On Mon, Aug 08, 2022 at 03:41:23AM +0100, Matthew Wilcox (Oracle) wrote:
> From: Kent Overstreet <kent.overstreet@xxxxxxxxx>
>
> This converts from seq_buf to printbuf. We're using printbuf in external
> buffer mode, so it's a direct conversion, aside from some trivial
> refactoring in cpu_show_meltdown() to make the code more consistent.
I don't object to the patch, but it would be nice if the commit log
hinted at what the advantage is. I assume it's faster/safer/better in
some way, but I have no idea what.
Also, cpu_show_meltdown() doesn't appear in this patch, so maybe
that's relevant to some other patch but not this one?
> Signed-off-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> Cc: linux-pci@xxxxxxxxxxxxxxx
> ---
> drivers/pci/p2pdma.c | 21 ++++++++-------------
> 1 file changed, 8 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index 4496a7c5c478..8e29e7cabad3 100644
> --- a/drivers/pci/p2pdma.c
> +++ b/drivers/pci/p2pdma.c
> @@ -18,7 +18,7 @@
> #include <linux/memremap.h>
> #include <linux/percpu-refcount.h>
> #include <linux/random.h>
> -#include <linux/seq_buf.h>
> +#include <linux/printbuf.h>
> #include <linux/xarray.h>
>
> struct pci_p2pdma {
> @@ -275,12 +275,9 @@ static int pci_bridge_has_acs_redir(struct pci_dev *pdev)
> return 0;
> }
>
> -static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)
> +static void prt_bus_devfn(struct printbuf *buf, struct pci_dev *pdev)
> {
> - if (!buf)
> - return;
> -
> - seq_buf_printf(buf, "%s;", pci_name(pdev));
> + prt_printf(buf, "%s;", pci_name(pdev));
> }
>
> static bool cpu_supports_p2pdma(void)
> @@ -454,13 +451,11 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
> struct pci_dev *a = provider, *b = client, *bb;
> bool acs_redirects = false;
> struct pci_p2pdma *p2pdma;
> - struct seq_buf acs_list;
> int acs_cnt = 0;
> int dist_a = 0;
> int dist_b = 0;
> char buf[128];
> -
> - seq_buf_init(&acs_list, buf, sizeof(buf));
> + struct printbuf acs_list = PRINTBUF_EXTERN(buf, sizeof(buf));
>
> /*
> * Note, we don't need to take references to devices returned by
> @@ -471,7 +466,7 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
> dist_b = 0;
>
> if (pci_bridge_has_acs_redir(a)) {
> - seq_buf_print_bus_devfn(&acs_list, a);
> + prt_bus_devfn(&acs_list, a);
> acs_cnt++;
> }
>
> @@ -500,7 +495,7 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
> break;
>
> if (pci_bridge_has_acs_redir(bb)) {
> - seq_buf_print_bus_devfn(&acs_list, bb);
> + prt_bus_devfn(&acs_list, bb);
> acs_cnt++;
> }
>
> @@ -515,11 +510,11 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
> }
>
> if (verbose) {
> - acs_list.buffer[acs_list.len-1] = 0; /* drop final semicolon */
> + acs_list.buf[acs_list.pos-1] = 0; /* drop final semicolon */
> pci_warn(client, "ACS redirect is set between the client and provider (%s)\n",
> pci_name(provider));
> pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",
> - acs_list.buffer);
> + acs_list.buf);
> }
> acs_redirects = true;
>
> --
> 2.35.1
>
