hfs: prevent btree data loss on ENOSPC

Inserting a new record in a btree may require splitting several of its
nodes.  If we hit ENOSPC halfway through, the new nodes will be left
orphaned and their records will be lost.  This could mean lost inodes or
extents.

Henceforth, check the available disk space before making any changes.
This still leaves the potential problem of corruption on ENOMEM.

There is no need to reserve space before deleting a catalog record, as we
do for hfsplus.  This difference is because hfs index nodes have fixed
length keys.

Link: http://lkml.kernel.org/r/ab5fc8a7d5ffccfd5f27b1cf2cb4ceb6c110da74.1536269131.git.ernesto.mnd.fernandez@gmail.com


Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>