Patchwork [v7,3/4] qemu-img: Add compare subcommand

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Submitter Miroslav Rezanina
Date Dec. 17, 2012, 1:39 p.m.
Message ID <1355751593-31535-4-git-send-email-mrezanin@redhat.com>
Download mbox | patch
Permalink /patch/206874/
State New
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Comments

Miroslav Rezanina - Dec. 17, 2012, 1:39 p.m.
From: Miroslav Rezanina <mrezanin@redhat.com>

This patch adds new qemu-img subcommand that compare content of two disk
images.

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 qemu-img-cmds.hx |   6 ++
 qemu-img.c       | 268 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 273 insertions(+), 1 deletion(-)
Eric Blake - Dec. 19, 2012, 6:12 p.m.
On 12/17/2012 06:39 AM, mrezanin@redhat.com wrote:
> From: Miroslav Rezanina <mrezanin@redhat.com>
> 
> This patch adds new qemu-img subcommand that compare content of two disk

s/compare/compares/

> images.
> 
> Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
> ---
> @@ -587,7 +587,7 @@ static int img_commit(int argc, char **argv)
>  }
>  
>  /*
> - * Returns true iff the first sector pointed to by 'buf' contains at least
> + * Returns true if the first sector pointed to by 'buf' contains at least

Spurious change.  'iff' is correct here, for its mathematical meaning of
if-and-only-if.

>   * a non-NUL byte.
>   *
>   * 'pnum' is set to the number of sectors (including and immediately following
> @@ -688,6 +688,272 @@ static int compare_sectors(const uint8_t *buf1, const uint8_t *buf2, int n,
>  
>  #define IO_BUF_SIZE (2 * 1024 * 1024)
>  
> +static int64_t sectors_to_bytes(int64_t sectors)
> +{
> +    return sectors << BDRV_SECTOR_BITS;

Worth checking for overflow?

> +static int check_empty_sectors(BlockDriverState *bs, int64_t sect_num,
> +                               int sect_count, const char *filename,
> +                               uint8_t *buffer, bool quiet)
> +{
> +    int pnum, ret = 0;
> +    ret = bdrv_read(bs, sect_num, buffer, sect_count);
> +    if (ret < 0) {
> +        error_report("Error while reading offset %" PRId64 " of %s: %s",
> +                     sectors_to_bytes(sect_num), filename, strerror(-ret));
> +        return ret;
> +    }
> +    ret = is_allocated_sectors(buffer, sect_count, &pnum);

Is this logic backwards?  Isn't it wasteful to read a sector prior to
seeing if it was actually allocated?
Miroslav Rezanina - Dec. 20, 2012, 7:44 p.m.
----- Original Message -----
> From: "Eric Blake" <eblake@redhat.com>
> To: mrezanin@redhat.com
> Cc: qemu-devel@nongnu.org, kwolf@redhat.com, pbonzini@redhat.com, stefanha@redhat.com
> Sent: Wednesday, December 19, 2012 7:12:49 PM
> Subject: Re: [Qemu-devel] [PATCH v7 3/4] qemu-img: Add compare subcommand
> 
> On 12/17/2012 06:39 AM, mrezanin@redhat.com wrote:
> > From: Miroslav Rezanina <mrezanin@redhat.com>
> > 
> > This patch adds new qemu-img subcommand that compare content of two
> > disk
> 
> s/compare/compares/
> 
> > images.
> > 
> > Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
> > ---
> > @@ -587,7 +587,7 @@ static int img_commit(int argc, char **argv)
> >  }
> >  
> >  /*
> > - * Returns true iff the first sector pointed to by 'buf' contains
> > at least
> > + * Returns true if the first sector pointed to by 'buf' contains
> > at least
> 
> Spurious change.  'iff' is correct here, for its mathematical meaning
> of
> if-and-only-if.

You're right. I probably just see iff and change it to if without checking
the reason.

