Possible bug when getting batched xattrs

[Joaquim Rocha <joaquim.rocha@xxxxxxx>]

Hi,

I need to get a list of xattrs from one object (so I'm batching them in 
one ObjectReadOperation) but I don't know in advance if all of those 
xattrs exist.

I was expecting to figure out the ones that don't exist from the return 
code of each getxattr call but I have however noticed that as soon one 
nonexistent xattr is processed, its return code gets correctly set to 
-ENODATA but the remaining xattrs are never checked. And what is worse, 
the remaining getxattr op's return codes get assigned to 0.

I am attaching a small test case I've quickly written that proves the 
case. (I am using Ceph 0.80.5)

Could you confirm that this is not the intended behavior (that all read 
op's calls should be processed)?


Thank you in advance,

--
Joaquim Rocha
http://www.joaquimrocha.com

#include <rados/librados.hpp>
#include <sstream>
#include <cstdio>
#include <sys/errno.h>

int main(int argc, char **argv)
{
  if (argc < 5)
  {
    fprintf(stdout, "Usage: %s CONFIGURATION_FILE POOL_NAME OBJ_NAME "
                    "ONE_EXISTING_XATTRIBUTE \n",
            argv[0]);

    return EINVAL;
  }

  librados::Rados rados;

  char *conf = argv[1];
  char *pool = argv[2];
  char *obj = argv[3];
  char *xattr = argv[4];

  rados.init(0);
  rados.conf_read_file(conf);
  rados.connect();

  librados::IoCtx ioctx;
  rados.ioctx_create(pool, ioctx);

  const size_t numXAttrs(5);
  librados::bufferlist buffs[numXAttrs];
  int xattrRets[numXAttrs];

  librados::ObjectReadOperation op;

  fprintf(stdout, "Ret codes before the op: \n");

  for (size_t i = 0; i < numXAttrs; i++)
  {
    xattrRets[i] = -1;
    fprintf(stdout, "  RET#%d: %d\n", i, xattrRets[i]);
  }

  fprintf(stdout, "\n--------\nData and ret codes after the op: \n");

  for (size_t i = 0; i < numXAttrs; i++)
  {
    std::stringstream stream;

    if (i == 0)
      stream << xattr;
    else
      stream << "nonexistent-xattr" << i;

    op.getxattr(stream.str().c_str(), &buffs[i], &xattrRets[i]);
  }

  ioctx.operate(obj, &op, 0);

  for (size_t i = 0; i < numXAttrs; i++)
  {
    librados::bufferlist *buff = &buffs[i];
    std::string value;

    if (buff->length() > 0)
      value = std::string(buff->c_str(), buff->length());

    fprintf(stdout, "  RET#%d: %s %d\n", i, value.c_str(), xattrRets[i]);
  }

  rados.shutdown();

  return 0;
}