cachefiles,netfs: sunset ondemand mode

It was an effort to enhance fscache as a kernel cache for lazy
pulling (at least according to previous Incremental FS discussion [1])
and EROFS over fscache was the in-tree user of this mode.

fscache has since evolved to be netfslib-oriented, serving network
filesystem inodes via the netfs library, but EROFS never acts as a
network filesystem and we need to cache golden filesystem images rather
than individual EROFS inodes.

Since EROFS over fscache is now removed, clean up netfs/fscache/
cachefiles upstream too.

[1] https://lore.kernel.org/r/CAOQ4uxi4dzxArY24YO=+kBCK2gGoq3Ptb8WkzCqSogPgU_R3dQ@mail.gmail.com

[dh] Fixed up comments on:
https://sashiko.dev/#/patchset/20260716103030.3065561-1-dhowells%40redhat.com
https://sashiko.dev/#/patchset/20260722130218.78958-1-dhowells%40redhat.com

Signed-off-by: Gao Xiang <xiang@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://patch.msgid.link/1046393.1786544127@warthog.procyon.org.uk
cc: Paulo Alcantara <pc@manguebit.org>
cc: netfs@lists.linux.dev
cc: linux-erofs@lists.ozlabs.org
cc: bpf@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

3 files changed, 1 insertions, 260 deletions

diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index d0b62d53eea9..f837a501008c 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -191,7 +191,6 @@ struct netfs_io_subrequest {
 #define NETFS_SREQ_COPY_TO_CACHE	0	/* Set if should copy the data to the cache */
 #define NETFS_SREQ_CLEAR_TAIL		1	/* Set if the rest of the read should be cleared */
 #define NETFS_SREQ_MADE_PROGRESS	4	/* Set if we transferred at least some data */
-#define NETFS_SREQ_ONDEMAND		5	/* Set if it's from on-demand read mode */
 #define NETFS_SREQ_BOUNDARY		6	/* Set if ends on hard boundary (eg. ceph object) */
 #define NETFS_SREQ_HIT_EOF		7	/* Set if short due to EOF */
 #define NETFS_SREQ_IN_PROGRESS		8	/* Unlocked when the subrequest completes */
@@ -374,14 +373,6 @@ struct netfs_cache_ops {
 			     loff_t *_start, size_t *_len, size_t upper_len,
 			     loff_t i_size, bool no_space_allocated_yet);
 
-	/* Prepare an on-demand read operation, shortening it to a cached/uncached
-	 * boundary as appropriate.
-	 */
-	enum netfs_io_source (*prepare_ondemand_read)(struct netfs_cache_resources *cres,
-						      loff_t start, size_t *_len,
-						      loff_t i_size,
-						      unsigned long *_flags, ino_t ino);
-
 	/* Query the occupancy of the cache in a region, returning where the
 	 * next chunk of data starts and how long it is.
 	 */
diff --git a/include/trace/events/cachefiles.h b/include/trace/events/cachefiles.h
index 6e3b1424eea4..9259bc71049e 100644
--- a/include/trace/events/cachefiles.h
+++ b/include/trace/events/cachefiles.h
@@ -31,10 +31,6 @@ enum cachefiles_obj_ref_trace {
 	cachefiles_obj_see_lookup_failed,
 	cachefiles_obj_see_withdraw_cookie,
 	cachefiles_obj_see_withdrawal,
-	cachefiles_obj_get_ondemand_fd,
-	cachefiles_obj_put_ondemand_fd,
-	cachefiles_obj_get_read_req,
-	cachefiles_obj_put_read_req,
 };
 
 enum fscache_why_object_killed {
@@ -129,11 +125,7 @@ enum cachefiles_error_trace {
 	EM(cachefiles_obj_see_lookup_cookie,	"SEE lookup_cookie")	\
 	EM(cachefiles_obj_see_lookup_failed,	"SEE lookup_failed")	\
 	EM(cachefiles_obj_see_withdraw_cookie,	"SEE withdraw_cookie")	\
-	EM(cachefiles_obj_see_withdrawal,	"SEE withdrawal")	\
-	EM(cachefiles_obj_get_ondemand_fd,      "GET ondemand_fd")	\
-	EM(cachefiles_obj_put_ondemand_fd,      "PUT ondemand_fd")	\
-	EM(cachefiles_obj_get_read_req,		"GET read_req")		\
-	E_(cachefiles_obj_put_read_req,		"PUT read_req")
+	E_(cachefiles_obj_see_withdrawal,	"SEE withdrawal")
 
