netfs: Refactor arguments for netfs_alloc_read_request

Pass start and len to the rreq allocator. This should ensure that the
fields are set so that ->init_request() can use them.

Also add a parameter to indicates the origin of the request.  Ceph can use
this to tell whether to get caps.

Changes
=======
ver #3)
 - Change the author to me as Jeff feels that most of the patch is my
   changes now.

ver #2)
 - Show the request origin in the netfs_rreq tracepoint.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Co-developed-by: David Howells <dhowells@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-cachefs@redhat.com

Link: https://lore.kernel.org/r/164622989020.3564931.17517006047854958747.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/164678208569.1200972.12153682697842916557.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/164692904155.2099075.14717645623034355995.stgit@warthog.procyon.org.uk/ # v3

fs/netfs/internal.h

@@ -17,9 +17,12 @@
 /*
  * objects.c
  */
-struct netfs_io_request *netfs_alloc_request(const struct netfs_request_ops *ops,
+struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
+					     struct file *file,
+					     const struct netfs_request_ops *ops,
 					     void *netfs_priv,
-					     struct file *file);
+					     loff_t start, size_t len,
+					     enum netfs_io_origin origin);
 void netfs_get_request(struct netfs_io_request *rreq, enum netfs_rreq_ref_trace what);
 void netfs_clear_subrequests(struct netfs_io_request *rreq, bool was_async);
 void netfs_put_request(struct netfs_io_request *rreq, bool was_async,

fs/netfs/objects.c

@@ -11,17 +11,24 @@
 /*
  * Allocate an I/O request and initialise it.
  */
-struct netfs_io_request *netfs_alloc_request(
-	const struct netfs_request_ops *ops, void *netfs_priv,
-	struct file *file)
+struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
+					     struct file *file,
+					     const struct netfs_request_ops *ops,
+					     void *netfs_priv,
+					     loff_t start, size_t len,
+					     enum netfs_io_origin origin)
 {
 	static atomic_t debug_ids;
 	struct netfs_io_request *rreq;
 
 	rreq = kzalloc(sizeof(struct netfs_io_request), GFP_KERNEL);
 	if (rreq) {
+		rreq->start	= start;
+		rreq->len	= len;
+		rreq->origin	= origin;
 		rreq->netfs_ops	= ops;
 		rreq->netfs_priv = netfs_priv;
+		rreq->mapping	= mapping;
 		rreq->inode	= file_inode(file);
 		rreq->i_size	= i_size_read(rreq->inode);
 		rreq->debug_id	= atomic_inc_return(&debug_ids);

fs/netfs/read_helper.c

@@ -763,12 +763,13 @@ void netfs_readahead(struct readahead_control *ractl,
 	if (readahead_count(ractl) == 0)
 		goto cleanup;
 
-	rreq = netfs_alloc_request(ops, netfs_priv, ractl->file);
+	rreq = netfs_alloc_request(ractl->mapping, ractl->file,
+				   ops, netfs_priv,
+				   readahead_pos(ractl),
+				   readahead_length(ractl),
+				   NETFS_READAHEAD);
 	if (!rreq)
 		goto cleanup;
-	rreq->mapping	= ractl->mapping;
-	rreq->start	= readahead_pos(ractl);
-	rreq->len	= readahead_length(ractl);
 
 	if (ops->begin_cache_operation) {
 		ret = ops->begin_cache_operation(rreq);
@@ -838,16 +839,15 @@ int netfs_readpage(struct file *file,
 
 	_enter("%lx", folio_index(folio));
 
