From: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> Prepare for the following patch when bdrv_pad_request() will be able to fail. Update the comments.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> Message-Id: <20201211183934.169161-5-vsement...@virtuozzo.com> Reviewed-by: Eric Blake <ebl...@redhat.com> [eblake: grammar tweak] Signed-off-by: Eric Blake <ebl...@redhat.com> --- block/io.c | 25 +++++++++++++++++++------ block/io.c.rej | 40 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 59 insertions(+), 6 deletions(-) create mode 100644 block/io.c.rej diff --git a/block/io.c b/block/io.c index c8c9dea55466..3b1aec366ede 100644 --- a/block/io.c +++ b/block/io.c @@ -2135,6 +2135,7 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child, uint64_t align = bs->bl.request_alignment; BdrvRequestPadding pad; int ret; + bool padded = false; trace_bdrv_co_pwritev(child->bs, offset, bytes, flags); @@ -2166,20 +2167,32 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child, return 0; } + if (!(flags & BDRV_REQ_ZERO_WRITE)) { + /* + * Pad request for following read-modify-write cycle. + * bdrv_co_do_zero_pwritev() does aligning by itself, so, we do + * alignment only if there is no ZERO flag. + */ + padded = bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, + &pad); + } + bdrv_inc_in_flight(bs); - /* - * Align write if necessary by performing a read-modify-write cycle. - * Pad qiov with the read parts and be sure to have a tracked request not - * only for bdrv_aligned_pwritev, but also for the reads of the RMW cycle. - */ tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_WRITE); if (flags & BDRV_REQ_ZERO_WRITE) { + assert(!padded); ret = bdrv_co_do_zero_pwritev(child, offset, bytes, flags, &req); goto out; } - if (bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad)) { + if (padded) { + /* + * Request was unaligned to request_alignment and therefore + * padded. We are going to do read-modify-write, and must + * serialize the request to prevent interactions of the + * widened region with other transactions. + */ bdrv_make_request_serialising(&req, align); bdrv_padding_rmw_read(child, &req, &pad, false); } diff --git a/block/io.c.rej b/block/io.c.rej new file mode 100644 index 000000000000..f52df016263b --- /dev/null +++ b/block/io.c.rej @@ -0,0 +1,40 @@ +diff a/block/io.c b/block/io.c (rejected hunks) +@@ -2138,20 +2139,32 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child, + return 0; + } + ++ if (!(flags & BDRV_REQ_ZERO_WRITE)) { ++ /* ++ * Pad request for following read-modify-write cycle. ++ * bdrv_co_do_zero_pwritev() does aligning by itself, so, we do ++ * alignment only if there is no ZERO flag. ++ */ ++ padded = bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, ++ &pad); ++ } ++ + bdrv_inc_in_flight(bs); +- /* +- * Align write if necessary by performing a read-modify-write cycle. +- * Pad qiov with the read parts and be sure to have a tracked request not +- * only for bdrv_aligned_pwritev, but also for the reads of the RMW cycle. +- */ + tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_WRITE); + + if (flags & BDRV_REQ_ZERO_WRITE) { ++ assert(!padded); + ret = bdrv_co_do_zero_pwritev(child, offset, bytes, flags, &req); + goto out; + } + +- if (bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad)) { ++ if (padded) { ++ /* ++ * Request was unaligned to request_alignment and therefore padded. ++ * We are going to do read-modify-write. User is not prepared to widened ++ * request intersections with other requests, so we serialize the ++ * request. ++ */ + bdrv_mark_request_serialising(&req, align); + bdrv_padding_rmw_read(child, &req, &pad, false); + } -- 2.30.0