linux-kernel - Re: [PATCH 3/5] xen-blkfront: switch from llist to list

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Message-ID: <20130319143105.GB32432@phenom.dumpdata.com>
Date:	Tue, 19 Mar 2013 10:31:05 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Roger Pau Monne <roger.pau@...rix.com>
Cc:	xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] xen-blkfront: switch from llist to list

On Mon, Mar 18, 2013 at 05:49:34PM +0100, Roger Pau Monne wrote:
> Replace the use of llist with list.
>

I applied this patch, but I changed the git commit to be:

 
commit 155b7edb51430a280f86c1e21b7be308b0d219d4
Author: Roger Pau Monne <roger.pau@...rix.com>
Date:   Mon Mar 18 17:49:34 2013 +0100

    xen-blkfront: switch from llist to list
    
    The git commit f84adf4921ae3115502f44ff467b04bf2f88cf04
    (xen-blkfront: drop the use of llist_for_each_entry_safe)
    
    was a stop-gate to fix a GCC4.1 bug. The appropiate way
    is to actually use an list instead of using an llist.
    
    As such this patch replaces the usage of llist with an
    list.
    
    Since we always manipulate the list while holding the io_lock, there's
    no need for additional locking (llist used previously is safe to use
    concurrently without additional locking).
    
    Signed-off-by: Roger Pau Monné <roger.pau@...rix.com>
    CC: stable@...r.kernel.org
    [v1: Redid the git commit description]
    Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 9620644..97324cd1 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -44,7 +44,7 @@
 #include <linux/mutex.h>
 #include <linux/scatterlist.h>
 #include <linux/bitmap.h>
-#include <linux/llist.h>
+#include <linux/list.h>
 
 #include <xen/xen.h>
 #include <xen/xenbus.h>
@@ -68,7 +68,7 @@ enum blkif_state {
 struct grant {
 	grant_ref_t gref;
 	unsigned long pfn;
-	struct llist_node node;
+	struct list_head node;
 };
 
 struct blk_shadow {
@@ -105,7 +105,7 @@ struct blkfront_info
 	struct work_struct work;
 	struct gnttab_free_callback callback;
 	struct blk_shadow shadow[BLK_RING_SIZE];
-	struct llist_head persistent_gnts;
+	struct list_head persistent_gnts;
 	unsigned int persistent_gnts_c;
 	unsigned long shadow_free;
 	unsigned int feature_flush;
@@ -371,10 +371,11 @@ static int blkif_queue_request(struct request *req)
 			lsect = fsect + (sg->length >> 9) - 1;
 
 			if (info->persistent_gnts_c) {
-				BUG_ON(llist_empty(&info->persistent_gnts));
-				gnt_list_entry = llist_entry(
-					llist_del_first(&info->persistent_gnts),
-					struct grant, node);
+				BUG_ON(list_empty(&info->persistent_gnts));
+				gnt_list_entry = list_first_entry(
+				                      &info->persistent_gnts,
+				                      struct grant, node);
+				list_del(&gnt_list_entry->node);
 
 				ref = gnt_list_entry->gref;
 				buffer_mfn = pfn_to_mfn(gnt_list_entry->pfn);
@@ -790,9 +791,8 @@ static void blkif_restart_queue(struct work_struct *work)
 
 static void blkif_free(struct blkfront_info *info, int suspend)
 {
-	struct llist_node *all_gnts;
-	struct grant *persistent_gnt, *tmp;
-	struct llist_node *n;
+	struct grant *persistent_gnt;
+	struct grant *n;
 
 	/* Prevent new requests being issued until we fix things up. */
 	spin_lock_irq(&info->io_lock);
@@ -804,20 +804,15 @@ static void blkif_free(struct blkfront_info *info, int suspend)
 
 	/* Remove all persistent grants */
 	if (info->persistent_gnts_c) {
-		all_gnts = llist_del_all(&info->persistent_gnts);
-		persistent_gnt = llist_entry(all_gnts, typeof(*(persistent_gnt)), node);
-		while (persistent_gnt) {
+		list_for_each_entry_safe(persistent_gnt, n,
+		                         &info->persistent_gnts, node) {
+			list_del(&persistent_gnt->node);
 			gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
 			__free_page(pfn_to_page(persistent_gnt->pfn));
-			tmp = persistent_gnt;
-			n = persistent_gnt->node.next;
-			if (n)
-				persistent_gnt = llist_entry(n, typeof(*(persistent_gnt)), node);
-			else
-				persistent_gnt = NULL;
-			kfree(tmp);
+			kfree(persistent_gnt);
+			info->persistent_gnts_c--;
 		}
-		info->persistent_gnts_c = 0;
+		BUG_ON(info->persistent_gnts_c != 0);
 	}
 
 	/* No more gnttab callback work. */
@@ -875,7 +870,7 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
 	}
 	/* Add the persistent grant into the list of free grants */
 	for (i = 0; i < s->req.u.rw.nr_segments; i++) {
-		llist_add(&s->grants_used[i]->node, &info->persistent_gnts);
+		list_add(&s->grants_used[i]->node, &info->persistent_gnts);
 		info->persistent_gnts_c++;
 	}
 }
@@ -1171,7 +1166,7 @@ static int blkfront_probe(struct xenbus_device *dev,
 	spin_lock_init(&info->io_lock);
 	info->xbdev = dev;
 	info->vdevice = vdevice;
-	init_llist_head(&info->persistent_gnts);
+	INIT_LIST_HEAD(&info->persistent_gnts);
 	info->persistent_gnts_c = 0;
 	info->connected = BLKIF_STATE_DISCONNECTED;
 	INIT_WORK(&info->work, blkif_restart_queue);
--
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