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Message-ID: <ge3bqyurfb7didh47rfai7fofsbbci5jui3m2ot42fv4arfyfz@gqi6a4arfo73>
Date: Tue, 2 Dec 2025 15:33:19 +0900
From: Koichiro Den <den@...inux.co.jp>
To: Frank Li <Frank.li@....com>
Cc: ntb@...ts.linux.dev, linux-pci@...r.kernel.org,
dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org, mani@...nel.org,
kwilczynski@...nel.org, kishon@...nel.org, bhelgaas@...gle.com, corbet@....net,
vkoul@...nel.org, jdmason@...zu.us, dave.jiang@...el.com, allenbh@...il.com,
Basavaraj.Natikar@....com, Shyam-sundar.S-k@....com, kurt.schwemmer@...rosemi.com,
logang@...tatee.com, jingoohan1@...il.com, lpieralisi@...nel.org, robh@...nel.org,
jbrunet@...libre.com, fancer.lancer@...il.com, arnd@...db.de, pstanner@...hat.com,
elfring@...rs.sourceforge.net
Subject: Re: [RFC PATCH v2 13/27] NTB: ntb_transport: Use seq_file for QP
stats debugfs
On Mon, Dec 01, 2025 at 02:50:19PM -0500, Frank Li wrote:
> On Sun, Nov 30, 2025 at 01:03:51AM +0900, Koichiro Den wrote:
> > The ./qp*/stats debugfs file for each NTB transport QP is currently
> > implemented with a hand-crafted kmalloc() buffer and a series of
> > scnprintf() calls. This is a pre-seq_file style pattern and makes future
> > extensions easy to truncate.
> >
> > Convert the stats file to use the seq_file helpers via
> > DEFINE_SHOW_ATTRIBUTE(), which simplifies the code and lets the seq_file
> > core handle buffering and partial reads.
> >
> > While touching this area, fix a bug in the per-QP debugfs directory
> > naming: the buffer used for "qp%d" was only 4 bytes, which truncates
> > names like "qp10" to "qp1" and causes multiple queues to share the same
> > directory. Enlarge the buffer and use sizeof() to avoid truncation.
> >
> > Signed-off-by: Koichiro Den <den@...inux.co.jp>
> > ---
>
> This one is indenpented with other, you may post seperately. So get merge
> this simple change quick.
Ok I'll do so, thanks.
(it was a semi-preparatory commit for [RFC PATCH v2 20/27], to avoid having
different styles from co-existing.)
Koichiro
>
> Reviewed-by: Frank Li <Frank.Li@....com>
> > drivers/ntb/ntb_transport.c | 136 +++++++++++-------------------------
> > 1 file changed, 41 insertions(+), 95 deletions(-)
> >
> > diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
> > index 3f3bc991e667..57b4c0511927 100644
> > --- a/drivers/ntb/ntb_transport.c
> > +++ b/drivers/ntb/ntb_transport.c
> > @@ -57,6 +57,7 @@
> > #include <linux/module.h>
> > #include <linux/pci.h>
> > #include <linux/slab.h>
> > +#include <linux/seq_file.h>
> > #include <linux/types.h>
> > #include <linux/uaccess.h>
> > #include <linux/mutex.h>
> > @@ -466,104 +467,49 @@ void ntb_transport_unregister_client(struct ntb_transport_client *drv)
> > }
> > EXPORT_SYMBOL_GPL(ntb_transport_unregister_client);
> >
> > -static ssize_t debugfs_read(struct file *filp, char __user *ubuf, size_t count,
> > - loff_t *offp)
> > +static int ntb_qp_debugfs_stats_show(struct seq_file *s, void *v)
> > {
> > - struct ntb_transport_qp *qp;
> > - char *buf;
> > - ssize_t ret, out_offset, out_count;
> > -
> > - qp = filp->private_data;
> > + struct ntb_transport_qp *qp = s->private;
> >
> > if (!qp || !qp->link_is_up)
> > return 0;
> >
> > - out_count = 1000;
> > -
> > - buf = kmalloc(out_count, GFP_KERNEL);
> > - if (!buf)
> > - return -ENOMEM;
> > + seq_puts(s, "\nNTB QP stats:\n\n");
> > +
> > + seq_printf(s, "rx_bytes - \t%llu\n", qp->rx_bytes);
> > + seq_printf(s, "rx_pkts - \t%llu\n", qp->rx_pkts);
> > + seq_printf(s, "rx_memcpy - \t%llu\n", qp->rx_memcpy);
> > + seq_printf(s, "rx_async - \t%llu\n", qp->rx_async);
> > + seq_printf(s, "rx_ring_empty - %llu\n", qp->rx_ring_empty);
> > + seq_printf(s, "rx_err_no_buf - %llu\n", qp->rx_err_no_buf);
> > + seq_printf(s, "rx_err_oflow - \t%llu\n", qp->rx_err_oflow);
> > + seq_printf(s, "rx_err_ver - \t%llu\n", qp->rx_err_ver);
> > + seq_printf(s, "rx_buff - \t0x%p\n", qp->rx_buff);
> > + seq_printf(s, "rx_index - \t%u\n", qp->rx_index);
> > + seq_printf(s, "rx_max_entry - \t%u\n", qp->rx_max_entry);
> > + seq_printf(s, "rx_alloc_entry - \t%u\n\n", qp->rx_alloc_entry);
> > +
> > + seq_printf(s, "tx_bytes - \t%llu\n", qp->tx_bytes);
> > + seq_printf(s, "tx_pkts - \t%llu\n", qp->tx_pkts);
> > + seq_printf(s, "tx_memcpy - \t%llu\n", qp->tx_memcpy);
> > + seq_printf(s, "tx_async - \t%llu\n", qp->tx_async);
> > + seq_printf(s, "tx_ring_full - \t%llu\n", qp->tx_ring_full);
> > + seq_printf(s, "tx_err_no_buf - %llu\n", qp->tx_err_no_buf);
> > + seq_printf(s, "tx_mw - \t0x%p\n", qp->tx_mw);
