On 30.12.24 10:49, Pavel Tikhomirov wrote:
Looks good. See small comment inline:
On 12/17/24 18:34, Alexander Atanasov wrote:
In some cases qcow2 is passed requests without bvec set and
zero bi_size - for such requests qcow2 resorts to inline bvecs
which in that case are invalid.
To address this:
- Check if bi_size is not zero, and only then use the inline bvecs.
- Properly count number of segments in a NULL bvec.
- Add warn on to catch if we have a requests without bvec and bi_size.
https://virtuozzo.atlassian.net/browse/PSBM-159903
Signed-off-by: Alexander Atanasov <alexander.atana...@virtuozzo.com>
---
drivers/md/dm-qcow2-map.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm-qcow2-map.c b/drivers/md/dm-qcow2-map.c
index 6585f3fac6e7..a28f6332dc08 100644
--- a/drivers/md/dm-qcow2-map.c
+++ b/drivers/md/dm-qcow2-map.c
@@ -308,6 +308,9 @@ static unsigned int qio_nr_segs(struct qio *qio)
struct bvec_iter iter;
struct bio_vec bv;
+ if (!qio->bi_io_vec)
+ return nr_segs;
maybe just "return 0" (to improve readability) ?
I will let that to Kostya to decide. nr_segs is what the function is
returning and it is initiallized to zero 4 lines before that return,
it is not visible in the diff thou. I find it better to use a consistent
return inside a function if it is returning a variable, i.e. return the
what we have computed so far. Not for particular case but in a larger
function it is easy to miss to update such place when new calculation is
performed, this is why i prefer it that way but i don't mind either.
+
qcow2_for_each_bvec(iter, bv, qio->bi_iter, qio->bi_io_vec)
nr_segs++;
@@ -1248,6 +1251,7 @@ static void __submit_rw_mapped(struct qcow2
*qcow2, struct qio *qio, u32 nr_segs
bvec = __bvec_iter_bvec(qio->bi_io_vec, qio->bi_iter);
pos = to_bytes(qio->bi_iter.bi_sector);
+ WARN_ON(qio->bi_iter.bi_size && !bvec);
iov_iter_bvec(&iter, rw, bvec, nr_segs, qio->bi_iter.bi_size);
iter.iov_offset = qio->bi_iter.bi_bvec_done;
@@ -3538,7 +3542,7 @@ static void prepare_one_embedded_qio(struct
qcow2 *qcow2, struct qio *qio,
} else {
/* Single bio already provides bvec array */
bvec = rq->bio->bi_io_vec;
- if (!bvec) {
+ if (!bvec && rq->bio->bi_iter.bi_size) {
bvec = rq->bio->bi_inline_vecs;
if (unlikely(!bvec)) {
QC_ERR(qcow2->tgt->ti, "Expecting inline bvec");
--
Regards,
Alexander Atanasov
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