On Thu, Sep 06, 2012 at 02:40:41PM +0800, Wang Sheng-Hui wrote:
> The memory allocation failure is BUG_ON in add_excluded_extent (following
> the code path) and btrfs_rmap_block. No need to BUG_ON -ENOMEM inside
> exclude_super_stripes itself.
No please.
> Its return value is always 0, and useless for its callers. Set it as void
> instead 0-returned.
btrfs_rmap_block itself contains a BUG_ON:
3980 int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
3981 u64 chunk_start, u64 physical, u64 devid,
3982 u64 **logical, int *naddrs, int *stripe_len)
3983 {
3984 struct extent_map_tree *em_tree = &map_tree->map_tree;
3985 struct extent_map *em;
3986 struct map_lookup *map;
3987 u64 *buf;
3988 u64 bytenr;
3989 u64 length;
3990 u64 stripe_nr;
3991 int i, j, nr = 0;
3992
3993 read_lock(&em_tree->lock);
3994 em = lookup_extent_mapping(em_tree, chunk_start, 1);
3995 read_unlock(&em_tree->lock);
3996
3997 BUG_ON(!em || em->start != chunk_start);
And this should be turned into an 'return error', thus giving a non-zero return
code that should be handled in the callers.
Eg. this patch attempts to do that
http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg15470.html
but has not been merged due to incorrect fix inside exclude_super_stripes
(introduced in the patch).
The same objection for return code cleanups will hold for any function that
returns 0 but is full of BUG_ONs.
david
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