| Message ID | 20201203222713.13507-5-vsementsov@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: prepare for 64bit | expand |
On Fri, Dec 04, 2020 at 01:27:13AM +0300, Vladimir Sementsov-Ogievskiy wrote: > Finally to be safe with calculations, to not calculate different > maximums for different nodes (depending on cluster size and > request_alignment), let's simply set QEMU_ALIGN_DOWN(INT64_MAX, 2^30) > as absolute maximum bytes length for Qemu. Actually, it's not much less > than INT64_MAX. > +/* > + * We want allow aligning requests and disk length up to any 32bit alignment > + * and don't afraid of overflow. > + * To achieve it, and in the same time use some pretty number as maximum disk > + * size, let's define maximum "length" (a limit for any offset/bytes request and > + * for disk size) to be the greatest power of 2 less than INT64_MAX. > + */ > +#define BDRV_MAX_ALIGNMENT (1L << 30) > +#define BDRV_MAX_LENGTH (QEMU_ALIGN_DOWN(INT64_MAX, BDRV_MAX_ALIGNMENT)) This change broke nbdkit tests. We test that qemu can handle a qemu NBD export of size 2^63 - 512, the largest size that (experimentally) we found qemu could safely handle. eg: https://github.com/libguestfs/nbdkit/blob/master/tests/test-memory-largest-for-qemu.sh Before this commit: $ nbdkit memory $(( 2**63 - 512 )) --run './qemu-img info "$uri"' image: nbd://localhost:10809 file format: raw virtual size: 8 EiB (9223372036854775296 bytes) disk size: unavailable After this commit: $ nbdkit memory $(( 2**63 - 512 )) --run './qemu-img info "$uri"' qemu-img: Could not open 'nbd://localhost:10809': Could not refresh total sector count: File too large Can I confirm that this limit is now the new official one and we should adjust nbdkit tests? Or was this change unintentional given that qemu seemed happy to handle 2^63 - 512 disks before? Note that nbdkit & libnbd support up to 2^63 - 1 bytes (we are not limited to whole sectors). Also the Linux kernel will let you create a /dev/nbdX device of size 2^63 - 1. Rich.
On Thu, Jan 07, 2021 at 09:58:17AM +0000, Richard W.M. Jones wrote: > On Fri, Dec 04, 2020 at 01:27:13AM +0300, Vladimir Sementsov-Ogievskiy wrote: > > Finally to be safe with calculations, to not calculate different > > maximums for different nodes (depending on cluster size and > > request_alignment), let's simply set QEMU_ALIGN_DOWN(INT64_MAX, 2^30) > > as absolute maximum bytes length for Qemu. Actually, it's not much less > > than INT64_MAX. > > > +/* > > + * We want allow aligning requests and disk length up to any 32bit alignment > > + * and don't afraid of overflow. > > + * To achieve it, and in the same time use some pretty number as maximum disk > > + * size, let's define maximum "length" (a limit for any offset/bytes request and > > + * for disk size) to be the greatest power of 2 less than INT64_MAX. > > + */ > > +#define BDRV_MAX_ALIGNMENT (1L << 30) > > +#define BDRV_MAX_LENGTH (QEMU_ALIGN_DOWN(INT64_MAX, BDRV_MAX_ALIGNMENT)) > > This change broke nbdkit tests. Actually that's not the only problem. It appears that we're unable to read or write the last sector of this disk: $ nbdkit memory $(( 2**63 - 2**30 )) --run 'build/qemu-io -r -f raw "$uri" -c "r -v $(( 2**63 - 2**30 - 512 )) 512" ' read failed: Input/output error $ nbdkit memory $(( 2**63 - 2**30 )) --run 'build/qemu-io -f raw "$uri" -c "w -P 3 $(( 2**63 - 2**30 - 512 )) 512" ' write failed: Input/output error You can play around with the constants. I found it's possible to read and write the non-aligned 512 bytes starting at 2^63-2^30-513. Could be a fencepost error somewhere in qemu? Rich.
