mirror of https://gitee.com/openkylin/linux.git
xen-blkback: implement safe iterator for the list of persistent grants
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>
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@ -161,10 +161,12 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
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static void make_response(struct xen_blkif *blkif, u64 id,
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unsigned short op, int st);
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#define foreach_grant(pos, rbtree, node) \
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for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node); \
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#define foreach_grant_safe(pos, n, rbtree, node) \
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for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
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(n) = rb_next(&(pos)->node); \
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&(pos)->node != NULL; \
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(pos) = container_of(rb_next(&(pos)->node), typeof(*(pos)), node))
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(pos) = container_of(n, typeof(*(pos)), node), \
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(n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)
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static void add_persistent_gnt(struct rb_root *root,
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@ -217,10 +219,11 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
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struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
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struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
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struct persistent_gnt *persistent_gnt;
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struct rb_node *n;
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int ret = 0;
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int segs_to_unmap = 0;
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foreach_grant(persistent_gnt, root, node) {
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foreach_grant_safe(persistent_gnt, n, root, node) {
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BUG_ON(persistent_gnt->handle ==
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BLKBACK_INVALID_HANDLE);
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gnttab_set_unmap_op(&unmap[segs_to_unmap],
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@ -230,9 +233,6 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
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persistent_gnt->handle);
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pages[segs_to_unmap] = persistent_gnt->page;
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rb_erase(&persistent_gnt->node, root);
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kfree(persistent_gnt);
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num--;
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if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
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!rb_next(&persistent_gnt->node)) {
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@ -241,6 +241,10 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num)
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BUG_ON(ret);
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segs_to_unmap = 0;
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}
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rb_erase(&persistent_gnt->node, root);
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kfree(persistent_gnt);
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num--;
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}
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BUG_ON(num != 0);
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}
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