netfs: Add support for caching single monolithic objects such as AFS dirs

Add support for caching the content of a file that contains a single
monolithic object that must be read/written with a single I/O operation,
such as an AFS directory.

Signed-off-by: David Howells <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
cc: Jeff Layton <[email protected]>
cc: Marc Dionne <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
Signed-off-by: Christian Brauner <[email protected]>

1 files changed, 8 insertions, 3 deletions

diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index 4ff4b587dc4b..c420e9dee0e4 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -137,14 +137,17 @@ static enum netfs_io_source netfs_cache_prepare_read(struct netfs_io_request *rr
 						     loff_t i_size)
 {
 	struct netfs_cache_resources *cres = &rreq->cache_resources;
+	enum netfs_io_source source;
 
 	if (!cres->ops)
 		return NETFS_DOWNLOAD_FROM_SERVER;
-	return cres->ops->prepare_read(subreq, i_size);
+	source = cres->ops->prepare_read(subreq, i_size);
+	trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
+	return source;
+
 }
 
-static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
-					bool was_async)
+void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error, bool was_async)
 {
 	struct netfs_io_subrequest *subreq = priv;
 
@@ -213,6 +216,8 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
 			unsigned long long zp = umin(ictx->zero_point, rreq->i_size);
 			size_t len = subreq->len;
 
+			if (unlikely(rreq->origin == NETFS_READ_SINGLE))
+				zp = rreq->i_size;
 			if (subreq->start >= zp) {
 				subreq->source = source = NETFS_FILL_WITH_ZEROES;
 				goto fill_with_zeroes;