> > + seq_printf(s, "tx_index (H) - \t%u\n", qp->tx_index);
> > + seq_printf(s, "RRI (T) - \t%u\n", qp->remote_rx_info->entry);
> > + seq_printf(s, "tx_max_entry - \t%u\n", qp->tx_max_entry);
> > + seq_printf(s, "free tx - \t%u\n", ntb_transport_tx_free_entry(qp));
> > + seq_putc(s, '\n');
> > +
> > + seq_printf(s, "Using TX DMA - \t%s\n", qp->tx_dma_chan ? "Yes" : "No");
> > + seq_printf(s, "Using RX DMA - \t%s\n", qp->rx_dma_chan ? "Yes" : "No");
> > + seq_printf(s, "QP Link - \t%s\n", qp->link_is_up ? "Up" : "Down");
> > + seq_putc(s, '\n');
> >
> > - out_offset = 0;
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "\nNTB QP stats:\n\n");
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_bytes - \t%llu\n", qp->rx_bytes);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_pkts - \t%llu\n", qp->rx_pkts);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_memcpy - \t%llu\n", qp->rx_memcpy);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_async - \t%llu\n", qp->rx_async);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_ring_empty - %llu\n", qp->rx_ring_empty);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_err_no_buf - %llu\n", qp->rx_err_no_buf);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_err_oflow - \t%llu\n", qp->rx_err_oflow);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_err_ver - \t%llu\n", qp->rx_err_ver);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_buff - \t0x%p\n", qp->rx_buff);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_index - \t%u\n", qp->rx_index);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_max_entry - \t%u\n", qp->rx_max_entry);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "rx_alloc_entry - \t%u\n\n", qp->rx_alloc_entry);
> > -
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "tx_bytes - \t%llu\n", qp->tx_bytes);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "tx_pkts - \t%llu\n", qp->tx_pkts);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "tx_memcpy - \t%llu\n", qp->tx_memcpy);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "tx_async - \t%llu\n", qp->tx_async);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "tx_ring_full - \t%llu\n", qp->tx_ring_full);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "tx_err_no_buf - %llu\n", qp->tx_err_no_buf);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "tx_mw - \t0x%p\n", qp->tx_mw);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "tx_index (H) - \t%u\n", qp->tx_index);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "RRI (T) - \t%u\n",
> > - qp->remote_rx_info->entry);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "tx_max_entry - \t%u\n", qp->tx_max_entry);
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "free tx - \t%u\n",
> > - ntb_transport_tx_free_entry(qp));
> > -
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "\n");
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "Using TX DMA - \t%s\n",
> > - qp->tx_dma_chan ? "Yes" : "No");
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "Using RX DMA - \t%s\n",
> > - qp->rx_dma_chan ? "Yes" : "No");
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "QP Link - \t%s\n",
> > - qp->link_is_up ? "Up" : "Down");
> > - out_offset += scnprintf(buf + out_offset, out_count - out_offset,
> > - "\n");
> > -
> > - if (out_offset > out_count)
> > - out_offset = out_count;
> > -
> > - ret = simple_read_from_buffer(ubuf, count, offp, buf, out_offset);
> > - kfree(buf);
> > - return ret;
> > -}
> > -
> > -static const struct file_operations ntb_qp_debugfs_stats = {
> > - .owner = THIS_MODULE,
> > - .open = simple_open,
> > - .read = debugfs_read,
> > -};
> > + return 0;
> > +}
> > +DEFINE_SHOW_ATTRIBUTE(ntb_qp_debugfs_stats);
> >
> > static void ntb_list_add(spinlock_t *lock, struct list_head *entry,
> > struct list_head *list)
> > @@ -1237,15 +1183,15 @@ static int ntb_transport_init_queue(struct ntb_transport_ctx *nt,
> > qp->tx_max_entry = tx_size / qp->tx_max_frame;
> >
> > if (nt->debugfs_node_dir) {
> > - char debugfs_name[4];
> > + char debugfs_name[8];
> >
> > - snprintf(debugfs_name, 4, "qp%d", qp_num);
> > + snprintf(debugfs_name, sizeof(debugfs_name), "qp%d", qp_num);
> > qp->debugfs_dir = debugfs_create_dir(debugfs_name,
> > nt->debugfs_node_dir);
> >
> > qp->debugfs_stats = debugfs_create_file("stats", S_IRUSR,
> > qp->debugfs_dir, qp,
> > - &ntb_qp_debugfs_stats);
> > + &ntb_qp_debugfs_stats_fops);
> > } else {
> > qp->debugfs_dir = NULL;
> > qp->debugfs_stats = NULL;
> > --
> > 2.48.1
> >
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