block: Read max write zeroes once for __blkdev_issue_write_zeroes()

As reported in [0], we may get a hang when formatting a XFS FS on a RAID0
drive.

Commit 73a768d5 ("block: factor out a blk_write_zeroes_limit helper")
changed __blkdev_issue_write_zeroes() to read the max write zeroes
value in the loop. This is not safe as max write zeroes may change in
value. Specifically for the case of [0], the value goes to 0, and we get
an infinite loop.

Lift the limit reading out of the loop.

[0] https://lore.kernel.org/linux-xfs/4d31268f-310b-4220-88a2-e191c3932a82@oracle.com/T/#t



Fixes: 73a768d5 ("block: factor out a blk_write_zeroes_limit helper")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240815163228.216051-2-john.g.garry@oracle.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>