> 
> >   * a non-NUL byte.
> >   *
> >   * 'pnum' is set to the number of sectors (including and
> >   immediately following
> > @@ -688,6 +688,272 @@ static int compare_sectors(const uint8_t
> > *buf1, const uint8_t *buf2, int n,
> >  
> >  #define IO_BUF_SIZE (2 * 1024 * 1024)
> >  
> > +static int64_t sectors_to_bytes(int64_t sectors)
> > +{
> > +    return sectors << BDRV_SECTOR_BITS;
> 
> Worth checking for overflow?
> 

I think it's not. This should be save as block driver should not allow sectors to
cause overflow.

> > +static int check_empty_sectors(BlockDriverState *bs, int64_t
> > sect_num,
> > +                               int sect_count, const char
> > *filename,
> > +                               uint8_t *buffer, bool quiet)
> > +{
> > +    int pnum, ret = 0;
> > +    ret = bdrv_read(bs, sect_num, buffer, sect_count);
> > +    if (ret < 0) {
> > +        error_report("Error while reading offset %" PRId64 " of
> > %s: %s",
> > +                     sectors_to_bytes(sect_num), filename,
> > strerror(-ret));
> > +        return ret;
> > +    }
> > +    ret = is_allocated_sectors(buffer, sect_count, &pnum);
> 
> Is this logic backwards?  Isn't it wasteful to read a sector prior to
> seeing if it was actually allocated?
> 
This is correct order. Function is_allocated_sector test if sectors contain any non-zero byte. We know that sector is "physically" allocated in the image, we test if it contains any data.
> --
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
> 
> 

Miroslav Rezanina

Patch

diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index 90b93e0..bc1ccfa 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -27,6 +27,12 @@  STEXI
 @item commit [-q] [-f @var{fmt}] [-t @var{cache}] @var{filename}
 ETEXI
 
+DEF("compare", img_compare,
+    "compare [-f fmt] [-F fmt] [-p] [-q] [-s] filename1 filename2")
+STEXI
+@item compare [-f @var{fmt}] [-F @var{fmt}] [-p] [-q] [-s] @var{filename1} @var{filename2}
+ETEXI
+
 DEF("convert", img_convert,
     "convert [-c] [-p] [-q] [-f fmt] [-t cache] [-O output_fmt] [-o options] [-s snapshot_name] [-S sparse_size] filename [filename2 [...]] output_filename")
 STEXI
diff --git a/qemu-img.c b/qemu-img.c
index b9a45f1..8b4f01f 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -587,7 +587,7 @@  static int img_commit(int argc, char **argv)
 }
 
 /*
- * Returns true iff the first sector pointed to by 'buf' contains at least
+ * Returns true if the first sector pointed to by 'buf' contains at least
  * a non-NUL byte.
  *
  * 'pnum' is set to the number of sectors (including and immediately following
@@ -688,6 +688,272 @@  static int compare_sectors(const uint8_t *buf1, const uint8_t *buf2, int n,
 
 #define IO_BUF_SIZE (2 * 1024 * 1024)
 
