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authorJan Kara <jack@suse.cz>2017-03-14 12:31:02 +0100
committerJan Kara <jack@suse.cz>2017-04-10 17:37:34 +0200
commit9dd813c15b2c101168808d4f5941a29985758973 (patch)
tree62646b8b8e4335b9d311bdcd3224d12308961c20 /fs/mount.h
parentc1f33073ac1b33510e956de7181438515e438db0 (diff)
downloadlwn-9dd813c15b2c101168808d4f5941a29985758973.tar.gz
lwn-9dd813c15b2c101168808d4f5941a29985758973.zip
fsnotify: Move mark list head from object into dedicated structure
Currently notification marks are attached to object (inode or vfsmnt) by a hlist_head in the object. The list is also protected by a spinlock in the object. So while there is any mark attached to the list of marks, the object must be pinned in memory (and thus e.g. last iput() deleting inode cannot happen). Also for list iteration in fsnotify() to work, we must hold fsnotify_mark_srcu lock so that mark itself and mark->obj_list.next cannot get freed. Thus we are required to wait for response to fanotify events from userspace process with fsnotify_mark_srcu lock held. That causes issues when userspace process is buggy and does not reply to some event - basically the whole notification subsystem gets eventually stuck. So to be able to drop fsnotify_mark_srcu lock while waiting for response, we have to pin the mark in memory and make sure it stays in the object list (as removing the mark waiting for response could lead to lost notification events for groups later in the list). However we don't want inode reclaim to block on such mark as that would lead to system just locking up elsewhere. This commit is the first in the series that paves way towards solving these conflicting lifetime needs. Instead of anchoring the list of marks directly in the object, we anchor it in a dedicated structure (fsnotify_mark_connector) and just point to that structure from the object. The following commits will also add spinlock protecting the list and object pointer to the structure. Reviewed-by: Miklos Szeredi <mszeredi@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/mount.h')
-rw-r--r--fs/mount.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/mount.h b/fs/mount.h
index 2826543a131d..bc409360a03b 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -59,7 +59,7 @@ struct mount {
struct mountpoint *mnt_mp; /* where is it mounted */
struct hlist_node mnt_mp_list; /* list mounts with the same mountpoint */
#ifdef CONFIG_FSNOTIFY
- struct hlist_head mnt_fsnotify_marks;
+ struct fsnotify_mark_connector *mnt_fsnotify_marks;
__u32 mnt_fsnotify_mask;
#endif
int mnt_id; /* mount identifier */