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authorNicolai Stange <nicstange@gmail.com>2017-10-31 00:15:47 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-11-07 20:25:02 +0100
commit7c8d469877b16d2c1cecf101a0abb7b218db85bc (patch)
treea6d2637db3d3d721e0079fd70e9f95ede449b942 /fs/debugfs
parent2ec16150179888b81717d1d3ce84e634f4736af2 (diff)
downloadlinux-7c8d469877b16d2c1cecf101a0abb7b218db85bc.tar.bz2
debugfs: add support for more elaborate ->d_fsdata
Currently, the user provided fops, "real_fops", are stored directly into ->d_fsdata. In order to be able to store more per-file state and thus prepare for more granular file removal protection, wrap the real_fops into a dynamically allocated container struct, debugfs_fsdata. A struct debugfs_fsdata gets allocated at file creation and freed from the newly intoduced ->d_release(). Finally, move the implementation of debugfs_real_fops() out of the public debugfs header such that struct debugfs_fsdata's declaration can be kept private. Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/debugfs')
-rw-r--r--fs/debugfs/file.c12
-rw-r--r--fs/debugfs/inode.c22
-rw-r--r--fs/debugfs/internal.h4
3 files changed, 35 insertions, 3 deletions
diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 6dabc4a10396..b6f5ddab66bf 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -97,6 +97,18 @@ EXPORT_SYMBOL_GPL(debugfs_use_file_finish);
#define F_DENTRY(filp) ((filp)->f_path.dentry)
+const struct file_operations *debugfs_real_fops(const struct file *filp)
+ __must_hold(&debugfs_srcu)
+{
+ struct debugfs_fsdata *fsd = F_DENTRY(filp)->d_fsdata;
+ /*
+ * Neither the pointer to the struct file_operations, nor its
+ * contents ever change -- srcu_dereference() is not needed here.
+ */
+ return fsd->real_fops;
+}
+EXPORT_SYMBOL_GPL(debugfs_real_fops);
+
static int open_proxy_open(struct inode *inode, struct file *filp)
{
const struct dentry *dentry = F_DENTRY(filp);
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index c59f015f386e..a9c3d3e9af39 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -185,6 +185,11 @@ static const struct super_operations debugfs_super_operations = {
.evict_inode = debugfs_evict_inode,
};
+static void debugfs_release_dentry(struct dentry *dentry)
+{
+ kfree(dentry->d_fsdata);
+}
+
static struct vfsmount *debugfs_automount(struct path *path)
{
debugfs_automount_t f;
@@ -194,6 +199,7 @@ static struct vfsmount *debugfs_automount(struct path *path)
static const struct dentry_operations debugfs_dops = {
.d_delete = always_delete_dentry,
+ .d_release = debugfs_release_dentry,
.d_automount = debugfs_automount,
};
@@ -341,24 +347,34 @@ static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
{
struct dentry *dentry;
struct inode *inode;
+ struct debugfs_fsdata *fsd;
+
+ fsd = kmalloc(sizeof(*fsd), GFP_KERNEL);
+ if (!fsd)
+ return NULL;
if (!(mode & S_IFMT))
mode |= S_IFREG;
BUG_ON(!S_ISREG(mode));
dentry = start_creating(name, parent);
- if (IS_ERR(dentry))
+ if (IS_ERR(dentry)) {
+ kfree(fsd);
return NULL;
+ }
inode = debugfs_get_inode(dentry->d_sb);
- if (unlikely(!inode))
+ if (unlikely(!inode)) {
+ kfree(fsd);
return failed_creating(dentry);
+ }
inode->i_mode = mode;
inode->i_private = data;
inode->i_fop = proxy_fops;
- dentry->d_fsdata = (void *)real_fops;
+ fsd->real_fops = real_fops;
+ dentry->d_fsdata = fsd;
d_instantiate(dentry, inode);
fsnotify_create(d_inode(dentry->d_parent), dentry);
diff --git a/fs/debugfs/internal.h b/fs/debugfs/internal.h
index b3e8443a1f47..512601eed3ce 100644
--- a/fs/debugfs/internal.h
+++ b/fs/debugfs/internal.h
@@ -19,4 +19,8 @@ extern const struct file_operations debugfs_noop_file_operations;
extern const struct file_operations debugfs_open_proxy_file_operations;
extern const struct file_operations debugfs_full_proxy_file_operations;
+struct debugfs_fsdata {
+ const struct file_operations *real_fops;
+};
+
#endif /* _DEBUGFS_INTERNAL_H_ */