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block/raw-posix: fix launching with failed disks 

Since commit c25f53b06e ("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>
This commit is contained in:
Stefan Hajnoczi 2015-03-05 15:38:17 -06:00 committed by Kevin Wolf
parent c095348b91
commit 22d182e82b
1 changed files with 27 additions and 2 deletions
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29
block/raw-posix.c
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@ -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;
}