+static int64_t sectors_to_bytes(int64_t sectors)
+{
+    return sectors << BDRV_SECTOR_BITS;
+}
+
+static int64_t sectors_to_process(int64_t total, int64_t from)
+{
+    int64_t ret = total - from;
+
+    if (ret > (IO_BUF_SIZE >> BDRV_SECTOR_BITS)) {
+        return IO_BUF_SIZE >> BDRV_SECTOR_BITS;
+    }
+
+    return ret;
+}
+
+/*
+ * Check if passed sectors are empty (not allocated or contain only 0 bytes)
+ *
+ * Returns 0 in case sectors are filled with 0, 1 if sectors contain non-zero
+ * data and negative value on error.
+ *
+ * @param bs:  Driver used for accessing file
+ * @param sect_num: Number of first sector to check
+ * @param sect_count: Number of sectors to check
+ * @param filename: Name of disk file we are checking (logging purpose)
+ * @param buffer: Allocated buffer for storing read data
+ * @param quiet: Flag for quiet mode
+ */
+static int check_empty_sectors(BlockDriverState *bs, int64_t sect_num,
+                               int sect_count, const char *filename,
+                               uint8_t *buffer, bool quiet)
+{
+    int pnum, ret = 0;
+    ret = bdrv_read(bs, sect_num, buffer, sect_count);
+    if (ret < 0) {
+        error_report("Error while reading offset %" PRId64 " of %s: %s",
+                     sectors_to_bytes(sect_num), filename, strerror(-ret));
+        return ret;
+    }
+    ret = is_allocated_sectors(buffer, sect_count, &pnum);
+    if (ret || pnum != sect_count) {
+        qprintf(quiet, "Content mismatch at offset %" PRId64 "!\n",
+                sectors_to_bytes(ret ? sect_num : sect_num + pnum));
+        return 1;
+    }
+
+    return 0;
+}
+
+/*
+ * Compares two images. Exit codes:
+ *
+ * 0 - Images are identical
+ * 1 - Images differ
+ * 2 - Error occurred
+ */
+static int img_compare(int argc, char **argv)
+{
+    const char *fmt1 = NULL, *fmt2 = NULL, *filename1, *filename2;
+    BlockDriverState *bs1, *bs2;
+    int64_t total_sectors1, total_sectors2;
+    uint8_t *buf1 = NULL, *buf2 = NULL;
+    int pnum1, pnum2;
+    int allocated1, allocated2;
+    int ret = 0; /* return value - 0 Ident, 1 Different, 2 Error */
+    int progress = 0, quiet = 0, strict = 0;
+    int64_t total_sectors;
+    int64_t sector_num = 0;
+    int64_t nb_sectors;
+    int c, pnum;
+    uint64_t bs_sectors;
+    uint64_t progress_base;
+
+    for (;;) {
+        c = getopt(argc, argv, "hpf:F:sq");
+        if (c == -1) {
+            break;
+        }
+        switch (c) {
+        case '?':
+        case 'h':
+            help();
+            break;
+        case 'f':
+            fmt1 = optarg;
+            break;
+        case 'F':
+            fmt2 = optarg;
+            break;
+        case 'p':
+            progress = 1;
+            break;
+        case 'q':
+            quiet = 1;
+            break;
+        case 's':
+            strict = 1;
+            break;
+        }
+    }
+
+    /* Progress is not shown in Quiet mode */
+    if (quiet) {
+        progress = 0;
+    }
+
+
+    if (optind > argc - 2) {
+        help();
+    }
+    filename1 = argv[optind++];
+    filename2 = argv[optind++];
+
+    /* Initialize before goto out */
+    qemu_progress_init(progress, 2.0);
+
+    bs1 = bdrv_new_open(filename1, fmt1, BDRV_O_FLAGS, true, quiet);
+    if (!bs1) {
+        error_report("Can't open file %s", filename1);
+        ret = 2;
+        goto out3;
+    }
+
+    bs2 = bdrv_new_open(filename2, fmt2, BDRV_O_FLAGS, true, quiet);
+    if (!bs2) {
+        error_report("Can't open file %s", filename2);
+        ret = 2;
+        goto out2;
+    }
+
+    buf1 = qemu_blockalign(bs1, IO_BUF_SIZE);
+    buf2 = qemu_blockalign(bs2, IO_BUF_SIZE);
+    bdrv_get_geometry(bs1, &bs_sectors);
+    total_sectors1 = bs_sectors;
+    bdrv_get_geometry(bs2, &bs_sectors);
+    total_sectors2 = bs_sectors;
+    total_sectors = MIN(total_sectors1, total_sectors2);
+    progress_base = MAX(total_sectors1, total_sectors2);
+
+    qemu_progress_print(0, 100);
+
+    if (strict && total_sectors1 != total_sectors2) {
+        ret = 1;
+        qprintf(quiet, "Strict mode: Image size mismatch!\n");
+        goto out;
+    }
+
+    for (;;) {
+        nb_sectors = sectors_to_process(total_sectors, sector_num);
+        if (nb_sectors <= 0) {
