Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | [PATCH printk v4 7/8] printk: use printk_buffers for devkmsg | Date | Thu, 5 Jan 2023 11:43:34 +0106 |
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Replace the individual @text_buf and @buf buffers in struct devkmsg_user with a struct printk_buffers. This reduces the number of buffers to keep track of. Also, since @text_buf is only used for ringbuffer reading and @buf is only used for output, it maps perfectly to the purpose and fields of struct printk_buffers.
As a side-effect, @text_buf was 8kB large, even though it only needed to be the max size of a ringbuffer record. By switching to struct printk_buffers, ~7kB less memory is allocated when opening /dev/kmsg.
And since struct printk_buffers will be used now, reduce duplicate code by calling printk_get_next_message() to handle the record reading and formatting.
Signed-off-by: John Ogness <john.ogness@linutronix.de> --- kernel/printk/printk.c | 32 ++++++++++++++------------------ 1 file changed, 14 insertions(+), 18 deletions(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 4fb7d29fb05d..e28a3736a399 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -695,15 +695,16 @@ static ssize_t msg_print_ext_body(char *buf, size_t size, return len; } +static bool printk_get_next_message(struct printk_message *pmsg, u64 seq, bool is_extended); + /* /dev/kmsg - userspace message inject/listen interface */ struct devkmsg_user { atomic64_t seq; struct ratelimit_state rs; struct mutex lock; - char buf[CONSOLE_EXT_LOG_MAX]; + struct printk_buffers pbufs; struct printk_info info; - char text_buf[CONSOLE_EXT_LOG_MAX]; struct printk_record record; }; @@ -787,7 +788,10 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, { struct devkmsg_user *user = file->private_data; struct printk_record *r = &user->record; - size_t len; + char *outbuf = &user->pbufs.outbuf[0]; + struct printk_message pmsg = { + .pbufs = &user->pbufs, + }; ssize_t ret; if (!user) @@ -797,7 +801,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, if (ret) return ret; - if (!prb_read_valid(prb, atomic64_read(&user->seq), r)) { + if (!printk_get_next_message(&pmsg, atomic64_read(&user->seq), true)) { if (file->f_flags & O_NONBLOCK) { ret = -EAGAIN; goto out; @@ -820,30 +824,25 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, goto out; } - if (r->info->seq != atomic64_read(&user->seq)) { + if (pmsg.dropped) { /* our last seen message is gone, return error and reset */ - atomic64_set(&user->seq, r->info->seq); + atomic64_set(&user->seq, pmsg.seq); ret = -EPIPE; goto out; } - len = info_print_ext_header(user->buf, sizeof(user->buf), r->info); - len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len, - &r->text_buf[0], r->info->text_len, - &r->info->dev_info); - - atomic64_set(&user->seq, r->info->seq + 1); + atomic64_set(&user->seq, pmsg.seq + 1); - if (len > count) { + if (pmsg.outbuf_len > count) { ret = -EINVAL; goto out; } - if (copy_to_user(buf, user->buf, len)) { + if (copy_to_user(buf, outbuf, pmsg.outbuf_len)) { ret = -EFAULT; goto out; } - ret = len; + ret = pmsg.outbuf_len; out: mutex_unlock(&user->lock); return ret; @@ -937,9 +936,6 @@ static int devkmsg_open(struct inode *inode, struct file *file) mutex_init(&user->lock); - prb_rec_init_rd(&user->record, &user->info, - &user->text_buf[0], sizeof(user->text_buf)); - atomic64_set(&user->seq, prb_first_valid_seq(prb)); file->private_data = user; -- 2.30.2
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