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authorStefan Hajnoczi <stefanha@redhat.com>2015-03-05 15:38:17 -0600
committerKevin Wolf <kwolf@redhat.com>2015-03-10 14:02:24 +0100
commit22d182e82b4ba2fb78b2cc22bcec4e6a440b0ad6 (patch)
treee7ee073dd85357041aa7d9d21169e20e09853dd9 /block/raw-posix.c
parentc095348b914b740d8364a2ccf748e4284de3b68b (diff)
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block/raw-posix: fix launching with failed disks
Since commit c25f53b06eba1575d5d0e92a0132455c97825b83 ("raw: Probe required direct I/O alignment") QEMU has failed to launch if image files produce I/O errors. Previously, QEMU would launch successfully and the guest would see the errors when attempting I/O. This is a regression and may prevent multipath I/O inside the guest, where QEMU must launch and let the guest figure out by itself which disks are online. Tweak the alignment probing code in raw-posix.c to explicitly look for EINVAL on Linux instead of bailing. The kernel refuses misaligned requests with this error code and other error codes can be ignored. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block/raw-posix.c')
-rw-r--r--block/raw-posix.c29
1 files changed, 27 insertions, 2 deletions
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 3263d2b..f0b4488 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -272,6 +272,31 @@ static int probe_physical_blocksize(int fd, unsigned int *blk_size)
#endif
}
+/* Check if read is allowed with given memory buffer and length.
+ *
+ * This function is used to check O_DIRECT memory buffer and request alignment.
+ */
+static bool raw_is_io_aligned(int fd, void *buf, size_t len)
+{
+ ssize_t ret = pread(fd, buf, len, 0);
+
+ if (ret >= 0) {
+ return true;
+ }
+
+#ifdef __linux__
+ /* The Linux kernel returns EINVAL for misaligned O_DIRECT reads. Ignore
+ * other errors (e.g. real I/O error), which could happen on a failed
+ * drive, since we only care about probing alignment.
+ */
+ if (errno != EINVAL) {
+ return true;
+ }
+#endif
+
+ return false;
+}
+
static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp)
{
BDRVRawState *s = bs->opaque;
@@ -307,7 +332,7 @@ static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp)
size_t align;
buf = qemu_memalign(MAX_BLOCKSIZE, 2 * MAX_BLOCKSIZE);
for (align = 512; align <= MAX_BLOCKSIZE; align <<= 1) {
- if (pread(fd, buf + align, MAX_BLOCKSIZE, 0) >= 0) {
+ if (raw_is_io_aligned(fd, buf + align, MAX_BLOCKSIZE)) {
s->buf_align = align;
break;
}
@@ -319,7 +344,7 @@ static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp)
size_t align;
buf = qemu_memalign(s->buf_align, MAX_BLOCKSIZE);
for (align = 512; align <= MAX_BLOCKSIZE; align <<= 1) {
- if (pread(fd, buf, align, 0) >= 0) {
+ if (raw_is_io_aligned(fd, buf, align)) {
bs->request_alignment = align;
break;
}