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kernfs: add kernfs_ops->open/release() callbacks

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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>
This commit is contained in:
Tejun Heo
2016-12-27 14:49:03 -05:00
parent a1d82aff5d
commit 0e67db2f9f
4 changed files with 57 additions and 8 deletions
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10
include/linux/kernfs.h
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@@ -46,6 +46,7 @@ enum kernfs_node_flag {
KERNFS_SUICIDAL = 0x0400,
KERNFS_SUICIDED = 0x0800,
KERNFS_EMPTY_DIR = 0x1000,
KERNFS_HAS_RELEASE = 0x2000,
};
/* @flags for kernfs_create_root() */
@@ -175,6 +176,7 @@ struct kernfs_open_file {
/* published fields */
struct kernfs_node *kn;
struct file *file;
struct seq_file *seq_file;
void *priv;
/* private fields, do not use outside kernfs proper */
@@ -186,10 +188,18 @@ struct kernfs_open_file {
size_t atomic_write_len;
bool mmapped:1;
bool released:1;
const struct vm_operations_struct *vm_ops;
};
struct kernfs_ops {
/*
* Optional open/release methods. Both are called with
* @of->seq_file populated.
*/
int (*open)(struct kernfs_open_file *of);
void (*release)(struct kernfs_open_file *of);
/*
* Read is handled by either seq_file or raw_read().
*