[PATCH v2 4/4] relayfs: support a counter tracking if data is too big to write
From: Jason Xing <hidden>
Date: 2025-05-15 06:17:54
Also in:
linux-block, lkml
Subsystem:
relay, the rest · Maintainers:
Andrew Morton, Jens Axboe, Jason Xing, Linus Torvalds
From: Jason Xing <kernelxing@tencent.com> It really doesn't matter if the user/admin knows what the last too big value is. Record how many times this case is triggered would be helpful. Solve the existing issue where relay_reset() doesn't restore the value. Store the counter in the per-cpu buffer structure instead of the global buffer structure. It also solves the racy condition which is likely to happen when a few of per-cpu buffers encounter the too big data case and then access the global field last_toobig without lock protection. Remove the printk in relay_close() since kernel module can directly call relay_dump() as they want. Reviewed-by: Yushan Zhou <redacted> Signed-off-by: Jason Xing <kernelxing@tencent.com> --- include/linux/relay.h | 5 +++-- kernel/relay.c | 12 ++++++------ 2 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/include/linux/relay.h b/include/linux/relay.h
index 3fb285716e34..08c1888c9c1a 100644
--- a/include/linux/relay.h
+++ b/include/linux/relay.h@@ -33,13 +33,15 @@ */ enum { RELAY_DUMP_BUF_FULL = (1 << 0), + RELAY_DUMP_WRT_BIG = (1 << 1), - RELAY_DUMP_LAST = RELAY_DUMP_BUF_FULL, + RELAY_DUMP_LAST = RELAY_DUMP_WRT_BIG, }; struct rchan_buf_stats { unsigned int full_count; /* counter for buffer full */ + unsigned int big_count; /* counter for too big to write */ }; /*
@@ -79,7 +81,6 @@ struct rchan const struct rchan_callbacks *cb; /* client callbacks */ struct kref kref; /* channel refcount */ void *private_data; /* for user-defined data */ - size_t last_toobig; /* tried to log event > subbuf size */ struct rchan_buf * __percpu *buf; /* per-cpu channel buffers */ int is_global; /* One global buffer ? */ struct list_head list; /* for channel list */
diff --git a/kernel/relay.c b/kernel/relay.c
index f47fc750e559..f4d1dcac164a 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c@@ -304,6 +304,7 @@ static void __relay_reset(struct rchan_buf *buf, unsigned int init) buf->data = buf->start; buf->offset = 0; buf->stats.full_count = 0; + buf->stats.big_count = 0; for (i = 0; i < buf->chan->n_subbufs; i++) buf->padding[i] = 0;
@@ -603,7 +604,7 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length) return length; toobig: - buf->chan->last_toobig = length; + buf->stats.big_count++; return 0; } EXPORT_SYMBOL_GPL(relay_switch_subbuf);
@@ -663,11 +664,6 @@ void relay_close(struct rchan *chan) if ((buf = *per_cpu_ptr(chan->buf, i))) relay_close_buf(buf); - if (chan->last_toobig) - printk(KERN_WARNING "relay: one or more items not logged " - "[item size (%zd) > sub-buffer size (%zd)]\n", - chan->last_toobig, chan->subbuf_size); - list_del(&chan->list); kref_put(&chan->kref, relay_destroy_channel); mutex_unlock(&relay_channels_mutex);
@@ -720,11 +716,15 @@ size_t relay_dump(struct rchan *chan, int flags) rbuf = *per_cpu_ptr(chan->buf, 0); if (flags & RELAY_DUMP_BUF_FULL) count = rbuf->stats.full_count; + else if (flags & RELAY_DUMP_WRT_BIG) + count = rbuf->stats.big_count; } else { for_each_online_cpu(i) { if ((rbuf = *per_cpu_ptr(chan->buf, i))) if (flags & RELAY_DUMP_BUF_FULL) count += rbuf->stats.full_count; + else if (flags & RELAY_DUMP_WRT_BIG) + count += rbuf->stats.big_count; } }
--
2.43.5