Re: [Qemu-devel] [PATCH v2 1/5] error: add error_set_file_open_failed

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 15 Mar 2012 00:55:10 +0200
Alon Levy <alevy@redhat.com> wrote:

> Signed-off-by: Alon Levy <alevy@redhat.com>
> ---
>  cpus.c               |    4 ++--
>  error.c              |   44 ++++++++++++++++++++++++++++++++++++++++++++
>  error.h              |    4 ++++
>  qerror.c             |   36 ++++++++++++++++++++++++++++++++++++
>  qerror.h             |   27 +++++++++++++++++++++++++++
>  qga/commands-posix.c |    2 +-
>  6 files changed, 114 insertions(+), 3 deletions(-)
> 
> diff --git a/cpus.c b/cpus.c
> index 17b055f..c87035f 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -1178,7 +1178,7 @@ void qmp_memsave(int64_t addr, int64_t size, const char *filename,
>  
>      f = fopen(filename, "wb");
>      if (!f) {
> -        error_set(errp, QERR_OPEN_FILE_FAILED, filename);
> +        error_set_file_open_failed(errp, filename, errno);
>          return;
>      }
>  
> @@ -1208,7 +1208,7 @@ void qmp_pmemsave(int64_t addr, int64_t size, const char *filename,
>  
>      f = fopen(filename, "wb");
>      if (!f) {
> -        error_set(errp, QERR_OPEN_FILE_FAILED, filename);
> +        error_set_file_open_failed(errp, filename, errno);
>          return;
>      }
>  
> diff --git a/error.c b/error.c
> index 990050f..b32d7f5 100644
> --- a/error.c
> +++ b/error.c
> @@ -144,3 +144,47 @@ void error_set_qobject(Error **errp, QObject *obj)
>  
>      *errp = err;
>  }
> +
> +void error_set_file_open_failed(Error **errp, const char *file_name, int ret)
> +{

I prefer having:

 void qemu_fopen_err(const char *filename, const char *mode, Error **errp);

It could live in osdep.c I think.

Also, please split this into two patches:

 1. Add all the errors
 2. Add qemu_fopen_err()

And don't change unrelated code. Other commands that will benefit from the
new function should be converted in a different series.

CC'ing Anthony in case he has a different suggestion for the fopen()
wrapper (of course we can an open() version too).

> +    const char *fmt = NULL;
> +
> +    switch (ret) {
> +    case EACCES:
> +        fmt = QERR_OPEN_FILE_EACCES;
> +        break;
> +    case EINTR:
> +        fmt = QERR_OPEN_FILE_EINTR;
> +        break;
> +    case EEXIST:
> +        fmt = QERR_OPEN_FILE_EEXIST;
> +        break;
> +    case EMFILE:
> +        fmt = QERR_OPEN_FILE_EMFILE;
> +        break;
> +    case ENOSPC:
> +        fmt = QERR_OPEN_FILE_ENOSPC;
> +        break;
> +    case EPERM:
> +        fmt = QERR_OPEN_FILE_EPERM;
> +        break;
> +    case EROFS:
> +        fmt = QERR_OPEN_FILE_EROFS;
> +        break;
> +    case ENOTDIR:
> +        fmt = QERR_OPEN_FILE_ENOTDIR;
> +        break;
> +    case EFBIG:
> +        fmt = QERR_OPEN_FILE_EFBIG;
> +        break;
> +    default:
> +        /*
> +         * EINVAL and ENOTSUP will result in the default
> +         *
> +         * ENOENT too, it's used by (for instance) bdrv_create_file for
> +         * a different purpose then open (2) so just give a generic error.
> +         */
> +        fmt = QERR_OPEN_FILE_FAILED;
> +    }
> +    error_set(errp, fmt, file_name);
> +}
> diff --git a/error.h b/error.h
> index 6361f40..f3a80f3 100644
> --- a/error.h
> +++ b/error.h
> @@ -67,4 +67,8 @@ void error_free(Error *err);
>   */
>  bool error_is_type(Error *err, const char *fmt);
>  
> +/**
> + * Helper to set error for a open (2) style return code.
> + */
> +void error_set_file_open_failed(Error **errp, const char *file_name, int ret);
>  #endif
> diff --git a/qerror.c b/qerror.c
> index f55d435..23c260b 100644
> --- a/qerror.c
> +++ b/qerror.c
> @@ -213,6 +213,42 @@ static const QErrorStringTable qerror_table[] = {
>          .desc      = "Could not open '%(filename)'",
>      },
>      {
> +        .error_fmt = QERR_OPEN_FILE_EINTR,
> +        .desc      = "Interrupted open of '%(filename)'",
> +    },

I see that you're adding _OPEN_FILE_ flavors to be able to pass the filename
in the error. But this just workarounds a limitation of qerror: we should be
able to set the error message at run-time.

