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debugfs: add support for more elaborate ->d_fsdata

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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>
This commit is contained in:
Nicolai Stange 2017-10-31 00:15:47 +01:00 • committed by Greg Kroah-Hartman
parent 2ec1615017
commit 7c8d469877
4 changed files with 38 additions and 20 deletions
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22
fs/debugfs/inode.c
View file

@ -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);