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xen-blkback: implement safe iterator for the list of persistent grants

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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
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Roger Pau Monne 2012-12-04 15:21:52 +01:00 committed by Konrad Rzeszutek Wilk
parent 07c540a0b5
commit 7dc341175a
1 changed files with 11 additions and 7 deletions
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18
drivers/block/xen-blkback/blkback.c
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@ -161,10 +161,12 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
static void make_response(struct xen_blkif *blkif, u64 id, static void make_response(struct xen_blkif *blkif, u64 id,
unsigned short op, int st); unsigned short op, int st);
#define foreach_grant(pos, rbtree, node) \ #define foreach_grant_safe(pos, n, rbtree, node) \
for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node); \ for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
(n) = rb_next(&(pos)->node); \
&(pos)->node != NULL; \ &(pos)->node != NULL; \
(pos) = container_of(rb_next(&(pos)->node), typeof(*(pos)), node)) (pos) = container_of(n, typeof(*(pos)), node), \
(n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)
static void add_persistent_gnt(struct rb_root *root, static void add_persistent_gnt(struct rb_root *root,
@ -217,10 +219,11 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST]; struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST]; struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
struct persistent_gnt *persistent_gnt; struct persistent_gnt *persistent_gnt;
struct rb_node *n;
int ret = 0; int ret = 0;
int segs_to_unmap = 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 == BUG_ON(persistent_gnt->handle ==
BLKBACK_INVALID_HANDLE); BLKBACK_INVALID_HANDLE);
gnttab_set_unmap_op(&unmap[segs_to_unmap], gnttab_set_unmap_op(&unmap[segs_to_unmap],
@ -230,9 +233,6 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
persistent_gnt->handle); persistent_gnt->handle);
pages[segs_to_unmap] = persistent_gnt->page; 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 || if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
!rb_next(&persistent_gnt->node)) { !rb_next(&persistent_gnt->node)) {
@ -241,6 +241,10 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
BUG_ON(ret); BUG_ON(ret);
segs_to_unmap = 0; segs_to_unmap = 0;
} }
rb_erase(&persistent_gnt->node, root);
kfree(persistent_gnt);
num--;
} }
BUG_ON(num != 0); BUG_ON(num != 0);
} }