From 49c0752600d22606b411ace75b22e65398999d95 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 3 Jun 2016 16:17:28 +0200 Subject: [PATCH] block: Prepare bdrv_aligned_preadv() for byte-aligned requests This patch makes bdrv_aligned_preadv() ready to accept byte-aligned requests. Note that this doesn't mean that such requests are actually made. The caller still ensures that all requests are aligned to at least 512 bytes. Signed-off-by: Kevin Wolf Reviewed-by: Eric Blake Reviewed-by: Stefan Hajnoczi --- block/io.c | 44 ++++++++++++++++++++------------------------ 1 file changed, 20 insertions(+), 24 deletions(-) diff --git a/block/io.c b/block/io.c index b6a2c800a173..e75bce263db9 100644 --- a/block/io.c +++ b/block/io.c @@ -963,11 +963,9 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs, { int ret; - int64_t sector_num = offset >> BDRV_SECTOR_BITS; - unsigned int nb_sectors = bytes >> BDRV_SECTOR_BITS; - - assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0); - assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0); + assert(is_power_of_2(align)); + assert((offset & (align - 1)) == 0); + assert((bytes & (align - 1)) == 0); assert(!qiov || bytes == qiov->size); assert((bs->open_flags & BDRV_O_NO_IO) == 0); assert(!(flags & ~BDRV_REQ_MASK)); @@ -987,9 +985,12 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs, } if (flags & BDRV_REQ_COPY_ON_READ) { + int64_t start_sector = offset >> BDRV_SECTOR_BITS; + int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE); + unsigned int nb_sectors = end_sector - start_sector; int pnum; - ret = bdrv_is_allocated(bs, sector_num, nb_sectors, &pnum); + ret = bdrv_is_allocated(bs, start_sector, nb_sectors, &pnum); if (ret < 0) { goto out; } @@ -1005,28 +1006,24 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs, ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0); } else { /* Read zeros after EOF */ - int64_t total_sectors, max_nb_sectors; + int64_t total_bytes, max_bytes; - total_sectors = bdrv_nb_sectors(bs); - if (total_sectors < 0) { - ret = total_sectors; + total_bytes = bdrv_getlength(bs); + if (total_bytes < 0) { + ret = total_bytes; goto out; } - max_nb_sectors = ROUND_UP(MAX(0, total_sectors - sector_num), - align >> BDRV_SECTOR_BITS); - if (nb_sectors < max_nb_sectors) { + max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align); + if (bytes < max_bytes) { ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0); - } else if (max_nb_sectors > 0) { + } else if (max_bytes > 0) { QEMUIOVector local_qiov; qemu_iovec_init(&local_qiov, qiov->niov); - qemu_iovec_concat(&local_qiov, qiov, 0, - max_nb_sectors * BDRV_SECTOR_SIZE); + qemu_iovec_concat(&local_qiov, qiov, 0, max_bytes); - ret = bdrv_driver_preadv(bs, offset, - max_nb_sectors * BDRV_SECTOR_SIZE, - &local_qiov, 0); + ret = bdrv_driver_preadv(bs, offset, max_bytes, &local_qiov, 0); qemu_iovec_destroy(&local_qiov); } else { @@ -1034,11 +1031,10 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs, } /* Reading beyond end of file is supposed to produce zeroes */ - if (ret == 0 && total_sectors < sector_num + nb_sectors) { - uint64_t offset = MAX(0, total_sectors - sector_num); - uint64_t bytes = (sector_num + nb_sectors - offset) * - BDRV_SECTOR_SIZE; - qemu_iovec_memset(qiov, offset * BDRV_SECTOR_SIZE, 0, bytes); + if (ret == 0 && total_bytes < offset + bytes) { + uint64_t zero_offset = MAX(0, total_bytes - offset); + uint64_t zero_bytes = offset + bytes - zero_offset; + qemu_iovec_memset(qiov, zero_offset, 0, zero_bytes); } }