5b15e2ecaf
Notable changes:
* The only big change is the switch to using a custom QIOChannel for
savevm-async, because the previously used QEMUFileOps was dropped.
Changes to the current implementation:
* Switch to vector based methods as required for an IO channel. For
short reads the passed-in IO vector is stuffed with zeroes at the
end, just to be sure.
* For reading: The documentation in include/io/channel.h states that
at least one byte should be read, so also error out when whe are
at the very end instead of returning 0.
* For reading: Fix off-by-one error when request goes beyond end.
The wrong code piece was:
if ((pos + size) > maxlen) {
size = maxlen - pos - 1;
}
Previously, the last byte would not be read. It's actually
possible to get a snapshot .raw file that has content all the way
up the final 512 byte (= BDRV_SECTOR_SIZE) boundary without any
trailing zero bytes (I wrote a script to do it).
Luckily, it didn't cause a real issue, because qemu_loadvm_state()
is not interested in the final (i.e. QEMU_VM_VMDESCRIPTION)
section. The buffer for reading it is simply freed up afterwards
and the function will assume that it read the whole section, even
if that's not the case.
* For writing: Make use of the generated blk_pwritev() wrapper
instead of manually wrapping the coroutine to simplify and save a
few lines.
* Adapt to changed interfaces for blk_{pread,pwrite}:
* a9262f551e ("block: Change blk_{pread,pwrite}() param order")
* 3b35d4542c ("block: Add a 'flags' param to blk_pread()")
* bf5b16fa40 ("block: Make blk_{pread,pwrite}() return 0 on success")
Those changes especially affected the qemu-img dd patches, because
the context also changed, but also some of our block drivers used
the functions.
* Drop qemu-common.h include: it got renamed after essentially
everything was moved to other headers. The only remaining user I
could find for things dropped from the header between 7.0 and 7.1
was qemu_get_vm_name() in the iscsi-initiatorname patch, but it
already includes the header to which the function was moved.
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
162 lines
5.3 KiB
Diff
162 lines
5.3 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Fabian Ebner <f.ebner@proxmox.com>
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Date: Tue, 17 May 2022 09:46:02 +0200
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Subject: [PATCH] Revert "block/rbd: implement bdrv_co_block_status"
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During backup, bdrv_co_block_status is called for each block copy
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chunk. When RBD is used, the current implementation with
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rbd_diff_iterate2() using whole_object=true takes about linearly more
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time, depending on the image size. Since there are linearly more
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chunks, the slowdown is quadratic, becoming unacceptable for large
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images (starting somewhere between 500-1000 GiB in my testing).
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This reverts commit 0347a8fd4c3faaedf119be04c197804be40a384b as a
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stop-gap measure, until it's clear how to make the implemenation
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more efficient.
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Upstream bug report:
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https://gitlab.com/qemu-project/qemu/-/issues/1026
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Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
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---
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block/rbd.c | 112 ----------------------------------------------------
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1 file changed, 112 deletions(-)
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diff --git a/block/rbd.c b/block/rbd.c
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index 98f4ba2620..efcbbe5949 100644
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--- a/block/rbd.c
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+++ b/block/rbd.c
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@@ -97,12 +97,6 @@ typedef struct RBDTask {
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int64_t ret;
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} RBDTask;
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-typedef struct RBDDiffIterateReq {
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- uint64_t offs;
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- uint64_t bytes;
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- bool exists;
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-} RBDDiffIterateReq;
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-
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static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
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BlockdevOptionsRbd *opts, bool cache,
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const char *keypairs, const char *secretid,
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@@ -1293,111 +1287,6 @@ static ImageInfoSpecific *qemu_rbd_get_specific_info(BlockDriverState *bs,
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return spec_info;
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}
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-/*
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- * rbd_diff_iterate2 allows to interrupt the exection by returning a negative
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- * value in the callback routine. Choose a value that does not conflict with
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- * an existing exitcode and return it if we want to prematurely stop the
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- * execution because we detected a change in the allocation status.