On Thu, Jan 07, 2021 at 10:56:12AM +0000, Richard W.M. Jones wrote: > On Thu, Jan 07, 2021 at 09:58:17AM +0000, Richard W.M. Jones wrote: > > On Fri, Dec 04, 2020 at 01:27:13AM +0300, Vladimir Sementsov-Ogievskiy wrote: > > > Finally to be safe with calculations, to not calculate different > > > maximums for different nodes (depending on cluster size and > > > request_alignment), let's simply set QEMU_ALIGN_DOWN(INT64_MAX, 2^30) > > > as absolute maximum bytes length for Qemu. Actually, it's not much less > > > than INT64_MAX. > > > > > +/* > > > + * We want allow aligning requests and disk length up to any 32bit alignment > > > + * and don't afraid of overflow. > > > + * To achieve it, and in the same time use some pretty number as maximum disk > > > + * size, let's define maximum "length" (a limit for any offset/bytes request and > > > + * for disk size) to be the greatest power of 2 less than INT64_MAX. > > > + */ > > > +#define BDRV_MAX_ALIGNMENT (1L << 30) > > > +#define BDRV_MAX_LENGTH (QEMU_ALIGN_DOWN(INT64_MAX, BDRV_MAX_ALIGNMENT)) > > > > This change broke nbdkit tests. > > Actually that's not the only problem. It appears that we're unable to > read or write the last sector of this disk: > > $ nbdkit memory $(( 2**63 - 2**30 )) --run 'build/qemu-io -r -f raw "$uri" -c "r -v $(( 2**63 - 2**30 - 512 )) 512" ' > read failed: Input/output error > > $ nbdkit memory $(( 2**63 - 2**30 )) --run 'build/qemu-io -f raw "$uri" -c "w -P 3 $(( 2**63 - 2**30 - 512 )) 512" ' > write failed: Input/output error > > You can play around with the constants. I found it's possible to read > and write the non-aligned 512 bytes starting at 2^63-2^30-513. Could > be a fencepost error somewhere in qemu? Actually this is a pre-existing bug in qemu. What happens is qemu-io calls qemu_strtosz("9223372035781033472") which returns 0x7fffffffc0000000 and no error. That answer is plain flat out wrong. The reason for that is qemu_strtosz uses floating point for the calculation(!) so is limited to 53 bits of precision and silently truncates. It happened we were just lucky that our earlier test with 2^63 - 1024 worked. Rich.
07.01.2021 12:58, Richard W.M. Jones wrote: > On Fri, Dec 04, 2020 at 01:27:13AM +0300, Vladimir Sementsov-Ogievskiy wrote: >> Finally to be safe with calculations, to not calculate different >> maximums for different nodes (depending on cluster size and >> request_alignment), let's simply set QEMU_ALIGN_DOWN(INT64_MAX, 2^30) >> as absolute maximum bytes length for Qemu. Actually, it's not much less >> than INT64_MAX. > >> +/* >> + * We want allow aligning requests and disk length up to any 32bit alignment >> + * and don't afraid of overflow. >> + * To achieve it, and in the same time use some pretty number as maximum disk >> + * size, let's define maximum "length" (a limit for any offset/bytes request and >> + * for disk size) to be the greatest power of 2 less than INT64_MAX. >> + */ >> +#define BDRV_MAX_ALIGNMENT (1L << 30) >> +#define BDRV_MAX_LENGTH (QEMU_ALIGN_DOWN(INT64_MAX, BDRV_MAX_ALIGNMENT)) > > This change broke nbdkit tests. > > We test that qemu can handle a qemu NBD export of size 2^63 - 512, the > largest size that (experimentally) we found qemu could safely handle. > eg: > > https://github.com/libguestfs/nbdkit/blob/master/tests/test-memory-largest-for-qemu.sh > > Before this commit: > > $ nbdkit memory $(( 2**63 - 512 )) --run './qemu-img info "$uri"' > image: nbd://localhost:10809 > file format: raw > virtual size: 8 EiB (9223372036854775296 bytes) > disk size: unavailable > > After this commit: > > $ nbdkit memory $(( 2**63 - 512 )) --run './qemu-img info "$uri"' > qemu-img: Could not open 'nbd://localhost:10809': Could not refresh total sector count: File too large > > Can I confirm that this limit is now the new official one and we > should adjust nbdkit tests? Or was this change unintentional given > that qemu seemed happy to handle 2^63 - 512 disks before? > > Note that nbdkit & libnbd support up to 2^63 - 1 bytes (we are not > limited to whole sectors). Also the Linux kernel will let you create > a /dev/nbdX device of size 2^63 - 1. > Hi Rich! The change is intentional. I think the benefit of having clean limit, allowing us to align up bytes to some alignment (which is a common operation) exceeds the loss of 1G at the end of 2**63 range. We get simpler and safer code. And anyway, new limit is not much worse than 2**63. If at some point we have a problem with it being too restrictive, it's than very likely that 2**63 would be too small as well, which will require so much work that our a bit more restrictive limit is unlikely to increase the difficulty.
