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fsnotify: Provide framework for dropping SRCU lock in ->handle_event

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fanotify wants to drop fsnotify_mark_srcu lock when waiting for response
from userspace so that the whole notification subsystem is not blocked
during that time. This patch provides a framework for safely getting
mark reference for a mark found in the object list which pins the mark
in that list. We can then drop fsnotify_mark_srcu, wait for userspace
response and then safely continue iteration of the object list once we
reaquire fsnotify_mark_srcu.

Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Jan Kara 2016-11-10 16:02:11 +01:00
parent f09b04a03e
commit abc77577a6
4 changed files with 94 additions and 0 deletions
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5
include/linux/fsnotify_backend.h
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@ -80,6 +80,7 @@ struct fsnotify_event;
struct fsnotify_mark;
struct fsnotify_event_private_data;
struct fsnotify_fname;
struct fsnotify_iter_info;
/*
* Each group much define these ops. The fsnotify infrastructure will call
@ -163,6 +164,8 @@ struct fsnotify_group {
struct fsnotify_event *overflow_event; /* Event we queue when the
* notification list is too
* full */
atomic_t user_waits; /* Number of tasks waiting for user
* response */
/* groups can define private fields here or use the void *private */
union {
@ -368,6 +371,8 @@ extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, un
extern void fsnotify_get_mark(struct fsnotify_mark *mark);
extern void fsnotify_put_mark(struct fsnotify_mark *mark);
extern void fsnotify_unmount_inodes(struct super_block *sb);
extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info);
extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info);
/* put here because inotify does some weird stuff when destroying watches */
extern void fsnotify_init_event(struct fsnotify_event *event,