[PATCH 2/2] rbd: add an option for md5 checksumming (v3)

[PATCH 2/2] rbd: add an option for md5 checksumming (v3)

[Christian Brunner]

We needed to get an md5 checksum of an rbd image. Since librbd is using a
lot of sparse operations, this was not possible without writing an image
to a local disk.

With this patch exporting the image is no longer needed. You can do
"rbd md5 image" and you will get the same output as you would call "md5sum".

V1 -> V2:
- use ceph::crypto classes
- support for sha1
- skip holes

V2 -> V3:
- better handling for holes

---
 src/rbd.cc |  140 ++++++++++++++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 118 insertions(+), 22 deletions(-)

diff --git a/src/rbd.cc b/src/rbd.cc
index a18c029..9a40941 100644
--- a/src/rbd.cc
+++ b/src/rbd.cc
@@ -38,6 +38,8 @@
 #include <time.h>
 #include <sys/ioctl.h>
 
+#include "common/ceph_crypto.h"
+
 #include "include/rbd_types.h"
 
 #include <linux/fs.h>
@@ -49,6 +51,30 @@
 
 static string dir_oid = RBD_DIRECTORY;
 static string dir_info_oid = RBD_INFO;
+static size_t lastofs;
+
+enum {
+  OPT_NO_CMD = 0,
+  OPT_LIST,
+  OPT_INFO,
+  OPT_CREATE,
+  OPT_RESIZE,
+  OPT_RM,
+  OPT_EXPORT,
+  OPT_IMPORT,
+  OPT_COPY,
+  OPT_RENAME,
+  OPT_SNAP_CREATE,
+  OPT_SNAP_ROLLBACK,
+  OPT_SNAP_REMOVE,
+  OPT_SNAP_LIST,
+  OPT_WATCH,
+  OPT_MAP,
+  OPT_UNMAP,
+  OPT_SHOWMAPPED,
+  OPT_MD5,
+  OPT_SHA1,
+};
 
 void usage()
 {
@@ -65,6 +91,8 @@ void usage()
        << "  export [image-name] [dest-path]           export image to file\n"
        << "  import [path] [dst-image]                 import image from file (dest defaults\n"
        << "                                            as the filename part of file)\n"
+       << "  md5 [image-name]                          print md5 checksum for image\n"
+       << "  sha1 [image-name]                         print sha1 checksum for image\n"
        << "  <cp | copy> [src-image] [dest-image]      copy image to dest\n"
        << "  <mv | rename> [src-image] [dest-image]    copy image to dest\n"
        << "  snap ls [image-name]                      dump list of image snapshots\n"
@@ -262,6 +290,78 @@ static int do_export(librbd::Image& image, const char *path)
   return 0;
 }
 
+static int hash_read_cb(uint64_t ofs, size_t len, const char *buf, void *arg)
+{
+  ceph::crypto::Digest *Hash = (ceph::crypto::Digest *)arg;
+  byte *hashbuf = (byte *) buf;
+  byte *tempbuf = NULL;
+
+  if (!buf) {
+    len = ofs-lastofs;
+    tempbuf = (byte *) malloc(len);
+    if (!tempbuf)
+      return -ENOMEM;
+    hashbuf = tempbuf;
+  }
+  Hash->Update((const byte *) hashbuf, len);
+
+  lastofs = ofs + len;
+
+  free(tempbuf);
+
+  return 0;
+}
+
+static int do_hash(librbd::Image& image, const char *imgname, int opt_cmd)
+{
+  int64_t r, i, digest_size;
+  byte *digest;
+  char hexval[] = "0123456789abcdef";
+  char *hexdigest;
+  librbd::image_info_t info;
+  ceph::crypto::Digest *Hash;
+
+  lastofs = 0;
+
+  if (opt_cmd == OPT_MD5) {
+    Hash = (ceph::crypto::Digest *) new ceph::crypto::MD5;
+  } else if (opt_cmd == OPT_SHA1) {
+    Hash = (ceph::crypto::Digest *) new ceph::crypto::SHA1;
+  } else {
+    return -1;
+  }
+
+  r = image.stat(info, sizeof(info));
+  if (r < 0)
+    return r;
+
+  r = image.read_iterate(0, info.size, hash_read_cb, (void *)Hash);
+  if (r < 0)
+    return r;
+
+  if (lastofs < info.size) {
+      hash_read_cb(info.size, 0, NULL, (void *)Hash);
+  }
+
+  digest_size = Hash->DigestSize();
+  digest = (byte *) malloc(digest_size);
+  hexdigest = (char *) malloc((digest_size * 2 + 1) * sizeof(char));
+  Hash->Final(digest);
+
+  for(i = 0; i < digest_size; i++){
+    hexdigest[i*2] = hexval[((digest[i] >> 4) & 0xF)];
+    hexdigest[(i*2) + 1] = hexval[(digest[i]) & 0x0F];
+  }
+  hexdigest[(digest_size*2)] = '\0';
+
+  cout << hexdigest << "  " << imgname << std::endl;
+
+  free(hexdigest);
+  free(digest);
+
+  return 0;
+}
+
 static const char *imgname_from_path(const char *path)
 {
   const char *imgname;
@@ -720,27 +820,6 @@ static int do_kernel_rm(const char *dev)
   return r;
 }
 
