netfs: zero the tail of a short DIO/unbuffered readgrafted

The buffered read collector zero-fills the tail of a short read that
stops below the inode's i_size (netfs_clear_unread()), so a read that
races an extending write still returns the expected number of bytes.
The non-buffered collector path does no such thing: it just records
how much was transferred.

Add the same zero-fill for the non-buffered case, gated on
NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short
result from it is known to be safe to treat as a hole, as opposed to
NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of
the file and should be reported short as-is. Only CLEAR_TAIL should
zero-fill here; a real EOF must stay a real short read.

No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest,
so this is inert on its own -- a following change teaches cifs to set
it in the one case that needs it.

Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

1 files changed, 45 insertions, 0 deletions

diff --git a/net/mac80211/debugfs_netdev.h b/net/mac80211/debugfs_netdev.h
new file mode 100644
index 000000000..a02ec0a41
--- /dev/null
+++ b/net/mac80211/debugfs_netdev.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Portions:
+ * Copyright (C) 2023 Intel Corporation
+ */
+/* routines exported for debugfs handling */
+
+#ifndef __IEEE80211_DEBUGFS_NETDEV_H
+#define __IEEE80211_DEBUGFS_NETDEV_H
+
+#include "ieee80211_i.h"
+
+#ifdef CONFIG_MAC80211_DEBUGFS
+void ieee80211_debugfs_remove_netdev(struct ieee80211_sub_if_data *sdata);
+void ieee80211_debugfs_rename_netdev(struct ieee80211_sub_if_data *sdata);
+void ieee80211_debugfs_recreate_netdev(struct ieee80211_sub_if_data *sdata,
+				       bool mld_vif);
+
+void ieee80211_link_debugfs_add(struct ieee80211_link_data *link);
+void ieee80211_link_debugfs_remove(struct ieee80211_link_data *link);
+
+void ieee80211_link_debugfs_drv_add(struct ieee80211_link_data *link);
+void ieee80211_link_debugfs_drv_remove(struct ieee80211_link_data *link);
+#else
+static inline void ieee80211_debugfs_remove_netdev(
+	struct ieee80211_sub_if_data *sdata)
+{}
+static inline void ieee80211_debugfs_rename_netdev(
+	struct ieee80211_sub_if_data *sdata)
+{}
+static inline void ieee80211_debugfs_recreate_netdev(
+	struct ieee80211_sub_if_data *sdata, bool mld_vif)
+{}
+static inline void ieee80211_link_debugfs_add(struct ieee80211_link_data *link)
+{}
+static inline void ieee80211_link_debugfs_remove(struct ieee80211_link_data *link)
+{}
+
+static inline void ieee80211_link_debugfs_drv_add(struct ieee80211_link_data *link)
+{}
+static inline void ieee80211_link_debugfs_drv_remove(struct ieee80211_link_data *link)
+{}
+#endif
+
+#endif /* __IEEE80211_DEBUGFS_NETDEV_H */