diff options
| -rw-r--r-- | fs/tracefs/event_inode.c | 22 | ||||
| -rw-r--r-- | include/linux/tracefs.h | 43 |
2 files changed, 63 insertions, 2 deletions
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 93d08e552483..8ac9abf7a3d5 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -615,7 +615,13 @@ static struct dentry *eventfs_root_lookup(struct inode *dir, entry = &ei->entries[i]; if (strcmp(name, entry->name) == 0) { void *cdata = data; - r = entry->callback(name, &mode, &cdata, &fops); + mutex_lock(&eventfs_mutex); + /* If ei->is_freed, then the event itself may be too */ + if (!ei->is_freed) + r = entry->callback(name, &mode, &cdata, &fops); + else + r = -1; + mutex_unlock(&eventfs_mutex); if (r <= 0) continue; ret = simple_lookup(dir, dentry, flags); @@ -749,7 +755,13 @@ static int dcache_dir_open_wrapper(struct inode *inode, struct file *file) void *cdata = data; entry = &ei->entries[i]; name = entry->name; - r = entry->callback(name, &mode, &cdata, &fops); + mutex_lock(&eventfs_mutex); + /* If ei->is_freed, then the event itself may be too */ + if (!ei->is_freed) + r = entry->callback(name, &mode, &cdata, &fops); + else + r = -1; + mutex_unlock(&eventfs_mutex); if (r <= 0) continue; d = create_file_dentry(ei, i, parent, name, mode, cdata, fops, false); @@ -819,6 +831,10 @@ static int dcache_readdir_wrapper(struct file *file, struct dir_context *ctx) * data = A pointer to @data, and the callback may replace it, which will * cause the file created to pass the new data to the open() call. * fops = the fops to use for the created file. + * + * NB. @callback is called while holding internal locks of the eventfs + * system. The callback must not call any code that might also call into + * the tracefs or eventfs system or it will risk creating a deadlock. */ struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode *parent, const struct eventfs_entry *entries, @@ -878,6 +894,8 @@ struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode * @data: The default data to pass to the files (an entry may override it). * * This function creates the top of the trace event directory. + * + * See eventfs_create_dir() for use of @entries. */ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry *parent, const struct eventfs_entry *entries, diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h index 13359b1a35d1..7a5fe17b6bf9 100644 --- a/include/linux/tracefs.h +++ b/include/linux/tracefs.h @@ -23,9 +23,52 @@ struct file_operations; struct eventfs_file; +/** + * eventfs_callback - A callback function to create dynamic files in eventfs + * @name: The name of the file that is to be created + * @mode: return the file mode for the file (RW access, etc) + * @data: data to pass to the created file ops + * @fops: the file operations of the created file + * + * The evetnfs files are dynamically created. The struct eventfs_entry array + * is passed to eventfs_create_dir() or eventfs_create_events_dir() that will + * be used to create the files within those directories. When a lookup + * or access to a file within the directory is made, the struct eventfs_entry + * array is used to find a callback() with the matching name that is being + * referenced (for lookups, the entire array is iterated and each callback + * will be called). + * + * The callback will be called with @name for the name of the file to create. + * The callback can return less than 1 to indicate that no file should be + * created. + * + * If a file is to be created, then @mode should be populated with the file + * mode (permissions) for which the file is created for. This would be + * used to set the created inode i_mode field. + * + * The @data should be set to the data passed to the other file operations + * (read, write, etc). Note, @data will also point to the data passed in + * to eventfs_create_dir() or eventfs_create_events_dir(), but the callback + * can replace the data if it chooses to. Otherwise, the original data + * will be used for the file operation functions. + * + * The @fops should be set to the file operations that will be used to create + * the inode. + * + * NB. This callback is called while holding internal locks of the eventfs + * system. The callback must not call any code that might also call into + * the tracefs or eventfs system or it will risk creating a deadlock. + */ typedef int (*eventfs_callback)(const char *name, umode_t *mode, void **data, const struct file_operations **fops); +/** + * struct eventfs_entry - dynamically created eventfs file call back handler + * @name: Then name of the dynamic file in an eventfs directory + * @callback: The callback to get the fops of the file when it is created + * + * See evenfs_callback() typedef for how to set up @callback. + */ struct eventfs_entry { const char *name; eventfs_callback callback; |