On Tue, Jan 16, 2024 at 05:55:32PM -0500, Steven Rostedt wrote: > From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx> > > The dentries and inodes are created in the readdir for the sole purpose of > getting a consistent inode number. Linus stated that is unnecessary, and > that all inodes can have the same inode number. For a virtual file system > they are pretty meaningless. > > Instead use a single unique inode number for all files and one for all > directories. > > Link: https://lore.kernel.org/all/20240116133753.2808d45e@xxxxxxxxxxxxxxxxxx/ > Link: https://lore.kernel.org/linux-trace-kernel/20240116211353.412180363@xxxxxxxxxxx > > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> > Cc: Christian Brauner <brauner@xxxxxxxxxx> > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > Cc: Ajay Kaher <ajay.kaher@xxxxxxxxxxxx> > Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> > --- > fs/tracefs/event_inode.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c > index fdff53d5a1f8..5edf0b96758b 100644 > --- a/fs/tracefs/event_inode.c > +++ b/fs/tracefs/event_inode.c > @@ -32,6 +32,10 @@ > */ > static DEFINE_MUTEX(eventfs_mutex); > > +/* Choose something "unique" ;-) */ > +#define EVENTFS_FILE_INODE_INO 0x12c4e37 > +#define EVENTFS_DIR_INODE_INO 0x134b2f5 > + > /* > * The eventfs_inode (ei) itself is protected by SRCU. It is released from > * its parent's list and will have is_freed set (under eventfs_mutex). > @@ -352,6 +356,9 @@ static struct dentry *create_file(const char *name, umode_t mode, > inode->i_fop = fop; > inode->i_private = data; > > + /* All files will have the same inode number */ > + inode->i_ino = EVENTFS_FILE_INODE_INO; > + > ti = get_tracefs(inode); > ti->flags |= TRACEFS_EVENT_INODE; > d_instantiate(dentry, inode); > @@ -388,6 +395,9 @@ static struct dentry *create_dir(struct eventfs_inode *ei, struct dentry *parent > inode->i_op = &eventfs_root_dir_inode_operations; > inode->i_fop = &eventfs_file_operations; > > + /* All directories will have the same inode number */ > + inode->i_ino = EVENTFS_DIR_INODE_INO; Regrettably, this leads to find failing on 6.8-rc1 (see xfs/55[89] in fstests): # find /sys/kernel/debug/tracing/ >/dev/null find: File system loop detected; ‘/sys/kernel/debug/tracing/events/initcall/initcall_finish’ is part of the same file system loop as ‘/sys/kernel/debug/tracing/events/initcall’. find: File system loop detected; ‘/sys/kernel/debug/tracing/events/initcall/initcall_start’ is part of the same file system loop as ‘/sys/kernel/debug/tracing/events/initcall’. find: File system loop detected; ‘/sys/kernel/debug/tracing/events/initcall/initcall_level’ is part of the same file system loop as ‘/sys/kernel/debug/tracing/events/initcall’. There were no such reports on 6.7.0; AFAICT find(1) is tripping over parent and child subdirectory having the same dev/i_ino. Changing this line to the following: /* All directories will NOT have the same inode number */ inode->i_ino = (unsigned long)inode; makes the messages about filesystem loops go away, though I don't think leaking raw kernel pointers is an awesome idea. --D > + > ti = get_tracefs(inode); > ti->flags |= TRACEFS_EVENT_INODE; > > -- > 2.43.0 > > >
