From: Max Reitz <mreitz@redhat.com>
To: qemu-block@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>,
Peter Maydell <peter.maydell@linaro.org>,
qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>
Subject: [PULL 5/5] block/file-posix: Let post-EOF fallocate serialize
Date: Mon, 4 Nov 2019 10:03:47 +0100 [thread overview]
Message-ID: <20191104090347.27278-6-mreitz@redhat.com> (raw)
In-Reply-To: <20191104090347.27278-1-mreitz@redhat.com>
The XFS kernel driver has a bug that may cause data corruption for qcow2
images as of qemu commit c8bb23cbdbe32f. 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>
---
block/file-posix.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/block/file-posix.c b/block/file-posix.c
index 0b7e904d48..1f0f61a02b 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2721,6 +2721,42 @@ raw_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int bytes,
RawPosixAIOData acb;
ThreadPoolFunc *handler;
+#ifdef CONFIG_FALLOCATE
+ if (offset + bytes > bs->total_sectors * BDRV_SECTOR_SIZE) {
+ BdrvTrackedRequest *req;
+ uint64_t end;
+
+ /*
+ * This is a workaround for a bug in the Linux XFS driver,
+ * where writes submitted through the AIO interface will be
+ * discarded if they happen beyond a concurrently running
+ * fallocate() that increases the file length (i.e., both the
+ * write and the fallocate() happen beyond the EOF).
+ *
+ * To work around it, we extend the tracked request for this
+ * zero write until INT64_MAX (effectively infinity), and mark
+ * it as serializing.
+ *
+ * We have to enable this workaround for all filesystems and
+ * AIO modes (not just XFS with aio=native), because for
+ * remote filesystems we do not know the host configuration.
+ */
+
+ req = bdrv_co_get_self_request(bs);
+ assert(req);
+ assert(req->type == BDRV_TRACKED_WRITE);
+ assert(req->offset <= offset);
+ assert(req->offset + req->bytes >= offset + bytes);
+
+ end = INT64_MAX & -(uint64_t)bs->bl.request_alignment;
+ req->bytes = end - req->offset;
+ req->overlap_bytes = req->bytes;
+
+ bdrv_mark_request_serialising(req, bs->bl.request_alignment);
+ bdrv_wait_serialising_requests(req);
+ }
+#endif
+
acb = (RawPosixAIOData) {
.bs = bs,
.aio_fildes = s->fd,
--
2.21.0
next prev parent reply other threads:[~2019-11-04 9:07 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-04 9:03 [PULL 0/5] Block patches for 4.2-rc0 Max Reitz
2019-11-04 9:03 ` [PULL 1/5] nvme: fix NSSRS offset in CAP register Max Reitz
2019-11-04 9:03 ` [PULL 2/5] block/block-copy: fix s->copy_size for compressed cluster Max Reitz
2019-11-04 9:03 ` [PULL 3/5] block: Make wait/mark serialising requests public Max Reitz
2019-11-04 9:03 ` [PULL 4/5] block: Add bdrv_co_get_self_request() Max Reitz
2019-11-04 9:03 ` Max Reitz [this message]
2019-11-06 11:56 ` [PULL 0/5] Block patches for 4.2-rc0 Peter Maydell
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191104090347.27278-6-mreitz@redhat.com \
--to=mreitz@redhat.com \
--cc=kwolf@redhat.com \
--cc=peter.maydell@linaro.org \
--cc=qemu-block@nongnu.org \
--cc=qemu-devel@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).