Not all callers care about which BDS owns the mapping for a given range of the file. This patch merely simplifies the callers by consolidating the logic in the common call point, while guaranteeing a non-NULL file to all the driver callbacks, for no semantic change. The only caller that does not care about pnum is bdrv_is_allocated, as invoked by vvfat; we can likewise add assertions that the rest of the stack does not have to worry about a NULL pnum.
Furthermore, this will also set the stage for a future cleanup: when a caller does not care about which BDS owns an offset, it would be nice to allow the driver to optimize things to not have to return BDRV_BLOCK_OFFSET_VALID in the first place. In the case of fragmented allocation (for example, it's fairly easy to create a qcow2 image where consecutive guest addresses are not at consecutive host addresses), the current contract requires bdrv_get_block_status() to clamp *pnum to the limit where host addresses are no longer consecutive, but allowing a NULL file means that *pnum could be set to the full length of known-allocated data. Signed-off-by: Eric Blake <ebl...@redhat.com> --- v3: rebase to recent changes (qcow2_measure), dropped R-b v2: use local variable and final transfer, rather than assignment of parameter to local [previously in different series]: v2: new patch, https://lists.gnu.org/archive/html/qemu-devel/2017-05/msg05645.html --- include/block/block_int.h | 10 ++++++---- block/io.c | 44 ++++++++++++++++++++++++++++---------------- block/mirror.c | 3 +-- block/qcow2.c | 8 ++------ qemu-img.c | 10 ++++------ 5 files changed, 41 insertions(+), 34 deletions(-) diff --git a/include/block/block_int.h b/include/block/block_int.h index 1d702c1..3b4977d 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -172,10 +172,12 @@ struct BlockDriver { int64_t offset, int bytes); /* - * Building block for bdrv_block_status[_above]. The driver should - * answer only according to the current layer, and should not - * set BDRV_BLOCK_ALLOCATED, but may set BDRV_BLOCK_RAW. See block.h - * for the meaning of _DATA, _ZERO, and _OFFSET_VALID. + * Building block for bdrv_block_status[_above] and + * bdrv_is_allocated[_above]. The driver should answer only + * according to the current layer, and should not set + * BDRV_BLOCK_ALLOCATED, but may set BDRV_BLOCK_RAW. See block.h + * for the meaning of _DATA, _ZERO, and _OFFSET_VALID. The block + * layer guarantees non-NULL pnum and file. */ int64_t coroutine_fn (*bdrv_co_get_block_status)(BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *pnum, diff --git a/block/io.c b/block/io.c index 8b6b6f2..0305e61 100644 --- a/block/io.c +++ b/block/io.c @@ -671,7 +671,6 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags) { int64_t target_sectors, ret, nb_sectors, sector_num = 0; BlockDriverState *bs = child->bs; - BlockDriverState *file; int n; target_sectors = bdrv_nb_sectors(bs); @@ -684,7 +683,7 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags) if (nb_sectors <= 0) { return 0; } - ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n, &file); + ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n, NULL); if (ret < 0) { error_report("error getting block status at sector %" PRId64 ": %s", sector_num, strerror(-ret)); @@ -1731,8 +1730,9 @@ int64_t coroutine_fn bdrv_co_get_block_status_from_backing(BlockDriverState *bs, * beyond the end of the disk image it will be clamped; if 'pnum' is set to * the end of the image, then the returned value will include BDRV_BLOCK_EOF. * - * If returned value is positive and BDRV_BLOCK_OFFSET_VALID bit is set, 'file' - * points to the BDS which the sector range is allocated in. + * If returned value is positive, BDRV_BLOCK_OFFSET_VALID bit is set, and + * 'file' is non-NULL, then '*file' points to the BDS which the sector range + * is allocated in. */ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs, int64_t sector_num, @@ -1742,15 +1742,22 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs, int64_t total_sectors; int64_t n; int64_t ret, ret2; + BlockDriverState *local_file = NULL; - *file = NULL; + assert(pnum); total_sectors = bdrv_nb_sectors(bs); if (total_sectors < 0) { + if (file) { + *file = NULL; + } return total_sectors; } if (sector_num >= total_sectors) { *pnum = 0; + if (file) { + *file = NULL; + } return BDRV_BLOCK_EOF; } @@ -1767,23 +1774,27 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs, } if (bs->drv->protocol_name) { ret |= BDRV_BLOCK_OFFSET_VALID | (sector_num * BDRV_SECTOR_SIZE); - *file = bs; + if (file) { + *file = bs; + } + } else if (file) { + *file = NULL; } return ret; } bdrv_inc_in_flight(bs); ret = bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors, pnum, - file); + &local_file); if (ret < 0) { *pnum = 0; goto out; } if (ret & BDRV_BLOCK_RAW) { - assert(ret & BDRV_BLOCK_OFFSET_VALID && *file); - ret = bdrv_co_get_block_status(*file, ret >> BDRV_SECTOR_BITS, - *pnum, pnum, file); + assert(ret & BDRV_BLOCK_OFFSET_VALID && local_file); + ret = bdrv_co_get_block_status(local_file, ret >> BDRV_SECTOR_BITS, + *pnum, pnum, &local_file); goto out; } @@ -1801,14 +1812,13 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs, } } - if (*file && *file != bs && + if (local_file && local_file != bs && (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) && (ret & BDRV_BLOCK_OFFSET_VALID)) { - BlockDriverState *file2; int file_pnum; - ret2 = bdrv_co_get_block_status(*file, ret >> BDRV_SECTOR_BITS, - *pnum, &file_pnum, &file2); + ret2 = bdrv_co_get_block_status(local_file, ret >> BDRV_SECTOR_BITS, + *pnum, &file_pnum, NULL); if (ret2 >= 0) { /* Ignore errors. This is just providing extra information, it * is useful but not necessary. @@ -1830,6 +1840,9 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs, } out: + if (file) { + *file = local_file; + } bdrv_dec_in_flight(bs); if (ret >= 0 && sector_num + *pnum == total_sectors) { ret |= BDRV_BLOCK_EOF; @@ -1933,7 +1946,6 @@ int64_t bdrv_get_block_status(BlockDriverState *bs, int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset, int64_t bytes, int64_t *pnum) { - BlockDriverState *file; int64_t sector_num = offset >> BDRV_SECTOR_BITS; int nb_sectors = bytes >> BDRV_SECTOR_BITS; int64_t ret; @@ -1942,7 +1954,7 @@ int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset, assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)); assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE) && bytes < INT_MAX); ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &psectors, - &file); + NULL); if (ret < 0) { return ret; } diff --git a/block/mirror.c b/block/mirror.c index dabcf92..b3ce763 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -391,7 +391,6 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s) int io_sectors; unsigned int io_bytes; int64_t io_bytes_acct; - BlockDriverState *file; enum MirrorMethod { MIRROR_METHOD_COPY, MIRROR_METHOD_ZERO, @@ -402,7 +401,7 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s) ret = bdrv_get_block_status_above(source, NULL, offset >> BDRV_SECTOR_BITS, nb_chunks * sectors_per_chunk, - &io_sectors, &file); + &io_sectors, NULL); io_bytes = io_sectors * BDRV_SECTOR_SIZE; if (ret < 0) { io_bytes = MIN(nb_chunks * s->granularity, max_io_bytes); diff --git a/block/qcow2.c b/block/qcow2.c index 85ee9b2..e9f0291 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2992,7 +2992,6 @@ static bool is_zero_sectors(BlockDriverState *bs, int64_t start, uint32_t count) { int nr; - BlockDriverState *file; int64_t res; if (start + count > bs->total_sectors) { @@ -3002,8 +3001,7 @@ static bool is_zero_sectors(BlockDriverState *bs, int64_t start, if (!count) { return true; } - res = bdrv_get_block_status_above(bs, NULL, start, count, - &nr, &file); + res = bdrv_get_block_status_above(bs, NULL, start, count, &nr, NULL); return res >= 0 && (res & BDRV_BLOCK_ZERO) && nr == count; } @@ -3669,13 +3667,11 @@ static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs, offset += pnum * BDRV_SECTOR_SIZE) { int nb_sectors = MIN(ssize - offset, INT_MAX) / BDRV_SECTOR_SIZE; - BlockDriverState *file; int64_t ret; ret = bdrv_get_block_status_above(in_bs, NULL, offset >> BDRV_SECTOR_BITS, - nb_sectors, - &pnum, &file); + nb_sectors, &pnum, NULL); if (ret < 0) { error_setg_errno(&local_err, -ret, "Unable to get block status"); diff --git a/qemu-img.c b/qemu-img.c index 2802214..3592b8d 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -1368,7 +1368,6 @@ static int img_compare(int argc, char **argv) for (;;) { int64_t status1, status2; - BlockDriverState *file; nb_sectors = sectors_to_process(total_sectors, sector_num); if (nb_sectors <= 0) { @@ -1376,7 +1375,7 @@ static int img_compare(int argc, char **argv) } status1 = bdrv_get_block_status_above(bs1, NULL, sector_num, total_sectors1 - sector_num, - &pnum1, &file); + &pnum1, NULL); if (status1 < 0) { ret = 3; error_report("Sector allocation test failed for %s", filename1); @@ -1386,7 +1385,7 @@ static int img_compare(int argc, char **argv) status2 = bdrv_get_block_status_above(bs2, NULL, sector_num, total_sectors2 - sector_num, - &pnum2, &file); + &pnum2, NULL); if (status2 < 0) { ret = 3; error_report("Sector allocation test failed for %s", filename2); @@ -1592,15 +1591,14 @@ static int convert_iteration_sectors(ImgConvertState *s, int64_t sector_num) n = MIN(s->total_sectors - sector_num, BDRV_REQUEST_MAX_SECTORS); if (s->sector_next_status <= sector_num) { - BlockDriverState *file; if (s->target_has_backing) { ret = bdrv_get_block_status(blk_bs(s->src[src_cur]), sector_num - src_cur_offset, - n, &n, &file); + n, &n, NULL); } else { ret = bdrv_get_block_status_above(blk_bs(s->src[src_cur]), NULL, sector_num - src_cur_offset, - n, &n, &file); + n, &n, NULL); } if (ret < 0) { return ret; -- 2.9.4