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- */
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-#define QEMU_RBD_EXIT_DIFF_ITERATE2 -9000
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-
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-static int qemu_rbd_diff_iterate_cb(uint64_t offs, size_t len,
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- int exists, void *opaque)
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-{
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- RBDDiffIterateReq *req = opaque;
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-
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- assert(req->offs + req->bytes <= offs);
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- /*
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- * we do not diff against a snapshot so we should never receive a callback
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- * for a hole.
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- */
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- assert(exists);
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-
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- if (!req->exists && offs > req->offs) {
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- /*
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- * we started in an unallocated area and hit the first allocated
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- * block. req->bytes must be set to the length of the unallocated area
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- * before the allocated area. stop further processing.
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- */
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- req->bytes = offs - req->offs;
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- return QEMU_RBD_EXIT_DIFF_ITERATE2;
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- }
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-
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- if (req->exists && offs > req->offs + req->bytes) {
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- /*
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- * we started in an allocated area and jumped over an unallocated area,
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- * req->bytes contains the length of the allocated area before the
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- * unallocated area. stop further processing.
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- */
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- return QEMU_RBD_EXIT_DIFF_ITERATE2;
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- }
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-
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- req->bytes += len;
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- req->exists = true;
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-
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- return 0;
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-}
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-
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-static int coroutine_fn qemu_rbd_co_block_status(BlockDriverState *bs,
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- bool want_zero, int64_t offset,
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- int64_t bytes, int64_t *pnum,
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- int64_t *map,
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- BlockDriverState **file)
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-{
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- BDRVRBDState *s = bs->opaque;
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- int status, r;
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- RBDDiffIterateReq req = { .offs = offset };
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- uint64_t features, flags;
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-
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- assert(offset + bytes <= s->image_size);
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-
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- /* default to all sectors allocated */
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- status = BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID;
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- *map = offset;
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- *file = bs;
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- *pnum = bytes;
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-
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- /* check if RBD image supports fast-diff */
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- r = rbd_get_features(s->image, &features);
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- if (r < 0) {
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- return status;
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- }
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- if (!(features & RBD_FEATURE_FAST_DIFF)) {
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- return status;
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- }
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-
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- /* check if RBD fast-diff result is valid */
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- r = rbd_get_flags(s->image, &flags);
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- if (r < 0) {
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- return status;
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- }
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- if (flags & RBD_FLAG_FAST_DIFF_INVALID) {
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- return status;
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- }
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-
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- r = rbd_diff_iterate2(s->image, NULL, offset, bytes, true, true,
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- qemu_rbd_diff_iterate_cb, &req);
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- if (r < 0 && r != QEMU_RBD_EXIT_DIFF_ITERATE2) {
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- return status;
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- }
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- assert(req.bytes <= bytes);
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- if (!req.exists) {
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- if (r == 0) {
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- /*
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- * rbd_diff_iterate2 does not invoke callbacks for unallocated
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- * areas. This here catches the case where no callback was
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- * invoked at all (req.bytes == 0).
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- */
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- assert(req.bytes == 0);
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- req.bytes = bytes;
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- }
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- status = BDRV_BLOCK_ZERO | BDRV_BLOCK_OFFSET_VALID;
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- }
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-
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- *pnum = req.bytes;
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- return status;
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-}
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-
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static int64_t qemu_rbd_getlength(BlockDriverState *bs)
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{
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BDRVRBDState *s = bs->opaque;
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@@ -1633,7 +1522,6 @@ static BlockDriver bdrv_rbd = {
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#ifdef LIBRBD_SUPPORTS_WRITE_ZEROES
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.bdrv_co_pwrite_zeroes = qemu_rbd_co_pwrite_zeroes,
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#endif
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- .bdrv_co_block_status = qemu_rbd_co_block_status,
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.bdrv_snapshot_create = qemu_rbd_snap_create,
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.bdrv_snapshot_delete = qemu_rbd_snap_remove,
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