Patchwork [RESEND] Properly use backing file argument to git-img convert

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Submitter Brad Campbell
Date Sept. 3, 2012, 7:46 a.m.
Message ID <1346658419-13829-1-git-send-email-brad@fnarfbargle.com>
Download mbox | patch
Permalink /patch/181306/
State New
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Comments

Brad Campbell - Sept. 3, 2012, 7:46 a.m.
Converting to an image with an output backing file would write out the contents
 of the source image whether or not it was already contained in the new backing
 file. This commit ensures that the source file is checked against the new
 backing file and output is only allocated if it obsoletes or extends data
 already in the supplied backing file.


Signed-off-by: Brad Campbell <brad@fnarfbargle.com>
---
 qemu-img.c |   74 ++++++++++++++++++++++++++++++++++++++++++++++-------------
 1 files changed, 57 insertions(+), 17 deletions(-)
Andreas Färber - Sept. 3, 2012, 2:23 p.m.
Am 03.09.2012 09:46, schrieb Brad Campbell:
>  Converting to an image with an output backing file would write out the contents
>  of the source image whether or not it was already contained in the new backing
>  file. This commit ensures that the source file is checked against the new
>  backing file and output is only allocated if it obsoletes or extends data
>  already in the supplied backing file.
> 
> 
> Signed-off-by: Brad Campbell <brad@fnarfbargle.com>

For a resend it would've been nice to get the typos out, I'm sure you
mean qemu-img. :) And it would be nice to have that marked as the topic
then so that it's easily recognized ("qemu-img: Bla bla").

> ---
>  qemu-img.c |   74 ++++++++++++++++++++++++++++++++++++++++++++++-------------
>  1 files changed, 57 insertions(+), 17 deletions(-)
> 
> diff --git a/qemu-img.c b/qemu-img.c
> index c8a70ff..3fb6cbf 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -629,11 +629,12 @@ static int img_convert(int argc, char **argv)
>      int progress = 0, flags;
>      const char *fmt, *out_fmt, *cache, *out_baseimg, *out_filename;
>      BlockDriver *drv, *proto_drv;
> -    BlockDriverState **bs = NULL, *out_bs = NULL;
> +    BlockDriverState **bs = NULL, *out_bs = NULL, *out_bf = NULL;
>      int64_t total_sectors, nb_sectors, sector_num, bs_offset;
> -    uint64_t bs_sectors;
> +    uint64_t bf_sectors, bs_sectors;
>      uint8_t * buf = NULL;
>      const uint8_t *buf1;
> +    uint8_t * bf_buf = NULL;

Should be *bf_buf despite the * buf line above (checkpatch.pl sometimes
mixes up multiplication and declaration of pointer variables).

>      BlockDriverInfo bdi;
>      QEMUOptionParameter *param = NULL, *create_options = NULL;
>      QEMUOptionParameter *out_baseimg_param;
[snip]

Note that the merge window for v1.3 is not yet open so you'll have to be
a bit patient before seeing your patch in qemu.git.

http://wiki.qemu.org/Planning/1.2

Regards,
Andreas
Brad Campbell - Sept. 4, 2012, 2:31 a.m.
On 03/09/12 22:23, Andreas Färber wrote:
> Am 03.09.2012 09:46, schrieb Brad Campbell:
>>   Converting to an image with an output backing file would write out the contents
>>   of the source image whether or not it was already contained in the new backing
>>   file. This commit ensures that the source file is checked against the new
>>   backing file and output is only allocated if it obsoletes or extends data
>>   already in the supplied backing file.
>>
>>
>> Signed-off-by: Brad Campbell <brad@fnarfbargle.com>
>
> For a resend it would've been nice to get the typos out, I'm sure you
> mean qemu-img. :) And it would be nice to have that marked as the topic
> then so that it's easily recognized ("qemu-img: Bla bla").

To be honest, with a typo that big I would never have picked it up 
myself no matter how many times I went over it. I'll take that 
suggestion for the topic, thanks.

>> ---
>>   qemu-img.c |   74 ++++++++++++++++++++++++++++++++++++++++++++++-------------
>>   1 files changed, 57 insertions(+), 17 deletions(-)
>>
>> diff --git a/qemu-img.c b/qemu-img.c
>> index c8a70ff..3fb6cbf 100644
>> --- a/qemu-img.c
>> +++ b/qemu-img.c
>> @@ -629,11 +629,12 @@ static int img_convert(int argc, char **argv)
>>       int progress = 0, flags;
>>       const char *fmt, *out_fmt, *cache, *out_baseimg, *out_filename;
>>       BlockDriver *drv, *proto_drv;
>> -    BlockDriverState **bs = NULL, *out_bs = NULL;
>> +    BlockDriverState **bs = NULL, *out_bs = NULL, *out_bf = NULL;
>>       int64_t total_sectors, nb_sectors, sector_num, bs_offset;
>> -    uint64_t bs_sectors;
>> +    uint64_t bf_sectors, bs_sectors;
>>       uint8_t * buf = NULL;
>>       const uint8_t *buf1;
>> +    uint8_t * bf_buf = NULL;
>
> Should be *bf_buf despite the * buf line above (checkpatch.pl sometimes
> mixes up multiplication and declaration of pointer variables).

I'll correct and re-send.

>>       BlockDriverInfo bdi;
>>       QEMUOptionParameter *param = NULL, *create_options = NULL;
>>       QEMUOptionParameter *out_baseimg_param;
> [snip]
>
> Note that the merge window for v1.3 is not yet open so you'll have to be
> a bit patient before seeing your patch in qemu.git.

