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Date: Mon, 26 Apr 2021 14:41:52 -0400
From: Gabriel Krisman Bertazi <krisman@...labora.com>
To: amir73il@...il.com, tytso@....edu, djwong@...nel.org
Cc: david@...morbit.com, jack@...e.com, dhowells@...hat.com,
khazhy@...gle.com, linux-fsdevel@...r.kernel.org,
linux-ext4@...r.kernel.org,
Gabriel Krisman Bertazi <krisman@...labora.com>,
kernel@...labora.com
Subject: [PATCH RFC 06/15] fanotify: Support submission through ring buffer
This adds support for the ring buffer mode in fanotify. It is enabled
by a new flag FAN_PREALLOC_QUEUE passed to fanotify_init. If this flag
is enabled, the group only allows marks that support the ring buffer
submission. In a following patch, FAN_ERROR will make use of this
mechanism.
Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
---
fs/notify/fanotify/fanotify.c | 77 +++++++++++++++++++---------
fs/notify/fanotify/fanotify_user.c | 81 ++++++++++++++++++------------
include/linux/fanotify.h | 5 +-
include/uapi/linux/fanotify.h | 1 +
4 files changed, 105 insertions(+), 59 deletions(-)
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index e3669d8a4a64..98591a8155a7 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -612,6 +612,26 @@ static struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
return event;
}
+static struct fanotify_event *fanotify_ring_get_slot(struct fsnotify_group *group,
+ u32 mask, const void *data,
+ int data_type)
+{
+ size_t size = 0;
+
+ pr_debug("%s: group=%p mask=%x size=%lu\n", __func__, group, mask, size);
+
+ return FANOTIFY_E(fsnotify_ring_alloc_event_slot(group, size));
+}
+
+static void fanotify_ring_write_event(struct fsnotify_group *group,
+ struct fanotify_event *event, u32 mask,
+ const void *data, __kernel_fsid_t *fsid)
+{
+ fanotify_init_event(group, event, 0, mask);
+
+ event->pid = get_pid(task_tgid(current));
+}
+
/*
* Get cached fsid of the filesystem containing the object from any connector.
* All connectors are supposed to have the same fsid, but we do not verify that
@@ -701,31 +721,38 @@ static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
return 0;
}
- event = fanotify_alloc_event(group, mask, data, data_type, dir,
- file_name, &fsid);
- ret = -ENOMEM;
- if (unlikely(!event)) {
- /*
- * We don't queue overflow events for permission events as
- * there the access is denied and so no event is in fact lost.
- */
- if (!fanotify_is_perm_event(mask))
- fsnotify_queue_overflow(group);
- goto finish;
- }
-
- fsn_event = &event->fse;
- ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
- if (ret) {
- /* Permission events shouldn't be merged */
- BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS);
- /* Our event wasn't used in the end. Free it. */
- fsnotify_destroy_event(group, fsn_event);
-
- ret = 0;
- } else if (fanotify_is_perm_event(mask)) {
- ret = fanotify_get_response(group, FANOTIFY_PERM(event),
- iter_info);
+ if (group->flags & FSN_SUBMISSION_RING_BUFFER) {
+ event = fanotify_ring_get_slot(group, mask, data, data_type);
+ if (IS_ERR(event))
+ return PTR_ERR(event);
+ fanotify_ring_write_event(group, event, mask, data, &fsid);
+ fsnotify_ring_commit_slot(group, &event->fse);
+ } else {
+ event = fanotify_alloc_event(group, mask, data, data_type, dir,
+ file_name, &fsid);
+ ret = -ENOMEM;
+ if (unlikely(!event)) {
+ /*
+ * We don't queue overflow events for permission events as
+ * there the access is denied and so no event is in fact lost.
+ */
+ if (!fanotify_is_perm_event(mask))
+ fsnotify_queue_overflow(group);
+ goto finish;
+ }
+ fsn_event = &event->fse;
+ ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
+ if (ret) {
+ /* Permission events shouldn't be merged */
+ BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS);
+ /* Our event wasn't used in the end. Free it. */
+ fsnotify_destroy_event(group, fsn_event);
+
+ ret = 0;
+ } else if (fanotify_is_perm_event(mask)) {
+ ret = fanotify_get_response(group, FANOTIFY_PERM(event),
+ iter_info);
+ }
}
finish:
if (fanotify_is_perm_event(mask))
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index fe605359af88..5031198bf7db 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -521,7 +521,9 @@ static ssize_t fanotify_read(struct file *file, char __user *buf,
* Permission events get queued to wait for response. Other
* events can be destroyed now.
*/
- if (!fanotify_is_perm_event(event->mask)) {
+ if (group->fanotify_data.flags & FAN_PREALLOC_QUEUE) {
+ fsnotify_ring_buffer_consume_event(group, &event->fse);
+ } else if (!fanotify_is_perm_event(event->mask)) {
fsnotify_destroy_event(group, &event->fse);
} else {
if (ret <= 0) {
@@ -587,40 +589,39 @@ static int fanotify_release(struct inode *ignored, struct file *file)
*/
fsnotify_group_stop_queueing(group);
- /*
- * Process all permission events on access_list and notification queue
- * and simulate reply from userspace.
