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[PATCH v2 5/5] qemu-img: Add --start-offset and --max-length to map


From: Eyal Moscovici
Subject: [PATCH v2 5/5] qemu-img: Add --start-offset and --max-length to map
Date: Thu, 7 May 2020 00:34:59 +0300

The mapping operation of large disks especially ones stored over a
long chain of QCOW2 files can take a long time to finish.
Additionally when mapping fails there was no way recover by
restarting the mapping from the failed location.

The new options, --start-offset and --max-length allows the user to
divide these type of map operations into shorter independent tasks.

Reviewed-by: Eric Blake <address@hidden>
Acked-by: Mark Kanda <address@hidden>
Co-developed-by: Yoav Elnekave <address@hidden>
Signed-off-by: Yoav Elnekave <address@hidden>
Signed-off-by: Eyal Moscovici <address@hidden>
---
 docs/tools/qemu-img.rst |  2 +-
 qemu-img-cmds.hx        |  4 ++--
 qemu-img.c              | 22 +++++++++++++++++++++-
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/docs/tools/qemu-img.rst b/docs/tools/qemu-img.rst
index 0080f83a76..f4ffe528ea 100644
--- a/docs/tools/qemu-img.rst
+++ b/docs/tools/qemu-img.rst
@@ -519,7 +519,7 @@ Command description:
     ``ImageInfoSpecific*`` QAPI object (e.g. ``ImageInfoSpecificQCow2``
     for qcow2 images).
 
-.. option:: map [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] 
[-U] FILENAME
+.. option:: map [--object OBJECTDEF] [--image-opts] [-f FMT] 
[--start-offset=OFFSET] [--max-length=LEN] [--output=OFMT] [-U] FILENAME
 
   Dump the metadata of image *FILENAME* and its backing file chain.
   In particular, this commands dumps the allocation state of every sector
diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index c9c54de1df..35f832816f 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -63,9 +63,9 @@ SRST
 ERST
 
 DEF("map", img_map,
-    "map [--object objectdef] [--image-opts] [-f fmt] [--output=ofmt] [-U] 
filename")
+    "map [--object objectdef] [--image-opts] [-f fmt] [--start-offset=offset] 
[--max-length=len] [--output=ofmt] [-U] filename")
 SRST
-.. option:: map [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] 
[-U] FILENAME
+.. option:: map [--object OBJECTDEF] [--image-opts] [-f FMT] 
[--start-offset=OFFSET] [--max-length=LEN] [--output=OFMT] [-U] FILENAME
 ERST
 
 DEF("measure", img_measure,
diff --git a/qemu-img.c b/qemu-img.c
index 0a140fe564..f59b2c0a7c 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -3003,6 +3003,8 @@ static int img_map(int argc, char **argv)
     int ret = 0;
     bool image_opts = false;
     bool force_share = false;
+    int64_t start_offset = 0;
+    int64_t max_length = -1;
 
     fmt = NULL;
     output = NULL;
@@ -3015,9 +3017,11 @@ static int img_map(int argc, char **argv)
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
             {"force-share", no_argument, 0, 'U'},
+            {"start-offset", required_argument, 0, 's'},
+            {"max-length", required_argument, 0, 'l'},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, ":f:hU",
+        c = getopt_long(argc, argv, ":f:s:l:hU",
                         long_options, &option_index);
         if (c == -1) {
             break;
@@ -3041,6 +3045,18 @@ static int img_map(int argc, char **argv)
         case OPTION_OUTPUT:
             output = optarg;
             break;
+        case 's':
+            start_offset = cvtnum("start offset", optarg);
+            if (start_offset < 0) {
+                return 1;
+            }
+            break;
+        case 'l':
+            max_length = cvtnum("max length", optarg);
+            if (max_length < 0) {
+                return 1;
+            }
+            break;
         case OPTION_OBJECT: {
             QemuOpts *opts;
             opts = qemu_opts_parse_noisily(&qemu_object_opts,
@@ -3091,7 +3107,11 @@ static int img_map(int argc, char **argv)
         error_report("Failed to get size for '%s'", filename);
         return 1;
     }
+    if (max_length != -1) {
+        length = MIN(start_offset + max_length, length);
+    }
 
+    curr.start = start_offset;
     while (curr.start + curr.length < length) {
         int64_t offset = curr.start + curr.length;
         int64_t n;
-- 
2.17.2 (Apple Git-113)




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