Fix: f_count replaced with f_ref in Linux 6.13.0-rc1

See upstream commit 90ee6ed776c06435a3fe79c7f5344761f52e1760:

    commit 90ee6ed776c06435a3fe79c7f5344761f52e1760
    Author: Christian Brauner <brauner@kernel.org>
    Date:   Mon Oct 7 16:23:59 2024 +0200

        fs: port files to file_ref

        Port files to rely on file_ref reference to improve scaling and gain
        overflow protection.

        - We continue to WARN during get_file() in case a file that is already
          marked dead is revived as get_file() is only valid if the caller
          already holds a reference to the file. This hasn't changed just the
          check changes.

        - The semantics for epoll and ttm's dmabuf usage have changed. Both
          epoll and ttm synchronize with __fput() to prevent the underlying file
          from beeing freed.

Change-Id: I9f376af50835f15f74ff7fc82bdb752e09f77222
Signed-off-by: Kienan Stewart <kstewart@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/include/wrapper/file_ref.h b/include/wrapper/file_ref.h
new file mode 100644 (file)
index 0000000..fd2b123
--- /dev/null
+++ b/include/wrapper/file_ref.h
@@ -0,0 +1,43 @@
+/*
+ * SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
+ * SPDX-FileCopyrightText: 2024 Kienan Stewart <kstewart@efficios.com>
+ */
+
+#ifndef LTTNG_WRAPPER_FILE_REF_H
+#define LTTNG_WRAPPER_FILE_REF_H
+
+#include <linux/file.h>
+#include <lttng/kernel-version.h>
+
+#if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(6,13,0))
+#include <linux/file_ref.h>
+
+static inline __must_check
+bool lttng_file_ref_get(struct file *file)
+{
+       return file_ref_get(&file->f_ref);
+}
+
+static inline
+bool lttng_file_ref_put(struct file *file)
+{
+       /* This is __must_check */
+       return file_ref_put(&file->f_ref);
+}
+
+#else
+static inline __must_check
+bool lttng_file_ref_get(struct file *file)
+{
+       atomic_long_add_unless(&file->f_count, 1, LONG_MAX);
+       return true;
+}
+
+static inline
+bool lttng_file_ref_put(struct file *file)
+{
+       atomic_long_dec(&file->f_count);
+       return true;
+}
+#endif
+#endif /* LTTNG_WRAPPER_FILE_REF_H */

diff --git a/src/lttng-abi.c b/src/lttng-abi.c
index b66d434f8216dcb9156adba814e229a620970bf7..c708c0d28f471375a80fcf0b7ffd2d6d69aa3114 100644 (file)
--- a/src/lttng-abi.c
+++ b/src/lttng-abi.c
@@ -35,6 +35,7 @@
 #include <ringbuffer/backend.h>
 #include <ringbuffer/frontend.h>
 #include <wrapper/compiler_attributes.h>
+#include <wrapper/file_ref.h>
 #include <wrapper/poll.h>
 #include <wrapper/file.h>
 #include <wrapper/kref.h>
@@ -543,7 +544,7 @@ int lttng_abi_create_channel(struct file *session_file,
                transport_name = "<unknown>";
                break;
        }
-       if (!atomic_long_add_unless(&session_file->f_count, 1, LONG_MAX)) {
+       if (!lttng_file_ref_get(session_file)) {
                ret = -EOVERFLOW;
                goto refcount_error;
        }
@@ -568,7 +569,7 @@ int lttng_abi_create_channel(struct file *session_file,
        return chan_fd;
 
 chan_error:
-       atomic_long_dec(&session_file->f_count);
+       lttng_file_ref_put(session_file);
 refcount_error:
        fput(chan_file);
 file_error:
@@ -1740,7 +1741,7 @@ int lttng_abi_open_event_notifier_group_stream(struct file *notif_file)
                return -ENOENT;
 