I'm not in any hurry, it's just that the mail config on the machine I 
used git send-email from is so broken that the mail to Kevin bounced, so 
I waited a week before I re-sent it just to avoid bombing the list. As 
it turns out it's still broken anyway.

Thanks for the feedback.

Regards,
Brad

Patch

diff --git a/qemu-img.c b/qemu-img.c
index c8a70ff..3fb6cbf 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -629,11 +629,12 @@  static int img_convert(int argc, char **argv)
     int progress = 0, flags;
     const char *fmt, *out_fmt, *cache, *out_baseimg, *out_filename;
     BlockDriver *drv, *proto_drv;
-    BlockDriverState **bs = NULL, *out_bs = NULL;
+    BlockDriverState **bs = NULL, *out_bs = NULL, *out_bf = NULL;
     int64_t total_sectors, nb_sectors, sector_num, bs_offset;
-    uint64_t bs_sectors;
+    uint64_t bf_sectors, bs_sectors;
     uint8_t * buf = NULL;
     const uint8_t *buf1;
+    uint8_t * bf_buf = NULL;
     BlockDriverInfo bdi;
     QEMUOptionParameter *param = NULL, *create_options = NULL;
     QEMUOptionParameter *out_baseimg_param;
@@ -797,6 +798,16 @@  static int img_convert(int argc, char **argv)
     out_baseimg_param = get_option_parameter(param, BLOCK_OPT_BACKING_FILE);
     if (out_baseimg_param) {
         out_baseimg = out_baseimg_param->value.s;
+
+        /* out_baseimg_parm != NULL even if there is no base img specified! */
+        if (out_baseimg) {
+            out_bf = bdrv_new_open(out_baseimg, NULL, BDRV_O_FLAGS);
+            if (!out_bf) {
+                ret = -1;
+                goto out;
+            }
+            bdrv_get_geometry(out_bf, &bf_sectors);
+        }
     }
 
     /* Check if compression is supported */
@@ -862,6 +873,9 @@  static int img_convert(int argc, char **argv)
     bs_offset = 0;
     bdrv_get_geometry(bs[0], &bs_sectors);
     buf = qemu_blockalign(out_bs, IO_BUF_SIZE);
+    if (out_baseimg) {
+        bf_buf = qemu_blockalign(out_bs, IO_BUF_SIZE);
+    }
 
     if (compress) {
         ret = bdrv_get_info(out_bs, &bdi);
@@ -979,31 +993,52 @@  static int img_convert(int argc, char **argv)
                 n = bs_offset + bs_sectors - sector_num;
             }
 
+            ret = bdrv_read(bs[bs_i], sector_num - bs_offset, buf, n);
+            if (ret < 0) {
+                error_report("error while reading sector %" PRId64 ": %s",
+                             sector_num - bs_offset, strerror(-ret));
+                goto out;
+            }
+	 
             if (has_zero_init) {
                 /* If the output image is being created as a copy on write image,
-                   assume that sectors which are unallocated in the input image
-                   are present in both the output's and input's base images (no
-                   need to copy them). */
+                   check that sectors which are unallocated in the input image
+                   are present in both the output's and input's base images (or 
+                   copy them). */
                 if (out_baseimg) {
-                    if (!bdrv_is_allocated(bs[bs_i], sector_num - bs_offset,
-                                           n, &n1)) {
-                        sector_num += n1;
-                        continue;
+                    if (sector_num < bf_sectors) {
+                        /* Check if source sectors match those in the new backing file and
+                           skip the copy if true. */
+                        n = MIN(n, bf_sectors - sector_num);
+                        ret = bdrv_read(out_bf, sector_num - bs_offset, bf_buf, n);
+                        if (ret < 0) {
+                            error_report("error while reading backing file");
+                            goto out;
+                        }
+                        if (!compare_sectors(buf, bf_buf, n, &n1)) {
+                            sector_num += n1;
+                            continue;
+                        }
+ 
+                    } else {
+                        /* Source file(s) is larger than the backing file. Just check for
+                           allocated sectors */
+                        if (!is_allocated_sectors_min(buf, n, &n1, min_sparse)) {
+                            /* if we got zero, how many of the next ones are zero? */
+                            is_allocated_sectors(buf, n, &n1);
+                            sector_num += n1;
+                            continue;
+                        }
                     }
-                    /* The next 'n1' sectors are allocated in the input image. Copy
-                       only those as they may be followed by unallocated sectors. */
+                    /* The next 'n1' sectors are allocated in the input image or the
+                       backing files are different. Copy only those as they may be 
+                       followed by unallocated sectors. */
                     n = n1;
                 }
             } else {
                 n1 = n;
             }
 
-            ret = bdrv_read(bs[bs_i], sector_num - bs_offset, buf, n);
-            if (ret < 0) {
-                error_report("error while reading sector %" PRId64 ": %s",
-                             sector_num - bs_offset, strerror(-ret));
-                goto out;
-            }
             /* NOTE: at the same time we convert, we do not write zero
                sectors to have a chance to compress the image. Ideally, we
                should add a specific call to have the info to go faster */
@@ -1037,6 +1072,7 @@  out:
     free_option_parameters(create_options);
     free_option_parameters(param);
     qemu_vfree(buf);
+    qemu_vfree(bf_buf);
     if (out_bs) {
         bdrv_delete(out_bs);
     }
@@ -1048,6 +1084,10 @@  out:
         }
         g_free(bs);
     }
+    if (out_bf) {
+        bdrv_delete(out_bf);
+    }
+
     if (ret) {
         return 1;
     }