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, 27 deletions

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 4aeccafa5dda..5512f448f609 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -403,7 +403,7 @@ static void ceph_readahead_cleanup(struct address_space *mapping, void *priv)
 		ceph_put_cap_refs(ci, got);
 }
 
-static const struct netfs_request_ops ceph_netfs_read_ops = {
+const struct netfs_request_ops ceph_netfs_ops = {
 	.init_request		= ceph_init_request,
 	.begin_cache_operation	= ceph_begin_cache_operation,
 	.issue_read		= ceph_netfs_issue_read,
@@ -413,28 +413,6 @@ static const struct netfs_request_ops ceph_netfs_read_ops = {
 	.cleanup		= ceph_readahead_cleanup,
 };
 
-/* read a single page, without unlocking it. */
-static int ceph_readpage(struct file *file, struct page *subpage)
-{
-	struct folio *folio = page_folio(subpage);
-	struct inode *inode = file_inode(file);
-	struct ceph_inode_info *ci = ceph_inode(inode);
-	struct ceph_vino vino = ceph_vino(inode);
-	size_t len = folio_size(folio);
-	u64 off = folio_file_pos(folio);
-
-	dout("readpage ino %llx.%llx file %p off %llu len %zu folio %p index %lu\n inline %d",
-	     vino.ino, vino.snap, file, off, len, folio, folio_index(folio),
-	     ci->i_inline_version != CEPH_INLINE_NONE);
-
-	return netfs_readpage(file, folio, &ceph_netfs_read_ops, NULL);
-}
-
-static void ceph_readahead(struct readahead_control *ractl)
-{
-	netfs_readahead(ractl, &ceph_netfs_read_ops, NULL);
-}
-
 #ifdef CONFIG_CEPH_FSCACHE
 static void ceph_set_page_fscache(struct page *page)
 {
@@ -1333,8 +1311,7 @@ static int ceph_write_begin(struct file *file, struct address_space *mapping,
 	struct folio *folio = NULL;
 	int r;
 
-	r = netfs_write_begin(file, inode->i_mapping, pos, len, 0, &folio, NULL,
-			      &ceph_netfs_read_ops, NULL);
+	r = netfs_write_begin(file, inode->i_mapping, pos, len, 0, &folio, NULL);
 	if (r == 0)
 		folio_wait_fscache(folio);
 	if (r < 0) {
@@ -1388,8 +1365,8 @@ out:
 }
 
 const struct address_space_operations ceph_aops = {
-	.readpage = ceph_readpage,
-	.readahead = ceph_readahead,
+	.readpage = netfs_readpage,
+	.readahead = netfs_readahead,
 	.writepage = ceph_writepage,
 	.writepages = ceph_writepages_start,
 	.write_begin = ceph_write_begin,