Re: [Xen-devel] [PATCH] ioemu block device extent checks

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Daniel P. Berrange writes ("Re: [Xen-devel] [PATCH] ioemu block device extent 
checks"):
>    The qcow driver though calls back into
> the raw driver for performing I/O on its underlying file. The qcow 
> driver relies on this file being grow-on-demand for purposes of allocating
> new qcow sectors. The safety checks cause this allocation to fail and
> it all goes downhill from there :-(  

Oh dear.  (I'm a bit surprised that it's taken this long to spot!)
Here is a patch for xen-unstable which I think will fix it.  Could you
give it a quick spin, if you have a suitable test setup ?

Sadly it's rather more intrusive than ideal, since it needs all of the
drivers which are going to extend files via their parents to announce
this, and a couple of bits of necessary infrastructure needed adding.

Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

diff -r 757cd7bb5e35 tools/ioemu/block-qcow.c
--- a/tools/ioemu/block-qcow.c  Fri Feb 22 16:49:56 2008 +0000
+++ b/tools/ioemu/block-qcow.c  Wed Feb 27 11:09:56 2008 +0000
@@ -95,7 +95,7 @@ static int qcow_open(BlockDriverState *b
     int len, i, shift, ret;
     QCowHeader header;
 
-    ret = bdrv_file_open(&s->hd, filename, flags);
+    ret = bdrv_file_open(&s->hd, filename, flags | BDRV_O_EXTENDABLE);
     if (ret < 0)
         return ret;
     if (bdrv_pread(s->hd, 0, &header, sizeof(header)) != sizeof(header))
diff -r 757cd7bb5e35 tools/ioemu/block-qcow2.c
--- a/tools/ioemu/block-qcow2.c Fri Feb 22 16:49:56 2008 +0000
+++ b/tools/ioemu/block-qcow2.c Wed Feb 27 11:09:56 2008 +0000
@@ -191,7 +191,7 @@ static int qcow_open(BlockDriverState *b
     int len, i, shift, ret;
     QCowHeader header;
 
-    ret = bdrv_file_open(&s->hd, filename, flags);
+    ret = bdrv_file_open(&s->hd, filename, flags | BDRV_O_EXTENDABLE);
     if (ret < 0)
         return ret;
     if (bdrv_pread(s->hd, 0, &header, sizeof(header)) != sizeof(header))
diff -r 757cd7bb5e35 tools/ioemu/block-raw.c
--- a/tools/ioemu/block-raw.c   Fri Feb 22 16:49:56 2008 +0000
+++ b/tools/ioemu/block-raw.c   Wed Feb 27 11:12:28 2008 +0000
@@ -1489,5 +1489,7 @@ BlockDriver bdrv_host_device = {
     .bdrv_pread = raw_pread,
     .bdrv_pwrite = raw_pwrite,
     .bdrv_getlength = raw_getlength,
+
+    .bdrv_flags = BLOCK_DRIVER_FLAG_EXTENDABLE
 };
 #endif /* _WIN32 */
diff -r 757cd7bb5e35 tools/ioemu/block-vmdk.c
--- a/tools/ioemu/block-vmdk.c  Fri Feb 22 16:49:56 2008 +0000
+++ b/tools/ioemu/block-vmdk.c  Wed Feb 27 11:10:02 2008 +0000
@@ -352,7 +352,7 @@ static int vmdk_open(BlockDriverState *b
     uint32_t magic;
     int l1_size, i, ret;
 
-    ret = bdrv_file_open(&s->hd, filename, flags);
+    ret = bdrv_file_open(&s->hd, filename, flags | BDRV_O_EXTENDABLE);
     if (ret < 0)
         return ret;
     if (bdrv_pread(s->hd, 0, &magic, sizeof(magic)) != sizeof(magic))
diff -r 757cd7bb5e35 tools/ioemu/block.c
--- a/tools/ioemu/block.c       Fri Feb 22 16:49:56 2008 +0000
+++ b/tools/ioemu/block.c       Wed Feb 27 11:13:57 2008 +0000
@@ -123,20 +123,23 @@ static int bdrv_rw_badreq_sectors(BlockD
 static int bdrv_rw_badreq_sectors(BlockDriverState *bs,
                                int64_t sector_num, int nb_sectors)
 {
-    return
+    return (
        nb_sectors < 0 ||
        nb_sectors > bs->total_sectors ||
-       sector_num > bs->total_sectors - nb_sectors;
+       sector_num > bs->total_sectors - nb_sectors
+       ) && !bs->extendable;
 }
 
 static int bdrv_rw_badreq_bytes(BlockDriverState *bs,
                                  int64_t offset, int count)
 {
     int64_t size = bs->total_sectors << SECTOR_BITS;
-    return
+    return (
        count < 0 ||
        count > size ||
-       offset > size - count;
+       offset > size - count
+       ) && !bs->extendable;
+    
 }
 
 void bdrv_register(BlockDriver *bdrv)
@@ -347,6 +350,12 @@ int bdrv_open2(BlockDriverState *bs, con
     bs->is_temporary = 0;
     bs->encrypted = 0;
 
+    if (flags & BDRV_O_EXTENDABLE) {
+       if (!(drv->bdrv_flags & BLOCK_DRIVER_FLAG_EXTENDABLE))
+           return -ENOSYS;
+       bs->extendable = 1;
+    }
+
     if (flags & BDRV_O_SNAPSHOT) {
         BlockDriverState *bs1;
         int64_t total_size;
diff -r 757cd7bb5e35 tools/ioemu/block_int.h
--- a/tools/ioemu/block_int.h   Fri Feb 22 16:49:56 2008 +0000
+++ b/tools/ioemu/block_int.h   Wed Feb 27 11:11:39 2008 +0000
@@ -23,6 +23,8 @@
  */
 #ifndef BLOCK_INT_H
 #define BLOCK_INT_H
+
+#define BLOCK_DRIVER_FLAG_EXTENDABLE  0x0001u
 
 struct BlockDriver {
     const char *format_name;
@@ -76,6 +78,7 @@ struct BlockDriver {
     int (*bdrv_eject)(BlockDriverState *bs, int eject_flag);
     int (*bdrv_set_locked)(BlockDriverState *bs, int locked);
     
+    unsigned bdrv_flags;
     BlockDriverAIOCB *free_aiocb;
     struct BlockDriver *next;
 };
@@ -87,6 +90,7 @@ struct BlockDriverState {
     int removable; /* if true, the media can be removed */
     int locked;    /* if true, the media cannot temporarily be ejected */
     int encrypted; /* if true, the media is encrypted */
+    int extendable;/* if true, we may write out of original range */
     /* event callback when inserting/removing */
     void (*change_cb)(void *opaque);
     void *change_opaque;
diff -r 757cd7bb5e35 tools/ioemu/vl.h
--- a/tools/ioemu/vl.h  Fri Feb 22 16:49:56 2008 +0000
+++ b/tools/ioemu/vl.h  Wed Feb 27 11:12:03 2008 +0000
@@ -614,6 +614,8 @@ typedef struct QEMUSnapshotInfo {
                                      use a disk image format on top of
                                      it (default for
                                      bdrv_file_open()) */
+#define BDRV_O_EXTENDABLE  0x0080 /* allow writes out of original size range;
+                                    only effective for some drivers */
 
 void bdrv_init(void);
 BlockDriver *bdrv_find_format(const char *format_name);

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