-	rreq = netfs_alloc_request(ops, netfs_priv, file);
+	rreq = netfs_alloc_request(folio->mapping, file, ops, netfs_priv,
+				   folio_file_pos(folio), folio_size(folio),
+				   NETFS_READPAGE);
 	if (!rreq) {
 		if (netfs_priv)
 			ops->cleanup(folio_file_mapping(folio), netfs_priv);
 		folio_unlock(folio);
 		return -ENOMEM;
 	}
-	rreq->mapping	= folio_file_mapping(folio);
-	rreq->start	= folio_file_pos(folio);
-	rreq->len	= folio_size(folio);
 
 	if (ops->begin_cache_operation) {
 		ret = ops->begin_cache_operation(rreq);
@@ -1008,12 +1008,11 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
 	}
 
 	ret = -ENOMEM;
-	rreq = netfs_alloc_request(ops, netfs_priv, file);
+	rreq = netfs_alloc_request(mapping, file, ops, netfs_priv,
+				   folio_file_pos(folio), folio_size(folio),
+				   NETFS_READ_FOR_WRITE);
 	if (!rreq)
 		goto error;
-	rreq->mapping		= folio_file_mapping(folio);
-	rreq->start		= folio_file_pos(folio);
-	rreq->len		= folio_size(folio);
 	rreq->no_unlock_folio	= folio_index(folio);
 	__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
 	netfs_priv = NULL;

include/linux/netfs.h

@@ -150,6 +150,12 @@ struct netfs_io_subrequest {
 #define NETFS_SREQ_NO_PROGRESS		4	/* Set if we didn't manage to read any data */
 };
 
+enum netfs_io_origin {
+	NETFS_READAHEAD,		/* This read was triggered by readahead */
+	NETFS_READPAGE,			/* This read is a synchronous read */
+	NETFS_READ_FOR_WRITE,		/* This read is to prepare a write */
+} __mode(byte);
+
 /*
  * Descriptor for an I/O helper request.  This is used to make multiple I/O
  * operations to a variety of data stores and then stitch the result together.
@@ -167,6 +173,7 @@ struct netfs_io_request {
 	size_t			submitted;	/* Amount submitted for I/O so far */
 	size_t			len;		/* Length of the request */
 	short			error;		/* 0 or error that occurred */
+	enum netfs_io_origin	origin;		/* Origin of the request */
 	loff_t			i_size;		/* Size of the file */
 	loff_t			start;		/* Start position */
 	pgoff_t			no_unlock_folio; /* Don't unlock this folio after read */

include/trace/events/netfs.h

@@ -21,6 +21,11 @@
 	EM(netfs_read_trace_readpage,		"READPAGE ")	\
 	E_(netfs_read_trace_write_begin,	"WRITEBEGN")
 
+#define netfs_rreq_origins					\
+	EM(NETFS_READAHEAD,			"RA")		\
+	EM(NETFS_READPAGE,			"RP")		\
+	E_(NETFS_READ_FOR_WRITE,		"RW")
+
 #define netfs_rreq_traces					\
 	EM(netfs_rreq_trace_assess,		"ASSESS ")	\
 	EM(netfs_rreq_trace_copy,		"COPY   ")	\
@@ -101,6 +106,7 @@ enum netfs_sreq_ref_trace { netfs_sreq_ref_traces } __mode(byte);
 #define E_(a, b) TRACE_DEFINE_ENUM(a);
 
 netfs_read_traces;
+netfs_rreq_origins;
 netfs_rreq_traces;
 netfs_sreq_sources;
 netfs_sreq_traces;
@@ -159,17 +165,20 @@ TRACE_EVENT(netfs_rreq,
 	    TP_STRUCT__entry(
 		    __field(unsigned int,		rreq		)
 		    __field(unsigned int,		flags		)
+		    __field(enum netfs_io_origin,	origin		)
 		    __field(enum netfs_rreq_trace,	what		)
 			     ),
 
 	    TP_fast_assign(
 		    __entry->rreq	= rreq->debug_id;
 		    __entry->flags	= rreq->flags;
+		    __entry->origin	= rreq->origin;
 		    __entry->what	= what;
 			   ),
 
-	    TP_printk("R=%08x %s f=%02x",
+	    TP_printk("R=%08x %s %s f=%02x",
 		      __entry->rreq,
+		      __print_symbolic(__entry->origin, netfs_rreq_origins),
 		      __print_symbolic(__entry->what, netfs_rreq_traces),
 		      __entry->flags)
 	    );