-enum {
-  OPT_NO_CMD = 0,
-  OPT_LIST,
-  OPT_INFO,
-  OPT_CREATE,
-  OPT_RESIZE,
-  OPT_RM,
-  OPT_EXPORT,
-  OPT_IMPORT,
-  OPT_COPY,
-  OPT_RENAME,
-  OPT_SNAP_CREATE,
-  OPT_SNAP_ROLLBACK,
-  OPT_SNAP_REMOVE,
-  OPT_SNAP_LIST,
-  OPT_WATCH,
-  OPT_MAP,
-  OPT_UNMAP,
-  OPT_SHOWMAPPED,
-};
-
 static int get_cmd(const char *cmd, bool *snapcmd)
 {
   if (strcmp(cmd, "snap") == 0) {
@@ -766,6 +845,10 @@ static int get_cmd(const char *cmd, bool *snapcmd)
       return OPT_EXPORT;
     if (strcmp(cmd, "import") == 0)
       return OPT_IMPORT;
+    if (strcmp(cmd, "md5") == 0)
+      return OPT_MD5;
+    if (strcmp(cmd, "sha1") == 0)
+      return OPT_SHA1;
     if (strcmp(cmd, "copy") == 0 ||
         strcmp(cmd, "cp") == 0)
       return OPT_COPY;
@@ -888,6 +971,10 @@ int main(int argc, const char **argv)
           case OPT_IMPORT:
             set_conf_param(CEPH_ARGPARSE_VAL, &path, &destname);
             break;
+          case OPT_MD5:
+          case OPT_SHA1:
+            set_conf_param(CEPH_ARGPARSE_VAL, &imgname, NULL);
+            break;
           case OPT_COPY:
           case OPT_RENAME:
             set_conf_param(CEPH_ARGPARSE_VAL, &imgname, &destname);
@@ -966,7 +1053,7 @@ int main(int argc, const char **argv)
       (opt_cmd == OPT_RESIZE || opt_cmd == OPT_INFO || opt_cmd == OPT_SNAP_LIST ||
        opt_cmd == OPT_SNAP_CREATE || opt_cmd == OPT_SNAP_ROLLBACK ||
        opt_cmd == OPT_SNAP_REMOVE || opt_cmd == OPT_EXPORT || opt_cmd == OPT_WATCH ||
-       opt_cmd == OPT_COPY)) {
+       opt_cmd == OPT_COPY || opt_cmd == OPT_MD5 || opt_cmd == OPT_SHA1 )) {
     r = rbd.open(io_ctx, image, imgname);
     if (r < 0) {
       cerr << "error opening image " << imgname << ": " << strerror(r) << std::endl;
@@ -1127,6 +1214,15 @@ int main(int argc, const char **argv)
     }
     break;
 
+  case OPT_MD5:
+  case OPT_SHA1:
+    r = do_hash(image, imgname, opt_cmd);
+    if (r < 0) {
+      cerr << "hashing failed: " << strerror(-r) << std::endl;
+      exit(1);
+    }
+    break;
+
   case OPT_COPY:
     r = do_copy(image, dest_io_ctx, destname);
     if (r < 0) {
-- 
1.7.1

Re: [PATCH 2/2] rbd: add an option for md5 checksumming (v3)

[Tommi Virtanen]

On Fri, Aug 26, 2011 at 11:51, Christian Brunner <chb@muc.de> wrote:
> +  if (!buf) {
> +    len = ofs-lastofs;
> +    tempbuf = (byte *) malloc(len);
> +    if (!tempbuf)
> +      return -ENOMEM;
> +    hashbuf = tempbuf;
> +  }
> +  Hash->Update((const byte *) hashbuf, len);

That'll still try to allocate 100GB of RAM for a 100GB hole. It needs
to loop through big holes in smaller chunks, feeding them to the hash
e.g. 8kB at a time. And at that point you might as well just use read
and not read_iterate, that'll do the memsetting etc for you, and then
you can use a static buffer and avoid malloc/free every round. There's
no shortcut to be had from "skipping" holes when you need to feed
bytes to a hash function.
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Re: [PATCH 2/2] rbd: add an option for md5 checksumming (v3)

[Yehuda Sadeh Weinraub]

On Fri, Aug 26, 2011 at 11:51 AM, Christian Brunner <chb@muc.de> wrote:
> +static int hash_read_cb(uint64_t ofs, size_t len, const char *buf, void *arg)
> +{
> +  ceph::crypto::Digest *Hash = (ceph::crypto::Digest *)arg;
> +  byte *hashbuf = (byte *) buf;

Looking at it again, hashbuf is pretty much useless, you can use buf directly.

