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[Qemu-devel] [PATCH 1/2] raw-posix: fix O_DIRECT short reads
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH 1/2] raw-posix: fix O_DIRECT short reads |
Date: |
Thu, 21 Aug 2014 13:44:07 +0100 |
The following O_DIRECT read from a <512 byte file fails:
$ truncate -s 320 test.img
$ qemu-io -n -c 'read -P 0 0 512' test.img
qemu-io: can't open device test.img: Could not read image for determining its
format: Invalid argument
Note that qemu-io completes successfully without the -n (O_DIRECT)
option.
This patch fixes qemu-iotests ./check -nocache -vmdk 059.
Suggested-by: Kevin Wolf <address@hidden>
Reported-by: Markus Armbruster <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
block/raw-posix.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 1194eb0..a48ce91 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -747,6 +747,15 @@ static ssize_t handle_aiocb_rw_linear(RawPosixAIOData
*aiocb, char *buf)
}
if (len == -1 && errno == EINTR) {
continue;
+ } else if (len == -1 && errno == EINVAL &&
+ (aiocb->bs->open_flags & BDRV_O_NOCACHE) &&
+ !(aiocb->aio_type & QEMU_AIO_WRITE) &&
+ offset > 0) {
+ /* O_DIRECT pread() may fail with EINVAL when offset is unaligned
+ * after a short read. Assume that O_DIRECT short reads only occur
+ * at EOF. Therefore this is a short read, not an I/O error.
+ */
+ break;
} else if (len == -1) {
offset = -errno;
break;
--
1.9.3