Re: [Qemu-devel] [PATCH v5 6/6] exec: improve error handling and reporting in file_ram_alloc() and gethugepagesize()

[Hu Tao]

On Wed, Aug 06, 2014 at 10:49:23PM +1000, Peter Crosthwaite wrote:
> You subject line is excessively long. How about just "improve RAM file
> error handling" and elaborate in a commit msg para?

After splitting both patches are improving of RAM file error handling.
I'll reword the subjects and drop this one.

> 
> On Wed, Aug 6, 2014 at 3:36 PM, Hu Tao <address@hidden> wrote:
> > This patch fixes two problems of memory-backend-file:
> >
> 
> It looks like two self contained changes. Any reason to not split?
> 
> > 1. If user adds a memory-backend-file object using object_add command,
> >    specifying a non-existing directory for property mem-path, qemu
> >    will core dump with message:
> >
> >      /nonexistingdir: No such file or directory
> >      Bad ram offset fffffffffffff000
> >      Aborted (core dumped)
> >
> >    with this patch, qemu reports error message like:
> >
> >      qemu-system-x86_64: -object 
> > memory-backend-file,mem-path=/nonexistingdir,id=mem-file0,size=128M:
> >      failed to stat file /nonexistingdir: No such file or directory
> >
> > 2. If user adds a memory-backend-file object using object_add command,
> >    specifying a size that is less than huge page size, qemu
> >    will core dump with message:
> >
> >      Bad ram offset fffffffffffff000
> >      Aborted (core dumped)
> >
> >    with this patch, qemu reports error message like:
> >
> >      qemu-system-x86_64: -object 
> > memory-backend-file,mem-path=/hugepages,id=mem-file0,size=1M: memory
> >      size 0x100000 should be euqal or larger than huge page size 0x200000
> 
> "equal".
> 
> >
> > Signed-off-by: Hu Tao <address@hidden>
> > ---
> >  exec.c | 21 ++++++++++++---------
> >  1 file changed, 12 insertions(+), 9 deletions(-)
> >
> > diff --git a/exec.c b/exec.c
> > index 7e60a44..6512820 100644
> > --- a/exec.c
> > +++ b/exec.c
> > @@ -996,7 +996,7 @@ void qemu_mutex_unlock_ramlist(void)
> >
> 
> >  #define HUGETLBFS_MAGIC       0x958458f6
> >
> > -static long gethugepagesize(const char *path)
> > +static long gethugepagesize(const char *path, Error **errp)
> >  {
> >      struct statfs fs;
> >      int ret;
> > @@ -1006,7 +1006,7 @@ static long gethugepagesize(const char *path)
> >      } while (ret != 0 && errno == EINTR);
> >
> >      if (ret != 0) {
> > -        perror(path);
> > +        error_setg_errno(errp, errno, "failed to get size of file %s", 
> > path);
> 
> I think your error message is imprecise. It's not the file size you
> are trying to get its the page size for that file (or its underlying
> file system I think).

changed to: failed to get page size of file

> 
> >          return 0;
> >      }
> >
> > @@ -1024,17 +1024,20 @@ static void *file_ram_alloc(RAMBlock *block,
> >      char *filename;
> >      char *sanitized_name;
> >      char *c;
> > -    void *area;
> > +    void *area = NULL;
> >      int fd;
> > -    unsigned long hpagesize;
> > +    uint64_t hpagesize;
> >
> > -    hpagesize = gethugepagesize(path);
> > -    if (!hpagesize) {
> > +    hpagesize = gethugepagesize(path, errp);
> > +    if (errp && *errp) {
> 
> More flow control dependent on non NULL errp. I think you want a
> local_err for safety here.

Okay.

> 
> >          goto error;
> >      }
> >
> >      if (memory < hpagesize) {
> > -        return NULL;
> > +        error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be euqal to "
> 
> "equal"

thanks!

> 
> Regards,
> Peter
> 
> > +                   "or larger than huge page size 0x%" PRIx64,
> > +                   memory, hpagesize);
> > +        goto error;
> >      }
> >
> >      if (kvm_enabled() && !kvm_has_sync_mmu()) {
> > @@ -1094,8 +1097,8 @@ static void *file_ram_alloc(RAMBlock *block,
> >      return area;
> >
> >  error:
> > -    if (mem_prealloc) {
> > -        exit(1);
> > +    if (area && area != MAP_FAILED) {
> > +        munmap(area, memory);
> >      }
> >      return NULL;
> >  }
> > --
> > 1.9.3
> >
> >