Re: [PATCH 5/6] eventfs: get rid of dentry pointers without refcounts
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2024-01-30 20:55:39
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On Tue, 30 Jan 2024 11:03:54 -0800 Linus Torvalds [off-list ref] wrote:
-static void free_ei(struct eventfs_inode *ei)
+static inline struct eventfs_inode *alloc_ei(const char *name)
{
- kfree_const(ei->name);
- kfree(ei->d_children);
- kfree(ei->entry_attrs);
- kfree(ei);
+ int namesize = strlen(name) + 1;
+ struct eventfs_inode *ei = kzalloc(sizeof(*ei) + namesize, GFP_KERNEL);
+
+ if (ei) {
+ memcpy((char *)ei->name, name, namesize);
+ kref_init(&ei->kref);
+ }I'm going to be putting back the ei->name pointer as the above actually adds more memory usage. The reason being is that all static trace events (not kprobes or other dynamic events) are created with the TRACE_EVENT() macro that points to a constant name. Passing in a const to kstrdup_const() checks if the name passed in is a constant or not. If it is, it doesn't allocate the name and just passes back the pointer. Removing the pointer to "name" removed 8 bytes on 64 bit machines from the eventfs_inode structure, but added strlen(name)+1 bytes to it, where the majority of trace event names are greater than 8 bytes, and are constant strings. Another reason for converting back to the way it was is I have moving the ei allocation to a slab on my TODO list. -- Steve
+ return ei; }
quoted hunk ↗ jump to hunk
diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h index 8f38740bfb5b..72db3bdc4dfb 100644 --- a/fs/tracefs/internal.h +++ b/fs/tracefs/internal.h@@ -34,8 +34,7 @@ struct eventfs_attr { * @entries: the array of entries representing the files in the directory * @name: the name of the directory to create * @children: link list into the child eventfs_inode - * @dentry: the dentry of the directory - * @d_children: The array of dentries to represent the files when created + * @events_dir: the dentry of the events directory * @entry_attrs: Saved mode and ownership of the @d_children * @attr: Saved mode and ownership of eventfs_inode itself * @data: The private data to pass to the callbacks@@ -44,12 +43,11 @@ struct eventfs_attr { * @nr_entries: The number of items in @entries */ struct eventfs_inode { + struct kref kref; struct list_head list; const struct eventfs_entry *entries; - const char *name; struct list_head children; - struct dentry *dentry; /* Check is_freed to access */ - struct dentry **d_children; + struct dentry *events_dir; struct eventfs_attr *entry_attrs; struct eventfs_attr attr; void *data;@@ -66,6 +64,7 @@ struct eventfs_inode { struct llist_node llist; struct rcu_head rcu; }; + const char name[]; }; static inline struct tracefs_inode *get_tracefs(const struct inode *inode)