Patchwork [v2,1/3] qemu-img: Add --backing-chain option to info command

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Submitter Stefan Hajnoczi
Date Oct. 15, 2012, 12:44 p.m.
Message ID <1350305057-6287-2-git-send-email-stefanha@redhat.com>
Download mbox | patch
Permalink /patch/191554/
State New
Headers show

Comments

Stefan Hajnoczi - Oct. 15, 2012, 12:44 p.m.
The qemu-img info --backing-chain option enumerates the backing file
chain.  For example, for base.qcow2 <- snap1.qcow2 <- snap2.qcow2 the
output becomes:

  $ qemu-img info --backing-chain snap2.qcow2
  image: snap2.qcow2
  file format: qcow2
  virtual size: 100M (104857600 bytes)
  disk size: 196K
  cluster_size: 65536
  backing file: snap1.qcow2
  backing file format: qcow2

  image: snap1.qcow2
  file format: qcow2
  virtual size: 100M (104857600 bytes)
  disk size: 196K
  cluster_size: 65536
  backing file: base.qcow2
  backing file format: qcow2

  image: base.qcow2
  file format: qcow2
  virtual size: 100M (104857600 bytes)
  disk size: 136K
  cluster_size: 65536

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 qemu-img.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 76 insertions(+), 22 deletions(-)
Kevin Wolf - Oct. 16, 2012, 10:04 a.m.
Am 15.10.2012 14:44, schrieb Stefan Hajnoczi:
> The qemu-img info --backing-chain option enumerates the backing file
> chain.  For example, for base.qcow2 <- snap1.qcow2 <- snap2.qcow2 the
> output becomes:
> 
>   $ qemu-img info --backing-chain snap2.qcow2
>   image: snap2.qcow2
>   file format: qcow2
>   virtual size: 100M (104857600 bytes)
>   disk size: 196K
>   cluster_size: 65536
>   backing file: snap1.qcow2
>   backing file format: qcow2
> 
>   image: snap1.qcow2
>   file format: qcow2
>   virtual size: 100M (104857600 bytes)
>   disk size: 196K
>   cluster_size: 65536
>   backing file: base.qcow2
>   backing file format: qcow2
> 
>   image: base.qcow2
>   file format: qcow2
>   virtual size: 100M (104857600 bytes)
>   disk size: 136K
>   cluster_size: 65536
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  qemu-img.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 76 insertions(+), 22 deletions(-)
> 
> diff --git a/qemu-img.c b/qemu-img.c
> index f17f187..c717f3e 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -1249,7 +1249,10 @@ static void dump_human_image_info(ImageInfo *info)
>      }
>  }
>  
> -enum {OPTION_OUTPUT = 256};
> +enum {
> +    OPTION_OUTPUT = 256,
> +    OPTION_BACKING_CHAIN = 257,
> +};
>  
>  typedef enum OutputFormat {
>      OFORMAT_JSON,
> @@ -1260,7 +1263,9 @@ static int img_info(int argc, char **argv)
>  {
>      int c;
>      OutputFormat output_format = OFORMAT_HUMAN;
> -    const char *filename, *fmt, *output;
> +    bool chain = false;
> +    const char *output;
> +    char *filename, *fmt;

Maybe I'm missing something, but where are the strings pointed at by
filename and fmt ever modified? If they aren't, strdup() isn't necessary
either.

Kevin
Stefan Hajnoczi - Oct. 16, 2012, 2:51 p.m.
On Tue, Oct 16, 2012 at 12:04:24PM +0200, Kevin Wolf wrote:
> Am 15.10.2012 14:44, schrieb Stefan Hajnoczi:
> > The qemu-img info --backing-chain option enumerates the backing file
> > chain.  For example, for base.qcow2 <- snap1.qcow2 <- snap2.qcow2 the
> > output becomes:
> > 
> >   $ qemu-img info --backing-chain snap2.qcow2
> >   image: snap2.qcow2
> >   file format: qcow2
> >   virtual size: 100M (104857600 bytes)
> >   disk size: 196K
> >   cluster_size: 65536
> >   backing file: snap1.qcow2
> >   backing file format: qcow2
> > 
> >   image: snap1.qcow2
> >   file format: qcow2
> >   virtual size: 100M (104857600 bytes)
> >   disk size: 196K
> >   cluster_size: 65536
> >   backing file: base.qcow2
> >   backing file format: qcow2
> > 
> >   image: base.qcow2
> >   file format: qcow2
> >   virtual size: 100M (104857600 bytes)
> >   disk size: 136K
> >   cluster_size: 65536
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> >  qemu-img.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++--------------
> >  1 file changed, 76 insertions(+), 22 deletions(-)
> > 
> > diff --git a/qemu-img.c b/qemu-img.c
> > index f17f187..c717f3e 100644
> > --- a/qemu-img.c
> > +++ b/qemu-img.c
> > @@ -1249,7 +1249,10 @@ static void dump_human_image_info(ImageInfo *info)
> >      }
> >  }
> >  
> > -enum {OPTION_OUTPUT = 256};
> > +enum {
> > +    OPTION_OUTPUT = 256,
> > +    OPTION_BACKING_CHAIN = 257,
> > +};
> >  
> >  typedef enum OutputFormat {
> >      OFORMAT_JSON,
> > @@ -1260,7 +1263,9 @@ static int img_info(int argc, char **argv)
> >  {
> >      int c;
> >      OutputFormat output_format = OFORMAT_HUMAN;
> > -    const char *filename, *fmt, *output;
> > +    bool chain = false;
> > +    const char *output;
> > +    char *filename, *fmt;
> 
> Maybe I'm missing something, but where are the strings pointed at by
> filename and fmt ever modified? If they aren't, strdup() isn't necessary
> either.

