From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NrvHr-0002Ji-FM for qemu-devel@nongnu.org; Wed, 17 Mar 2010 11:35:59 -0400 Received: from [199.232.76.173] (port=46909 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NrvHq-0002JY-N5 for qemu-devel@nongnu.org; Wed, 17 Mar 2010 11:35:58 -0400 Received: from Debian-exim by monty-python.gnu.org with spam-scanned (Exim 4.60) (envelope-from ) id 1NrvHn-0008OU-U8 for qemu-devel@nongnu.org; Wed, 17 Mar 2010 11:35:58 -0400 Received: from mail-pw0-f45.google.com ([209.85.160.45]:51869) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NrvHn-0008OI-8D for qemu-devel@nongnu.org; Wed, 17 Mar 2010 11:35:55 -0400 Received: by pwi9 with SMTP id 9so803104pwi.4 for ; Wed, 17 Mar 2010 08:35:54 -0700 (PDT) Message-ID: <4BA0F6D6.9090009@codemonkey.ws> Date: Wed, 17 Mar 2010 10:35:50 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] Use snapshots from backing disks References: <377f3a9b1003081713v6f39fae2sb15f80073d13215a@mail.gmail.com> In-Reply-To: <377f3a9b1003081713v6f39fae2sb15f80073d13215a@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Rob Earhart Cc: qemu-devel@nongnu.org On 03/08/2010 07:13 PM, Rob Earhart wrote: > Modify the snapshot load path to find and load snapshots contained in backing > disks, useful when the current disk is a differencing disk. > > Add the source of a snapshot when listing snapshots. > > This should only break backwards compatibility for scenarios depending on not > being able to load snapshots from backing disks (which doesn't seem like a > problem), and for code which parses the snapshot list output (if any). > > Signed-off-by: Rob Earhart > Your patch is whitespace damaged. Please use a different mailer (like git-send-email). Regards, Anthony Liguori > --- > block.c | 10 +++++ > block.h | 2 + > block/qcow2-snapshot.c | 105 ++++++++++++++++++++++++++++++++++++------------ > qemu-img.c | 25 +++++++----- > savevm.c | 92 +++++++++++++++++++++++++++++------------- > 5 files changed, 170 insertions(+), 64 deletions(-) > > diff --git a/block.c b/block.c > index 31d1ba4..3588700 100644 > --- a/block.c > +++ b/block.c > @@ -1481,6 +1481,16 @@ void bdrv_get_backing_filename(BlockDriverState *bs, > } > } > > +const char *bdrv_get_filename(BlockDriverState *bs) > +{ > + return bs->filename; > +} > + > +BlockDriverState* bdrv_get_backing_bdrv(BlockDriverState *bs) > +{ > + return bs->backing_hd; > +} > + > int bdrv_write_compressed(BlockDriverState *bs, int64_t sector_num, > const uint8_t *buf, int nb_sectors) > { > diff --git a/block.h b/block.h > index edf5704..1d04322 100644 > --- a/block.h > +++ b/block.h > @@ -179,6 +179,8 @@ int bdrv_get_info(BlockDriverState *bs, > BlockDriverInfo *bdi); > const char *bdrv_get_encrypted_filename(BlockDriverState *bs); > void bdrv_get_backing_filename(BlockDriverState *bs, > char *filename, int filename_size); > +const char *bdrv_get_filename(BlockDriverState *bs); > +BlockDriverState* bdrv_get_backing_bdrv(BlockDriverState *bs); > int bdrv_snapshot_create(BlockDriverState *bs, > QEMUSnapshotInfo *sn_info); > int