On Fri, 07/06 21:30, Vladimir Sementsov-Ogievskiy wrote: > Here two things are fixed: > > 1. Architecture > > On each recursion step, we go to the child of src or dst, only for one > of them. So, it's wrong to create tracked requests for both on each > step. It leads to tracked requests duplication. > > 2. Wait for serializing requests on write path independently of > BDRV_REQ_NO_SERIALISING > > Before commit 9ded4a01149 "backup: Use copy offloading", > BDRV_REQ_NO_SERIALISING was used for only one case: read in > copy-on-write operation during backup. Also, the flag was handled only > on read path (in bdrv_co_preadv and bdrv_aligned_preadv). > > After 9ded4a01149, flag is used for not waiting serializing operations > on backup target (in same case of copy-on-write operation). This > behavior change is unsubstantiated and potentially dangerous, let's > drop it and add additional asserts and documentation. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> > --- > include/block/block.h | 13 +++++++ > block/io.c | 103 > +++++++++++++++++++++++++++++++------------------- > 2 files changed, 78 insertions(+), 38 deletions(-) > > diff --git a/include/block/block.h b/include/block/block.h > index e5c7759a0c..a06a4d27de 100644 > --- a/include/block/block.h > +++ b/include/block/block.h > @@ -50,6 +50,19 @@ typedef enum { > * opened with BDRV_O_UNMAP. > */ > BDRV_REQ_MAY_UNMAP = 0x4, > + > + /* The BDRV_REQ_NO_SERIALISING means that we don't want to > + * wait_serialising_requests(), when reading. > + * > + * This flag is used for backup copy on write operation, when we need to > + * read old data before write (write notifier triggered). It is ok, due > to > + * we already waited for serializing requests in initiative write (see > + * bdrv_aligned_pwritev), and it is necessary for the case when > initiative > + * write is serializing itself (we'll dead lock waiting it). > + * > + * The described case is the only usage for the flag for now, so, it is > + * supported only for read operation and restricted for write. > + */ > BDRV_REQ_NO_SERIALISING = 0x8, > BDRV_REQ_FUA = 0x10, > BDRV_REQ_WRITE_COMPRESSED = 0x20, > diff --git a/block/io.c b/block/io.c > index 1a2272fad3..621b21c455 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -1572,6 +1572,8 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild > *child, > max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, > INT_MAX), > align); > > + /* BDRV_REQ_NO_SERIALISING is only for read operation */ > + assert(!(flags & BDRV_REQ_NO_SERIALISING)); > waited = wait_serialising_requests(req); > assert(!waited || !req->serialising); > assert(req->overlap_offset <= offset); > @@ -2888,15 +2890,19 @@ void bdrv_unregister_buf(BlockDriverState *bs, void > *host) > } > } > > -static int coroutine_fn bdrv_co_copy_range_internal(BdrvChild *src, > - uint64_t src_offset, > - BdrvChild *dst, > - uint64_t dst_offset, > - uint64_t bytes, > - BdrvRequestFlags flags, > - bool recurse_src) > +/* Common part of bdrv_co_copy_range_from and bdrv_co_copy_range_to. > + * > + * Return -errno on failure, > + * 0 if successfully handled by bdrv_co_pwrite_zeroes > + * 1 to continue copy_range operation > + */ > +static int coroutine_fn bdrv_co_copy_range_check(BdrvChild *src, > + uint64_t src_offset, > + BdrvChild *dst, > + uint64_t dst_offset, > + uint64_t bytes, > + BdrvRequestFlags flags) > { > - BdrvTrackedRequest src_req, dst_req; > int ret; > > if (!dst || !dst->bs) { > @@ -2923,33 +2929,8 @@ static int coroutine_fn > bdrv_co_copy_range_internal(BdrvChild *src, > || src->bs->encrypted || dst->bs->encrypted) { > return -ENOTSUP; > } > - bdrv_inc_in_flight(src->bs); > - bdrv_inc_in_flight(dst->bs); > - tracked_request_begin(&src_req, src->bs, src_offset, > - bytes, BDRV_TRACKED_READ); > - tracked_request_begin(&dst_req, dst->bs, dst_offset, > - bytes, BDRV_TRACKED_WRITE); > > - if (!(flags & BDRV_REQ_NO_SERIALISING)) { > - wait_serialising_requests(&src_req); > - wait_serialising_requests(&dst_req); > - } > - if (recurse_src) { > - ret = src->bs->drv->bdrv_co_copy_range_from(src->bs, > - src, src_offset, > - dst, dst_offset, > - bytes, flags); > - } else { > - ret = dst->bs->drv->bdrv_co_copy_range_to(dst->bs, > - src, src_offset, > - dst, dst_offset, > - bytes, flags); > - } > - tracked_request_end(&src_req); > - tracked_request_end(&dst_req); > - bdrv_dec_in_flight(src->bs); > - bdrv_dec_in_flight(dst->bs); > - return ret; > + return 1; > } > > /* Copy range from @src to @dst. > @@ -2960,8 +2941,31 @@ int coroutine_fn bdrv_co_copy_range_from(BdrvChild > *src, uint64_t src_offset, > BdrvChild *dst, uint64_t dst_offset, > uint64_t bytes, BdrvRequestFlags > flags) > { > - return bdrv_co_copy_range_internal(src, src_offset, dst, dst_offset, > - bytes, flags, true); > + BdrvTrackedRequest req; > + int ret; > + > + ret = bdrv_co_copy_range_check(src, src_offset, dst, dst_offset, bytes, > + flags);
I don't like a function called _check to already do I/O here. Instead, I think this is cleaner: --- diff --git a/block/io.c b/block/io.c index 1a2272fad3..694a94dfae 100644 --- a/block/io.c +++ b/block/io.c @@ -2923,32 +2923,34 @@ static int coroutine_fn bdrv_co_copy_range_internal(BdrvChild *src, || src->bs->encrypted || dst->bs->encrypted) { return -ENOTSUP; } - bdrv_inc_in_flight(src->bs); - bdrv_inc_in_flight(dst->bs); - tracked_request_begin(&src_req, src->bs, src_offset, - bytes, BDRV_TRACKED_READ); - tracked_request_begin(&dst_req, dst->bs, dst_offset, - bytes, BDRV_TRACKED_WRITE); - if (!(flags & BDRV_REQ_NO_SERIALISING)) { - wait_serialising_requests(&src_req); - wait_serialising_requests(&dst_req); - } if (recurse_src) { + bdrv_inc_in_flight(src->bs); + tracked_request_begin(&src_req, src->bs, src_offset, + bytes, BDRV_TRACKED_READ); + if (!(flags & BDRV_REQ_NO_SERIALISING)) { + wait_serialising_requests(&src_req); + } ret = src->bs->drv->bdrv_co_copy_range_from(src->bs, src, src_offset, dst, dst_offset, bytes, flags); + tracked_request_end(&src_req); + bdrv_dec_in_flight(src->bs); } else { + bdrv_inc_in_flight(dst->bs); + tracked_request_begin(&dst_req, dst->bs, dst_offset, + bytes, BDRV_TRACKED_WRITE); + /* BDRV_REQ_NO_SERIALISING is only for read operation, so we ignore it + * in flags. */ + wait_serialising_requests(&dst_req); ret = dst->bs->drv->bdrv_co_copy_range_to(dst->bs, src, src_offset, dst, dst_offset, bytes, flags); + tracked_request_end(&dst_req); + bdrv_dec_in_flight(dst->bs); } - tracked_request_end(&src_req); - tracked_request_end(&dst_req); - bdrv_dec_in_flight(src->bs); - bdrv_dec_in_flight(dst->bs); return ret; }