- */
- spin_lock(&group->notification_lock);
- while (!list_empty(&group->fanotify_data.access_list)) {
- struct fanotify_perm_event *event;
-
- event = list_first_entry(&group->fanotify_data.access_list,
- struct fanotify_perm_event, fae.fse.list);
- list_del_init(&event->fae.fse.list);
- finish_permission_event(group, event, FAN_ALLOW);
+ if (!(group->flags & FSN_SUBMISSION_RING_BUFFER)) {
+ /*
+ * Process all permission events on access_list and notification queue
+ * and simulate reply from userspace.
+ */
spin_lock(&group->notification_lock);
- }
-
- /*
- * Destroy all non-permission events. For permission events just
- * dequeue them and set the response. They will be freed once the
- * response is consumed and fanotify_get_response() returns.
- */
- while (!fsnotify_notify_queue_is_empty(group)) {
- struct fanotify_event *event;
-
- event = FANOTIFY_E(fsnotify_remove_first_event(group));
- if (!(event->mask & FANOTIFY_PERM_EVENTS)) {
- spin_unlock(&group->notification_lock);
- fsnotify_destroy_event(group, &event->fse);
- } else {
- finish_permission_event(group, FANOTIFY_PERM(event),
- FAN_ALLOW);
+ while (!list_empty(&group->fanotify_data.access_list)) {
+ struct fanotify_perm_event *event;
+ event = list_first_entry(&group->fanotify_data.access_list,
+ struct fanotify_perm_event, fae.fse.list);
+ list_del_init(&event->fae.fse.list);
+ finish_permission_event(group, event, FAN_ALLOW);
+ spin_lock(&group->notification_lock);
}
- spin_lock(&group->notification_lock);
+ /*
+ * Destroy all non-permission events. For permission events just
+ * dequeue them and set the response. They will be freed once the
+ * response is consumed and fanotify_get_response() returns.
+ */
+ while (!fsnotify_notify_queue_is_empty(group)) {
+ struct fanotify_event *event;
+ event = FANOTIFY_E(fsnotify_remove_first_event(group));
+ if (!(event->mask & FANOTIFY_PERM_EVENTS)) {
+ spin_unlock(&group->notification_lock);
+ fsnotify_destroy_event(group, &event->fse);
+ } else {
+ finish_permission_event(group, FANOTIFY_PERM(event),
+ FAN_ALLOW);
+ }
+ spin_lock(&group->notification_lock);
+ }
+ spin_unlock(&group->notification_lock);
}
- spin_unlock(&group->notification_lock);
/* Response for all permission events it set, wakeup waiters */
wake_up(&group->fanotify_data.access_waitq);
@@ -981,6 +982,16 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
if (flags & FAN_NONBLOCK)
f_flags |= O_NONBLOCK;
+ if (flags & FAN_PREALLOC_QUEUE) {
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ if (flags & FAN_UNLIMITED_QUEUE)
+ return -EINVAL;
+
+ fsn_flags = FSN_SUBMISSION_RING_BUFFER;
+ }
+
/* fsnotify_alloc_group takes a ref. Dropped in fanotify_release */
group = fsnotify_alloc_user_group(&fanotify_fsnotify_ops, fsn_flags);
if (IS_ERR(group)) {
@@ -1223,6 +1234,10 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
goto fput_and_out;
}
+ if ((group->flags & FSN_SUBMISSION_RING_BUFFER) &&
+ (mask & ~FANOTIFY_SUBMISSION_BUFFER_EVENTS))
+ goto fput_and_out;
+
ret = fanotify_find_path(dfd, pathname, &path, flags,
(mask & ALL_FSNOTIFY_EVENTS), obj_type);
if (ret)
@@ -1327,7 +1342,7 @@ SYSCALL32_DEFINE6(fanotify_mark,
*/
static int __init fanotify_user_setup(void)
{
- BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 10);
+ BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 11);
BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9);
fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index 3e9c56ee651f..5a4cefb4b1c3 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -23,7 +23,8 @@
#define FANOTIFY_INIT_FLAGS (FANOTIFY_CLASS_BITS | FANOTIFY_FID_BITS | \
FAN_REPORT_TID | \
FAN_CLOEXEC | FAN_NONBLOCK | \
- FAN_UNLIMITED_QUEUE | FAN_UNLIMITED_MARKS)
+ FAN_UNLIMITED_QUEUE | FAN_UNLIMITED_MARKS | \
+ FAN_PREALLOC_QUEUE)
#define FANOTIFY_MARK_TYPE_BITS (FAN_MARK_INODE | FAN_MARK_MOUNT | \
FAN_MARK_FILESYSTEM)
@@ -71,6 +72,8 @@
FANOTIFY_PERM_EVENTS | \
FAN_Q_OVERFLOW | FAN_ONDIR)
+#define FANOTIFY_SUBMISSION_BUFFER_EVENTS 0
+
#define ALL_FANOTIFY_EVENT_BITS (FANOTIFY_OUTGOING_EVENTS | \
FANOTIFY_EVENT_FLAGS)
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index fbf9c5c7dd59..b283531549f1 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -49,6 +49,7 @@
#define FAN_UNLIMITED_QUEUE 0x00000010
#define FAN_UNLIMITED_MARKS 0x00000020
#define FAN_ENABLE_AUDIT 0x00000040
+#define FAN_PREALLOC_QUEUE 0x00000080
/* Flags to determine fanotify event format */
#define FAN_REPORT_TID 0x00000100 /* event->pid is thread id */
--
2.31.0
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