> +  byte *tempbuf = NULL;
> +
> +  if (!buf) {
> +    len = ofs-lastofs;

Why setting len here? len was already passed in.

> +    tempbuf = (byte *) malloc(len);
> +    if (!tempbuf)
> +      return -ENOMEM;
> +    hashbuf = tempbuf;

buf = tempbuf;

> +  }
> +  Hash->Update((const byte *) hashbuf, len);
> +
> +  lastofs = ofs + len;

you don't need lastofs either.

> +
> +  free(tempbuf);
> +
> +  return 0;
> +}
> +
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Re: [PATCH 2/2] rbd: add an option for md5 checksumming (v3)

[Yehuda Sadeh Weinraub]

On Fri, Aug 26, 2011 at 12:10 PM, Tommi Virtanen
<tommi.virtanen@dreamhost.com> wrote:
> On Fri, Aug 26, 2011 at 11:51, Christian Brunner <chb@muc.de> wrote:
>> +  if (!buf) {
>> +    len = ofs-lastofs;
>> +    tempbuf = (byte *) malloc(len);
>> +    if (!tempbuf)
>> +      return -ENOMEM;
>> +    hashbuf = tempbuf;
>> +  }
>> +  Hash->Update((const byte *) hashbuf, len);
>
> That'll still try to allocate 100GB of RAM for a 100GB hole. It needs
> to loop through big holes in smaller chunks, feeding them to the hash
> e.g. 8kB at a time. And at that point you might as well just use read
> and not read_iterate, that'll do the memsetting etc for you, and then
> you can use a static buffer and avoid malloc/free every round. There's
> no shortcut to be had from "skipping" holes when you need to feed
> bytes to a hash function.

Well, when using read_iterate you avoid reading extra data over the
network when the object (chunk) exists (and is sparse). We can
probably have some optimization here, and only allocate and memset a
buffer once for the case where len == objsize and reuse it later.

Yehuda
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Re: [PATCH 2/2] rbd: add an option for md5 checksumming (v3)

[Christian Brunner]

2011/8/26 Yehuda Sadeh Weinraub <yehudasa@gmail.com>:
> On Fri, Aug 26, 2011 at 11:51 AM, Christian Brunner <chb@muc.de> wrote:
>> +static int hash_read_cb(uint64_t ofs, size_t len, const char *buf, void *arg)
>> +{
>> +  ceph::crypto::Digest *Hash = (ceph::crypto::Digest *)arg;
>> +  byte *hashbuf = (byte *) buf;
>
> Looking at it again, hashbuf is pretty much useless, you can use buf directly.
>
>> +  byte *tempbuf = NULL;
>> +
>> +  if (!buf) {
>> +    len = ofs-lastofs;
>
> Why setting len here? len was already passed in.

Ah - then I didn't understand what read_iterate is doing. I was
thinking, that the callback is not called for missing objects.

>
>> +    tempbuf = (byte *) malloc(len);

Do we need a memset here?

>> +    if (!tempbuf)
>> +      return -ENOMEM;
>> +    hashbuf = tempbuf;
>
> buf = tempbuf;
>
>> +  }
>> +  Hash->Update((const byte *) hashbuf, len);
>> +
>> +  lastofs = ofs + len;
>
> you don't need lastofs either.
>
>> +
>> +  free(tempbuf);
>> +
>> +  return 0;
>> +}
>> +

Christian
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Re: [PATCH 2/2] rbd: add an option for md5 checksumming (v3)

[Yehuda Sadeh Weinraub]

On Fri, Aug 26, 2011 at 12:52 PM, Christian Brunner <chb@muc.de> wrote:
> 2011/8/26 Yehuda Sadeh Weinraub <yehudasa@gmail.com>:
>> On Fri, Aug 26, 2011 at 11:51 AM, Christian Brunner <chb@muc.de> wrote:
>>> +static int hash_read_cb(uint64_t ofs, size_t len, const char *buf, void *arg)
>>> +{
>>> +  ceph::crypto::Digest *Hash = (ceph::crypto::Digest *)arg;
>>> +  byte *hashbuf = (byte *) buf;
>>
>> Looking at it again, hashbuf is pretty much useless, you can use buf directly.
>>
>>> +  byte *tempbuf = NULL;
>>> +
>>> +  if (!buf) {
>>> +    len = ofs-lastofs;
>>
>> Why setting len here? len was already passed in.
>
> Ah - then I didn't understand what read_iterate is doing. I was
> thinking, that the callback is not called for missing objects.
>
>>
>>> +    tempbuf = (byte *) malloc(len);
>
> Do we need a memset here?
>
You can memset, or calloc instead.

