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Subject[RFC PATCH 03/17] tracefs: De-globalize instances' callbacks
Date
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 <alexander.shishkin@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
---
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);
}
}
--
2.14.1
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