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| author | Josef Bacik <josef@redhat.com> | 2011-05-11 12:17:34 -0400 |
|---|---|---|
| committer | Josef Bacik <josef@redhat.com> | 2011-05-23 13:03:10 -0400 |
| commit | cb25c2ea6a79702ab7895b873c6c43e0d3bc3c72 (patch) | |
| tree | 08d112b38a1e017b563035b78861288dbf0d2fd6 /fs/btrfs/ctree.c | |
| parent | af60bed24eb0e3b6d93eaa6bb395a5721e6c09a8 (diff) | |
| download | lwn-cb25c2ea6a79702ab7895b873c6c43e0d3bc3c72.tar.gz lwn-cb25c2ea6a79702ab7895b873c6c43e0d3bc3c72.zip | |
Btrfs: map the node block when looking for readahead targets
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@redhat.com>
Diffstat (limited to 'fs/btrfs/ctree.c')
| -rw-r--r-- | 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 84d7ca1fe0ba..009bcf7f1e4b 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); + } 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; + } } /* |