linux-kernel - [PATCH] drm: qxl: ratelimit pr_info message, reduce log spamming

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Message-Id: <20170912094548.30603-1-colin.king@canonical.com>
Date:   Tue, 12 Sep 2017 10:45:48 +0100
From:   Colin King <colin.king@...onical.com>
To:     Dave Airlie <airlied@...hat.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        virtualization@...ts.linux-foundation.org,
        dri-devel@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm: qxl: ratelimit pr_info message, reduce log spamming

From: Colin Ian King <colin.king@...onical.com>

Simply mmap'ing /dev/dri/card0 repeatedly will spam the kernel
log with qxl_mmap information messages. The following example code
illustrates this:

int main(void)
{
	int fd = open("/dev/dri/card0", O_RDONLY);
	if (fd == -1)
		err(1, "open failed");

	for (;;) {
		void *m = mmap(NULL, 4096, PROT_READ,
			MAP_SHARED, fd, 0);
		if (m != MAP_FAILED)
			munmap(m, 4096);
	}
}

Reduce the spamming by ratelimiting the pr_info messages.

Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/gpu/drm/qxl/qxl_ttm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/qxl/qxl_ttm.c b/drivers/gpu/drm/qxl/qxl_ttm.c
index 7ecf8a4b9fe6..6502e699f462 100644
--- a/drivers/gpu/drm/qxl/qxl_ttm.c
+++ b/drivers/gpu/drm/qxl/qxl_ttm.c
@@ -124,7 +124,7 @@ int qxl_mmap(struct file *filp, struct vm_area_struct *vma)
 	int r;
 
 	if (unlikely(vma->vm_pgoff < DRM_FILE_PAGE_OFFSET)) {
-		pr_info("%s: vma->vm_pgoff (%ld) < DRM_FILE_PAGE_OFFSET\n",
+		pr_info_ratelimited("%s: vma->vm_pgoff (%ld) < DRM_FILE_PAGE_OFFSET\n",
 			__func__, vma->vm_pgoff);
 		return -EINVAL;
 	}
-- 
2.14.1