On 11.05.2011 23:35, Josef Bacik wrote:
> If we have particularly full nodes, we could call btrfs_node_blockptr up to 32
> times, which is 32 pairs of kmap/kunmap, which _sucks_. So go ahead and map the
> extent buffer while we look for readahead targets. Thanks,
>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxx>
> ---
> fs/btrfs/ctree.c | 23 +++++++++++++++++++++--
> 1 files changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
> index 84d7ca1..009bcf7 100644
> --- a/fs/btrfs/ctree.c
> +++ b/fs/btrfs/ctree.c
> @@ -1229,6 +1229,7 @@ static void reada_for_search(struct btrfs_root *root,
> u64 search;
> u64 target;
> u64 nread = 0;
> + u64 gen;
> int direction = path->reada;
> struct extent_buffer *eb;
> u32 nr;
> @@ -1256,6 +1257,15 @@ static void reada_for_search(struct btrfs_root *root,
> nritems = btrfs_header_nritems(node);
> nr = slot;
> while (1) {
> + if (!node->map_token) {
> + unsigned long offset = btrfs_node_key_ptr_offset(nr);
> + map_private_extent_buffer(node, offset,
> + sizeof(struct btrfs_key_ptr),
> + &node->map_token,
> + &node->kaddr,
> + &node->map_start,
> + &node->map_len, KM_USER1);
You can't do that. It puts us in atomic context, and the following
readahead_tree_block will try a memory allocation with GFP_NOFS,
which leads to a BUG: sleeping function called from invalid context.
It didn't fall on our feet earlier because you also turned off
readahead, but scrub still uses it.
-Arne
> + }
> if (direction < 0) {
> if (nr == 0)
> break;
> @@ -1273,14 +1283,23 @@ static void reada_for_search(struct btrfs_root *root,
> search = btrfs_node_blockptr(node, nr);
> if ((search <= target && target - search <= 65536) ||
> (search > target && search - target <= 65536)) {
> - readahead_tree_block(root, search, blocksize,
> - btrfs_node_ptr_generation(node, nr));
> + gen = btrfs_node_ptr_generation(node, nr);
> + if (node->map_token) {
> + unmap_extent_buffer(node, node->map_token,
> + KM_USER1);
> + node->map_token = NULL;
> + }
> + readahead_tree_block(root, search, blocksize, gen);
> nread += blocksize;
> }
> nscan++;
> if ((nread > 65536 || nscan > 32))
> break;
> }
> + if (node->map_token) {
> + unmap_extent_buffer(node, node->map_token, KM_USER1);
> + node->map_token = NULL;
> + }
> }
>
> /*
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