On Fri, Jan 08, 2021 at 01:51:35PM +0300, Vladimir Sementsov-Ogievskiy wrote: > 07.01.2021 12:58, Richard W.M. Jones wrote: > >On Fri, Dec 04, 2020 at 01:27:13AM +0300, Vladimir Sementsov-Ogievskiy wrote: > >>Finally to be safe with calculations, to not calculate different > >>maximums for different nodes (depending on cluster size and > >>request_alignment), let's simply set QEMU_ALIGN_DOWN(INT64_MAX, 2^30) > >>as absolute maximum bytes length for Qemu. Actually, it's not much less > >>than INT64_MAX. > > > >>+/* > >>+ * We want allow aligning requests and disk length up to any 32bit alignment > >>+ * and don't afraid of overflow. > >>+ * To achieve it, and in the same time use some pretty number as maximum disk > >>+ * size, let's define maximum "length" (a limit for any offset/bytes request and > >>+ * for disk size) to be the greatest power of 2 less than INT64_MAX. > >>+ */ > >>+#define BDRV_MAX_ALIGNMENT (1L << 30) > >>+#define BDRV_MAX_LENGTH (QEMU_ALIGN_DOWN(INT64_MAX, BDRV_MAX_ALIGNMENT)) > > > >This change broke nbdkit tests. > > > >We test that qemu can handle a qemu NBD export of size 2^63 - 512, the > >largest size that (experimentally) we found qemu could safely handle. > >eg: > > > > https://github.com/libguestfs/nbdkit/blob/master/tests/test-memory-largest-for-qemu.sh > > > >Before this commit: > > > > $ nbdkit memory $(( 2**63 - 512 )) --run './qemu-img info "$uri"' > > image: nbd://localhost:10809 > > file format: raw > > virtual size: 8 EiB (9223372036854775296 bytes) > > disk size: unavailable > > > >After this commit: > > > > $ nbdkit memory $(( 2**63 - 512 )) --run './qemu-img info "$uri"' > > qemu-img: Could not open 'nbd://localhost:10809': Could not refresh total sector count: File too large > > > >Can I confirm that this limit is now the new official one and we > >should adjust nbdkit tests? Or was this change unintentional given > >that qemu seemed happy to handle 2^63 - 512 disks before? > > > >Note that nbdkit & libnbd support up to 2^63 - 1 bytes (we are not > >limited to whole sectors). Also the Linux kernel will let you create > >a /dev/nbdX device of size 2^63 - 1. > > > > Hi Rich! The change is intentional. > > I think the benefit of having clean limit, allowing us to align up > bytes to some alignment (which is a common operation) exceeds the > loss of 1G at the end of 2**63 range. We get simpler and safer > code. And anyway, new limit is not much worse than 2**63. That's fine, as long as we settle on this. I've updated the nbdkit tests: https://github.com/libguestfs/nbdkit/commit/c3ec8c951e39a0f921252c162c236f23c588d2bd > If at some > point we have a problem with it being too restrictive, it's than > very likely that 2**63 would be too small as well, which will > require so much work that our a bit more restrictive limit is > unlikely to increase the difficulty. The next step is definitely working on 128 bit offsets! https://rwmj.wordpress.com/2011/10/03/when-will-disk-sizes-go-beyond-64-bits/ Rich.
