fscache: Remove the contents of the fscache driver, pending rewrite

Remove the code that comprises the fscache driver as it's going to be
substantially rewritten, with the majority of the code being erased in the
rewrite.

A small piece of linux/fscache.h is left as that is #included by a bunch of
network filesystems.

Signed-off-by: David Howells <[email protected]>
Reviewed-by: Jeff Layton <[email protected]>
cc: [email protected]
Link: https://lore.kernel.org/r/163819578724.215744.18210619052245724238.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906884814.143852.6727245089843862889.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967077097.1823006.1377665951499979089.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021485548.640689.13876080567388696162.stgit@warthog.procyon.org.uk/ # v4

fs/9p/vfs_addr.c

@@ -76,9 +76,7 @@ static void v9fs_req_cleanup(struct address_space *mapping, void *priv)
  */
 static bool v9fs_is_cache_enabled(struct inode *inode)
 {
-	struct fscache_cookie *cookie = v9fs_inode_cookie(V9FS_I(inode));
-
-	return fscache_cookie_enabled(cookie) && !hlist_empty(&cookie->backing_objects);
+	return fscache_cookie_enabled(v9fs_inode_cookie(V9FS_I(inode)));
 }
 
 /**
@@ -87,9 +85,13 @@ static bool v9fs_is_cache_enabled(struct inode *inode)
  */
 static int v9fs_begin_cache_operation(struct netfs_read_request *rreq)
 {
+#ifdef CONFIG_9P_FSCACHE
 	struct fscache_cookie *cookie = v9fs_inode_cookie(V9FS_I(rreq->inode));
 
 	return fscache_begin_read_operation(rreq, cookie);
+#else
+	return -ENOBUFS;
+#endif
 }
 
 static const struct netfs_read_request_ops v9fs_req_ops = {

fs/Makefile

@@ -67,7 +67,6 @@ obj-$(CONFIG_DLM)		+= dlm/
 
 # Do not add any filesystems before this line
 obj-$(CONFIG_NETFS_SUPPORT)	+= netfs/
-obj-$(CONFIG_FSCACHE)		+= fscache/
 obj-$(CONFIG_REISERFS_FS)	+= reiserfs/
 obj-$(CONFIG_EXT4_FS)		+= ext4/
 # We place ext4 before ext2 so that clean ext3 root fs's do NOT mount using the

fs/afs/file.c

@@ -352,16 +352,18 @@ static void afs_init_rreq(struct netfs_read_request *rreq, struct file *file)
 
 static bool afs_is_cache_enabled(struct inode *inode)
 {
-	struct fscache_cookie *cookie = afs_vnode_cache(AFS_FS_I(inode));
-
-	return fscache_cookie_enabled(cookie) && !hlist_empty(&cookie->backing_objects);
+	return fscache_cookie_enabled(afs_vnode_cache(AFS_FS_I(inode)));
 }
 
 static int afs_begin_cache_operation(struct netfs_read_request *rreq)
 {
+#ifdef CONFIG_AFS_FSCACHE
 	struct afs_vnode *vnode = AFS_FS_I(rreq->inode);
 
 	return fscache_begin_read_operation(rreq, afs_vnode_cache(vnode));
+#else
+	return -ENOBUFS;
+#endif
 }
 
 static int afs_check_write_begin(struct file *file, loff_t pos, unsigned len,

fs/fscache/Kconfig

@@ -1,43 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
-config FSCACHE
-	tristate "General filesystem local caching manager"
-	select NETFS_SUPPORT
-	help
-	  This option enables a generic filesystem caching manager that can be
-	  used by various network and other filesystems to cache data locally.
-	  Different sorts of caches can be plugged in, depending on the
-	  resources available.
-
-	  See Documentation/filesystems/caching/fscache.rst for more information.
-
-config FSCACHE_STATS
-	bool "Gather statistical information on local caching"
-	depends on FSCACHE && PROC_FS
-	select NETFS_STATS
-	help
-	  This option causes statistical information to be gathered on local
-	  caching and exported through file:
-
-		/proc/fs/fscache/stats
-
-	  The gathering of statistics adds a certain amount of overhead to
-	  execution as there are a quite a few stats gathered, and on a
-	  multi-CPU system these may be on cachelines that keep bouncing
-	  between CPUs.  On the other hand, the stats are very useful for
-	  debugging purposes.  Saying 'Y' here is recommended.
-
-	  See Documentation/filesystems/caching/fscache.rst for more information.
-
-config FSCACHE_DEBUG
-	bool "Debug FS-Cache"
-	depends on FSCACHE
-	help
-	  This permits debugging to be dynamically enabled in the local caching
-	  management module.  If this is set, the debugging output may be
-	  enabled by setting bits in /sys/modules/fscache/parameter/debug.
-
-	  See Documentation/filesystems/caching/fscache.rst for more information.
-
 config FSCACHE_OLD_API
 	bool