From: Yoshihiro YUNOMAE <yoshihiro.yunomae...@hitachi.com> Current tracing_saved_cmdlines_read() implementation is naive; It allocates a large buffer, constructs output data to that buffer for each read operation, and then copies a portion of the buffer to the user space buffer. This has several issues such as slow memory allocation, high CPU usage, and even corruption of the output data.
The seq_read infrastructure is made to handle this type of work. By converting it to use seq_read() the code becomes smaller, simplified, as well as correct. Link: http://lkml.kernel.org/p/20140220084431.3839.51793.stgit@yunodevel Signed-off-by: Hidehiro Kawai <hidehiro.kawai...@hitachi.com> Cc: Namhyung Kim <namhy...@kernel.org> Cc: Masami Hiramatsu <masami.hiramatsu...@hitachi.com> Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae...@hitachi.com> Cc: Frederic Weisbecker <fweis...@gmail.com> Cc: Ingo Molnar <mi...@redhat.com> Cc: linux-kernel@vger.kernel.org Signed-off-by: Steven Rostedt <rost...@goodmis.org> --- kernel/trace/trace.c | 89 +++++++++++++++++++++++++++++++--------------------- 1 file changed, 54 insertions(+), 35 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index eb228b9de170..1855dae73f34 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3699,55 +3699,74 @@ static const struct file_operations tracing_readme_fops = { .llseek = generic_file_llseek, }; -static ssize_t -tracing_saved_cmdlines_read(struct file *file, char __user *ubuf, - size_t cnt, loff_t *ppos) +static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos) { - char *buf_comm; - char *file_buf; - char *buf; - int len = 0; - int pid; - int i; + unsigned int *ptr = v; - file_buf = kmalloc(SAVED_CMDLINES*(16+TASK_COMM_LEN), GFP_KERNEL); - if (!file_buf) - return -ENOMEM; + if (*pos || m->count) + ptr++; - buf_comm = kmalloc(TASK_COMM_LEN, GFP_KERNEL); - if (!buf_comm) { - kfree(file_buf); - return -ENOMEM; - } + (*pos)++; + + for (; ptr < &map_cmdline_to_pid[SAVED_CMDLINES]; ptr++) { + if (*ptr == -1 || *ptr == NO_CMDLINE_MAP) + continue; - buf = file_buf; + return ptr; + } - for (i = 0; i < SAVED_CMDLINES; i++) { - int r; + return NULL; +} - pid = map_cmdline_to_pid[i]; - if (pid == -1 || pid == NO_CMDLINE_MAP) - continue; +static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos) +{ + void *v; + loff_t l = 0; - trace_find_cmdline(pid, buf_comm); - r = sprintf(buf, "%d %s\n", pid, buf_comm); - buf += r; - len += r; + v = &map_cmdline_to_pid[0]; + while (l <= *pos) { + v = saved_cmdlines_next(m, v, &l); + if (!v) + return NULL; } - len = simple_read_from_buffer(ubuf, cnt, ppos, - file_buf, len); + return v; +} - kfree(file_buf); - kfree(buf_comm); +static void saved_cmdlines_stop(struct seq_file *m, void *v) +{ +} - return len; +static int saved_cmdlines_show(struct seq_file *m, void *v) +{ + char buf[TASK_COMM_LEN]; + unsigned int *pid = v; + + trace_find_cmdline(*pid, buf); + seq_printf(m, "%d %s\n", *pid, buf); + return 0; +} + +static const struct seq_operations tracing_saved_cmdlines_seq_ops = { + .start = saved_cmdlines_start, + .next = saved_cmdlines_next, + .stop = saved_cmdlines_stop, + .show = saved_cmdlines_show, +}; + +static int tracing_saved_cmdlines_open(struct inode *inode, struct file *filp) +{ + if (tracing_disabled) + return -ENODEV; + + return seq_open(filp, &tracing_saved_cmdlines_seq_ops); } static const struct file_operations tracing_saved_cmdlines_fops = { - .open = tracing_open_generic, - .read = tracing_saved_cmdlines_read, - .llseek = generic_file_llseek, + .open = tracing_saved_cmdlines_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, }; static ssize_t -- 2.0.0.rc2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
