| Message ID | 1425509290-14048-1-git-send-email-stefanha@redhat.com |
|---|---|
| State | New |
| Headers | show |
Am 04.03.2015 um 23:48 hat Stefan Hajnoczi geschrieben: > 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> This seems to conflict with the geometry series. Please rebase on the current block branch. Also, I would be surprised if this had been working by design. It's probably more by chance. If we want to make this a supported case, we need to add a qemu-iotests case, as this seems to be easy to break accidentally. Kevin
On Thu, Mar 05, 2015 at 01:53:57PM +0100, Kevin Wolf wrote: > Am 04.03.2015 um 23:48 hat Stefan Hajnoczi geschrieben: > > 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> > > This seems to conflict with the geometry series. Please rebase on the > current block branch. > > Also, I would be surprised if this had been working by design. It's > probably more by chance. If we want to make this a supported case, we > need to add a qemu-iotests case, as this seems to be easy to break > accidentally. Will send v2. Stefan
diff --git a/block/raw-posix.c b/block/raw-posix.c index b5f077a..6eb3925 100644 --- a/block/raw-posix.c +++ b/block/raw-posix.c @@ -218,6 +218,31 @@ static int raw_normalize_devicepath(const char **filename) } #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; @@ -267,7 +292,7 @@ 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; } @@ -279,7 +304,7 @@ 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; }
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> --- block/raw-posix.c | 29 +++++++++++++++++++++++++++-- 1 file changed, 27 insertions(+), 2 deletions(-)