lkml.org 
[lkml]   [2012]   [Dec]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v4 1/3] xen-blkback: implement safe iterator for the list of persistent grants
Date
Change foreach_grant iterator to a safe version, that allows freeing
the element while iterating. Also move the free code in
free_persistent_gnts to prevent freeing the element before the rb_next
call.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad@kernel.org>
Cc: xen-devel@lists.xen.org
---
Changes since v2:
* Implement the same semantics as list_for_each_safe, using type *
instead of rb_node * as the temporary cursor.
---
drivers/block/xen-blkback/blkback.c | 23 ++++++++++++++---------
1 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 74374fb..8808028 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -161,10 +161,14 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
static void make_response(struct xen_blkif *blkif, u64 id,
unsigned short op, int st);

-#define foreach_grant(pos, rbtree, node) \
- for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node); \
- &(pos)->node != NULL; \
- (pos) = container_of(rb_next(&(pos)->node), typeof(*(pos)), node))
+#define foreach_grant_safe(pos, n, rbtree, node) \
+ for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node),\
+ (n) = container_of(((&(pos)->node != NULL) ? \
+ rb_next(&(pos)->node) : NULL), typeof(*(pos)), node); \
+ &(pos)->node != NULL; \
+ (pos) = n, \
+ (n) = container_of(((&(pos)->node != NULL) ? \
+ rb_next(&(pos)->node) : NULL), typeof(*(pos)), node))


static void add_persistent_gnt(struct rb_root *root,
@@ -216,11 +220,11 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
{
struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
- struct persistent_gnt *persistent_gnt;
+ struct persistent_gnt *persistent_gnt, *n;
int ret = 0;
int segs_to_unmap = 0;

- foreach_grant(persistent_gnt, root, node) {
+ foreach_grant_safe(persistent_gnt, n, root, node) {
BUG_ON(persistent_gnt->handle ==
BLKBACK_INVALID_HANDLE);
gnttab_set_unmap_op(&unmap[segs_to_unmap],
@@ -230,9 +234,6 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
persistent_gnt->handle);

pages[segs_to_unmap] = persistent_gnt->page;
- rb_erase(&persistent_gnt->node, root);
- kfree(persistent_gnt);
- num--;

if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
!rb_next(&persistent_gnt->node)) {
@@ -241,6 +242,10 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
BUG_ON(ret);
segs_to_unmap = 0;
}
+
+ rb_erase(&persistent_gnt->node, root);
+ kfree(persistent_gnt);
+ num--;
}
BUG_ON(num != 0);
}
--
1.7.7.5 (Apple Git-26)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2012-12-13 12:01    [W:0.040 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site