From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56931) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1W5uYa-0006W8-F2 for qemu-devel@nongnu.org; Wed, 22 Jan 2014 04:57:17 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1W5uYP-0005F3-Q8 for qemu-devel@nongnu.org; Wed, 22 Jan 2014 04:57:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48230) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1W5uYP-0005Eo-J9 for qemu-devel@nongnu.org; Wed, 22 Jan 2014 04:57:01 -0500 Date: Wed, 22 Jan 2014 10:56:58 +0100 From: Kevin Wolf Message-ID: <20140122095658.GD10065@dhcp-200-207.str.redhat.com> References: <0736abebce5d519c6901d08af0f623129f843438.1390373621.git.hutao@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0736abebce5d519c6901d08af0f623129f843438.1390373621.git.hutao@cn.fujitsu.com> Subject: Re: [Qemu-devel] [PATCH v3 1/4] qcow2: remove n_start and n_end of qcow2_alloc_cluster_offset() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Hu Tao Cc: qemu-devel@nongnu.org, Max Reitz Am 22.01.2014 um 07:57 hat Hu Tao geschrieben: > n_start can be actually calculated from offset. The number of > sectors to be allocated(n_end - n_start) can be passed in in > num. By removing n_start and n_end, we can save two parameters. > > The side effect is there is a bug in qcow2.c:preallocate() that > passes incorrect n_start to qcow2_alloc_cluster_offset() is > fixed. The bug can be triggerred by a larger cluster size than > the default value(65536), for example: > > ./qemu-img create -f qcow2 \ > -o 'cluster_size=131072,preallocation=metadata' file.img 4G > > Reviewed-by: Max Reitz > Signed-off-by: Hu Tao > --- > block/qcow2-cluster.c | 14 ++++++-------- > block/qcow2.c | 6 +++--- > block/qcow2.h | 2 +- > trace-events | 2 +- > 4 files changed, 11 insertions(+), 13 deletions(-) > > diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c > index 8534084..c57f39d 100644 > --- a/block/qcow2-cluster.c > +++ b/block/qcow2-cluster.c > @@ -1182,7 +1182,7 @@ fail: > * Return 0 on success and -errno in error cases > */ > int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset, > - int n_start, int n_end, int *num, uint64_t *host_offset, QCowL2Meta **m) > + int *num, uint64_t *host_offset, QCowL2Meta **m) > { > BDRVQcowState *s = bs->opaque; > uint64_t start, remaining; > @@ -1190,15 +1190,13 @@ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset, > uint64_t cur_bytes; > int ret; > > - trace_qcow2_alloc_clusters_offset(qemu_coroutine_self(), offset, > - n_start, n_end); > + trace_qcow2_alloc_clusters_offset(qemu_coroutine_self(), offset, *num); > > - assert(n_start * BDRV_SECTOR_SIZE == offset_into_cluster(s, offset)); > - offset = start_of_cluster(s, offset); > + assert((offset & ~BDRV_SECTOR_MASK) == 0); > > again: > - start = offset + (n_start << BDRV_SECTOR_BITS); > - remaining = (n_end - n_start) << BDRV_SECTOR_BITS; > + start = offset; > + remaining = *num << BDRV_SECTOR_BITS; > cluster_offset = 0; > *host_offset = 0; > cur_bytes = 0; > @@ -1284,7 +1282,7 @@ again: > } > } > > - *num = (n_end - n_start) - (remaining >> BDRV_SECTOR_BITS); > + *num -= remaining >> BDRV_SECTOR_BITS; > assert(*num > 0); > assert(*host_offset != 0); > > diff --git a/block/qcow2.c b/block/qcow2.c > index 8ec9db1..a0596ec 100644 > --- a/block/qcow2.c > +++ b/block/qcow2.c > @@ -1016,14 +1016,14 @@ static coroutine_fn int qcow2_co_writev(BlockDriverState *bs, > > trace_qcow2_writev_start_part(qemu_coroutine_self()); > index_in_cluster = sector_num & (s->cluster_sectors - 1); > - n_end = index_in_cluster + remaining_sectors; > + cur_nr_sectors = remaining_sectors; > if (s->crypt_method && > n_end > QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors) { > n_end = QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors; > } You don't want to change n_end here any more, this should affect cur_nr_sectors now. n_end becomes completely unused then and can be removed. I wonder why the compiler doesn't complain here, this is uninitialised use and a write-only variable at the same time. Kevin