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author | 2010-07-14 12:42:02 +0200 | |
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committer | 2010-07-20 17:42:10 -0500 | |
commit | 7cf46ee61e071fb02780c2dc635886aa81a8c262 (patch) | |
tree | 569560155dc755eabda9c06263ef90ff811db0e2 | |
parent | vpc: Use bdrv_(p)write_sync for metadata writes (diff) | |
download | qemu-kvm-7cf46ee61e071fb02780c2dc635886aa81a8c262.tar.gz qemu-kvm-7cf46ee61e071fb02780c2dc635886aa81a8c262.tar.bz2 qemu-kvm-7cf46ee61e071fb02780c2dc635886aa81a8c262.zip |
block: Fix early failure in multiwrite
bdrv_aio_writev may call the callback immediately (and it will commonly do so
in error cases). Current code doesn't consider this. For details see the
comment added by this patch.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 453f9a1652629e5805995b165be2e634c8487139)
Conflicts:
block.c
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r-- | block.c | 37 |
1 files changed, 30 insertions, 7 deletions
@@ -1802,8 +1802,29 @@ int bdrv_aio_multiwrite(BlockDriverState *bs, BlockRequest *reqs, int num_reqs) // Check for mergable requests num_reqs = multiwrite_merge(bs, reqs, num_reqs, mcb); - // Run the aio requests + /* + * Run the aio requests. As soon as one request can't be submitted + * successfully, fail all requests that are not yet submitted (we must + * return failure for all requests anyway) + * + * num_requests cannot be set to the right value immediately: If + * bdrv_aio_writev fails for some request, num_requests would be too high + * and therefore multiwrite_cb() would never recognize the multiwrite + * request as completed. We also cannot use the loop variable i to set it + * when the first request fails because the callback may already have been + * called for previously submitted requests. Thus, num_requests must be + * incremented for each request that is submitted. + * + * The problem that callbacks may be called early also means that we need + * to take care that num_requests doesn't become 0 before all requests are + * submitted - multiwrite_cb() would consider the multiwrite request + * completed. A dummy request that is "completed" by a manual call to + * multiwrite_cb() takes care of this. + */ + mcb->num_requests = 1; + for (i = 0; i < num_reqs; i++) { + mcb->num_requests++; acb = bdrv_aio_writev(bs, reqs[i].sector, reqs[i].qiov, reqs[i].nb_sectors, multiwrite_cb, mcb); @@ -1811,23 +1832,25 @@ int bdrv_aio_multiwrite(BlockDriverState *bs, BlockRequest *reqs, int num_reqs) // We can only fail the whole thing if no request has been // submitted yet. Otherwise we'll wait for the submitted AIOs to // complete and report the error in the callback. - if (mcb->num_requests == 0) { - reqs[i].error = -EIO; + if (i == 0) { goto fail; } else { - mcb->num_requests++; multiwrite_cb(mcb, -EIO); break; } - } else { - mcb->num_requests++; } } + /* Complete the dummy request */ + multiwrite_cb(mcb, 0); + return 0; fail: - free(mcb); + for (i = 0; i < mcb->num_callbacks; i++) { + reqs[i].error = -EIO; + } + qemu_free(mcb); return -1; } |