readahead: implement minimal readahead logic based on fanotify(), mincore() and readahead()

1 files changed, 98 insertions, 0 deletions

diff --git a/src/linux/fanotify.h b/src/linux/fanotify.h
new file mode 100644
index 0000000000..63531a6b4d
--- /dev/null
+++ b/src/linux/fanotify.h
@@ -0,0 +1,98 @@
+#ifndef _LINUX_FANOTIFY_H
+#define _LINUX_FANOTIFY_H
+
+#include <linux/types.h>
+
+/* the following events that user-space can register for */
+#define FAN_ACCESS		0x00000001	/* File was accessed */
+#define FAN_MODIFY		0x00000002	/* File was modified */
+#define FAN_CLOSE_WRITE		0x00000008	/* Unwrittable file closed */
+#define FAN_CLOSE_NOWRITE	0x00000010	/* Writtable file closed */
+#define FAN_OPEN		0x00000020	/* File was opened */
+
+#define FAN_EVENT_ON_CHILD	0x08000000	/* interested in child events */
+
+/* FIXME currently Q's have no limit.... */
+#define FAN_Q_OVERFLOW		0x00004000	/* Event queued overflowed */
+
+#define FAN_OPEN_PERM		0x00010000	/* File open in perm check */
+#define FAN_ACCESS_PERM		0x00020000	/* File accessed in perm check */
+
+/* helper events */
+#define FAN_CLOSE		(FAN_CLOSE_WRITE | FAN_CLOSE_NOWRITE) /* close */
+
+/* flags used for fanotify_init() */
+#define FAN_CLOEXEC		0x00000001
+#define FAN_NONBLOCK		0x00000002
+
+#define FAN_ALL_INIT_FLAGS	(FAN_CLOEXEC | FAN_NONBLOCK)
+
+/* flags used for fanotify_modify_mark() */
+#define FAN_MARK_ADD		0x00000001
+#define FAN_MARK_REMOVE		0x00000002
+#define FAN_MARK_DONT_FOLLOW	0x00000004
+#define FAN_MARK_ONLYDIR	0x00000008
+#define FAN_MARK_MOUNT		0x00000010
+#define FAN_MARK_IGNORED_MASK	0x00000020
+#define FAN_MARK_IGNORED_SURV_MODIFY	0x00000040
+#define FAN_MARK_FLUSH		0x00000080
+
+#define FAN_ALL_MARK_FLAGS	(FAN_MARK_ADD |\
+				 FAN_MARK_REMOVE |\
+				 FAN_MARK_DONT_FOLLOW |\
+				 FAN_MARK_ONLYDIR |\
+				 FAN_MARK_MOUNT |\
+				 FAN_MARK_IGNORED_MASK |\
+				 FAN_MARK_IGNORED_SURV_MODIFY)
+
+/*
+ * All of the events - we build the list by hand so that we can add flags in
+ * the future and not break backward compatibility.  Apps will get only the
+ * events that they originally wanted.  Be sure to add new events here!
+ */
+#define FAN_ALL_EVENTS (FAN_ACCESS |\
+			FAN_MODIFY |\
+			FAN_CLOSE |\
+			FAN_OPEN)
+
+/*
+ * All events which require a permission response from userspace
+ */
+#define FAN_ALL_PERM_EVENTS (FAN_OPEN_PERM |\
+			     FAN_ACCESS_PERM)
+
+#define FAN_ALL_OUTGOING_EVENTS	(FAN_ALL_EVENTS |\
+				 FAN_ALL_PERM_EVENTS |\
+				 FAN_Q_OVERFLOW)
+
+#define FANOTIFY_METADATA_VERSION	2
+
+struct fanotify_event_metadata {
+	__u32 event_len;
+	__u32 vers;
+	__u64 mask;
+	__s32 fd;
+	__s32 pid;
+} __attribute__ ((packed));
+
+struct fanotify_response {
+	__s32 fd;
+	__u32 response;
+} __attribute__ ((packed));
+
+/* Legit userspace responses to a _PERM event */
+#define FAN_ALLOW	0x01
+#define FAN_DENY	0x02
+
+/* Helper functions to deal with fanotify_event_metadata buffers */
+#define FAN_EVENT_METADATA_LEN (sizeof(struct fanotify_event_metadata))
+
+#define FAN_EVENT_NEXT(meta, len) ((len) -= (meta)->event_len, \
+				   (struct fanotify_event_metadata*)(((char *)(meta)) + \
+				   (meta)->event_len))
+
+#define FAN_EVENT_OK(meta, len)	((long)(len) >= (long)FAN_EVENT_METADATA_LEN && \
+				(long)(meta)->event_len >= (long)FAN_EVENT_METADATA_LEN && \
+				(long)(meta)->event_len <= (long)(len))
+
+#endif /* _LINUX_FANOTIFY_H */