[Linux-cachefs] [PATCH 2/2] netfs: add a new flag indicating that readahead should not be done

[Jeff Layton]

With ceph, if we don't have appropriate caps, then it's best to give up
on doing any readahead. Add a mechanism to allow its init_rreq op to
indicate that.

Signed-off-by: Jeff Layton <jlayton at kernel.org>
---
 fs/netfs/read_helper.c | 5 +++++
 include/linux/netfs.h  | 1 +
 2 files changed, 6 insertions(+)

diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index d7129d2229e2..3f1a503d81b4 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -925,6 +925,8 @@ void netfs_readahead(struct readahead_control *ractl)
 					readahead_length(ractl), true);
 	if (!rreq)
 		return;
+	if (test_bit(NETFS_RREQ_DENY_READAHEAD, &rreq->flags))
+		goto cleanup_free;
 
 	ret = netfs_begin_cache_operation(rreq, ctx);
 	if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
@@ -989,6 +991,7 @@ int netfs_readpage(struct file *file, struct page *subpage)
 					folio_size(folio), false);
 	if (!rreq)
 		goto nomem;
+	WARN_ON_ONCE(test_bit(NETFS_RREQ_DENY_READAHEAD, &rreq->flags));
 
 	ret = netfs_begin_cache_operation(rreq, ctx);
 	if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) {
@@ -1179,6 +1182,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
 					folio_size(folio), false);
 	if (!rreq)
 		goto error;
+	WARN_ON_ONCE(test_bit(NETFS_RREQ_DENY_READAHEAD, &rreq->flags));
 	rreq->start		= folio_file_pos(folio);
 	rreq->len		= folio_size(folio);
 	rreq->no_unlock_folio	= folio_index(folio);
@@ -1288,6 +1292,7 @@ int netfs_prefetch_for_write(struct file *file, struct folio *folio,
 	if (!rreq)
 		goto error;
 
+	WARN_ON_ONCE(test_bit(NETFS_RREQ_DENY_READAHEAD, &rreq->flags));
 	rreq->no_unlock_folio	= folio_index(folio);
 	__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
 	ret = netfs_begin_cache_operation(rreq, ctx);
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 8361db18d572..3bf1854e511d 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -209,6 +209,7 @@ struct netfs_read_request {
 #define NETFS_RREQ_IN_PROGRESS		5	/* Unlocked when the request completes */
 #define NETFS_RREQ_DECRYPT		6	/* Decrypted when the request completes */
 #define NETFS_RREQ_READAHEAD		7	/* This is a readahead op */
+#define NETFS_RREQ_DENY_READAHEAD	8	/* Abort the readahead */
 	const struct netfs_request_ops *netfs_ops;
 };
 
-- 
2.31.1