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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> Message-Id: <20201203222713.13507-5-vsementsov@virtuozzo.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com> |
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| authz | ||
| block | ||
| chardev | ||
| crypto | ||
| disas | ||
| exec | ||
| fpu | ||
| hw | ||
| io | ||
| libdecnumber | ||
| migration | ||
| monitor | ||
| net | ||
| qapi | ||
| qemu | ||
| qom | ||
| scsi | ||
| standard-headers | ||
| sysemu | ||
| tcg | ||
| ui | ||
| user | ||
| elf.h | ||
| glib-compat.h | ||
| qemu-common.h | ||
| qemu-io.h | ||
| trace-tcg.h | ||