netfs: Extend the netfs_io_*request structs to handle writes

Modify the netfs_io_request struct to act as a point around which writes
can be coordinated.  It represents and pins a range of pages that need
writing and a list of regions of dirty data in that range of pages.

If RMW is required, the original data can be downloaded into the bounce
buffer, decrypted if necessary, the modifications made, then the modified
data can be reencrypted/recompressed and sent back to the server.

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, 14 insertions, 1 deletions

diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 44cd13ad695a..f302123a3e38 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -118,6 +118,9 @@ enum netfs_io_source {
 	NETFS_DOWNLOAD_FROM_SERVER,
 	NETFS_READ_FROM_CACHE,
 	NETFS_INVALID_READ,
+	NETFS_UPLOAD_TO_SERVER,
+	NETFS_WRITE_TO_CACHE,
+	NETFS_INVALID_WRITE,
 } __mode(byte);
 
 typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error,
@@ -149,9 +152,14 @@ struct netfs_cache_resources {
 };
 
 /*
- * Descriptor for a single component subrequest.
+ * Descriptor for a single component subrequest.  Each operation represents an
+ * individual read/write from/to a server, a cache, a journal, etc..
+ *
+ * The buffer iterator is persistent for the life of the subrequest struct and
+ * the pages it points to can be relied on to exist for the duration.
  */
 struct netfs_io_subrequest {
+	struct work_struct	work;
 	struct netfs_io_request *rreq;		/* Supervising I/O request */
 	struct list_head	rreq_link;	/* Link in rreq->subrequests */
 	struct iov_iter		io_iter;	/* Iterator for this subrequest */
@@ -176,6 +184,8 @@ enum netfs_io_origin {
 	NETFS_READAHEAD,		/* This read was triggered by readahead */
 	NETFS_READPAGE,			/* This read is a synchronous read */
 	NETFS_READ_FOR_WRITE,		/* This read is to prepare a write */
+	NETFS_WRITEBACK,		/* This write was triggered by writepages */
+	nr__netfs_io_origin
 } __mode(byte);
 
 /*
@@ -198,6 +208,7 @@ struct netfs_io_request {
 	struct bio_vec		*direct_bv;	/* DIO buffer list (when handling iovec-iter) */
 	unsigned int		direct_bv_count; /* Number of elements in direct_bv[] */
 	unsigned int		debug_id;
+	unsigned int		subreq_counter;	/* Next subreq->debug_index */
 	atomic_t		nr_outstanding;	/* Number of ops in progress */
 	atomic_t		nr_copy_ops;	/* Number of copy-to-cache ops in progress */
 	size_t			submitted;	/* Amount submitted for I/O so far */
@@ -216,6 +227,8 @@ struct netfs_io_request {
 #define NETFS_RREQ_DONT_UNLOCK_FOLIOS	3	/* Don't unlock the folios on completion */
 #define NETFS_RREQ_FAILED		4	/* The request failed */
 #define NETFS_RREQ_IN_PROGRESS		5	/* Unlocked when the request completes */
+#define NETFS_RREQ_WRITE_TO_CACHE	7	/* Need to write to the cache */
+#define NETFS_RREQ_UPLOAD_TO_SERVER	8	/* Need to write to the server */
 	const struct netfs_request_ops *netfs_ops;
 };