Re: [Xen-devel] [PATCH 2/2] tools/xenstore: Accumulate errors in xenstore-ls and exit appropriately

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of David 
> Woodhouse
> Sent: 19 March 2020 20:40
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Juergen Gross <jgross@xxxxxxxx>; Ian Jackson <ian.jackson@xxxxxxxxxxxxx>; 
> Wei Liu <wl@xxxxxxx>
> Subject: [Xen-devel] [PATCH 2/2] tools/xenstore: Accumulate errors in 
> xenstore-ls and exit
> appropriately
> 
> From: David Woodhouse <dwmw@xxxxxxxxxxxx>
> 
> Report only one error to stderr for each node, regardless of whether it's
> xs_read, xs_get_permissions or xs_directory on the child that fails.
> 
> Always exit with a non-zero code if any failure happens, reporting the
> last error that occurred.
> 
> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
> ---
>  tools/xenstore/xenstore_client.c | 35 ++++++++++++++++++++++++--------
>  1 file changed, 26 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/xenstore/xenstore_client.c 
> b/tools/xenstore/xenstore_client.c
> index ae7ed3eb9e..0c891961ae 100644
> --- a/tools/xenstore/xenstore_client.c
> +++ b/tools/xenstore/xenstore_client.c
> @@ -140,7 +140,7 @@ static int show_whole_path = 0;
> 
>  #define MIN(a, b) (((a) < (b))? (a) : (b))
> 
> -static void do_ls(struct xs_handle *h, char *path, int cur_depth, int 
> show_perms)
> +static int do_ls(struct xs_handle *h, char *path, int cur_depth, int 
> show_perms, int error, int
> ignore_errors)
>  {
>      char **e;
>      char *newpath, *val;
> @@ -150,9 +150,16 @@ static void do_ls(struct xs_handle *h, char *path, int 
> cur_depth, int show_perms
> 
>      e = xs_directory(h, XBT_NULL, path, &num);
>      if (e == NULL) {
> -        if (cur_depth && errno == ENOENT) {
> -            /* If a node disappears while recursing, silently move on. */
> -            return;
> +        if (cur_depth && (errno == ENOENT || errno == EACCES)) {
> +            /*
> +             * If a node disappears or becomes inaccessible while traversing,
> +             * only print an error if previous operations on this node 
> haven't
> +             * done do. Then move on.
> +             */
> +            error = errno;
> +            if (!ignore_errors)
> +                warn("xs_directory (%s)", path);
> +            return error;
>          }
> 
>          err(1, "xs_directory (%s)", path);
> @@ -197,7 +204,8 @@ static void do_ls(struct xs_handle *h, char *path, int 
> cur_depth, int show_perms
> 
>          /* Print value */
>          if (val == NULL) {
> -            printf(":\n");
> +            error = errno;
> +            printf(": (%s)", strerror(error));
>          }
>          else {
>              if (max_width < (linewid + len + TAG_LEN)) {
> @@ -222,7 +230,11 @@ static void do_ls(struct xs_handle *h, char *path, int 
> cur_depth, int show_perms
>          if (show_perms) {
>              perms = xs_get_permissions(h, XBT_NULL, newpath, &nperms);
>              if (perms == NULL) {
> -                warn("\ncould not access permissions for %s", e[i]);
> +                error = errno;
> +                val = NULL;
> +                /* Don't repeat an error message if xs_read() already failed 
> */
> +                if (val)

How can the code get here? The line above the comment always sets val to NULL.

  Paul

> +                    warn("could not access permissions for %s", e[i]);
>              }
>              else {
>                  int i;
> @@ -238,11 +250,13 @@ static void do_ls(struct xs_handle *h, char *path, int 
> cur_depth, int show_perms
>          }
> 
>          putchar('\n');
> -
> -        do_ls(h, newpath, cur_depth+1, show_perms);
> +
> +        error = do_ls(h, newpath, cur_depth+1, show_perms, error, !val);
>      }
>      free(e);
>      free(newpath);
> +
> +    return error;
>  }
> 
>  static void
> @@ -448,7 +462,10 @@ perform(enum mode mode, int optind, int argc, char 
> **argv, struct xs_handle *xsh
>              break;
>          }
>          case MODE_ls: {
> -            do_ls(xsh, argv[optind], 0, prefix);
> +            int error = do_ls(xsh, argv[optind], 0, prefix, 0, 0);
> +            if (error) {
> +                errx(1, "Errors during traversal. Last error: %s", 
> strerror(error));
> +            }
>              optind++;
>              break;
>          }
> --
> 2.21.0
> 
> 
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