On 2024/11/1 19:08, Andrii Nakryiko wrote:
On Tue, Oct 29, 2024 at 5:17 PM Juntong Deng <juntong.deng@xxxxxxxxxxx> wrote:
This patch adds struct file related CRIB kfuncs.
bpf_fget_task() is used to get a pointer to the struct file
corresponding to the task file descriptor. Note that this function
acquires a reference to struct file.
bpf_get_file_ops_type() is used to determine what exactly this file
is based on the file operations, such as socket, eventfd, timerfd,
pipe, etc, in order to perform different checkpoint/restore processing
for different file types. This function currently has only one return
value, FILE_OPS_UNKNOWN, but will increase with the file types that
CRIB supports for checkpoint/restore.
Signed-off-by: Juntong Deng <juntong.deng@xxxxxxxxxxx>
---
kernel/bpf/crib/crib.c | 4 ++++
kernel/bpf/crib/files.c | 44 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 48 insertions(+)
Please CC Christian Brauner and fs mailing list
(linux-fsdevel@xxxxxxxxxxxxxxx, both cc'ed) on changes like this (this
entire patch set)
Thanks for your reply!
I will CC Christian Brauner and fs mailing list in the next
patch series.
diff --git a/kernel/bpf/crib/crib.c b/kernel/bpf/crib/crib.c
index e6536ee9a845..78ddd19d5693 100644
--- a/kernel/bpf/crib/crib.c
+++ b/kernel/bpf/crib/crib.c
@@ -14,6 +14,10 @@ BTF_ID_FLAGS(func, bpf_iter_task_file_next, KF_ITER_NEXT | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_iter_task_file_get_fd)
BTF_ID_FLAGS(func, bpf_iter_task_file_destroy, KF_ITER_DESTROY)
+BTF_ID_FLAGS(func, bpf_fget_task, KF_ACQUIRE | KF_TRUSTED_ARGS | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_get_file_ops_type, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_put_file, KF_RELEASE)
+
BTF_KFUNCS_END(bpf_crib_kfuncs)
static const struct btf_kfunc_id_set bpf_crib_kfunc_set = {
diff --git a/kernel/bpf/crib/files.c b/kernel/bpf/crib/files.c
index ececf150303f..8e0e29877359 100644
--- a/kernel/bpf/crib/files.c
+++ b/kernel/bpf/crib/files.c
@@ -5,6 +5,14 @@
#include <linux/fdtable.h>
#include <linux/net.h>
+/**
+ * This enum will grow with the file types that CRIB supports for
+ * checkpoint/restore.
+ */
+enum {
+ FILE_OPS_UNKNOWN = 0
+};
+
struct bpf_iter_task_file {
__u64 __opaque[3];
} __aligned(8);
@@ -102,4 +110,40 @@ __bpf_kfunc void bpf_iter_task_file_destroy(struct bpf_iter_task_file *it)
fput(kit->file);
}
+/**
+ * bpf_fget_task() - Get a pointer to the struct file corresponding to
+ * the task file descriptor
+ *
+ * Note that this function acquires a reference to struct file.
+ *
+ * @task: the specified struct task_struct
+ * @fd: the file descriptor
+ *
+ * @returns the corresponding struct file pointer if found,
+ * otherwise returns NULL
+ */
+__bpf_kfunc struct file *bpf_fget_task(struct task_struct *task, unsigned int fd)
+{
+ struct file *file;
+
+ file = fget_task(task, fd);
+ return file;
+}
+
+/**
+ * bpf_get_file_ops_type() - Determine what exactly this file is based on
+ * the file operations, such as socket, eventfd, timerfd, pipe, etc
+ *
+ * This function will grow with the file types that CRIB supports for
+ * checkpoint/restore.
+ *
+ * @file: a pointer to the struct file
+ *
+ * @returns the file operations type
+ */
+__bpf_kfunc unsigned int bpf_get_file_ops_type(struct file *file)
+{
+ return FILE_OPS_UNKNOWN;
+}
+
this is not very supportable, users can do the same by accessing
file->f_op and comparing it to a set of known struct file_operations
references.
Yes, users can access file->f_op, but there seems to be no way for
users to get references to struct file_operations for the various file
types? For example, how does a user get a reference to socket_file_ops?
Also, currently the struct file_operations for most of the file types
are static, and I cannot even get a reference to them in
crib/files.c directly.
My future plan is to add functions like is_socket_file_ops to the
corresponding files (e.g. net/socket.c).
__bpf_kfunc_end_defs();
--
2.39.5