 #define cachefiles_coherency_traces					\
 	EM(cachefiles_coherency_check_aux,	"BAD aux ")		\
@@ -687,180 +679,6 @@ TRACE_EVENT(cachefiles_io_error,
 		      __entry->error)
 	    );
 
-TRACE_EVENT(cachefiles_ondemand_open,
-	    TP_PROTO(struct cachefiles_object *obj, struct cachefiles_msg *msg,
-		     struct cachefiles_open *load),
-
-	    TP_ARGS(obj, msg, load),
-
-	    TP_STRUCT__entry(
-		    __field(unsigned int,	obj)
-		    __field(unsigned int,	msg_id)
-		    __field(unsigned int,	object_id)
-		    __field(unsigned int,	fd)
-		    __field(unsigned int,	flags)
-			     ),
-
-	    TP_fast_assign(
-		    __entry->obj	= obj ? obj->debug_id : 0;
-		    __entry->msg_id	= msg->msg_id;
-		    __entry->object_id	= msg->object_id;
-		    __entry->fd		= load->fd;
-		    __entry->flags	= load->flags;
-			   ),
-
-	    TP_printk("o=%08x mid=%x oid=%x fd=%d f=%x",
-		      __entry->obj,
-		      __entry->msg_id,
-		      __entry->object_id,
-		      __entry->fd,
-		      __entry->flags)
-	    );
-
-TRACE_EVENT(cachefiles_ondemand_copen,
-	    TP_PROTO(struct cachefiles_object *obj, unsigned int msg_id,
-		     long len),
-
-	    TP_ARGS(obj, msg_id, len),
-
-	    TP_STRUCT__entry(
-		    __field(unsigned int,	obj)
-		    __field(unsigned int,	msg_id)
-		    __field(long,		len)
-			     ),
-
-	    TP_fast_assign(
-		    __entry->obj	= obj ? obj->debug_id : 0;
-		    __entry->msg_id	= msg_id;
-		    __entry->len	= len;
-			   ),
-
-	    TP_printk("o=%08x mid=%x l=%lx",
-		      __entry->obj,
-		      __entry->msg_id,
-		      __entry->len)
-	    );
-
-TRACE_EVENT(cachefiles_ondemand_close,
-	    TP_PROTO(struct cachefiles_object *obj, struct cachefiles_msg *msg),
-
-	    TP_ARGS(obj, msg),
-
-	    TP_STRUCT__entry(
-		    __field(unsigned int,	obj)
-		    __field(unsigned int,	msg_id)
-		    __field(unsigned int,	object_id)
-			     ),
-
-	    TP_fast_assign(
-		    __entry->obj	= obj ? obj->debug_id : 0;
-		    __entry->msg_id	= msg->msg_id;
-		    __entry->object_id	= msg->object_id;
-			   ),
-
-	    TP_printk("o=%08x mid=%x oid=%x",
-		      __entry->obj,
-		      __entry->msg_id,
-		      __entry->object_id)
-	    );
-
-TRACE_EVENT(cachefiles_ondemand_read,
-	    TP_PROTO(struct cachefiles_object *obj, struct cachefiles_msg *msg,
-		     struct cachefiles_read *load),
-
-	    TP_ARGS(obj, msg, load),
-
-	    TP_STRUCT__entry(
-		    __field(unsigned int,	obj)
-		    __field(unsigned int,	msg_id)
-		    __field(unsigned int,	object_id)
-		    __field(loff_t,		start)
-		    __field(size_t,		len)
-			     ),
-
-	    TP_fast_assign(
-		    __entry->obj	= obj ? obj->debug_id : 0;
-		    __entry->msg_id	= msg->msg_id;
-		    __entry->object_id	= msg->object_id;
-		    __entry->start	= load->off;
-		    __entry->len	= load->len;
-			   ),
-
-	    TP_printk("o=%08x mid=%x oid=%x s=%llx l=%zx",
-		      __entry->obj,
-		      __entry->msg_id,
-		      __entry->object_id,
-		      __entry->start,
-		      __entry->len)
-	    );
-
-TRACE_EVENT(cachefiles_ondemand_cread,
-	    TP_PROTO(struct cachefiles_object *obj, unsigned int msg_id),
-
-	    TP_ARGS(obj, msg_id),
-
-	    TP_STRUCT__entry(
-		    __field(unsigned int,	obj)
-		    __field(unsigned int,	msg_id)
-			     ),
-
-	    TP_fast_assign(
-		    __entry->obj	= obj ? obj->debug_id : 0;
-		    __entry->msg_id	= msg_id;
-			   ),
-
-	    TP_printk("o=%08x mid=%x",
-		      __entry->obj,
-		      __entry->msg_id)
-	    );
-
-TRACE_EVENT(cachefiles_ondemand_fd_write,
-	    TP_PROTO(struct cachefiles_object *obj, struct inode *backer,
-		     loff_t start, size_t len),
-
-	    TP_ARGS(obj, backer, start, len),
-
-	    TP_STRUCT__entry(
-		    __field(unsigned int,	obj)
-		    __field(unsigned int,	backer)
-		    __field(loff_t,		start)
-		    __field(size_t,		len)
-			     ),
-
-	    TP_fast_assign(
-		    __entry->obj	= obj ? obj->debug_id : 0;
-		    __entry->backer	= backer->i_ino;
-		    __entry->start	= start;
-		    __entry->len	= len;
-			   ),
-
-	    TP_printk("o=%08x iB=%x s=%llx l=%zx",
-		      __entry->obj,
-		      __entry->backer,
-		      __entry->start,
-		      __entry->len)
-	    );
-
-TRACE_EVENT(cachefiles_ondemand_fd_release,
-	    TP_PROTO(struct cachefiles_object *obj, int object_id),
-
-	    TP_ARGS(obj, object_id),
-
-	    TP_STRUCT__entry(
-		    __field(unsigned int,	obj)
-		    __field(unsigned int,	object_id)
-			     ),
-
-	    TP_fast_assign(
-		    __entry->obj	= obj ? obj->debug_id : 0;
-		    __entry->object_id	= object_id;
-			   ),
-
-	    TP_printk("o=%08x oid=%x",
-		      __entry->obj,
-		      __entry->object_id)
-	    );
-
 #endif /* _TRACE_CACHEFILES_H */
 
