On Wed, 4 Nov 2015 09:11:18 +0800 Jiaxing Wang <[email protected]> wrote:
> Currently tracing_init_dentry() returns -ENODEV when debugfs is not > initialized, which causes tracefs not populated with tracing files and > directories, so we will get an empty directory even after we manually > mount tracefs. > > We can make tracing_init_dentry() return NULL as long as tracefs > is initialized and get a populated tracefs. > > We also need to make global_trace.dir not NULL in order to pass the checks > in tracing_get_dentry() and add_tracer_options(). > > Also added stub debugfs_create_automount() for when debugfs is not > configured in. > > Signed-off-by: Jiaxing Wang <[email protected]> > --- > include/linux/debugfs.h | 8 ++++++++ > kernel/trace/Kconfig | 1 - > kernel/trace/trace.c | 29 +++++++++++++++++------------ > 3 files changed, 25 insertions(+), 13 deletions(-) > > diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h > index 9beb636..b42ef88 100644 > --- a/include/linux/debugfs.h > +++ b/include/linux/debugfs.h > @@ -160,6 +160,14 @@ static inline struct dentry > *debugfs_create_symlink(const char *name, > return ERR_PTR(-ENODEV); > } > > +static inline struct dentry *debugfs_create_automount(const char *name, > + struct dentry *parent, > + struct vfsmount *(*f)(void *), > + void *data) > +{ > + return ERR_PTR(-ENODEV); > +} This part needs an Acked-by from Greg KH. > + > static inline void debugfs_remove(struct dentry *dentry) > { } > > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > index 1153c43..59f6377f 100644 > --- a/kernel/trace/Kconfig > +++ b/kernel/trace/Kconfig > @@ -95,7 +95,6 @@ config RING_BUFFER_ALLOW_SWAP > > config TRACING > bool > - select DEBUG_FS > select RING_BUFFER > select STACKTRACE if STACKTRACE_SUPPORT > select TRACEPOINTS > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 6e79408..6dd064e 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -6706,6 +6706,8 @@ static struct vfsmount *trace_automount(void *ingore) > return mnt; > } > > +#define TRACE_TOP_DIR_ENTRY ((struct dentry *)1) > + > /** > * tracing_init_dentry - initialize top level trace array > * > @@ -6716,27 +6718,30 @@ static struct vfsmount *trace_automount(void *ingore) > struct dentry *tracing_init_dentry(void) > { > struct trace_array *tr = &global_trace; > + struct dentry *traced; > > /* The top level trace array uses NULL as parent */ > if (tr->dir) > return NULL; > > - if (WARN_ON(!debugfs_initialized())) > + if (WARN_ON(!tracefs_initialized())) > return ERR_PTR(-ENODEV); > > - /* > - * As there may still be users that expect the tracing > - * files to exist in debugfs/tracing, we must automount > - * the tracefs file system there, so older tools still > - * work with the newer kerenl. > - */ > - tr->dir = debugfs_create_automount("tracing", NULL, > - trace_automount, NULL); > - if (!tr->dir) { > - pr_warn_once("Could not create debugfs directory 'tracing'\n"); > - return ERR_PTR(-ENOMEM); > + if (debugfs_initialized()) { > + /* > + * As there may still be users that expect the tracing > + * files to exist in debugfs/tracing, we must automount > + * the tracefs file system there, so older tools still > + * work with the newer kerenl. > + */ > + traced = debugfs_create_automount("tracing", NULL, > + trace_automount, NULL); > + if (!traced) > + pr_warn_once("Could not create debugfs directory > 'tracing'\n"); This should return a warning, and please keep the tr->dir instead of this new traced variable. > } > > + tr->dir = TRACE_TOP_DIR_ENTRY; > + Also, no need to add this, because if debugfs is not initialize, then tr->dir would be ERR_PTR(-ENODEV), which still works as tr->dir is not NULL. -- Steve > return NULL; > } > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
