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blktrace: use rbuf->stats.full as a drop indicator in relayfs

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Replace internal subbuf_start in blktrace with the default policy in
relayfs.

Remove dropped field from struct blktrace.  Correspondingly, call the
common helper in relay.  By incrementing full_count to keep track of how
many times we encountered a full buffer issue, user space will know how
many events were lost.

Link: https://lkml.kernel.org/r/20250612061201.34272-5-kerneljasonxing@gmail.com
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Yushan Zhou <katrinzhou@tencent.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Jason Xing 2025-06-12 14:12:00 +08:00 • committed by Andrew Morton
parent a53202ce7f
commit 7f2173894f
1 changed files with 2 additions and 20 deletions
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22
kernel/trace/blktrace.c
View file

@ -415,9 +415,10 @@ static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
size_t count, loff_t *ppos)
{
struct blk_trace *bt = filp->private_data;
size_t dropped = relay_stats(bt->rchan, RELAY_STATS_BUF_FULL);
char buf[16];
snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));
snprintf(buf, sizeof(buf), "%zu\n", dropped);
return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
}
@ -456,23 +457,6 @@ static const struct file_operations blk_msg_fops = {
.llseek = noop_llseek,
};
/*
* Keep track of how many times we encountered a full subbuffer, to aid
* the user space app in telling how many lost events there were.
*/
static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
void *prev_subbuf)
{
struct blk_trace *bt;
if (!relay_buf_full(buf))
return 1;
bt = buf->chan->private_data;
atomic_inc(&bt->dropped);
return 0;
}
static int blk_remove_buf_file_callback(struct dentry *dentry)
{
debugfs_remove(dentry);
@ -491,7 +475,6 @@ static struct dentry *blk_create_buf_file_callback(const char *filename,
}
static const struct rchan_callbacks blk_relay_callbacks = {
.subbuf_start = blk_subbuf_start_callback,
.create_buf_file = blk_create_buf_file_callback,
.remove_buf_file = blk_remove_buf_file_callback,
};
@ -580,7 +563,6 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
}
bt->dev = dev;
atomic_set(&bt->dropped, 0);
INIT_LIST_HEAD(&bt->running_list);
ret = -EIO;