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Subject[RFC PATCH 04/17] tracefs: Add ->unlink callback to tracefs_dir_ops
Date
In addition to mkdir and rmdir, also allow unlink operation within the
'instances' directory if such callback is defined.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
---
fs/tracefs/inode.c | 36 +++++++++++++++++++++++++++++++++++-
include/linux/tracefs.h | 3 ++-
kernel/trace/trace.c | 8 +++++++-
3 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index b14f03a655..fba5a0ce07 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -53,6 +53,7 @@ static const struct file_operations tracefs_file_operations = {
struct tracefs_dir_ops {
int (*mkdir)(const char *name);
int (*rmdir)(const char *name);
+ int (*unlink)(const char *name);
};

static char *get_dname(struct dentry *dentry)
@@ -124,10 +125,41 @@ static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
return ret;
}

+static int tracefs_syscall_unlink(struct inode *inode, struct dentry *dentry)
+{
+ struct tracefs_dir_ops *tracefs_ops = dentry->d_fsdata;
+ char *name;
+ int ret;
+
+ name = get_dname(dentry);
+ if (!name)
+ return -ENOMEM;
+
+ /*
+ * The unlink call can call the generic functions that create
+ * the files within the tracefs system. It is up to the individual
+ * unlink routine to handle races.
+ * This time we need to unlock not only the parent (inode) but
+ * also the file that is being deleted.
+ */
+ inode_unlock(inode);
+ inode_unlock(dentry->d_inode);
+
+ ret = tracefs_ops->unlink(name);
+
+ inode_lock_nested(inode, I_MUTEX_PARENT);
+ inode_lock(dentry->d_inode);
+
+ kfree(name);
+
+ return ret;
+}
+
static const struct inode_operations tracefs_dir_inode_operations = {
.lookup = simple_lookup,
.mkdir = tracefs_syscall_mkdir,
.rmdir = tracefs_syscall_rmdir,
+ .unlink = tracefs_syscall_unlink,
};

static struct inode *tracefs_get_inode(struct super_block *sb)
@@ -485,7 +517,8 @@ struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
*/
struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *parent,
int (*mkdir)(const char *name),
- int (*rmdir)(const char *name))
+ int (*rmdir)(const char *name),
+ int (*unlink)(const char *name))
{
struct tracefs_dir_ops *tracefs_ops = parent ? parent->d_fsdata : NULL;
struct dentry *dentry;
@@ -505,6 +538,7 @@ struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *pare

tracefs_ops->mkdir = mkdir;
tracefs_ops->rmdir = rmdir;
+ tracefs_ops->unlink = unlink;
dentry->d_fsdata = tracefs_ops;

return dentry;
diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h
index 5b727a17be..e5bd1f01b6 100644
--- a/include/linux/tracefs.h
+++ b/include/linux/tracefs.h
@@ -36,7 +36,8 @@ void tracefs_remove_recursive(struct dentry *dentry);

struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *parent,
int (*mkdir)(const char *name),
- int (*rmdir)(const char *name));
+ int (*rmdir)(const char *name),
+ int (*unlink)(const char *name));

bool tracefs_initialized(void);

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 44004d8aa3..b9abd2029e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -7792,11 +7792,17 @@ static int instance_rmdir(const char *name)
return ret;
}

+static int instance_unlink(const char *name)
+{
+ return -EACCES;
+}
+
static __init void create_trace_instances(struct dentry *d_tracer)
{
trace_instance_dir = tracefs_create_instance_dir("instances", d_tracer,
instance_mkdir,
- instance_rmdir);
+ instance_rmdir,
+ instance_unlink);
if (WARN_ON(!trace_instance_dir))
return;
}
--
2.14.1
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