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block/file-posix: Let post-EOF fallocate serialize
The XFS kernel driver has a bug that may cause data corruption for qcow2
images as of qemu commit c8bb23cbdb
. We can work around it by
treating post-EOF fallocates as serializing up until infinity (INT64_MAX
in practice).
Cc: qemu-stable@nongnu.org
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20191101152510.11719-4-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
parent
c28107e9e5
commit
292d06b925
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@ -2721,6 +2721,42 @@ raw_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int bytes,
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RawPosixAIOData acb;
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ThreadPoolFunc *handler;
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#ifdef CONFIG_FALLOCATE
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if (offset + bytes > bs->total_sectors * BDRV_SECTOR_SIZE) {
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BdrvTrackedRequest *req;
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uint64_t end;
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/*
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* This is a workaround for a bug in the Linux XFS driver,
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* where writes submitted through the AIO interface will be
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* discarded if they happen beyond a concurrently running
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* fallocate() that increases the file length (i.e., both the
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* write and the fallocate() happen beyond the EOF).
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*
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* To work around it, we extend the tracked request for this
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* zero write until INT64_MAX (effectively infinity), and mark
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* it as serializing.
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*
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* We have to enable this workaround for all filesystems and
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* AIO modes (not just XFS with aio=native), because for
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* remote filesystems we do not know the host configuration.
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*/
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req = bdrv_co_get_self_request(bs);
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assert(req);
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assert(req->type == BDRV_TRACKED_WRITE);
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assert(req->offset <= offset);
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assert(req->offset + req->bytes >= offset + bytes);
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end = INT64_MAX & -(uint64_t)bs->bl.request_alignment;
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req->bytes = end - req->offset;
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req->overlap_bytes = req->bytes;
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bdrv_mark_request_serialising(req, bs->bl.request_alignment);
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bdrv_wait_serialising_requests(req);
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}
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#endif
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acb = (RawPosixAIOData) {
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.bs = bs,
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.aio_fildes = s->fd,
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