On 12/6/20 6:53 AM, Tom Yan wrote:
At least the SCSI disk driver is "benevolent" when it try to decide
whether the device actually supports write zeroes, i.e. unless the
device explicity report otherwise, it assumes it does at first.
Therefore before we pile up bios that would fail at the end, we try
the command/request once, as not doing so could trigger quite a
disaster in at least certain case. For example, the host controller
can be messed up entirely when one does `blkdiscard -z` a UAS drive.
Signed-off-by: Tom Yan <tom.ty89@xxxxxxxxx>
---
block/blk-lib.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/block/blk-lib.c b/block/blk-lib.c
index e90614fd8d6a..c1e9388a8fb8 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -250,6 +250,7 @@ static int __blkdev_issue_write_zeroes(struct block_device *bdev,
struct bio *bio = *biop;
unsigned int max_write_zeroes_sectors;
struct request_queue *q = bdev_get_queue(bdev);
+ int i = 0;
if (!q)
return -ENXIO;
@@ -264,7 +265,17 @@ static int __blkdev_issue_write_zeroes(struct block_device *bdev,
return -EOPNOTSUPP;
while (nr_sects) {
- bio = blk_next_bio(bio, 0, gfp_mask);
+ if (i != 1) {
+ bio = blk_next_bio(bio, 0, gfp_mask);
+ } else {
+ submit_bio_wait(bio);
+ bio_put(bio);
+
+ if (bdev_write_zeroes_sectors(bdev) == 0)
+ return -EOPNOTSUPP;
+ else
+ bio = bio_alloc(gfp_mask, 0);
+ }
bio->bi_iter.bi_sector = sector;
bio_set_dev(bio, bdev);
bio->bi_opf = REQ_OP_WRITE_ZEROES;
@@ -280,6 +291,7 @@ static int __blkdev_issue_write_zeroes(struct block_device *bdev,
nr_sects = 0;
}
cond_resched();
+ i++;
}
*biop = bio;
We do want to keep the chain of bios intact such that end_io processing
will recurse back to the original end_io callback.
As such we need to call bio_chain on the first bio, submit that
(possibly with submit_bio_wait()), and then decide whether we can /
should continue.
With your patch we'll lose the information that indeed other bios might
be linked to the original one.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