07.01.2021 15:20, Richard W.M. Jones wrote: > On Thu, Jan 07, 2021 at 10:56:12AM +0000, Richard W.M. Jones wrote: >> On Thu, Jan 07, 2021 at 09:58:17AM +0000, Richard W.M. Jones wrote: >>> On Fri, Dec 04, 2020 at 01:27:13AM +0300, Vladimir Sementsov-Ogievskiy wrote: >>>> Finally to be safe with calculations, to not calculate different >>>> maximums for different nodes (depending on cluster size and >>>> request_alignment), let's simply set QEMU_ALIGN_DOWN(INT64_MAX, 2^30) >>>> as absolute maximum bytes length for Qemu. Actually, it's not much less >>>> than INT64_MAX. >>> >>>> +/* >>>> + * We want allow aligning requests and disk length up to any 32bit alignment >>>> + * and don't afraid of overflow. >>>> + * To achieve it, and in the same time use some pretty number as maximum disk >>>> + * size, let's define maximum "length" (a limit for any offset/bytes request and >>>> + * for disk size) to be the greatest power of 2 less than INT64_MAX. >>>> + */ >>>> +#define BDRV_MAX_ALIGNMENT (1L << 30) >>>> +#define BDRV_MAX_LENGTH (QEMU_ALIGN_DOWN(INT64_MAX, BDRV_MAX_ALIGNMENT)) >>> >>> This change broke nbdkit tests. >> >> Actually that's not the only problem. It appears that we're unable to >> read or write the last sector of this disk: >> >> $ nbdkit memory $(( 2**63 - 2**30 )) --run 'build/qemu-io -r -f raw "$uri" -c "r -v $(( 2**63 - 2**30 - 512 )) 512" ' >> read failed: Input/output error >> >> $ nbdkit memory $(( 2**63 - 2**30 )) --run 'build/qemu-io -f raw "$uri" -c "w -P 3 $(( 2**63 - 2**30 - 512 )) 512" ' >> write failed: Input/output error >> >> You can play around with the constants. I found it's possible to read >> and write the non-aligned 512 bytes starting at 2^63-2^30-513. Could >> be a fencepost error somewhere in qemu? > > Actually this is a pre-existing bug in qemu. > > What happens is qemu-io calls qemu_strtosz("9223372035781033472") > which returns 0x7fffffffc0000000 and no error. That answer is plain > flat out wrong. The reason for that is qemu_strtosz uses floating > point for the calculation(!) so is limited to 53 bits of precision and > silently truncates. Hmm.. Seems it wants to support floats, like 1.5G.. Don't seem to be very useful, but why not. I think we should call qemu_strtou64 first, and only if it fails or leaves '.', 'e' or 'E' (anything else?) as end character we should do all this floating point logic. > > It happened we were just lucky that our earlier test with > 2^63 - 1024 worked. > > Rich. >
On Fri, Jan 08, 2021 at 02:14:30PM +0300, Vladimir Sementsov-Ogievskiy wrote: > 07.01.2021 15:20, Richard W.M. Jones wrote: > > On Thu, Jan 07, 2021 at 10:56:12AM +0000, Richard W.M. Jones wrote: > > > On Thu, Jan 07, 2021 at 09:58:17AM +0000, Richard W.M. Jones wrote: > > > > On Fri, Dec 04, 2020 at 01:27:13AM +0300, Vladimir Sementsov-Ogievskiy wrote: > > > > > Finally to be safe with calculations, to not calculate different > > > > > maximums for different nodes (depending on cluster size and > > > > > request_alignment), let's simply set QEMU_ALIGN_DOWN(INT64_MAX, 2^30) > > > > > as absolute maximum bytes length for Qemu. Actually, it's not much less > > > > > than INT64_MAX. > > > > > > > > > +/* > > > > > + * We want allow aligning requests and disk length up to any 32bit alignment > > > > > + * and don't afraid of overflow. > > > > > + * To achieve it, and in the