bdrv_snapshot_goto(BlockDriverState *bs, > diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c > index 8ddaea2..ca06fcf 100644 > --- a/block/qcow2-snapshot.c > +++ b/block/qcow2-snapshot.c > @@ -191,16 +191,23 @@ static int qcow_write_snapshots(BlockDriverState *bs) > static void find_new_snapshot_id(BlockDriverState *bs, > char *id_str, int id_str_size) > { > - BDRVQcowState *s = bs->opaque; > - QCowSnapshot *sn; > - int i, id, id_max = 0; > + int id_max = 0; > + > + assert(bs); > + > + do { > + BDRVQcowState *s = bs->opaque; > + QCowSnapshot *sn; > + int i, id; > + > + for(i = 0; i< s->nb_snapshots; i++) { > + sn = s->snapshots + i; > + id = strtoul(sn->id_str, NULL, 10); > + if (id> id_max) > + id_max = id; > + } > + } while ((bs = bdrv_get_backing_bdrv(bs))); > > - for(i = 0; i< s->nb_snapshots; i++) { > - sn = s->snapshots + i; > - id = strtoul(sn->id_str, NULL, 10); > - if (id> id_max) > - id_max = id; > - } > snprintf(id_str, id_str_size, "%d", id_max + 1); > } > > @@ -316,41 +323,88 @@ int qcow2_snapshot_goto(BlockDriverState *bs, > const char *snapshot_id) > { > BDRVQcowState *s = bs->opaque; > QCowSnapshot *sn; > - int i, snapshot_index, l1_size2; > + int i, snapshot_index, l1_size2, ret; > > snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id); > - if (snapshot_index< 0) > - return -ENOENT; > + > + if (snapshot_index< 0) { > + /* if there is a backing file, use it. In this case, the > + * current image needs to be reset to be consistent > + */ > + if (bs->backing_hd) { > + ret = bdrv_snapshot_goto(bs->backing_hd, snapshot_id); > + if (ret< 0) { > + return ret; > + } > + /* reset the sectors of the current image (Note: there can > + * still be snapshots, so the refcounts must be kept > + * consistent) > + */ > + if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, > + s->l1_size, -1)< 0) { > + return -EIO; > + } > + l1_size2 = s->l1_size * sizeof(uint64_t); > + memset(s->l1_table, 0, l1_size2); > + if (bdrv_pwrite(s->hd, s->l1_table_offset, > + s->l1_table, l1_size2) != l1_size2) { > + return -EIO; > + } > + return 0; > + } else { > + return -ENOENT; > + } > + } > + > + assert(0<= snapshot_index); > + > sn =&s->snapshots[snapshot_index]; > > - if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, > s->l1_size, -1)< 0) > - goto fail; > + /* if the file is read-only, all can be done by updating the > + * in-memory L1 table. Otherwise, we'll need to do some writes. > + */ > > - if (qcow2_grow_l1_table(bs, sn->l1_size)< 0) > - goto fail; > + if (!bs->read_only) { > + if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, > + s->l1_size, -1) > +< 0) { > + return -EIO; > + } > + } > + > + if (qcow2_grow_l1_table(bs, sn->l1_size)< 0) { > + return -EIO; > + } > > s->l1_size = sn->l1_size; > l1_size2 = s->l1_size * sizeof(uint64_t); > /* copy the snapshot l1 table to the current l1 table */ > if (bdrv_pread(s->hd, sn->l1_table_offset, > - s->l1_table, l1_size2) != l1_size2) > - goto fail; > - if (bdrv_pwrite(s->hd, s->l1_table_offset, > - s->l1_table, l1_size2) != l1_size2) > - goto fail; > + s->l1_table, l1_size2) != l1_size2) { > + return -EIO; > + } > + if (!bs->read_only) { > + if (bdrv_pwrite(s->hd, s->l1_table_offset, > + s->l1_table, l1_size2) != l1_size2) { > + return -EIO; > + } > + } > for(i = 0;i< s->l1_size; i++) { > be64_to_cpus(&s->l1_table[i]); > } > > - if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, > s->l1_size, 1)< 0) > - goto fail; > + if (!bs->read_only) { > + if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, > + s->l1_size, 1) > +< 0) { > + return -EIO; > + } > + } > > #ifdef DEBUG_ALLOC > qcow2_check_refcounts(bs); > #endif > return 0; > - fail: > - return -EIO; > } > > int qcow2_snapshot_delete(BlockDriverState *bs, const char *snapshot_id) > @@ -416,4 +470,3 @@ int qcow2_snapshot_list(BlockDriverState *bs, > QEMUSnapshotInfo **psn_tab) > *psn_tab = sn_tab; > return s->nb_snapshots; > } > - > diff --git a/qemu-img.c b/qemu-img.c > index 0c9f2d4..345a768 100644 > --- a/qemu-img.c > +++ b/qemu-img.c > @@ -873,16 +873,21 @@ static void dump_snapshots(BlockDriverState *bs) > int nb_sns, i; > char buf[256]; > > - nb_sns = bdrv_snapshot_list(bs,&sn_tab); > - if (nb_sns<= 0) > - return; > - printf("Snapshot list:\n"); > - printf("%s\n", bdrv_snapshot_dump(buf, sizeof(buf), NULL)); > - for(i = 0; i< nb_sns; i++) { > - sn =&sn_tab[i]; > - printf("%s\n", bdrv_snapshot_dump(buf, sizeof(buf), sn)); > - } > - qemu_free(sn_tab); > + assert(bs); > + > + do { > + nb_sns = bdrv_snapshot_list(bs,&sn_tab); > + if (nb_sns<= 0) > + continue; > + printf("Snapshot list (from %s):\n", > + bdrv_get_filename(bs)); > + printf("%s\n", bdrv_snapshot_dump(buf, sizeof(buf), NULL)); > + for(i = 0; i< nb_sns; i++) { > + sn =&sn_tab[i]; > + printf("%s\n", bdrv_snapshot_dump(buf, sizeof(buf), sn)); > + } > + qemu_free(sn_tab); > + } while ((bs = bdrv_get_backing_bdrv(bs))); > } > > static int img_info(int argc, char **argv) > diff --git a/savevm.c b/savevm.c > index 2fd3de6..8a81c42 100644 > --- a/savevm.c > +++ b/savevm.c > @@ -1616,25 +1616,53 @@ static BlockDriverState *get_bs_snapshots(void) > return bs; > } > > +/* Find a snapshot with the given name. > + * sn_bs is an out parameter: if NULL, only the current BlockDriverState (bs) > + * is checked; otherwise, *sb_bs is set to point to the backing block driver > + * state where the found snapshot resides. > + */ > static int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info, > - const char *name) > + const char *name, BlockDriverState **sn_bs) > { > QEMUSnapshotInfo *sn_tab, *sn; > int nb_sns, i, ret; > > + assert(bs); > + > ret = -ENOENT; > - nb_sns = bdrv_snapshot_list(bs,&sn_tab); > - if (nb_sns< 0) > - return ret; > - for(i = 0; i< nb_sns; i++) { > - sn =&sn_tab[i]; > - if (!strcmp(sn->id_str, name) || !strcmp(sn->name, name)) { > - *sn_info = *sn; > - ret = 0; > + do { > + nb_sns = bdrv_snapshot_list(bs,&sn_tab); > + if (nb_sns< 0) { > + if (nb_sns == -ENOTSUP) { > + /* If this device does not support snapshots, > + * its backing file still might; continue on > + * to the backing file. > + */ > + continue; > + } else { > + return ret; > + } > + } > + for (i = 0; i< nb_sns; i++) { > + sn =&sn_tab[i]; > + if (!strcmp(sn->id_str, name) || !strcmp(sn->name, name)) { > + *sn_info = *sn; > + if (sn_bs != 0) { > + *sn_bs = bs; > + } > + ret = 0; > + break; > + } > + } > + qemu_free(sn_tab); > + if (ret == 0) { > break; > } > - } > - qemu_free(sn_tab); > + if (!sn_bs) { > + break; > + } > + } while ((bs = bdrv_get_backing_bdrv(bs))); > + > return ret; > } > > @@ -1651,7 +1679,7 @@ static int del_existing_snapshots(Monitor *mon, > const char *name) > QTAILQ_FOREACH(dinfo,&drives, next) { > bs = dinfo->bdrv; > if (bdrv_can_snapshot(bs)&& > - bdrv_snapshot_find(bs, snapshot, name)>= 0) > + bdrv_snapshot_find(bs, snapshot, name, NULL)>= 0) > { > ret = bdrv_snapshot_delete(bs, name); > if (ret< 0) { > @@ -1696,7 +1724,7 @@ void do_savevm(Monitor *mon, const QDict *qdict) > > memset(sn, 0, sizeof(*sn)); > if (name) { > - ret = bdrv_snapshot_find(bs, old_sn, name); > + ret = bdrv_snapshot_find(bs, old_sn, name, NULL); > if (ret>= 0) { > pstrcpy(sn->name, sizeof(sn->name), old_sn->name); > pstrcpy(sn->id_str, sizeof(sn->id_str), old_sn->id_str); > @@ -1759,7 +1787,7 @@ void do_savevm(Monitor *mon, const QDict *qdict) > int load_vmstate(Monitor *mon, const char *name) > { > DriveInfo *dinfo; > - BlockDriverState *bs, *bs1; > + BlockDriverState *bs, *bs1, *sn_bs; > QEMUSnapshotInfo sn; > QEMUFile *f; > int ret; > @@ -1804,12 +1832,12 @@ int load_vmstate(Monitor *mon, const char *name) > } > > /* Don't even try to load empty VM states */ > - ret = bdrv_snapshot_find(bs,&sn, name); > + ret = bdrv_snapshot_find(bs,&sn, name,&sn_bs); > if ((ret>= 0)&& (sn.vm_state_size == 0)) > return -EINVAL; > > /* restore the VM state */ > - f = qemu_fopen_bdrv(bs, 0); > + f = qemu_fopen_bdrv(sn_bs, 0); > if (!f) { > monitor_printf(mon, "Could not open VM state file\n"); > return -EINVAL; > @@ -1876,17 +1904,25 @@ void do_info_snapshots(Monitor *mon) > } > monitor_printf(mon, "\n"); > > - nb_sns = bdrv_snapshot_list(bs,&sn_tab); > - if (nb_sns< 0) { > - monitor_printf(mon, "bdrv_snapshot_list: error %d\n", nb_sns); > - return; > - } > - monitor_printf(mon, "Snapshot list (from %s):\n", > - bdrv_get_device_name(bs)); > - monitor_printf(mon, "%s\n", bdrv_snapshot_dump(buf, sizeof(buf), NULL)); > - for(i = 0; i< nb_sns; i++) { > - sn =&sn_tab[i]; > - monitor_printf(mon, "%s\n", bdrv_snapshot_dump(buf, sizeof(buf), sn)); > + for (; bs; bs = bdrv_get_backing_bdrv(bs)) { > + nb_sns = bdrv_snapshot_list(bs,&sn_tab); > + if (nb_sns< 0) { > + monitor_printf(mon, "bdrv_snapshot_list: error %d\n", nb_sns); > + continue; > + } > + const char* device_name = bdrv_get_device_name(bs); > + if (device_name&& device_name[0]) { > + monitor_printf(mon, "Snapshot list (device %s, from %s):\n", > + device_name, bdrv_get_filename(bs)); > + } else { > + monitor_printf(mon, "Snapshot list (from %s):\n", > + bdrv_get_filename(bs)); > + } > + monitor_printf(mon, "%s\n", bdrv_snapshot_dump(buf, > sizeof(buf), NULL)); > + for(i = 0; i< nb_sns; i++) { > + sn =&sn_tab[i]; > + monitor_printf(mon, "%s\n", bdrv_snapshot_dump(buf, > sizeof(buf), sn)); > + } > + qemu_free(sn_tab); > } > - qemu_free(sn_tab); > } >