It's necessary because the loop strdups the current image's backing
file, then frees the current image info (including the original backing
file string).  To avoid special cases for the topmost image filename/fmt
we just strdup them.

Stefan

Patch

diff --git a/qemu-img.c b/qemu-img.c
index f17f187..c717f3e 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1249,7 +1249,10 @@  static void dump_human_image_info(ImageInfo *info)
     }
 }
 
-enum {OPTION_OUTPUT = 256};
+enum {
+    OPTION_OUTPUT = 256,
+    OPTION_BACKING_CHAIN = 257,
+};
 
 typedef enum OutputFormat {
     OFORMAT_JSON,
@@ -1260,7 +1263,9 @@  static int img_info(int argc, char **argv)
 {
     int c;
     OutputFormat output_format = OFORMAT_HUMAN;
-    const char *filename, *fmt, *output;
+    bool chain = false;
+    const char *output;
+    char *filename, *fmt;
     BlockDriverState *bs;
     ImageInfo *info;
 
@@ -1272,6 +1277,7 @@  static int img_info(int argc, char **argv)
             {"help", no_argument, 0, 'h'},
             {"format", required_argument, 0, 'f'},
             {"output", required_argument, 0, OPTION_OUTPUT},
+            {"backing-chain", no_argument, 0, OPTION_BACKING_CHAIN},
             {0, 0, 0, 0}
         };
         c = getopt_long(argc, argv, "f:h",
@@ -1285,17 +1291,20 @@  static int img_info(int argc, char **argv)
             help();
             break;
         case 'f':
-            fmt = optarg;
+            fmt = g_strdup(optarg);
             break;
         case OPTION_OUTPUT:
             output = optarg;
             break;
+        case OPTION_BACKING_CHAIN:
+            chain = true;
+            break;
         }
     }
     if (optind >= argc) {
         help();
     }
-    filename = argv[optind++];
+    filename = g_strdup(argv[optind++]);
 
     if (output && !strcmp(output, "json")) {
         output_format = OFORMAT_JSON;
@@ -1303,31 +1312,76 @@  static int img_info(int argc, char **argv)
         output_format = OFORMAT_HUMAN;
     } else if (output) {
         error_report("--output must be used with human or json as argument.");
-        return 1;
+        goto err;
     }
 
-    bs = bdrv_new_open(filename, fmt, BDRV_O_FLAGS | BDRV_O_NO_BACKING, false);
-    if (!bs) {
-        return 1;
+    if (chain && output_format == OFORMAT_JSON) {
+        printf("[\n");
     }
 
-    info = g_new0(ImageInfo, 1);
-    collect_image_info(bs, info, filename, fmt);
+    do {
+        bs = bdrv_new_open(filename, fmt, BDRV_O_FLAGS | BDRV_O_NO_BACKING,
+                           false);
+        if (!bs) {
+            goto err;
+        }
 
-    switch (output_format) {
-    case OFORMAT_HUMAN:
-        dump_human_image_info(info);
-        dump_snapshots(bs);
-        break;
-    case OFORMAT_JSON:
-        collect_snapshots(bs, info);
-        dump_json_image_info(info);
-        break;
-    }
+        info = g_new0(ImageInfo, 1);
+        collect_image_info(bs, info, filename, fmt);
 
-    qapi_free_ImageInfo(info);
-    bdrv_delete(bs);
+        switch (output_format) {
+        case OFORMAT_HUMAN:
+            dump_human_image_info(info);
+            dump_snapshots(bs);
+            break;
+        case OFORMAT_JSON:
+            collect_snapshots(bs, info);
+            dump_json_image_info(info);
+            break;
+        }
+
+        g_free(filename);
+        g_free(fmt);
+        filename = NULL;
+        fmt = NULL;
+
+        if (chain) {
+            if (info->has_full_backing_filename) {
+                filename = g_strdup(info->full_backing_filename);
+            } else if (info->has_backing_filename) {
+                filename = g_strdup(info->backing_filename);
+            }
+
+            if (filename && info->has_backing_filename_format) {
+                fmt = g_strdup(info->backing_filename_format);
+            }
+
+            /* Print delimiters between items */
+            if (filename) {
+                switch (output_format) {
+                case OFORMAT_HUMAN:
+                    printf("\n");
+                    break;
+                case OFORMAT_JSON:
+                    printf(",\n");
+                    break;
+                }
+            }
+        }
+
+        qapi_free_ImageInfo(info);
+        bdrv_delete(bs);
+    } while (filename);
+
+    if (chain && output_format == OFORMAT_JSON) {
+        printf("]\n");
+    }
     return 0;
+
+err:
+    g_free(filename);
+    g_free(fmt);
+    return 1;
 }
 
 #define SNAPSHOT_LIST   1