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 73a768d5f955 ("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/[email protected]/T/#t

Fixes: 73a768d5f955 ("block: factor out a blk_write_zeroes_limit helper")
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: John Garry <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

0 files changed, 0 insertions, 0 deletions