gfs2: deallocate inodes in gfs2_create_inode

[ Upstream commit 2c63986d ]

When creating and destroying inodes, we are relying on the inode hash
table to make sure that for a given inode number, only a single inode
will exist.  We then link that inode to its inode and iopen glock and
let those glocks point back at the inode.  However, when iget_failed()
is called, the inode is removed from the inode hash table before
gfs_evict_inode() is called, and uniqueness is no longer guaranteed.

Commit f1046a472b70 ("gfs2: gl_object races fix") was trying to work
around that problem by detaching the inode glock from the inode before
calling iget_failed(), but that broke the inode deallocation code in
gfs_evict_inode().

To fix that, deallocate partially created inodes in gfs2_create_inode()
instead of relying on gfs_evict_inode() for doing that.

This means that gfs2_evict_inode() and its helper functions will no
longer see partially created inodes, and so some simplifications are
possible there.

Fixes: 9ffa1888 ("gfs2: gl_object races fix")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>