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, 14 insertions, 14 deletions

diff --git a/fs/ceph/cache.c b/fs/ceph/cache.c
index 7d22850623ef..ddea99922073 100644
--- a/fs/ceph/cache.c
+++ b/fs/ceph/cache.c
@@ -29,26 +29,25 @@ void ceph_fscache_register_inode_cookie(struct inode *inode)
 	if (!(inode->i_state & I_NEW))
 		return;
 
-	WARN_ON_ONCE(ci->fscache);
+	WARN_ON_ONCE(ci->netfs_ctx.cache);
 
-	ci->fscache = fscache_acquire_cookie(fsc->fscache, 0,
-					     &ci->i_vino, sizeof(ci->i_vino),
-					     &ci->i_version, sizeof(ci->i_version),
-					     i_size_read(inode));
+	ci->netfs_ctx.cache =
+		fscache_acquire_cookie(fsc->fscache, 0,
+				       &ci->i_vino, sizeof(ci->i_vino),
+				       &ci->i_version, sizeof(ci->i_version),
+				       i_size_read(inode));
 }
 
-void ceph_fscache_unregister_inode_cookie(struct ceph_inode_info* ci)
+void ceph_fscache_unregister_inode_cookie(struct ceph_inode_info *ci)
 {
-	struct fscache_cookie *cookie = ci->fscache;
-
-	fscache_relinquish_cookie(cookie, false);
+	fscache_relinquish_cookie(ceph_fscache_cookie(ci), false);
 }
 
 void ceph_fscache_use_cookie(struct inode *inode, bool will_modify)
 {
 	struct ceph_inode_info *ci = ceph_inode(inode);
 
-	fscache_use_cookie(ci->fscache, will_modify);
+	fscache_use_cookie(ceph_fscache_cookie(ci), will_modify);
 }
 
 void ceph_fscache_unuse_cookie(struct inode *inode, bool update)
@@ -58,9 +57,10 @@ void ceph_fscache_unuse_cookie(struct inode *inode, bool update)
 	if (update) {
 		loff_t i_size = i_size_read(inode);
 
-		fscache_unuse_cookie(ci->fscache, &ci->i_version, &i_size);
+		fscache_unuse_cookie(ceph_fscache_cookie(ci),
+				     &ci->i_version, &i_size);
 	} else {
-		fscache_unuse_cookie(ci->fscache, NULL, NULL);
+		fscache_unuse_cookie(ceph_fscache_cookie(ci), NULL, NULL);
 	}
 }
 
@@ -69,14 +69,14 @@ void ceph_fscache_update(struct inode *inode)
 	struct ceph_inode_info *ci = ceph_inode(inode);
 	loff_t i_size = i_size_read(inode);
 
-	fscache_update_cookie(ci->fscache, &ci->i_version, &i_size);
+	fscache_update_cookie(ceph_fscache_cookie(ci), &ci->i_version, &i_size);
 }
 
 void ceph_fscache_invalidate(struct inode *inode, bool dio_write)
 {
 	struct ceph_inode_info *ci = ceph_inode(inode);
 
-	fscache_invalidate(ceph_inode(inode)->fscache,
+	fscache_invalidate(ceph_fscache_cookie(ci),
 			   &ci->i_version, i_size_read(inode),
 			   dio_write ? FSCACHE_INVAL_DIO_WRITE : 0);
 }