+            break;
+        }
+        allocated1 = bdrv_is_allocated_above(bs1, NULL, sector_num, nb_sectors,
+                                             &pnum1);
+        allocated2 = bdrv_is_allocated_above(bs2, NULL, sector_num, nb_sectors,
+                                             &pnum2);
+        nb_sectors = MIN(pnum1, pnum2);
+
+        if (allocated1 == allocated2) {
+            if (allocated1) {
+                ret = bdrv_read(bs1, sector_num, buf1, nb_sectors);
+                if (ret < 0) {
+                    error_report("error while reading offset %" PRId64 " of %s:"
+                                 " %s", sectors_to_bytes(sector_num), filename1,
+                                  strerror(-ret));
+                    ret = 2;
+                    goto out;
+                }
+                ret = bdrv_read(bs2, sector_num, buf2, nb_sectors);
+                if (ret < 0) {
+                    error_report("error while reading offset %" PRId64
+                                 " of %s: %s", sectors_to_bytes(sector_num),
+                                 filename2, strerror(-ret));
+                    ret = 2;
+                    goto out;
+                }
+                ret = compare_sectors(buf1, buf2, nb_sectors, &pnum);
+                if (ret || pnum != nb_sectors) {
+                    ret = 1;
+                    qprintf(quiet, "Content mismatch at offset %" PRId64 "!\n",
+                            sectors_to_bytes(
+                                ret ? sector_num : sector_num + pnum));
+                    goto out;
+                }
+            }
+        } else {
+            if (strict) {
+                ret = 1;
+                qprintf(quiet, "Strict mode: Offset %" PRId64
+                        " allocation mismatch!\n",
+                        sectors_to_bytes(sector_num));
+                goto out;
+            }
+
+            if (allocated1) {
+                ret = check_empty_sectors(bs1, sector_num, nb_sectors,
+                                         filename1, buf1, quiet);
+            } else {
+                ret = check_empty_sectors(bs2, sector_num, nb_sectors,
+                                         filename2, buf1, quiet);
+            }
+            if (ret) {
+                if (ret < 0) {
+                    ret = 2;
+                }
+                goto out;
+            }
+        }
+        sector_num += nb_sectors;
+        qemu_progress_print(((float) nb_sectors / progress_base)*100, 100);
+    }
+
+    if (total_sectors1 != total_sectors2) {
+        BlockDriverState *bs_over;
+        int64_t total_sectors_over;
+        const char *filename_over;
+
+        qprintf(quiet, "Warning: Image size mismatch!\n");
+        if (total_sectors1 > total_sectors2) {
+            total_sectors_over = total_sectors1;
+            bs_over = bs1;
+            filename_over = filename1;
+        } else {
+            total_sectors_over = total_sectors2;
+            bs_over = bs2;
+            filename_over = filename2;
+        }
+
+        for (;;) {
+            nb_sectors = sectors_to_process(total_sectors_over, sector_num);
+            if (nb_sectors <= 0) {
+                break;
+            }
+            ret = bdrv_is_allocated_above(bs_over, NULL, sector_num,
+                                          nb_sectors, &pnum);
+            nb_sectors = pnum;
+            if (ret) {
+                ret = check_empty_sectors(bs_over, sector_num, nb_sectors,
+                                          filename_over, buf1, quiet);
+                if (ret) {
+                    if (ret < 0) {
+                        ret = 2;
+                    }
+                    goto out;
+                }
+            }
+            sector_num += nb_sectors;
+            qemu_progress_print(((float) nb_sectors / progress_base)*100, 100);
+        }
+    }
+
+    qprintf(quiet, "Images are identical.\n");
+    ret = 0;
+
+out:
+    bdrv_delete(bs2);
+    qemu_vfree(buf1);
+    qemu_vfree(buf2);
+out2:
+    bdrv_delete(bs1);
+out3:
+    qemu_progress_end();
+    return ret;
+}
+
 static int img_convert(int argc, char **argv)
 {
     int c, ret = 0, n, n1, bs_n, bs_i, compress, cluster_size, cluster_sectors;