kernfs: add kernfs_ops->open/release() callbacks
Add ->open/release() methods to kernfs_ops. ->open() is called when
the file is opened and ->release() when the file is either released or
severed. These callbacks can be used, for example, to manage
persistent caching objects over multiple seq_file iterations.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Acked-by: Zefan Li <lizefan@huawei.com>
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index d0b6fb1..20c3962 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -708,7 +708,8 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
if (error)
goto err_free;
- ((struct seq_file *)file->private_data)->private = of;
+ of->seq_file = file->private_data;
+ of->seq_file->private = of;
/* seq_file clears PWRITE unconditionally, restore it if WRITE */
if (file->f_mode & FMODE_WRITE)
@@ -717,13 +718,22 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
/* make sure we have open node struct */
error = kernfs_get_open_node(kn, of);
if (error)
- goto err_close;
+ goto err_seq_release;
+
+ if (ops->open) {
+ /* nobody has access to @of yet, skip @of->mutex */
+ error = ops->open(of);
+ if (error)
+ goto err_put_node;
+ }
/* open succeeded, put active references */
kernfs_put_active(kn);
return 0;
-err_close:
+err_put_node:
+ kernfs_put_open_node(kn, of);
+err_seq_release:
seq_release(inode, file);
err_free:
kfree(of->prealloc_buf);
@@ -733,11 +743,32 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
return error;
}
+/* used from release/drain to ensure that ->release() is called exactly once */
+static void kernfs_release_file(struct kernfs_node *kn,
+ struct kernfs_open_file *of)
+{
+ if (!(kn->flags & KERNFS_HAS_RELEASE))
+ return;
+
+ mutex_lock(&of->mutex);
+ if (!of->released) {
+ /*
+ * A file is never detached without being released and we
+ * need to be able to release files which are deactivated
+ * and being drained. Don't use kernfs_ops().
+ */
+ kn->attr.ops->release(of);
+ of->released = true;
+ }
+ mutex_unlock(&of->mutex);
+}
+
static int kernfs_fop_release(struct inode *inode, struct file *filp)
{
struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;
struct kernfs_open_file *of = kernfs_of(filp);
+ kernfs_release_file(kn, of);
kernfs_put_open_node(kn, of);
seq_release(inode, filp);
kfree(of->prealloc_buf);
@@ -746,12 +777,12 @@ static int kernfs_fop_release(struct inode *inode, struct file *filp)
return 0;
}
-void kernfs_unmap_bin_file(struct kernfs_node *kn)
+void kernfs_drain_open_files(struct kernfs_node *kn)
{
struct kernfs_open_node *on;
struct kernfs_open_file *of;
- if (!(kn->flags & KERNFS_HAS_MMAP))
+ if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
return;
spin_lock_irq(&kernfs_open_node_lock);
@@ -763,10 +794,16 @@ void kernfs_unmap_bin_file(struct kernfs_node *kn)
return;
mutex_lock(&kernfs_open_file_mutex);
+
list_for_each_entry(of, &on->files, list) {
struct inode *inode = file_inode(of->file);
- unmap_mapping_range(inode->i_mapping, 0, 0, 1);
+
+ if (kn->flags & KERNFS_HAS_MMAP)
+ unmap_mapping_range(inode->i_mapping, 0, 0, 1);
+
+ kernfs_release_file(kn, of);
}
+
mutex_unlock(&kernfs_open_file_mutex);
kernfs_put_open_node(kn, NULL);
@@ -965,6 +1002,8 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
kn->flags |= KERNFS_HAS_SEQ_SHOW;
if (ops->mmap)
kn->flags |= KERNFS_HAS_MMAP;
+ if (ops->release)
+ kn->flags |= KERNFS_HAS_RELEASE;
rc = kernfs_add_one(kn);
if (rc) {