        /* The event_notifier notification fd holds a reference on the event_notifier group */
-       if (!atomic_long_add_unless(&notif_file->f_count, 1, LONG_MAX)) {
+       if (!lttng_file_ref_get(notif_file)) {
                ret = -EOVERFLOW;
                goto refcount_error;
        }
@@ -1755,7 +1756,7 @@ int lttng_abi_open_event_notifier_group_stream(struct file *notif_file)
        return ret;
 
 fd_error:
-       atomic_long_dec(&notif_file->f_count);
+       lttng_file_ref_put(notif_file);
 refcount_error:
        event_notifier_group->ops->priv->buffer_read_close(buf);
        return ret;
@@ -1881,7 +1882,7 @@ int lttng_abi_create_event(struct file *channel_file,
                goto file_error;
        }
        /* The event holds a reference on the channel */
-       if (!atomic_long_add_unless(&channel_file->f_count, 1, LONG_MAX)) {
+       if (!lttng_file_ref_get(channel_file)) {
                ret = -EOVERFLOW;
                goto refcount_error;
        }
@@ -1947,7 +1948,7 @@ int lttng_abi_create_event(struct file *channel_file,
        return event_fd;
 
 event_error:
-       atomic_long_dec(&channel_file->f_count);
+       lttng_file_ref_put(channel_file);
 refcount_error:
        fput(event_file);
 file_error:
@@ -2109,7 +2110,7 @@ int lttng_abi_create_event_notifier(struct file *event_notifier_group_file,
        }
 
        /* The event notifier holds a reference on the event notifier group. */
-       if (!atomic_long_add_unless(&event_notifier_group_file->f_count, 1, LONG_MAX)) {
+       if (!lttng_file_ref_get(event_notifier_group_file)) {
                ret = -EOVERFLOW;
                goto refcount_error;
        }
@@ -2184,7 +2185,7 @@ int lttng_abi_create_event_notifier(struct file *event_notifier_group_file,
        return event_notifier_fd;
 
 event_notifier_error:
-       atomic_long_dec(&event_notifier_group_file->f_count);
+       lttng_file_ref_put(event_notifier_group_file);
 refcount_error:
        fput(event_notifier_file);
 file_error:
@@ -2257,7 +2258,7 @@ long lttng_abi_event_notifier_group_create_error_counter(
 
        counter_len = error_counter_conf->dimensions[0].size;
 
-       if (!atomic_long_add_unless(&event_notifier_group_file->f_count, 1, LONG_MAX)) {
+       if (!lttng_file_ref_get(event_notifier_group_file)) {
                ret = -EOVERFLOW;
                goto refcount_error;
        }
@@ -2289,7 +2290,7 @@ long lttng_abi_event_notifier_group_create_error_counter(
        return counter_fd;
 
 counter_error:
-       atomic_long_dec(&event_notifier_group_file->f_count);
+       lttng_file_ref_put(event_notifier_group_file);
 refcount_error:
        fput(counter_file);
 file_error:

diff --git a/src/lttng-events.c b/src/lttng-events.c
index e3ce3e746a1c2997e2bea77a222590d0ab1f38e1..a3ffd1e4a11fb67588e0d6601097f42529e8ea03 100644 (file)
--- a/src/lttng-events.c
+++ b/src/lttng-events.c
@@ -29,6 +29,7 @@
 #include <linux/dmi.h>
 
 #include <wrapper/compiler_attributes.h>
+#include <wrapper/file_ref.h>
 #include <wrapper/uuid.h>
 #include <wrapper/vmalloc.h>   /* for wrapper_vmalloc_sync_mappings() */
 #include <wrapper/random.h>
@@ -1948,7 +1949,7 @@ int lttng_session_list_tracker_ids(struct lttng_kernel_session *session,
                ret = PTR_ERR(tracker_ids_list_file);
                goto file_error;
        }
-       if (!atomic_long_add_unless(&session->priv->file->f_count, 1, LONG_MAX)) {
+       if (!lttng_file_ref_get(session->priv->file)) {
                ret = -EOVERFLOW;
                goto refcount_error;
        }
@@ -1964,7 +1965,7 @@ int lttng_session_list_tracker_ids(struct lttng_kernel_session *session,
        return file_fd;
 
 open_error:
-       atomic_long_dec(&session->priv->file->f_count);
+       lttng_file_ref_put(session->priv->file);
 refcount_error:
        fput(tracker_ids_list_file);
 file_error: