Re: [PATCH 00/16 v3] tracing: Add new file system tracefs

[Al Viro]

On Mon, Jan 26, 2015 at 03:42:59PM -0500, Steven Rostedt wrote:
> On Mon, 26 Jan 2015 19:30:49 +0000
> Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> 
> > You are still fighting an inconvenient API, but now it's not debugfs one -
> > it's your copy thereof.  Why not give your instances/ an inode_operations
> > of its own?  One with ->mkdir() and ->rmdir(), leaving all other directories
> > as-is.  That way you don't need the secondary methods at all.  And sure,
> > debugfs_create_dir() grabs ->i_mutex on parent, making you drop that in
> > your ->mkdir() if you want to call it.  But now you are not talking to it -
> > just to your own code, where you are free to change the calling conventions,
> > making it caller's responsibility to get that ->i_mutex.  The same goes for
> > the rmdir side...
> 
> The vfs layer grabs the i_mutex, which needs to be dropped.

What for?  Just keep it through your instance_mkdir/instance_rmdir and be
done with that.  Sure, it means that you need variants of file/directory
creation/removal primitives that would assume that parent is already locked
by caller (and would leave unlocking to the caller as well).  So add them...
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/