same time use some pretty number as maximum disk > > > > > + * size, let's define maximum "length" (a limit for any offset/bytes request and > > > > > + * for disk size) to be the greatest power of 2 less than INT64_MAX. > > > > > + */ > > > > > +#define BDRV_MAX_ALIGNMENT (1L << 30) > > > > > +#define BDRV_MAX_LENGTH (QEMU_ALIGN_DOWN(INT64_MAX, BDRV_MAX_ALIGNMENT)) > > > > > > > > This change broke nbdkit tests. > > > > > > Actually that's not the only problem. It appears that we're unable to > > > read or write the last sector of this disk: > > > > > > $ nbdkit memory $(( 2**63 - 2**30 )) --run 'build/qemu-io -r -f raw "$uri" -c "r -v $(( 2**63 - 2**30 - 512 )) 512" ' > > > read failed: Input/output error > > > > > > $ nbdkit memory $(( 2**63 - 2**30 )) --run 'build/qemu-io -f raw "$uri" -c "w -P 3 $(( 2**63 - 2**30 - 512 )) 512" ' > > > write failed: Input/output error > > > > > > You can play around with the constants. I found it's possible to read > > > and write the non-aligned 512 bytes starting at 2^63-2^30-513. Could > > > be a fencepost error somewhere in qemu? > > > > Actually this is a pre-existing bug in qemu. > > > > What happens is qemu-io calls qemu_strtosz("9223372035781033472") > > which returns 0x7fffffffc0000000 and no error. That answer is plain > > flat out wrong. The reason for that is qemu_strtosz uses floating > > point for the calculation(!) so is limited to 53 bits of precision and > > silently truncates. > > Hmm.. Seems it wants to support floats, like 1.5G.. Don't seem to be very useful, but why not. I think we should call qemu_strtou64 first, and only if it fails or leaves '.', 'e' or 'E' (anything else?) as end character we should do all this floating point logic. I'm not sure we actually care about the floating point exponent syntax suffixes. The test suite doesn't cover that format, only the plain fractional parts. It should be possible to avoid floating point entirely if we just split on "." and then use int64 arithmetic to scale the two parts before recombining them. Regards, Daniel
On 1/7/21 6:20 AM, Richard W.M. Jones wrote: >> Actually that's not the only problem. It appears that we're unable to >> read or write the last sector of this disk: >> >> $ nbdkit memory $(( 2**63 - 2**30 )) --run 'build/qemu-io -r -f raw "$uri" -c "r -v $(( 2**63 - 2**30 - 512 )) 512" ' >> read failed: Input/output error >> >> $ nbdkit memory $(( 2**63 - 2**30 )) --run 'build/qemu-io -f raw "$uri" -c "w -P 3 $(( 2**63 - 2**30 - 512 )) 512" ' >> write failed: Input/output error >> >> You can play around with the constants. I found it's possible to read >> and write the non-aligned 512 bytes starting at 2^63-2^30-513. Could >> be a fencepost error somewhere in qemu? > > Actually this is a pre-existing bug in qemu. > > What happens is qemu-io calls qemu_strtosz("9223372035781033472") > which returns 0x7fffffffc0000000 and no error. That answer is plain > flat out wrong. The reason for that is qemu_strtosz uses floating > point for the calculation(!) so is limited to 53 bits of precision and > silently truncates. I'm working a patch for that soon. It was easy to fix things to parse with full 64 bits of precision while still allowing a fractional bump (for things like 1.5M), but harder to chase down all the spots in the testsuite that are impacted by our parser now being more accurate.
