netfs: Add a netfs inode context

Add a netfs_i_context struct that should be included in the network
filesystem's own inode struct wrapper, directly after the VFS's inode
struct, e.g.:

	struct my_inode {
		struct {
			/* These must be contiguous */
			struct inode		vfs_inode;
			struct netfs_i_context	netfs_ctx;
		};
	};

The netfs_i_context struct so far contains a single field for the network
filesystem to use - the cache cookie:

	struct netfs_i_context {
		...
		struct fscache_cookie	*cache;
	};

Three functions are provided to help with this:

 (1) void netfs_i_context_init(struct inode *inode,
			       const struct netfs_request_ops *ops);

     Initialise the netfs context and set the operations.

 (2) struct netfs_i_context *netfs_i_context(struct inode *inode);

     Find the netfs context from the VFS inode.

 (3) struct inode *netfs_inode(struct netfs_i_context *ctx);

     Find the VFS inode from the netfs context.

Changes
=======
ver #4)
 - Fix netfs_is_cache_enabled() to check cookie->cache_priv to see if a
   cache is present[3].
 - Fix netfs_skip_folio_read() to zero out all of the page, not just some
   of it[3].

ver #3)
 - Split out the bit to move ceph cap-getting on readahead into
   ceph_init_request()[1].
 - Stick in a comment to the netfs inode structs indicating the contiguity
   requirements[2].

ver #2)
 - Adjust documentation to match.
 - Use "#if IS_ENABLED()" in netfs_i_cookie(), not "#ifdef".
 - Move the cap check from ceph_readahead() to ceph_init_request() to be
   called from netfslib.
 - Remove ceph_readahead() and use  netfs_readahead() directly instead.

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

Link: https://lore.kernel.org/r/8af0d47f17d89c06bbf602496dd845f2b0bf25b3.camel@kernel.org/ [1]
Link: https://lore.kernel.org/r/beaf4f6a6c2575ed489adb14b257253c868f9a5c.camel@kernel.org/ [2]
Link: https://lore.kernel.org/r/3536452.1647421585@warthog.procyon.org.uk/ [3]
Link: https://lore.kernel.org/r/164622984545.3564931.15691742939278418580.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/164678213320.1200972.16807551936267647470.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/164692909854.2099075.9535537286264248057.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/306388.1647595110@warthog.procyon.org.uk/ # v4

1 files changed, 8 insertions, 9 deletions

diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 0b4b519682f1..e1c65aa8d3b6 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -17,13 +17,11 @@
 #include <linux/posix_acl.h>
 #include <linux/refcount.h>
 #include <linux/security.h>
+#include <linux/netfs.h>
+#include <linux/fscache.h>
 
 #include <linux/ceph/libceph.h>
 
-#ifdef CONFIG_CEPH_FSCACHE
-#include <linux/fscache.h>
-#endif
-
 /* large granularity for statfs utilization stats to facilitate
  * large volume sizes on 32-bit machines. */
 #define CEPH_BLOCK_SHIFT   22  /* 4 MB */
@@ -317,6 +315,11 @@ struct ceph_inode_xattrs_info {
  * Ceph inode.
  */
 struct ceph_inode_info {
+	struct {
+		/* These must be contiguous */
+		struct inode vfs_inode;
+		struct netfs_i_context netfs_ctx; /* Netfslib context */
+	};
 	struct ceph_vino i_vino;   /* ceph ino + snap */
 
 	spinlock_t i_ceph_lock;
@@ -427,11 +430,6 @@ struct ceph_inode_info {
 
 	struct work_struct i_work;
 	unsigned long  i_work_mask;
-
-#ifdef CONFIG_CEPH_FSCACHE
-	struct fscache_cookie *fscache;
-#endif
-	struct inode vfs_inode; /* at end */
 };
 
 static inline struct ceph_inode_info *
@@ -1215,6 +1213,7 @@ extern void __ceph_touch_fmode(struct ceph_inode_info *ci,
 
 /* addr.c */
 extern const struct address_space_operations ceph_aops;
+extern const struct netfs_request_ops ceph_netfs_ops;
 extern int ceph_mmap(struct file *file, struct vm_area_struct *vma);
 extern int ceph_uninline_data(struct file *file);
 extern int ceph_pool_perm_check(struct inode *inode, int need);