btrfs: remove roots ulist when checking data extent sharedness

Currently btrfs_is_data_extent_shared() is passing a ulist for the roots
argument of find_parent_nodes(), however it does not use that ulist for
anything and for this context that list always ends up with at most one
element.

Since find_parent_nodes() is able to deal with a NULL ulist for its roots
argument, make btrfs_is_data_extent_shared() pass it NULL and avoid the
burden of allocating memory for the unnused roots ulist, initializing it,
releasing it and allocating one struct ulist_node for it during the call
to find_parent_nodes().

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 4caff30..4d8573f 100644 (file)
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -1664,7 +1664,6 @@ struct btrfs_backref_share_check_ctx *btrfs_alloc_backref_share_check_ctx(void)
                return NULL;
 
        ulist_init(&ctx->refs);
-       ulist_init(&ctx->roots);
 
        return ctx;
 }
@@ -1675,7 +1674,6 @@ void btrfs_free_backref_share_ctx(struct btrfs_backref_share_check_ctx *ctx)
                return;
 
        ulist_release(&ctx->refs);
-       ulist_release(&ctx->roots);
        kfree(ctx);
 }
 
@@ -1718,7 +1716,6 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
        };
        int level;
 
-       ulist_init(&ctx->roots);
        ulist_init(&ctx->refs);
 
        trans = btrfs_join_transaction_nostart(root);
@@ -1742,7 +1739,7 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
                bool cached;
 
                ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, &ctx->refs,
-                                       &ctx->roots, NULL, &shared, false);
+                                       NULL, NULL, &shared, false);
                if (ret == BACKREF_FOUND_SHARED) {
                        /* this is the only condition under which we return 1 */
                        ret = 1;
@@ -1810,7 +1807,6 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
                up_read(&fs_info->commit_root_sem);
        }
 out:
-       ulist_release(&ctx->roots);
        ulist_release(&ctx->refs);
        return ret;
 }

diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h
index 8da0ba6..5f468f0 100644 (file)
--- a/fs/btrfs/backref.h
+++ b/fs/btrfs/backref.h
@@ -26,7 +26,6 @@ struct btrfs_backref_shared_cache_entry {
 struct btrfs_backref_share_check_ctx {
        /* Ulists used during backref walking. */
        struct ulist refs;
-       struct ulist roots;
        /*
         * A path from a root to a leaf that has a file extent item pointing to
         * a given data extent should never exceed the maximum b+tree height.