I think the best thing to do is to have QERR_EINTR instead, with a generic
message like "Operation has been interrupted" and we can improve QError to
extend it to contain the file name.

This is valid for all errors below.

> +    {
> +        .error_fmt = QERR_OPEN_FILE_EACCES,
> +        .desc      = "Cannot access '%(filename)'",
> +    },

We already have PermissionDenied.

> +    {
> +        .error_fmt = QERR_OPEN_FILE_EEXIST,
> +        .desc      = "File already exists '%(filename)'",
> +    },

I wouldn't mind not having this one because most of the time qemu doesn't
care if the file already exists.

> +    {
> +        .error_fmt = QERR_OPEN_FILE_EMFILE,
> +        .desc      = "Max open files when opening '%(filename)'",
> +    },

This is an exception for what I said about _OPEN_FILE_ flavors above, this
is fine because it's really a file error.

> +    {
> +        .error_fmt = QERR_OPEN_FILE_ENOSPC,
> +        .desc      = "No space left opening '%(filename)'",
> +    },
> +    {
> +        .error_fmt = QERR_OPEN_FILE_EPERM,
> +        .desc      = "Permission denied (EPERM) for '%(filename)'",
> +    },

I wouldn't mind reporting EACCESS and EPERM the same.

> +    {
> +        .error_fmt = QERR_OPEN_FILE_EROFS,
> +        .desc      = "Read only filesystem opening '%(filename)'",
> +    },

Let's have a QERR_READ_ONLY.

> +    {
> +        .error_fmt = QERR_OPEN_FILE_ENOTDIR,
> +        .desc      = "Directory related error opening '%(filename)'",
> +    },
> +    {
> +        .error_fmt = QERR_OPEN_FILE_EFBIG,
> +        .desc      = "File too big opening '%(filename)'",
> +    },
> +    {
>          .error_fmt = QERR_PERMISSION_DENIED,
>          .desc      = "Insufficient permission to perform this operation",
>      },
> diff --git a/qerror.h b/qerror.h
> index e26c635..6ab9b8d 100644
> --- a/qerror.h
> +++ b/qerror.h
> @@ -181,6 +181,33 @@ QError *qobject_to_qerror(const QObject *obj);
>  #define QERR_OPEN_FILE_FAILED \
>      "{ 'class': 'OpenFileFailed', 'data': { 'filename': %s } }"
>  
> +#define QERR_OPEN_FILE_EINTR \
> +    "{ 'class': 'OpenFileEINTR', 'data': { 'filename': %s } }"
> +
> +#define QERR_OPEN_FILE_EACCES \
> +    "{ 'class': 'OpenFileEACCES', 'data': { 'filename': %s } }"
> +
> +#define QERR_OPEN_FILE_EEXIST \
> +    "{ 'class': 'OpenFileEEXIST', 'data': { 'filename': %s } }"
> +
> +#define QERR_OPEN_FILE_EMFILE \
> +    "{ 'class': 'OpenFileEMFILE', 'data': { 'filename': %s } }"
> +
> +#define QERR_OPEN_FILE_ENOSPC \
> +    "{ 'class': 'OpenFileENOSPC', 'data': { 'filename': %s } }"
> +
> +#define QERR_OPEN_FILE_EPERM \
> +    "{ 'class': 'OpenFileEPERM', 'data': { 'filename': %s } }"
> +
> +#define QERR_OPEN_FILE_EROFS \
> +    "{ 'class': 'OpenFileEROFS', 'data': { 'filename': %s } }"
> +
> +#define QERR_OPEN_FILE_ENOTDIR \
> +    "{ 'class': 'OpenFileENOTDIR', 'data': { 'filename': %s } }"
> +
> +#define QERR_OPEN_FILE_EFBIG \
> +    "{ 'class': 'OpenFileEFBIG', 'data': { 'filename': %s } }"
> +
>  #define QERR_PERMISSION_DENIED \
>      "{ 'class': 'PermissionDenied', 'data': {} }"
>  
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 7b2be2f..4e5ef7f 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -134,7 +134,7 @@ int64_t qmp_guest_file_open(const char *path, bool has_mode, const char *mode, E
>      slog("guest-file-open called, filepath: %s, mode: %s", path, mode);
>      fh = fopen(path, mode);
>      if (!fh) {
> -        error_set(err, QERR_OPEN_FILE_FAILED, path);
> +        error_set_file_open_failed(err, path, errno);
>          return -1;
>      }
>