netfs: Move pinning-for-writeback from fscache to netfs

Move the resource pinning-for-writeback from fscache code to netfslib code.
This is used to keep a cache backing object pinned whilst we have dirty
pages on the netfs inode in the pagecache such that VM writeback will be
able to reach it.

Whilst we're at it, switch the parameters of netfs_unpin_writeback() to
match ->write_inode() so that it can be used for that directly.

Note that this mechanism could be more generically useful than that for
network filesystems.  Quite often they have to keep around other resources
(e.g. authentication tokens or network connections) until the writeback is
complete.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org

1 files changed, 9 insertions, 24 deletions

diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index 39db7c01e30a..131b83c31f85 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -317,30 +317,15 @@ out:
 	return copied;
 }
 
-#ifdef CONFIG_9P_FSCACHE
-/*
- * Mark a page as having been made dirty and thus needing writeback.  We also
- * need to pin the cache object to write back to.
- */
-static bool v9fs_dirty_folio(struct address_space *mapping, struct folio *folio)
-{
-	struct v9fs_inode *v9inode = V9FS_I(mapping->host);
-
-	return fscache_dirty_folio(mapping, folio, v9fs_inode_cookie(v9inode));
-}
-#else
-#define v9fs_dirty_folio filemap_dirty_folio
-#endif
-
 const struct address_space_operations v9fs_addr_operations = {
-	.read_folio = netfs_read_folio,
-	.readahead = netfs_readahead,
-	.dirty_folio = v9fs_dirty_folio,
-	.writepage = v9fs_vfs_writepage,
-	.write_begin = v9fs_write_begin,
-	.write_end = v9fs_write_end,
-	.release_folio = v9fs_release_folio,
+	.read_folio	= netfs_read_folio,
+	.readahead	= netfs_readahead,
+	.dirty_folio	= netfs_dirty_folio,
+	.writepage	= v9fs_vfs_writepage,
+	.write_begin	= v9fs_write_begin,
+	.write_end	= v9fs_write_end,
+	.release_folio	= v9fs_release_folio,
 	.invalidate_folio = v9fs_invalidate_folio,
-	.launder_folio = v9fs_launder_folio,
-	.direct_IO = v9fs_direct_IO,
+	.launder_folio	= v9fs_launder_folio,
+	.direct_IO	= v9fs_direct_IO,
 };