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, 6 insertions, 6 deletions

diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
index ae18827e156b..657b19e60118 100644
--- a/fs/netfs/objects.c
+++ b/fs/netfs/objects.c
@@ -13,12 +13,12 @@
  */
 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 inode *inode = file ? file_inode(file) : mapping->host;
+	struct netfs_i_context *ctx = netfs_i_context(inode);
 	struct netfs_io_request *rreq;
 	int ret;
 
@@ -29,11 +29,10 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
 	rreq->start	= start;
 	rreq->len	= len;
 	rreq->origin	= origin;
-	rreq->netfs_ops	= ops;
-	rreq->netfs_priv = netfs_priv;
+	rreq->netfs_ops	= ctx->ops;
 	rreq->mapping	= mapping;
-	rreq->inode	= file_inode(file);
-	rreq->i_size	= i_size_read(rreq->inode);
+	rreq->inode	= inode;
+	rreq->i_size	= i_size_read(inode);
 	rreq->debug_id	= atomic_inc_return(&debug_ids);
 	INIT_LIST_HEAD(&rreq->subrequests);
 	INIT_WORK(&rreq->work, netfs_rreq_work);
@@ -76,6 +75,7 @@ static void netfs_free_request(struct work_struct *work)
 {
 	struct netfs_io_request *rreq =
 		container_of(work, struct netfs_io_request, work);
+
 	netfs_clear_subrequests(rreq, false);
 	if (rreq->netfs_priv)
 		rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);