diff --git a/include/block/block.h b/include/block/block.h index c9d7c58765..5b81e33e94 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -142,6 +142,16 @@ typedef struct HDGeometry { INT_MAX >> BDRV_SECTOR_BITS) #define BDRV_REQUEST_MAX_BYTES (BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS) +/* + * We want allow aligning requests and disk length up to any 32bit alignment + * and don't afraid of overflow. + * To achieve it, and in the same time use some pretty number as maximum disk + * size, let's define maximum "length" (a limit for any offset/bytes request and + * for disk size) to be the greatest power of 2 less than INT64_MAX. + */ +#define BDRV_MAX_ALIGNMENT (1L << 30) +#define BDRV_MAX_LENGTH (QEMU_ALIGN_DOWN(INT64_MAX, BDRV_MAX_ALIGNMENT)) + /* * Allocation status flags for bdrv_block_status() and friends. * diff --git a/include/block/block_int.h b/include/block/block_int.h index 95d9333be1..1eeafc118c 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -70,6 +70,12 @@ enum BdrvTrackedRequestType { BDRV_TRACKED_TRUNCATE, }; +/* + * That is not quite good that BdrvTrackedRequest structure is public, + * as block/io.c is very careful about incoming offset/bytes being + * correct. Be sure to assert bdrv_check_request() succeeded after any + * modification of BdrvTrackedRequest object out of block/io.c + */ typedef struct BdrvTrackedRequest { BlockDriverState *bs; int64_t offset; @@ -87,6 +93,8 @@ typedef struct BdrvTrackedRequest { struct BdrvTrackedRequest *waiting_for; } BdrvTrackedRequest; +int bdrv_check_request(int64_t offset, int64_t bytes); + struct BlockDriver { const char *format_name; int instance_size; diff --git a/block.c b/block.c index f1cedac362..1a8494e19c 100644 --- a/block.c +++ b/block.c @@ -961,6 +961,11 @@ int refresh_total_sectors(BlockDriverState *bs, int64_t hint) } bs->total_sectors = hint; + + if (bs->total_sectors * BDRV_SECTOR_SIZE > BDRV_MAX_LENGTH) { + return -EFBIG; + } + return 0; } @@ -5534,6 +5539,7 @@ void bdrv_get_backing_filename(BlockDriverState *bs, int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) { + int ret; BlockDriver *drv = bs->drv; /* if bs->drv == NULL, bs is closed, so there's nothing to do here */ if (!drv) { @@ -5547,7 +5553,16 @@ int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) return -ENOTSUP; } memset(bdi, 0, sizeof(*bdi)); - return drv->bdrv_get_info(bs, bdi); + ret = drv->bdrv_get_info(bs, bdi); + if (ret < 0) { + return ret; + } + + if (bdi->cluster_size > BDRV_MAX_ALIGNMENT) { + return -EINVAL; + } + + return 0; } ImageInfoSpecific *bdrv_get_specific_info(BlockDriverState *bs, diff --git a/block/file-posix.c b/block/file-posix.c index 1b35bd6cfa..fd0a8d0dbf 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -2926,7 +2926,6 @@ raw_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int bytes, #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, @@ -2950,8 +2949,9 @@ raw_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int bytes, 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->bytes = BDRV_MAX_LENGTH - req->offset; + + assert(bdrv_check_request(req->offset, req->bytes) == 0); bdrv_mark_request_serialising(req, bs->bl.request_alignment); } diff --git a/block/io.c b/block/io.c index ef75a5abb4..6343d85476 100644 --- a/block/io.c +++ b/block/io.c @@ -176,6 +176,13 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp) /* Then let the driver override it */ if (drv->bdrv_refresh_limits) { drv->bdrv_refresh_limits(bs, errp); + if (*errp) { + return; + } + } + + if (bs->bl.request_alignment > BDRV_MAX_ALIGNMENT) { + error_setg(errp, "Driver requires too large request alignment"); } } @@ -884,13 +891,31 @@ static bool coroutine_fn bdrv_wait_serialising_requests(BdrvTrackedRequest *self return waited; } -static int bdrv_check_byte_request(int64_t offset, size_t size) +int bdrv_check_request(int64_t offset, int64_t bytes) { - if (size > BDRV_REQUEST_MAX_BYTES) { + if (offset < 0 || bytes < 0) { return -EIO; } - if (offset < 0) { + if (bytes > BDRV_MAX_LENGTH) { + return -EIO; + } + + if (offset > BDRV_MAX_LENGTH - bytes) { + return -EIO; + } + + return 0; +} + +static int bdrv_check_request32(int64_t offset, int64_t bytes) +{ + int ret = bdrv_check_request(offset, bytes); + if (ret < 0) { + return ret; + } + + if (bytes > BDRV_REQUEST_MAX_BYTES) { return -EIO; } @@ -1641,7 +1666,7 @@ int coroutine_fn bdrv_co_preadv_part(BdrvChild *child, return -ENOMEDIUM; } - ret = bdrv_check_byte_request(offset, bytes); + ret = bdrv_check_request32(offset, bytes); if (ret < 0) { return ret; } @@ -2057,7 +2082,7 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child, return -ENOMEDIUM; } - ret = bdrv_check_byte_request(offset, bytes); + ret = bdrv_check_request32(offset, bytes); if (ret < 0) { return ret; } @@ -2787,8 +2812,9 @@ int coroutine_fn bdrv_co_pdiscard(BdrvChild *child, int64_t offset, return -EPERM; } - if (offset < 0 || bytes < 0 || bytes > INT64_MAX - offset) { - return -EIO; + ret = bdrv_check_request(offset, bytes); + if (ret < 0) { + return ret; } /* Do nothing if disabled. */ @@ -3047,7 +3073,7 @@ static int coroutine_fn bdrv_co_copy_range_internal( if (!dst || !dst->bs || !bdrv_is_inserted(dst->bs)) { return -ENOMEDIUM; } - ret = bdrv_check_byte_request(dst_offset, bytes); + ret = bdrv_check_request32(dst_offset, bytes); if (ret) { return ret; } @@ -3058,7 +3084,7 @@ static int coroutine_fn bdrv_co_copy_range_internal( if (!src || !src->bs || !bdrv_is_inserted(src->bs)) { return -ENOMEDIUM; } - ret = bdrv_check_byte_request(src_offset, bytes); + ret = bdrv_check_request32(src_offset, bytes); if (ret) { return ret; } @@ -3188,6 +3214,13 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact, return -EINVAL; } + ret = bdrv_check_request(offset, 0); + if (ret < 0) { + error_setg(errp, "Required too big image size, it must be not greater " + "than %" PRId64, BDRV_MAX_LENGTH); + return ret; + } + old_size = bdrv_getlength(bs); if (old_size < 0) { error_setg_errno(errp, -old_size, "Failed to get old image size"); diff --git a/tests/test-write-threshold.c b/tests/test-write-threshold.c index 97ca12f710..4cf032652d 100644 --- a/tests/test-write-threshold.c +++ b/tests/test-write-threshold.c @@ -64,6 +64,8 @@ static void test_threshold_not_trigger(void) req.offset = 1024; req.bytes = 1024; + assert(bdrv_check_request(req.offset, req.bytes) == 0); + bdrv_write_threshold_set(&bs, threshold); amount = bdrv_write_threshold_exceeded(&bs, &req); g_assert_cmpuint(amount, ==, 0); @@ -82,6 +84,8 @@ static void test_threshold_trigger(void) req.offset = (4 * 1024 * 1024) - 1024; req.bytes = 2 * 1024; + assert(bdrv_check_request(req.offset, req.bytes) == 0); + bdrv_write_threshold_set(&bs, threshold); amount = bdrv_write_threshold_exceeded(&bs, &req); g_assert_cmpuint(amount, >=, 1024); diff --git a/tests/qemu-iotests/206 b/tests/qemu-iotests/206 index 11bc51f256..021d94142e 100755 --- a/tests/qemu-iotests/206 +++ b/tests/qemu-iotests/206 @@ -201,7 +201,7 @@ with iotests.FilePath('t.qcow2') as disk_path, \ vm.launch() for size in [ 1234, 18446744073709551104, 9223372036854775808, - 9223372036854775296 ]: + 9223372036854775296, 9223372035781033984 ]: vm.blockdev_create({ 'driver': imgfmt, 'file': 'node0', 'size': size }) diff --git a/tests/qemu-iotests/206.out b/tests/qemu-iotests/206.out index a100849fcb..e8a36de00b 100644 --- a/tests/qemu-iotests/206.out +++ b/tests/qemu-iotests/206.out @@ -180,6 +180,12 @@ Job failed: Could not resize image: Image size cannot be negative {"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "qcow2", "file": "node0", "size": 9223372036854775296}}} {"return": {}} +Job failed: Could not resize image: Required too big image size, it must be not greater than 9223372035781033984 +{"execute": "job-dismiss", "arguments": {"id": "job0"}} +{"return": {}} + +{"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "qcow2", "file": "node0", "size": 9223372035781033984}}} +{"return": {}} Job failed: Could not resize image: Failed to grow the L1 table: File too large {"execute": "job-dismiss", "arguments": {"id": "job0"}} {"return": {}}