 /* This part must be outside protection */
diff --git a/include/uapi/linux/cachefiles.h b/include/uapi/linux/cachefiles.h
deleted file mode 100644
index 78caa73e5343..000000000000
--- a/include/uapi/linux/cachefiles.h
+++ /dev/null
@@ -1,68 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
-#ifndef _LINUX_CACHEFILES_H
-#define _LINUX_CACHEFILES_H
-
-#include <linux/types.h>
-#include <linux/ioctl.h>
-
-/*
- * Fscache ensures that the maximum length of cookie key is 255. The volume key
- * is controlled by netfs, and generally no bigger than 255.
- */
-#define CACHEFILES_MSG_MAX_SIZE	1024
-
-enum cachefiles_opcode {
-	CACHEFILES_OP_OPEN,
-	CACHEFILES_OP_CLOSE,
-	CACHEFILES_OP_READ,
-};
-
-/*
- * Message Header
- *
- * @msg_id	a unique ID identifying this message
- * @opcode	message type, CACHEFILE_OP_*
- * @len		message length, including message header and following data
- * @object_id	a unique ID identifying a cache file
- * @data	message type specific payload
- */
-struct cachefiles_msg {
-	__u32 msg_id;
-	__u32 opcode;
-	__u32 len;
-	__u32 object_id;
-	__u8  data[];
-};
-
-/*
- * @data contains the volume_key followed directly by the cookie_key. volume_key
- * is a NUL-terminated string; @volume_key_size indicates the size of the volume
- * key in bytes. cookie_key is binary data, which is netfs specific;
- * @cookie_key_size indicates the size of the cookie key in bytes.
- *
- * @fd identifies an anon_fd referring to the cache file.
- */
-struct cachefiles_open {
-	__u32 volume_key_size;
-	__u32 cookie_key_size;
-	__u32 fd;
-	__u32 flags;
-	__u8  data[];
-};
-
-/*
- * @off		indicates the starting offset of the requested file range
- * @len		indicates the length of the requested file range
- */
-struct cachefiles_read {
-	__u64 off;
-	__u64 len;
-};
-
-/*
- * Reply for READ request
- * @arg for this ioctl is the @id field of READ request.
- */
-#define CACHEFILES_IOC_READ_COMPLETE	_IOW(0x98, 1, int)
-
-#endif