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, 4 insertions, 39 deletions

diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index 91d3926c9559..ed06f3c34e98 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -78,17 +78,6 @@ static void v9fs_req_cleanup(struct address_space *mapping, void *priv)
 }
 
 /**
- * v9fs_is_cache_enabled - Determine if caching is enabled for an inode
- * @inode: The inode to check
- */
-static bool v9fs_is_cache_enabled(struct inode *inode)
-{
-	struct fscache_cookie *cookie = v9fs_inode_cookie(V9FS_I(inode));
-
-	return fscache_cookie_enabled(cookie) && cookie->cache_priv;
-}
-
-/**
  * v9fs_begin_cache_operation - Begin a cache operation for a read
  * @rreq: The read request
  */
@@ -103,37 +92,14 @@ static int v9fs_begin_cache_operation(struct netfs_io_request *rreq)
 #endif
 }
 
-static const struct netfs_request_ops v9fs_req_ops = {
+const struct netfs_request_ops v9fs_req_ops = {
 	.init_request		= v9fs_init_request,
-	.is_cache_enabled	= v9fs_is_cache_enabled,
 	.begin_cache_operation	= v9fs_begin_cache_operation,
 	.issue_read		= v9fs_issue_read,
 	.cleanup		= v9fs_req_cleanup,
 };
 
 /**
- * v9fs_vfs_readpage - read an entire page in from 9P
- * @file: file being read
- * @page: structure to page
- *
- */
-static int v9fs_vfs_readpage(struct file *file, struct page *page)
-{
-	struct folio *folio = page_folio(page);
-
-	return netfs_readpage(file, folio, &v9fs_req_ops, NULL);
-}
-
-/**
- * v9fs_vfs_readahead - read a set of pages from 9P
- * @ractl: The readahead parameters
- */
-static void v9fs_vfs_readahead(struct readahead_control *ractl)
-{
-	netfs_readahead(ractl, &v9fs_req_ops, NULL);
-}
-
-/**
  * v9fs_release_page - release the private state associated with a page
  * @page: The page to be released
  * @gfp: The caller's allocation restrictions
@@ -326,8 +292,7 @@ static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
 	 * file.  We need to do this before we get a lock on the page in case
 	 * there's more than one writer competing for the same cache block.
 	 */
-	retval = netfs_write_begin(filp, mapping, pos, len, flags, &folio, fsdata,
-				   &v9fs_req_ops, NULL);
+	retval = netfs_write_begin(filp, mapping, pos, len, flags, &folio, fsdata);
 	if (retval < 0)
 		return retval;
 
@@ -388,8 +353,8 @@ static int v9fs_set_page_dirty(struct page *page)
 #endif
 
 const struct address_space_operations v9fs_addr_operations = {
-	.readpage = v9fs_vfs_readpage,
-	.readahead = v9fs_vfs_readahead,
+	.readpage = netfs_readpage,
+	.readahead = netfs_readahead,
 	.set_page_dirty = v9fs_set_page_dirty,
 	.writepage = v9fs_vfs_writepage,
 	.write_begin = v9fs_write_begin,