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qcow2: Don't write with BDRV_O_INCOMING

PATCH Applied Kevin Wolf 3 participants 3 messages Mar 11, 2014 Block layer

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Kevin Wolf

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#0 lore raw

PATCH 1/1 qcow2: Don't write with BDRV_O_INCOMING

qcow2_open() causes writes when repairing an image with the dirty flag set and when clearing autoclear flags. It shouldn't do this when another qemu instance is still actively working on this image file.

One effect of the bug is that images may have a cleared dirty flag while the migration source host still has it in use with lazy refcounts enabled, so refcounts are not accurate and the dirty flag must remain set.

Signed-off-by Kevin Wolf <[email protected]>
---
 block/qcow2.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)
block/qcow2.c +7 -5
index b5b1e8c..da82646 100644
@@ -644,7 +644,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     }
 
     /* Clear unknown autoclear feature bits */
-    if (!bs->read_only && s->autoclear_features != 0) {
+    if (!bs->read_only && !(flags & BDRV_O_INCOMING) && s->autoclear_features) {
         s->autoclear_features = 0;
         ret = qcow2_update_header(bs);
         if (ret < 0) {

@@ -657,7 +657,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     qemu_co_mutex_init(&s->lock);
 
     /* Repair image if dirty */
-    if (!(flags & BDRV_O_CHECK) && !bs->read_only &&
+    if (!(flags & (BDRV_O_CHECK | BDRV_O_INCOMING)) && !bs->read_only &&
         (s->incompatible_features & QCOW2_INCOMPAT_DIRTY)) {
         BdrvCheckResult result = {0};
 

@@ -1137,10 +1137,12 @@ static void qcow2_close(BlockDriverState *bs)
     /* else pre-write overlap checks in cache_destroy may crash */
     s->l1_table = NULL;
 
-    qcow2_cache_flush(bs, s->l2_table_cache);
-    qcow2_cache_flush(bs, s->refcount_block_cache);
+    if (!(bs->open_flags & BDRV_O_INCOMING)) {
+        qcow2_cache_flush(bs, s->l2_table_cache);
+        qcow2_cache_flush(bs, s->refcount_block_cache);
 
-    qcow2_mark_clean(bs);
+        qcow2_mark_clean(bs);
+    }
 
     qcow2_cache_destroy(bs, s->l2_table_cache);
     qcow2_cache_destroy(bs, s->refcount_block_cache);
Signature · 1 line
1.8.1.4
Reviewed-by on v1 1/1
#1 lore raw
Quoted 9 lines · Kevin Wolf

qcow2_open() causes writes when repairing an image with the dirty flag set and when clearing autoclear flags. It shouldn't do this when another qemu instance is still actively working on this image file.

One effect of the bug is that images may have a cleared dirty flag while the migration source host still has it in use with lazy refcounts enabled, so refcounts are not accurate and the dirty flag must remain set.

Quoted 4 lines
Signed-off-by Kevin Wolf <[email protected]>
---
 block/qcow2.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)
Reviewed-by Eric Blake <[email protected]>
Signature · 2 lines
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org
Applied
#2 lore raw
In reply to Kevin Wolf
Quoted 9 lines · Kevin Wolf

qcow2_open() causes writes when repairing an image with the dirty flag set and when clearing autoclear flags. It shouldn't do this when another qemu instance is still actively working on this image file.

One effect of the bug is that images may have a cleared dirty flag while the migration source host still has it in use with lazy refcounts enabled, so refcounts are not accurate and the dirty flag must remain set.

Quoted 4 lines
Signed-off-by Kevin Wolf <[email protected]>
---
 block/qcow2.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan