For zoned devices, write zeroes must be split at the zone boundary
which is represented as chunk_sectors. For other uses like the
internally RAIDed NVMe devices it is probably at least useful.
Enhance get_max_io_size to know about write zeroes and use it in
bio_split_write_zeroes. Also add a comment about the seemingly
nonsensical zero max_write_zeroes limit.
Fixes: 885fa13f6559 ("block: implement splitting of REQ_OP_WRITE_ZEROES bios")
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
block/blk-merge.c | 35 +++++++++++++++++++++++------------
1 file changed, 23 insertions(+), 12 deletions(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index d813d799cee7..f440919b6c6f 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -166,17 +166,6 @@ struct bio *bio_split_discard(struct bio *bio, const struct queue_limits *lim,
return bio_submit_split(bio, split_sectors);
}
-struct bio *bio_split_write_zeroes(struct bio *bio,
- const struct queue_limits *lim, unsigned *nsegs)
-{
- *nsegs = 0;
- if (!lim->max_write_zeroes_sectors)
- return bio;
- if (bio_sectors(bio) <= lim->max_write_zeroes_sectors)
- return bio;
- return bio_submit_split(bio, lim->max_write_zeroes_sectors);
-}
-
static inline unsigned int blk_boundary_sectors(const struct queue_limits *lim,
bool is_atomic)
{
@@ -211,7 +200,9 @@ static inline unsigned get_max_io_size(struct bio *bio,
* We ignore lim->max_sectors for atomic writes because it may less
* than the actual bio size, which we cannot tolerate.
*/
- if (is_atomic)
+ if (bio_op(bio) == REQ_OP_WRITE_ZEROES)
+ max_sectors = lim->max_write_zeroes_sectors;
+ else if (is_atomic)
max_sectors = lim->atomic_write_max_sectors;
else
max_sectors = lim->max_sectors;
@@ -398,6 +389,26 @@ struct bio *bio_split_zone_append(struct bio *bio,
return bio_submit_split(bio, split_sectors);
}
+struct bio *bio_split_write_zeroes(struct bio *bio,
+ const struct queue_limits *lim, unsigned *nsegs)
+{
+ unsigned int max_sectors = get_max_io_size(bio, lim);
+
+ *nsegs = 0;
+
+ /*
+ * An unset limit should normally not happen, as bio submission is keyed
+ * off having a non-zero limit. But SCSI can clear the limit in the
+ * I/O completion handler, and we can race and see this. Splitting to a
+ * zero limit obviously doesn't make sense, so band-aid it here.
+ */
+ if (!max_sectors)
+ return bio;
+ if (bio_sectors(bio) <= max_sectors)
+ return bio;
+ return bio_submit_split(bio, max_sectors);
+}
+
/**
* bio_split_to_limits - split a bio to fit the queue limits
* @bio: bio to be split
--
2.45.2
