Attachment 159150 Details for Bug 186008 – grab a rerfecnce to pages we are allocating

[patch] grab a rerfecnce to pages we are allocating

grab-ref-sg-page.patch (text/plain), 1.50 KB, created by Mike Christie on 2007-07-13 11:13:10 UTC

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Creator: Mike Christie

Created: 2007-07-13 11:13:10 UTC

Size: 1.50 KB

patch

obsolete

>--- linux-2.6.9/drivers/scsi/sg.c	2007-07-12 16:29:05.000000000 -0500
>+++ linux-2.6.9.work/drivers/scsi/sg.c	2007-07-13 04:06:11.000000000 -0500
>@@ -2551,8 +2551,9 @@ sg_page_malloc(int rqSz, int lowDma, int
> {
> 	char *resp = NULL;
> 	int page_mask;
>-	int order, a_size;
>+	int order, a_size, offset;
> 	int resSz = rqSz;
>+	struct page *tmppage;
> 
> 	if (rqSz <= 0)
> 		return resp;
>@@ -2571,6 +2572,19 @@ sg_page_malloc(int rqSz, int lowDma, int
> 		resp = (char *) __get_free_pages(page_mask, order);	/* try half */
> 		resSz = a_size;
> 	}
>+
>+	/*
>+	 * The first page has a refcount of one, but all others will
>+	 * have zero. Lower levels will then do gets and puts on the page
>+	 * so we must get a reference here which will be released in
>+	 * sg_page_free.
>+	 */
>+	tmppage = virt_to_page(resp);
>+	for (offset = PAGE_SIZE; offset < resSz; offset += PAGE_SIZE) {
>+		tmppage++;
>+		get_page(tmppage);
>+	}
>+
> 	if (resp) {
> 		if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
> 			memset(resp, 0, resSz);
>@@ -2583,12 +2597,21 @@ sg_page_malloc(int rqSz, int lowDma, int
> static void
> sg_page_free(char *buff, int size)
> {
>-	int order, a_size;
>+	int order, a_size, offset;
>+	struct page *tmppage;
> 
> 	if (!buff)
> 		return;
> 	for (order = 0, a_size = PAGE_SIZE; a_size < size;
> 	     order++, a_size <<= 1) ;
>+
>+	tmppage = virt_to_page(buff);
>+	for (offset = PAGE_SIZE; offset < size; offset += PAGE_SIZE) {
>+		tmppage++;
>+		BUG_ON(page_count(tmppage) != 1);
>+		set_page_count(tmppage, 0);
>+	}
>+
> 	free_pages((unsigned long) buff, order);
> }
>

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Attachments on bug 186008: 126368 | 154358 | 159150 | 159221