From 11e63c7fc863d08e5a2e0243bfbc01279f174a26 Mon Sep 17 00:00:00 2001 From: Kevin Wolf <kwolf@redhat.com> Date: Fri, 18 Jun 2010 15:22:25 -0300 Subject: [PATCH 07/18] qcow2: Allow qcow2_get_cluster_offset to return errors RH-Author: Kevin Wolf <kwolf@redhat.com> Message-id: <1276874554-9820-8-git-send-email-kwolf@redhat.com> Patchwork-id: 9982 O-Subject: [RHEL-5.6 KVM PATCH 07/16] qcow2: Allow qcow2_get_cluster_offset to return errors Bugzilla: 605701 RH-Acked-by: Juan Quintela <quintela@redhat.com> RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com> RH-Acked-by: Christoph Hellwig <chellwig@redhat.com> RH-Acked-by: Jes Sorensen <Jes.Sorensen@redhat.com> Bugzilla: 605701 Upstream commit: 1c46efaa0a175e468772405385ca26a1e35dd94c qcow2_get_cluster_offset() looks up a given virtual disk offset and returns the offset of the corresponding cluster in the image file. Errors (e.g. L2 table can't be read) are currenctly indicated by a return value of 0, which is unfortuately the same as for any unallocated cluster. So in effect we can't check for errors. This makes the old return value a by-reference parameter and returns the usual 0/-errno error code. Signed-off-by: Kevin Wolf <kwolf@redhat.com> --- qemu/block-qcow2.c | 51 +++++++++++++++++++++++++++++++++++---------------- 1 files changed, 35 insertions(+), 16 deletions(-) Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> --- qemu/block-qcow2.c | 51 +++++++++++++++++++++++++++++++++++---------------- 1 files changed, 35 insertions(+), 16 deletions(-) diff --git a/qemu/block-qcow2.c b/qemu/block-qcow2.c index 20e9e0b..ced586b 100644 --- a/qemu/block-qcow2.c +++ b/qemu/block-qcow2.c @@ -784,25 +784,25 @@ static int count_contiguous_free_clusters(uint64_t nb_clusters, uint64_t *l2_tab /* * get_cluster_offset * - * For a given offset of the disk image, return cluster offset in - * qcow2 file. + * For a given offset of the disk image, find the cluster offset in + * qcow2 file. The offset is stored in *cluster_offset. * * on entry, *num is the number of contiguous clusters we'd like to * access following offset. * * on exit, *num is the number of contiguous clusters we can read. * - * Return 1, if the offset is found - * Return 0, otherwise. + * Return 0, if the offset is found + * Return -errno, otherwise. * */ -static uint64_t get_cluster_offset(BlockDriverState *bs, - uint64_t offset, int *num) +static int get_cluster_offset(BlockDriverState *bs, uint64_t offset, + int *num, uint64_t *cluster_offset) { BDRVQcowState *s = bs->opaque; int l1_index, l2_index; - uint64_t l2_offset, *l2_table, cluster_offset; + uint64_t l2_offset, *l2_table; int l1_bits, c; int index_in_cluster, nb_available, nb_needed, nb_clusters; @@ -825,7 +825,7 @@ static uint64_t get_cluster_offset(BlockDriverState *bs, nb_needed = nb_available; } - cluster_offset = 0; + *cluster_offset = 0; /* seek the the l2 offset in the l1 table */ @@ -844,16 +844,17 @@ static uint64_t get_cluster_offset(BlockDriverState *bs, l2_offset &= ~QCOW_OFLAG_COPIED; l2_table = l2_load(bs, l2_offset); - if (l2_table == NULL) - return 0; + if (l2_table == NULL) { + return -EIO; + } /* find the cluster offset for the given disk offset */ l2_index = (offset >> s->cluster_bits) & (s->l2_size - 1); - cluster_offset = be64_to_cpu(l2_table[l2_index]); + *cluster_offset = be64_to_cpu(l2_table[l2_index]); nb_clusters = size_to_clusters(s, nb_needed << 9); - if (!cluster_offset) { + if (!*cluster_offset) { /* how many empty clusters ? */ c = count_contiguous_free_clusters(nb_clusters, &l2_table[l2_index]); } else { @@ -869,7 +870,8 @@ out: *num = nb_available - index_in_cluster; - return cluster_offset & ~QCOW_OFLAG_COPIED; + *cluster_offset &=~QCOW_OFLAG_COPIED; + return 0; } /* @@ -1223,9 +1225,15 @@ static int qcow_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *pnum) { uint64_t cluster_offset; + int ret; *pnum = nb_sectors; - cluster_offset = get_cluster_offset(bs, sector_num << 9, pnum); + /* FIXME We can get errors here, but the bdrv_is_allocated interface can't + * pass them on today */ + ret = get_cluster_offset(bs, sector_num << 9, pnum, &cluster_offset); + if (ret < 0) { + *pnum = 0; + } return (cluster_offset != 0); } @@ -1304,7 +1312,13 @@ static int qcow_read(BlockDriverState *bs, int64_t sector_num, while (nb_sectors > 0) { n = nb_sectors; - cluster_offset = get_cluster_offset(bs, sector_num << 9, &n); + + ret = get_cluster_offset(bs, sector_num << 9, &n, + &cluster_offset); + if (ret < 0) { + return ret; + } + index_in_cluster = sector_num & (s->cluster_sectors - 1); if (!cluster_offset) { if (bs->backing_hd) { @@ -1457,7 +1471,12 @@ fail: /* prepare next AIO request */ acb->n = acb->nb_sectors; - acb->cluster_offset = get_cluster_offset(bs, acb->sector_num << 9, &acb->n); + ret = get_cluster_offset(bs, acb->sector_num << 9, + &acb->n, &acb->cluster_offset); + if (ret < 0) { + goto fail; + } + index_in_cluster = acb->sector_num & (s->cluster_sectors - 1); if (!acb->cluster_offset) { -- 1.7.0.3