From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Fabian Ebner Date: Tue, 17 May 2022 09:46:02 +0200 Subject: [PATCH] Revert "block/rbd: implement bdrv_co_block_status" During backup, bdrv_co_block_status is called for each block copy chunk. When RBD is used, the current implementation with rbd_diff_iterate2() using whole_object=true takes about linearly more time, depending on the image size. Since there are linearly more chunks, the slowdown is quadratic, becoming unacceptable for large images (starting somewhere between 500-1000 GiB in my testing). This reverts commit 0347a8fd4c3faaedf119be04c197804be40a384b as a stop-gap measure, until it's clear how to make the implemenation more efficient. Upstream bug report: https://gitlab.com/qemu-project/qemu/-/issues/1026 Signed-off-by: Fabian Ebner --- block/rbd.c | 112 ---------------------------------------------------- 1 file changed, 112 deletions(-) diff --git a/block/rbd.c b/block/rbd.c index 0913a0af39..1dab254517 100644 --- a/block/rbd.c +++ b/block/rbd.c @@ -108,12 +108,6 @@ typedef struct RBDTask { int64_t ret; } RBDTask; -typedef struct RBDDiffIterateReq { - uint64_t offs; - uint64_t bytes; - bool exists; -} RBDDiffIterateReq; - static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx, BlockdevOptionsRbd *opts, bool cache, const char *keypairs, const char *secretid, @@ -1456,111 +1450,6 @@ static ImageInfoSpecific *qemu_rbd_get_specific_info(BlockDriverState *bs, return spec_info; } -/* - * rbd_diff_iterate2 allows to interrupt the exection by returning a negative - * value in the callback routine. Choose a value that does not conflict with - * an existing exitcode and return it if we want to prematurely stop the - * execution because we detected a change in the allocation status. - */ -#define QEMU_RBD_EXIT_DIFF_ITERATE2 -9000 - -static int qemu_rbd_diff_iterate_cb(uint64_t offs, size_t len, - int exists, void *opaque) -{ - RBDDiffIterateReq *req = opaque; - - assert(req->offs + req->bytes <= offs); - /* - * we do not diff against a snapshot so we should never receive a callback - * for a hole. - */ - assert(exists); - - if (!req->exists && offs > req->offs) { - /* - * we started in an unallocated area and hit the first allocated - * block. req->bytes must be set to the length of the unallocated area - * before the allocated area. stop further processing. - */ - req->bytes = offs - req->offs; - return QEMU_RBD_EXIT_DIFF_ITERATE2; - } - - if (req->exists && offs > req->offs + req->bytes) { - /* - * we started in an allocated area and jumped over an unallocated area, - * req->bytes contains the length of the allocated area before the - * unallocated area. stop further processing. - */ - return QEMU_RBD_EXIT_DIFF_ITERATE2; - } - - req->bytes += len; - req->exists = true; - - return 0; -} - -static int coroutine_fn qemu_rbd_co_block_status(BlockDriverState *bs, - bool want_zero, int64_t offset, - int64_t bytes, int64_t *pnum, - int64_t *map, - BlockDriverState **file) -{ - BDRVRBDState *s = bs->opaque; - int status, r; - RBDDiffIterateReq req = { .offs = offset }; - uint64_t features, flags; - - assert(offset + bytes <= s->image_size); - - /* default to all sectors allocated */ - status = BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID; - *map = offset; - *file = bs; - *pnum = bytes; - - /* check if RBD image supports fast-diff */ - r = rbd_get_features(s->image, &features); - if (r < 0) { - return status; - } - if (!(features & RBD_FEATURE_FAST_DIFF)) { - return status; - } - - /* check if RBD fast-diff result is valid */ - r = rbd_get_flags(s->image, &flags); - if (r < 0) { - return status; - } - if (flags & RBD_FLAG_FAST_DIFF_INVALID) { - return status; - } - - r = rbd_diff_iterate2(s->image, NULL, offset, bytes, true, true, - qemu_rbd_diff_iterate_cb, &req); - if (r < 0 && r != QEMU_RBD_EXIT_DIFF_ITERATE2) { - return status; - } - assert(req.bytes <= bytes); - if (!req.exists) { - if (r == 0) { - /* - * rbd_diff_iterate2 does not invoke callbacks for unallocated - * areas. This here catches the case where no callback was - * invoked at all (req.bytes == 0). - */ - assert(req.bytes == 0); - req.bytes = bytes; - } - status = BDRV_BLOCK_ZERO | BDRV_BLOCK_OFFSET_VALID; - } - - *pnum = req.bytes; - return status; -} - static int64_t coroutine_fn qemu_rbd_co_getlength(BlockDriverState *bs) { BDRVRBDState *s = bs->opaque; @@ -1796,7 +1685,6 @@ static BlockDriver bdrv_rbd = { #ifdef LIBRBD_SUPPORTS_WRITE_ZEROES .bdrv_co_pwrite_zeroes = qemu_rbd_co_pwrite_zeroes, #endif - .bdrv_co_block_status = qemu_rbd_co_block_status, .bdrv_snapshot_create = qemu_rbd_snap_create, .bdrv_snapshot_delete = qemu_rbd_snap_remove,