Yehuda
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Re: [PATCH 2/2] rbd: add an option for md5 checksumming (v3)

[Tommi Virtanen]

On Fri, Aug 26, 2011 at 12:25, Yehuda Sadeh Weinraub <yehudasa@gmail.com> wrote:
> On Fri, Aug 26, 2011 at 12:10 PM, Tommi Virtanen
> <tommi.virtanen@dreamhost.com> wrote:
>> e.g. 8kB at a time. And at that point you might as well just use read
>> and not read_iterate, that'll do the memsetting etc for you, and then
>> you can use a static buffer and avoid malloc/free every round. There's
>> no shortcut to be had from "skipping" holes when you need to feed
>> bytes to a hash function.
>
> Well, when using read_iterate you avoid reading extra data over the
> network when the object (chunk) exists (and is sparse). We can
> probably have some optimization here, and only allocate and memset a
> buffer once for the case where len == objsize and reuse it later.

Reading src/librbd.cc, I don't see the holes going over the wire in
either case. read() is just a simple wrapper on top of read_iterate(),
that memsets to 0 in case of a hole. Which in this case he was doing
manually, so why not just use read() in the first place.

Re: [PATCH 2/2] rbd: add an option for md5 checksumming (v3)

[Christian Brunner]

2011/8/26 Tommi Virtanen <tommi.virtanen@dreamhost.com>:
> On Fri, Aug 26, 2011 at 12:25, Yehuda Sadeh Weinraub <yehudasa@gmail.com> wrote:
>> On Fri, Aug 26, 2011 at 12:10 PM, Tommi Virtanen
>> <tommi.virtanen@dreamhost.com> wrote:
>>> e.g. 8kB at a time. And at that point you might as well just use read
>>> and not read_iterate, that'll do the memsetting etc for you, and then
>>> you can use a static buffer and avoid malloc/free every round. There's
>>> no shortcut to be had from "skipping" holes when you need to feed
>>> bytes to a hash function.
>>
>> Well, when using read_iterate you avoid reading extra data over the
>> network when the object (chunk) exists (and is sparse). We can
>> probably have some optimization here, and only allocate and memset a
>> buffer once for the case where len == objsize and reuse it later.
>
> Reading src/librbd.cc, I don't see the holes going over the wire in
> either case. read() is just a simple wrapper on top of read_iterate(),
> that memsets to 0 in case of a hole. Which in this case he was doing
> manually, so why not just use read() in the first place.

I think Yehuda meant that we could reuse the buffer to avoid the
malloc/memset for every hole.

But I think that the need for optimization in this case isn't really
that big and the code is simpler to read without having a global
buffer of zeros.

Christian

Re: [PATCH 2/2] rbd: add an option for md5 checksumming (v3)

[Yehuda Sadeh Weinraub]

On Fri, Aug 26, 2011 at 1:03 PM, Tommi Virtanen
<tommi.virtanen@dreamhost.com> wrote:
> On Fri, Aug 26, 2011 at 12:25, Yehuda Sadeh Weinraub <yehudasa@gmail.com> wrote:
>> On Fri, Aug 26, 2011 at 12:10 PM, Tommi Virtanen
>> <tommi.virtanen@dreamhost.com> wrote:
>>> e.g. 8kB at a time. And at that point you might as well just use read
>>> and not read_iterate, that'll do the memsetting etc for you, and then
>>> you can use a static buffer and avoid malloc/free every round. There's
>>> no shortcut to be had from "skipping" holes when you need to feed
>>> bytes to a hash function.
>>
>> Well, when using read_iterate you avoid reading extra data over the
>> network when the object (chunk) exists (and is sparse). We can
>> probably have some optimization here, and only allocate and memset a
>> buffer once for the case where len == objsize and reuse it later.
>
> Reading src/librbd.cc, I don't see the holes going over the wire in
> either case. read() is just a simple wrapper on top of read_iterate(),
> that memsets to 0 in case of a hole. Which in this case he was doing
> manually, so why not just use read() in the first place.
>

Yeah, you're right.. the librbd::read() already does everything.