fs/hfsplus/extents.c: fix concurrent acess of alloc_blocks

fs/hfsplus/extents.c: fix concurrent acess of alloc_blocks

Concurrent access to alloc_blocks in hfsplus_inode_info() is protected
by extents_lock mutex.  This patch fixes two instances where
alloc_blocks modification was not protected with this lock.

This fixes possible allocation bitmap corruption in race conditions
while extending and truncating files.

[[email protected]: take extents_lock before taking a copy of ->alloc_blocks]
[[email protected]: remove now-unused label `out']
Signed-off-by: Sougata Santra <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Cc: Vyacheslav Dubeyko <[email protected]>
Cc: Alexey Khoroshilov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>