We are going to modify block layer to work with 64bit requests. And first step is moving to int64_t type for both offset and bytes arguments in all block request related functions. It's mostly safe (when widening signed or unsigned int to int64_t), but switching from uint64_t is questionable. So, let's first establish the set of requests we want to work with. First signed int64_t should be enough, as off_t is signed anyway. Then, obviously offset + bytes should not overflow. And most interesting: (offset + bytes) being aligned up should not overflow as well. Aligned to what alignment? First thing that comes in mind is bs->bl.request_alignment, as we align up request to this alignment. But there is another thing: look at bdrv_mark_request_serialising(). It aligns request up to some given alignment. And this parameter may be bdrv_get_cluster_size(), which is often a lot greater than bs->bl.request_alignment. Note also, that bdrv_mark_request_serialising() uses signed int64_t for calculations. So, actually, we already depend on some restrictions. Happily, bdrv_get_cluster_size() returns int and bs->bl.request_alignment has 32bit unsigned type, but defined to be a power of 2 less than INT_MAX. So, we may establish, that INT_MAX is absolute maximum for any kind of alignment that may occur with the request. Note, that bdrv_get_cluster_size() is not documented to return power of 2, still bdrv_mark_request_serialising() behaves like it is. Also, backup uses bdi.cluster_size and is not prepared to it not being power of 2. So, let's establish that Qemu supports only power-of-2 clusters and alignments. So, alignment can't be greater than 2^30. Finally to be safe with calculations, to not calculate different maximums for different nodes (depending on cluster size and request_alignment), let's simply set QEMU_ALIGN_DOWN(INT64_MAX, 2^30) as absolute maximum bytes length for Qemu. Actually, it's not much less than INT64_MAX. OK, then, let's apply it to block/io. Let's consider all block/io entry points of offset/bytes: 4 bytes/offset interface functions: bdrv_co_preadv_part(), bdrv_co_pwritev_part(), bdrv_co_copy_range_internal() and bdrv_co_pdiscard() and we check them all with bdrv_check_request(). We also have one entry point with only offset: bdrv_co_truncate(). Check the offset. And one public structure: BdrvTrackedRequest. Happily, it has only three external users: file-posix.c: adopted by this patch write-threshold.c: only read fields test-write-threshold.c: sets obviously small constant values Better is to make the structure private and add corresponding interfaces.. Still it's not obvious what kind of interface is needed for file-posix.c. Let's keep it public but add corresponding assertions. After this patch we'll convert functions in block/io.c to int64_t bytes and offset parameters. We can assume that offset/bytes pair always satisfy new restrictions, and make corresponding assertions where needed. If we reach some offset/bytes point in block/io.c missing bdrv_check_request() it is considered a bug. As well, if block/io.c modifies a offset/bytes request, expanding it more then aligning up to request_alignment, it's a bug too. For all io requests except for discard we keep for now old restriction of 32bit request length. iotest 206 output error message changed, as now test disk size is larger than new limit. Add one more test case with new maximum disk size to cover too-big-L1 case. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> --- include/block/block.h | 10 +++++++ include/block/block_int.h | 8 ++++++ block.c | 17 +++++++++++- block/file-posix.c | 6 ++--- block/io.c | 51 +++++++++++++++++++++++++++++------- tests/test-write-threshold.c | 4 +++ tests/qemu-iotests/206 | 2 +- tests/qemu-iotests/206.out | 6 +++++ 8 files changed, 90 insertions(+), 14 deletions(-)