xfs: flush delalloc blocks on ENOSPC in xfs_trans_alloc_icreate

xfs: flush delalloc blocks on ENOSPC in xfs_trans_alloc_icreate

xfs_trans_alloc_icreate() can fail with ENOSPC when delalloc
reservations have consumed most of the available block count
(fdblocks).  xfs_trans_alloc() already retries internally with
xfs_blockgc_flush_all(), but that only trims post-EOF speculative
preallocation and may not free enough space for the transaction
reservation.

Add a retry with xfs_flush_inodes() when xfs_trans_alloc() returns
ENOSPC.  This forces writeback of all dirty inodes via
sync_inodes_sb(), converting delalloc reservations to real
allocations and freeing the over-reserved portion back to fdblocks.

This fixes all callers of xfs_trans_alloc_icreate() and removes
the existing caller-level retry from xfs_create(), which is now
handled centrally.

Signed-off-by: Ravi Singh <ravising@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>