I just stumbled across this patch (and the following one). What purpose would this have? The "instances" directory is used to make multiple buffers. Why would we have more than one?
-- Steve On Tue, 5 Sep 2017 16:30:12 +0300 Alexander Shishkin <[email protected]> wrote: > Currently, tracefs has exactly one special 'instances' subdirectory, where > the caller can have their own .mkdir/.rmdir callbacks, which allow the > caller to handle user's mkdir/rmdir inside that directory. Tracefs allows > one set of these callbacks (tracefs_dir_ops). > > This patch de-globalizes tracefs_dir_ops so that it's possible to have > multiple such subdirectories. > > Signed-off-by: Alexander Shishkin <[email protected]> > Cc: Steven Rostedt <[email protected]> > --- > fs/tracefs/inode.c | 35 +++++++++++++++++++++++++---------- > 1 file changed, 25 insertions(+), 10 deletions(-) > > diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c > index bea8ad876b..b14f03a655 100644 > --- a/fs/tracefs/inode.c > +++ b/fs/tracefs/inode.c > @@ -50,10 +50,10 @@ static const struct file_operations > tracefs_file_operations = { > .llseek = noop_llseek, > }; > > -static struct tracefs_dir_ops { > +struct tracefs_dir_ops { > int (*mkdir)(const char *name); > int (*rmdir)(const char *name); > -} tracefs_ops; > +}; > > static char *get_dname(struct dentry *dentry) > { > @@ -72,6 +72,7 @@ static char *get_dname(struct dentry *dentry) > > static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, > umode_t mode) > { > + struct tracefs_dir_ops *tracefs_ops = dentry->d_parent->d_fsdata; > char *name; > int ret; > > @@ -85,7 +86,7 @@ static int tracefs_syscall_mkdir(struct inode *inode, > struct dentry *dentry, umo > * mkdir routine to handle races. > */ > inode_unlock(inode); > - ret = tracefs_ops.mkdir(name); > + ret = tracefs_ops->mkdir(name); > inode_lock(inode); > > kfree(name); > @@ -95,6 +96,7 @@ static int tracefs_syscall_mkdir(struct inode *inode, > struct dentry *dentry, umo > > static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry) > { > + struct tracefs_dir_ops *tracefs_ops = dentry->d_fsdata; > char *name; > int ret; > > @@ -112,7 +114,7 @@ static int tracefs_syscall_rmdir(struct inode *inode, > struct dentry *dentry) > inode_unlock(inode); > inode_unlock(dentry->d_inode); > > - ret = tracefs_ops.rmdir(name); > + ret = tracefs_ops->rmdir(name); > > inode_lock_nested(inode, I_MUTEX_PARENT); > inode_lock(dentry->d_inode); > @@ -342,6 +344,9 @@ static struct dentry *start_creating(const char *name, > struct dentry *parent) > if (IS_ERR(dentry)) { > inode_unlock(parent->d_inode); > simple_release_fs(&tracefs_mount, &tracefs_mount_count); > + } else { > + /* propagate dir ops */ > + dentry->d_fsdata = parent->d_fsdata; > } > > return dentry; > @@ -482,18 +487,25 @@ struct dentry *tracefs_create_instance_dir(const char > *name, struct dentry *pare > int (*mkdir)(const char *name), > int (*rmdir)(const char *name)) > { > + struct tracefs_dir_ops *tracefs_ops = parent ? parent->d_fsdata : NULL; > struct dentry *dentry; > > - /* Only allow one instance of the instances directory. */ > - if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir)) > + if (WARN_ON(tracefs_ops)) > + return NULL; > + > + tracefs_ops = kzalloc(sizeof(*tracefs_ops), GFP_KERNEL); > + if (!tracefs_ops) > return NULL; > > dentry = __create_dir(name, parent, &tracefs_dir_inode_operations); > - if (!dentry) > + if (!dentry) { > + kfree(tracefs_ops); > return NULL; > + } > > - tracefs_ops.mkdir = mkdir; > - tracefs_ops.rmdir = rmdir; > + tracefs_ops->mkdir = mkdir; > + tracefs_ops->rmdir = rmdir; > + dentry->d_fsdata = tracefs_ops; > > return dentry; > } > @@ -513,8 +525,11 @@ static int __tracefs_remove(struct dentry *dentry, > struct dentry *parent) > simple_unlink(parent->d_inode, dentry); > break; > } > - if (!ret) > + if (!ret) { > d_delete(dentry); > + if (dentry->d_fsdata != parent->d_fsdata) > + kfree(dentry->d_fsdata); > + } > dput(dentry); > } > }
