_REASONS				\
+	EM( FUSE_ISIZE_WRITE_CLAIM,	"write_claim")	\
+	EM( FUSE_ISIZE_WRITE_RETRACT,	"write_retract")\
+	EMe(FUSE_ISIZE_ATTR,		"attr")
+
+#undef EM
+#undef EMe
+#define EM(a, b)	TRACE_DEFINE_ENUM(a);
+#define EMe(a, b)	TRACE_DEFINE_ENUM(a);
+FUSE_ISIZE_REASONS
+#undef EM
+#undef EMe
+#define EM(a, b)	{ a, b },
+#define EMe(a, b)	{ a, b }
+
+/*
+ * Under DLM i_size is this node's view only; recording every change with its
+ * reason is what lets a lost update be tied to the local EOF at writeback.
+ */
+TRACE_EVENT(fuse_isize_change,
+	TP_PROTO(struct inode *inode, loff_t old_size, loff_t new_size,
+		 int reason),
+
+	TP_ARGS(inode, old_size, new_size, reason),
+
+	TP_STRUCT__entry(
+		__field(dev_t,		connection)
+		__field(uint64_t,	nodeid)
+		__field(loff_t,		old_size)
+		__field(loff_t,		new_size)
+		__field(int,		reason)
+	),
+
+	TP_fast_assign(
+		__entry->connection	=	get_fuse_conn(inode)->dev;
+		__entry->nodeid		=	get_fuse_inode(inode)->nodeid;
+		__entry->old_size	=	old_size;
+		__entry->new_size	=	new_size;
+		__entry->reason		=	reason;
+	),
+
+	TP_printk("connection %u nodeid %llu i_size %lld -> %lld (%s)",
+		  __entry->connection, __entry->nodeid, __entry->old_size,
+		  __entry->new_size,
+		  __print_symbolic(__entry->reason, FUSE_ISIZE_REASONS))
+);
+
+TRACE_EVENT(fuse_writeback_range,
+	TP_PROTO(struct inode *inode, u64 pos, unsigned int len,
+		 u64 end_pos, unsigned int send_len),
+
+	TP_ARGS(inode, pos, len, end_pos, send_len),
+
+	TP_STRUCT__entry(
+		__field(dev_t,		connection)
+		__field(uint64_t,	nodeid)
+		__field(uint64_t,	pos)
+		__field(uint32_t,	len)
+		__field(uint32_t,	send_len)
+		__field(uint64_t,	end_pos)
+		__field(loff_t,		i_size)
+	),
+
+	TP_fast_assign(
+		__entry->connection	=	get_fuse_conn(inode)->dev;
+		__entry->nodeid		=	get_fuse_inode(inode)->nodeid;
+		__entry->pos		=	pos;
+		__entry->len		=	len;
+		__entry->send_len	=	send_len;
+		__entry->end_pos	=	end_pos;
+		__entry->i_size		=	i_size_read(inode);
+	),
+
+	TP_printk("connection %u nodeid %llu pos %llu len %u send %u end_pos %llu i_size %lld",
+		  __entry->connection, __entry->nodeid, __entry->pos,
+		  __entry->len, __entry->send_len, __entry->end_pos,
+		  __entry->i_size)
+);
+
+TRACE_EVENT(fuse_readfolio_reply,
+	TP_PROTO(struct inode *inode, loff_t pos, size_t len,
+		 ssize_t res),
+
+	TP_ARGS(inode, pos, len, res),
+
+	TP_STRUCT__entry(
+		__field(dev_t,		connection)
+		__field(uint64_t,	nodeid)
+		__field(loff_t,		pos)
+		__field(size_t,		len)
+		__field(ssize_t,	res)
+		__field(loff_t,		i_size)
+	),
+
+	TP_fast_assign(
+		__entry->connection	=	get_fuse_conn(inode)->dev;
+		__entry->nodeid		=	get_fuse_inode(inode)->nodeid;
+		__entry->pos		=	pos;
+		__entry->len		=	len;
+		__entry->res		=	res;
+		__entry->i_size		=	i_size_read(inode);
+	),
+
+	TP_printk("connection %u nodeid %llu pos %lld len %zu res %zd i_size %lld",
+		  __entry->connection, __entry->nodeid, __entry->pos,
+		  __entry->len, __entry->res, __entry->i_size)
+);
+
 #endif /* _TRACE_FUSE_H */
 
 #undef TRACE_INCLUDE_PATH

fs/fuse/inode.c

@@ -10,6 +10,7 @@
 #include "fuse_dlm_cache.h"
 #include "fuse_dev_i.h"
 #include "dev_uring_i.h"
+#include "fuse_trace.h"
 
 #include <linux/dax.h>
 #include <linux/pagemap.h>
@@ -660,8 +661,12 @@ static void fuse_change_attributes_i(struct inode *inode, struct fuse_attr *attr
 	 * attr->size coming from server can be stale. We cannot trust it.
 	 * Only update i_size if SIZE was actually returned by the server.
 	 */
-	if (have_size && !(cache_mask & STATX_SIZE))
+	if (have_size && !(cache_mask & STATX_SIZE)) {
 		i_size_write(inode, attr->size);
+		if (oldsize != attr->size)
+			trace_fuse_isize_change(inode, oldsize, attr->size,
+						FUSE_ISIZE_ATTR);
+	}
 	spin_unlock(&fi->lock);
 
 	/*