diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2018-01-05 13:02:46 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-01-05 13:02:46 -0800 |
commit | 89876f275e8d562912d9c238cd888b52065cf25c (patch) | |
tree | d67ca119f5cac8bd1bb503e7368a0bf126177643 | |
parent | 12e971b652e3166c3039e09ad2cb5568fc7f040a (diff) | |
parent | ec35e48b286959991cdbb886f1bdeda4575c80b4 (diff) |
Merge tag 'for-4.15-rc7-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull btrfs fixes from David Sterba:
"We have two more fixes for 4.15, both aimed for stable.
The leak fix is obvious, the second patch fixes a bug revealed by the
refcount API, when it behaves differently than previous atomic_t and
reports refs going from 0 to 1 in one case"
* tag 'for-4.15-rc7-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: fix refcount_t usage when deleting btrfs_delayed_nodes
btrfs: Fix flush bio leak
-rw-r--r-- | fs/btrfs/delayed-inode.c | 45 | ||||
-rw-r--r-- | fs/btrfs/volumes.c | 1 |
2 files changed, 34 insertions, 12 deletions
diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c index 5d73f79ded8b..056276101c63 100644 --- a/fs/btrfs/delayed-inode.c +++ b/fs/btrfs/delayed-inode.c @@ -87,6 +87,7 @@ static struct btrfs_delayed_node *btrfs_get_delayed_node( spin_lock(&root->inode_lock); node = radix_tree_lookup(&root->delayed_nodes_tree, ino); + if (node) { if (btrfs_inode->delayed_node) { refcount_inc(&node->refs); /* can be accessed */ @@ -94,9 +95,30 @@ static struct btrfs_delayed_node *btrfs_get_delayed_node( spin_unlock(&root->inode_lock); return node; } - btrfs_inode->delayed_node = node; - /* can be accessed and cached in the inode */ - refcount_add(2, &node->refs); + + /* + * It's possible that we're racing into the middle of removing + * this node from the radix tree. In this case, the refcount + * was zero and it should never go back to one. Just return + * NULL like it was never in the radix at all; our release + * function is in the process of removing it. + * + * Some implementations of refcount_inc refuse to bump the + * refcount once it has hit zero. If we don't do this dance + * here, refcount_inc() may decide to just WARN_ONCE() instead + * of actually bumping the refcount. + * + * If this node is properly in the radix, we want to bump the + * refcount twice, once for the inode and once for this get + * operation. + */ + if (refcount_inc_not_zero(&node->refs)) { + refcount_inc(&node->refs); + btrfs_inode->delayed_node = node; + } else { + node = NULL; + } + spin_unlock(&root->inode_lock); return node; } @@ -254,17 +276,18 @@ static void __btrfs_release_delayed_node( mutex_unlock(&delayed_node->mutex); if (refcount_dec_and_test(&delayed_node->refs)) { - bool free = false; struct btrfs_root *root = delayed_node->root; + spin_lock(&root->inode_lock); - if (refcount_read(&delayed_node->refs) == 0) { - radix_tree_delete(&root->delayed_nodes_tree, - delayed_node->inode_id); - free = true; - } + /* + * Once our refcount goes to zero, nobody is allowed to bump it + * back up. We can delete it now. + */ + ASSERT(refcount_read(&delayed_node->refs) == 0); + radix_tree_delete(&root->delayed_nodes_tree, + delayed_node->inode_id); spin_unlock(&root->inode_lock); - if (free) - kmem_cache_free(delayed_node_cache, delayed_node); + kmem_cache_free(delayed_node_cache, delayed_node); } } diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 49810b70afd3..a25684287501 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -237,7 +237,6 @@ static struct btrfs_device *__alloc_device(void) kfree(dev); return ERR_PTR(-ENOMEM); } - bio_get(dev->flush_bio); INIT_LIST_HEAD(&dev->dev_list); INIT_LIST_HEAD(&dev->dev_alloc_list); |