70 lines
2.6 KiB
Diff
70 lines
2.6 KiB
Diff
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From 7db05c8a732fbdc986a40aadf0de6dd23057d044 Mon Sep 17 00:00:00 2001
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From: Max Reitz <mreitz@redhat.com>
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Date: Fri, 1 Nov 2019 16:25:10 +0100
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Subject: [PATCH] block/file-posix: Let post-EOF fallocate serialize
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The XFS kernel driver has a bug that may cause data corruption for qcow2
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images as of qemu commit c8bb23cbdbe32f. We can work around it by
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treating post-EOF fallocates as serializing up until infinity (INT64_MAX
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in practice).
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Cc: qemu-stable@nongnu.org
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Message-id: 20191101152510.11719-4-mreitz@redhat.com
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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(cherry picked from commit 292d06b925b2787ee6f2430996b95651cae42fce)
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Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
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---
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block/file-posix.c | 36 ++++++++++++++++++++++++++++++++++++
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1 file changed, 36 insertions(+)
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diff --git a/block/file-posix.c b/block/file-posix.c
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index 992eb4a798..c5df61b477 100644
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--- a/block/file-posix.c
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+++ b/block/file-posix.c
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@@ -2623,6 +2623,42 @@ 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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+ /*
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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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+
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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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+
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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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+
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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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+
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acb = (RawPosixAIOData) {
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.bs = bs,
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.aio_fildes = s->fd,
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--
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2.23.0
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