From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Fabian Ebner <f.ebner@proxmox.com>
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 <f.ebner@proxmox.com>
---
block/rbd.c | 112 ----------------------------------------------------
1 file changed, 112 deletions(-)
diff --git a/block/rbd.c b/block/rbd.c
index 98f4ba2620..efcbbe5949 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -97,12 +97,6 @@ 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,
@@ -1293,111 +1287,6 @@ 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 qemu_rbd_getlength(BlockDriverState *bs)
{
BDRVRBDState *s = bs->opaque;
@@ -1633,7 +1522,6 @@ 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,