Btrfs: don't always do readahead

Our readahead is sort of sloppy, and really isn't always needed.  For example if
ls is doing a stating ls (which is the default) it's going to stat in non-disk
order, so if say you have a directory with a stupid amount of files, readahead
is going to do nothing but waste time in the case of doing the stat.  Taking the
unconditional readahead out made my test go from 57 minutes to 36 minutes.  This
means that everywhere we do loop through the tree we want to make sure we do set
path->reada properly, so I went through and found all of the places where we
loop through the path and set reada to 1.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index f7a0a64b868f416bfec613c8673371a0eb6a3d83..f61c16c1481af95688d238ffacac91f6433d214f 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -48,8 +48,6 @@ struct btrfs_path *btrfs_alloc_path(void)
 {
        struct btrfs_path *path;
        path = kmem_cache_zalloc(btrfs_path_cachep, GFP_NOFS);
-       if (path)
-               path->reada = 1;
        return path;
 }
 

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 96be624503183bd63b3aff6c4ac65e8dc0e341c1..1ba2cc58eab5eca00562dc96a71a30d7027d5087 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -347,7 +347,7 @@ static int caching_kthread(void *data)
         */
        path->skip_locking = 1;
        path->search_commit_root = 1;
-       path->reada = 2;
+       path->reada = 1;
 
        key.objectid = last;
        key.offset = 0;
@@ -8556,6 +8556,7 @@ int btrfs_read_block_groups(struct btrfs_root *root)
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
+       path->reada = 1;
 
        cache_gen = btrfs_super_cache_generation(&root->fs_info->super_copy);
        if (cache_gen != 0 &&

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index dd5938a7de211ca9eaa2eab406bad82392dcfa95..6228a304b547118f6ac6ea542b26d3418849316b 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4242,7 +4242,9 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
                filp->f_pos = 2;
        }
        path = btrfs_alloc_path();
-       path->reada = 2;
+       if (!path)
+               return -ENOMEM;
+       path->reada = 1;
 
        btrfs_set_key_type(&key, key_type);
        key.offset = filp->f_pos;
@@ -5043,7 +5045,15 @@ again:
 
        if (!path) {
                path = btrfs_alloc_path();
-               BUG_ON(!path);
+               if (!path) {
+                       err = -ENOMEM;
+                       goto out;
+               }
+               /*
+                * Chances are we'll be called again, so go ahead and do
+                * readahead
+                */
+               path->reada = 1;
        }
 
        ret = btrfs_lookup_file_extent(trans, root, path,

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 09c30d37d43e58df93d2300aa5eac3766381de36..5872b41581f42a5ec355f53c37180be4c73df7cd 100644 (file)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -676,6 +676,8 @@ struct backref_node *build_backref_tree(struct reloc_control *rc,
                err = -ENOMEM;
                goto out;
        }
+       path1->reada = 1;
+       path2->reada = 2;
 
        node = alloc_backref_node(cache);
        if (!node) {
@@ -1996,6 +1998,7 @@ static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
+       path->reada = 1;
 
        reloc_root = root->reloc_root;
        root_item = &reloc_root->root_item;
@@ -3297,6 +3300,7 @@ static int find_data_references(struct reloc_control *rc,
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
+       path->reada = 1;
 
        root = read_fs_root(rc->extent_root->fs_info, ref_root);
        if (IS_ERR(root)) {
@@ -3665,6 +3669,7 @@ static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
+       path->reada = 1;
 
        ret = prepare_to_relocate(rc);
        if (ret) {
@@ -4090,6 +4095,7 @@ int btrfs_recover_relocation(struct btrfs_root *root)
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
+       path->reada = -1;
 
        key.objectid = BTRFS_TREE_RELOC_OBJECTID;
        key.type = BTRFS_ROOT_ITEM_KEY;