On Wed, 01 Nov 2023 13:25:49 -0400 Steven Rostedt <rost...@goodmis.org> wrote:
> From: "Steven Rostedt (Google)" <rost...@goodmis.org> > > Looking at how dentry is removed via the tracefs system, I found that > eventfs does not do everything that it did under tracefs. The tracefs > removal of a dentry calls simple_recursive_removal() that does a lot more > than a simple d_invalidate(). > > As it should be a requirement that any eventfs_inode that has a dentry, so > does its parent. When removing a eventfs_inode, if it has a dentry, a call > to simple_recursive_removal() on that dentry should clean up all the > dentries underneath it. > > Add WARN_ON_ONCE() to check for the parent having a dentry if any children > do. This looks good to me. Reviewed-by: Masami Hiramatsu (Google) <mhira...@kernel.org> Thanks, > > Link: https://lore.kernel.org/all/20231101022553.GE1957730@ZenIV/ > > Cc: sta...@vger.kernel.org > Cc: Al Viro <v...@zeniv.linux.org.uk> > Fixes: 5bdcd5f5331a2 ("eventfs: Implement removal of meta data from eventfs") > Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org> > --- > Changes since the last patch: > https://lore.kernel.org/linux-trace-kernel/20231031144703.71eef...@gandalf.local.home > > - Was originally called: eventfs: Process deletion of dentry more thoroughly > > - Al Viro pointed out that I could use simple_recursive_removal() instead. > I had originally thought that I could not, but looking deeper into it, > and realizing that if a dentry exists on any eventfs_inode, then all > the parent eventfs_inode of that would als have a dentry. Hence, calling > simple_recursive_removal() on the top dentry would clean up all the > children dentries as well. Doing it his way cleans up the code quite > a bit! > > fs/tracefs/event_inode.c | 77 +++++++++++++++++++++++----------------- > fs/tracefs/internal.h | 2 -- > 2 files changed, 44 insertions(+), 35 deletions(-) > > diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c > index 0087a3f455f1..f8a594a50ae6 100644 > --- a/fs/tracefs/event_inode.c > +++ b/fs/tracefs/event_inode.c > @@ -967,30 +967,29 @@ static void unhook_dentry(struct dentry *dentry) > { > if (!dentry) > return; > - > - /* Keep the dentry from being freed yet (see eventfs_workfn()) */ > + /* > + * Need to add a reference to the dentry that is expected by > + * simple_recursive_removal(), which will include a dput(). > + */ > dget(dentry); > > - dentry->d_fsdata = NULL; > - d_invalidate(dentry); > - mutex_lock(&eventfs_mutex); > - /* dentry should now have at least a single reference */ > - WARN_ONCE((int)d_count(dentry) < 1, > - "dentry %px (%s) less than one reference (%d) after > invalidate\n", > - dentry, dentry->d_name.name, d_count(dentry)); > - mutex_unlock(&eventfs_mutex); > + /* > + * Also add a reference for the dput() in eventfs_workfn(). > + * That is required as that dput() will free the ei after > + * the SRCU grace period is over. > + */ > + dget(dentry); > } > > /** > * eventfs_remove_rec - remove eventfs dir or file from list > * @ei: eventfs_inode to be removed. > - * @head: the list head to place the deleted @ei and children > * @level: prevent recursion from going more than 3 levels deep. > * > * This function recursively removes eventfs_inodes which > * contains info of files and/or directories. > */ > -static void eventfs_remove_rec(struct eventfs_inode *ei, struct list_head > *head, int level) > +static void eventfs_remove_rec(struct eventfs_inode *ei, int level) > { > struct eventfs_inode *ei_child; > > @@ -1009,13 +1008,26 @@ static void eventfs_remove_rec(struct eventfs_inode > *ei, struct list_head *head, > /* search for nested folders or files */ > list_for_each_entry_srcu(ei_child, &ei->children, list, > lockdep_is_held(&eventfs_mutex)) { > - eventfs_remove_rec(ei_child, head, level + 1); > + /* Children only have dentry if parent does */ > + WARN_ON_ONCE(ei_child->dentry && !ei->dentry); > + eventfs_remove_rec(ei_child, level + 1); > } > > + > ei->is_freed = 1; > > + for (int i = 0; i < ei->nr_entries; i++) { > + if (ei->d_children[i]) { > + /* Children only have dentry if parent does */ > + WARN_ON_ONCE(!ei->dentry); > + unhook_dentry(ei->d_children[i]); > + } > + } > + > + unhook_dentry(ei->dentry); > + > list_del_rcu(&ei->list); > - list_add_tail(&ei->del_list, head); > + call_srcu(&eventfs_srcu, &ei->rcu, free_rcu_ei); > } > > /** > @@ -1026,30 +1038,22 @@ static void eventfs_remove_rec(struct eventfs_inode > *ei, struct list_head *head, > */ > void eventfs_remove_dir(struct eventfs_inode *ei) > { > - struct eventfs_inode *tmp; > - LIST_HEAD(ei_del_list); > + struct dentry *dentry; > > if (!ei) > return; > > - /* > - * Move the deleted eventfs_inodes onto the ei_del_list > - * which will also set the is_freed value. Note, this has to be > - * done under the eventfs_mutex, but the deletions of > - * the dentries must be done outside the eventfs_mutex. > - * Hence moving them to this temporary list. > - */ > mutex_lock(&eventfs_mutex); > - eventfs_remove_rec(ei, &ei_del_list, 0); > + dentry = ei->dentry; > + eventfs_remove_rec(ei, 0); > mutex_unlock(&eventfs_mutex); > > - list_for_each_entry_safe(ei, tmp, &ei_del_list, del_list) { > - for (int i = 0; i < ei->nr_entries; i++) > - unhook_dentry(ei->d_children[i]); > - unhook_dentry(ei->dentry); > - list_del(&ei->del_list); > - call_srcu(&eventfs_srcu, &ei->rcu, free_rcu_ei); > - } > + /* > + * If any of the ei children has a dentry, then the ei itself > + * must have a dentry. > + */ > + if (dentry) > + simple_recursive_removal(dentry, NULL); > } > > /** > @@ -1060,10 +1064,17 @@ void eventfs_remove_dir(struct eventfs_inode *ei) > */ > void eventfs_remove_events_dir(struct eventfs_inode *ei) > { > - struct dentry *dentry = ei->dentry; > + struct dentry *dentry; > > + dentry = ei->dentry; > eventfs_remove_dir(ei); > > - /* Matches the dget() from eventfs_create_events_dir() */ > + /* > + * Matches the dget() done by tracefs_start_creating() > + * in eventfs_create_events_dir() when it the dentry was > + * created. In other words, it's a normal dentry that > + * sticks around while the other ei->dentry are created > + * and destroyed dynamically. > + */ > dput(dentry); > } > diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h > index 06a1f220b901..ccee18ca66c7 100644 > --- a/fs/tracefs/internal.h > +++ b/fs/tracefs/internal.h > @@ -55,12 +55,10 @@ struct eventfs_inode { > /* > * Union - used for deletion > * @llist: for calling dput() if needed after RCU > - * @del_list: list of eventfs_inode to delete > * @rcu: eventfs_inode to delete in RCU > */ > union { > struct llist_node llist; > - struct list_head del_list; > struct rcu_head rcu; > }; > unsigned int is_freed:1; > -- > 2.42.0 -- Masami Hiramatsu (Google) <mhira...@kernel.org>
