anon-inode: Don't readlink fd/fd multiple times

The is_foo_link readlinks the lfd to check. This makes
anon-inodes dumping readlink several times to find proper
dump ops. Optimize this thing.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

eventfd.c

@@ -33,9 +33,9 @@ struct eventfd_file_info {
 };
 
 /* Checks if file descriptor @lfd is eventfd */
-int is_eventfd_link(int lfd)
+int is_eventfd_link(char *link)
 {
-	return is_anon_link_type(lfd, "[eventfd]");
+	return is_anon_link_type(link, "[eventfd]");
 }
 
 static void pr_info_eventfd(char *action, EventfdFileEntry *efe)

eventpoll.c

@@ -41,9 +41,9 @@ struct eventpoll_tfd_file_info {
 static LIST_HEAD(eventpoll_tfds);
 
 /* Checks if file descriptor @lfd is eventfd */
-int is_eventpoll_link(int lfd)
+int is_eventpoll_link(char *link)
 {
-	return is_anon_link_type(lfd, "[eventpoll]");
+	return is_anon_link_type(link, "[eventpoll]");
 }
 
 static void pr_info_eventpoll_tfd(char *action, EventpollTfdEntry *e)

files.c

@@ -316,24 +316,23 @@ static int dump_one_file(struct parasite_ctl *ctl, int fd, int lfd, struct fd_op
 		return dump_chrdev(&p, lfd, fdinfo);
 
 	if (p.fs_type == ANON_INODE_FS_MAGIC) {
-		if (is_eventfd_link(lfd))
+		char link[32];
+
+		if (read_fd_link(lfd, link, sizeof(link)) < 0)
+			return -1;
+
+		if (is_eventfd_link(link))
 			ops = &eventfd_dump_ops;
-		else if (is_eventpoll_link(lfd))
+		else if (is_eventpoll_link(link))
 			ops = &eventpoll_dump_ops;
-		else if (is_inotify_link(lfd))
+		else if (is_inotify_link(link))
 			ops = &inotify_dump_ops;
-		else if (is_fanotify_link(lfd))
+		else if (is_fanotify_link(link))
 			ops = &fanotify_dump_ops;
-		else if (is_signalfd_link(lfd))
+		else if (is_signalfd_link(link))
 			ops = &signalfd_dump_ops;
-		else {
-			char more[64];
-
-			if (read_fd_link(fd, more, sizeof(more)) < 0)
-				more[0] = '\0';
-
-			return dump_unsupp_fd(&p, lfd, fdinfo, "anon", more);
-		}
+		else
+			return dump_unsupp_fd(&p, lfd, fdinfo, "anon", link);
 
 		return do_dump_gen_file(&p, lfd, ops, fdinfo);
 	}
@@ -416,6 +415,7 @@ static int predump_one_fd(int pid, int fd)
 	int lfd, ret = 0;
 	struct statfs buf;
 	const struct fdtype_ops *ops;
+	char link[32];
 
 	/*
 	 * This should look like the dump_task_files_seized,
@@ -435,9 +435,14 @@ static int predump_one_fd(int pid, int fd)
 	if (buf.f_type != ANON_INODE_FS_MAGIC)
 		goto out;
 
-	if (is_inotify_link(lfd))
+	if (read_fd_link(lfd, link, sizeof(link)) < 0) {
+		ret = -1;
+		goto out;
+	}
+
+	if (is_inotify_link(link))
 		ops = &inotify_dump_ops;
-	else if (is_fanotify_link(lfd))
+	else if (is_fanotify_link(link))
 		ops = &fanotify_dump_ops;
 	else
 		goto out;

fsnotify.c

@@ -74,15 +74,15 @@ static LIST_HEAD(inotify_info_head);
 static LIST_HEAD(fanotify_info_head);
 
 /* Checks if file descriptor @lfd is inotify */
-int is_inotify_link(int lfd)
+int is_inotify_link(char *link)
 {
-	return is_anon_link_type(lfd, "inotify");
+	return is_anon_link_type(link, "inotify");
 }
 
 /* Checks if file descriptor @lfd is fanotify */
-int is_fanotify_link(int lfd)
+int is_fanotify_link(char *link)
 {
-	return is_anon_link_type(lfd, "[fanotify]");
+	return is_anon_link_type(link, "[fanotify]");
 }
 
 static void decode_handle(fh_t *handle, FhEntry *img)

include/eventfd.h

@@ -3,7 +3,7 @@
 
 #include "files.h"
 
-extern int is_eventfd_link(int lfd);
+extern int is_eventfd_link(char *link);
 extern const struct fdtype_ops eventfd_dump_ops;
 extern struct collect_image_info eventfd_cinfo;
 

include/eventpoll.h

@@ -3,7 +3,7 @@
 
 #include "files.h"
 
-extern int is_eventpoll_link(int lfd);
+extern int is_eventpoll_link(char *link);
 extern const struct fdtype_ops eventpoll_dump_ops;
 extern struct collect_image_info epoll_tfd_cinfo;
 extern struct collect_image_info epoll_cinfo;

include/fsnotify.h

@@ -10,8 +10,8 @@ struct fsnotify_params {
 	u32	evflags;
 };
 
-extern int is_inotify_link(int lfd);
-extern int is_fanotify_link(int lfd);
+extern int is_inotify_link(char *link);
+extern int is_fanotify_link(char *link);
 extern const struct fdtype_ops inotify_dump_ops;
 extern const struct fdtype_ops fanotify_dump_ops;
 extern struct collect_image_info inotify_cinfo;

include/signalfd.h

@@ -3,7 +3,7 @@
 
 struct cr_fdset;
 struct fd_parms;
-extern int is_signalfd_link(int lfd);
+extern int is_signalfd_link(char *link);
 extern const struct fdtype_ops signalfd_dump_ops;
 extern struct collect_image_info signalfd_cinfo;
 

include/util.h

@@ -234,7 +234,7 @@ static inline dev_t kdev_to_odev(u32 kdev)
 }
 
 extern int copy_file(int fd_in, int fd_out, size_t bytes);
-extern int is_anon_link_type(int lfd, char *type);
+extern int is_anon_link_type(char *link, char *type);
 
 #define is_hex_digit(c)				\
 	(((c) >= '0' && (c) <= '9')	||	\

signalfd.c

@@ -20,9 +20,9 @@ struct signalfd_info {
 	struct file_desc	d;
 };
 
-int is_signalfd_link(int lfd)
+int is_signalfd_link(char *link)
 {
-	return is_anon_link_type(lfd, "[signalfd]");
+	return is_anon_link_type(link, "[signalfd]");
 }
 
 struct signalfd_dump_arg {

util.c

@@ -425,12 +425,9 @@ int read_fd_link(int lfd, char *buf, size_t size)
 	return ret;
 }
 
-int is_anon_link_type(int lfd, char *type)
+int is_anon_link_type(char *link, char *type)
 {
-	char link[32], aux[32];
-
-	if (read_fd_link(lfd, link, sizeof(link)) < 0)
-		return -1;
+	char aux[32];
 
 	snprintf(aux, sizeof(aux), "anon_inode:%s", type);
 	return !strcmp(link, aux);