Could somebody explain when would the second part of that test _not_ be true?
if (!ret && !hlist_empty(&inode->i_dentry))
ret = ext4_sync_parent(inode);
inode is that of an opened file; how could it possibly _not_ have a dentry
alias? Is that code actually supposed to check if the sucker is not
unlinked? If so, it's not what we are actually checking - pinned dentry
remains positive (and unhashed) after unlink(2). What's more, the loop
in ext4_sync_parent() is vulnerable to races with rmdir(2) - if you
get unlink and rmdir of ancestors between
next = igrab(d_inode(dentry->d_parent));
and
inode = next;
ret = sync_mapping_buffers(inode->i_mapping);
if (ret)
break;
ret = sync_inode_metadata(inode, 1);
if (ret)
break;
you are risking interesting things done in the middle of rmdir and/or
unlink; that might be actually safe, but in that case it's worth a comment
explaining that.
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