Re: [Qemu-devel] [PATCH v2] qemu-io: add pattern file for write command

[Max Reitz]

On 29.05.19 13:46, Denis Plotnikov wrote:
> The patch allows to provide a pattern file for write
> command. There was no similar ability before.
> ---
>  qemu-io-cmds.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 54 insertions(+), 4 deletions(-)
> 
> diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
> index 09750a23ce..148f2ff92a 100644
> --- a/qemu-io-cmds.c
> +++ b/qemu-io-cmds.c
> @@ -21,6 +21,7 @@
>  #include "qemu/option.h"
>  #include "qemu/timer.h"
>  #include "qemu/cutils.h"
> +#include "string.h"
>  
>  #define CMD_NOFILE_OK   0x01
>  
> @@ -343,6 +344,35 @@ static void *qemu_io_alloc(BlockBackend *blk, size_t 
> len, int pattern)
>      return buf;
>  }
>  
> +static void *qemu_io_alloc_from_file(BlockBackend *blk, size_t len,
> +                                     char *file_name)
> +{
> +    void *buf;
> +    FILE *f = fopen(file_name, "r");
> +
> +    if (!f) {
> +        printf("cannot open file '%s'\n", file_name);

strerror(errno) would probably be helpful.

> +        return NULL;
> +    }
> +
> +    if (qemuio_misalign) {
> +        len += MISALIGN_OFFSET;
> +    }
> +    buf = blk_blockalign(blk, len);
> +    memset(buf, 0, len);
> +
> +    if (!fread(buf, sizeof(char), len, f)) {

(1) You should probably check ferror(f),

(2) Currently, on a short read, the rest in buf is unallocated.  I think
it would be nicest if the pattern would be repeated to fill the whole
buffer.

> +        printf("file '%s' is empty\n", file_name);
> +        qemu_vfree(buf);
> +        return NULL;
> +    }
> +
> +    if (qemuio_misalign) {
> +        buf += MISALIGN_OFFSET;

This still uses pointer arithmetic on a void * pointer as Vladimir has
said.  Making buf a char * pointer should be the simplest way to fix this.

> +    }
> +    return buf;
> +}
> +
>  static void qemu_io_free(void *p)
>  {
>      if (qemuio_misalign) {
> @@ -965,7 +995,7 @@ static const cmdinfo_t write_cmd = {
>      .perm       = BLK_PERM_WRITE,
>      .argmin     = 2,
>      .argmax     = -1,
> -    .args       = "[-bcCfnquz] [-P pattern] off len",
> +    .args       = "[-bcCfnquz] [-P pattern | -s source_file] off len",
>      .oneline    = "writes a number of bytes at a specified offset",
>      .help       = write_help,
>  };
> @@ -974,7 +1004,7 @@ static int write_f(BlockBackend *blk, int argc, char 
> **argv)
>  {
>      struct timeval t1, t2;
>      bool Cflag = false, qflag = false, bflag = false;
> -    bool Pflag = false, zflag = false, cflag = false;
> +    bool Pflag = false, zflag = false, cflag = false, sflag = false;
>      int flags = 0;
>      int c, cnt, ret;
>      char *buf = NULL;
> @@ -983,8 +1013,9 @@ static int write_f(BlockBackend *blk, int argc, char 
> **argv)
>      /* Some compilers get confused and warn if this is not initialized.  */
>      int64_t total = 0;
>      int pattern = 0xcd;
> +    char *file_name;
>  
> -    while ((c = getopt(argc, argv, "bcCfnpP:quz")) != -1) {
> +    while ((c = getopt(argc, argv, "bcCfnpP:quzs:")) != -1) {
>          switch (c) {
>          case 'b':
>              bflag = true;
> @@ -1020,6 +1051,10 @@ static int write_f(BlockBackend *blk, int argc, char 
> **argv)
>          case 'z':
>              zflag = true;
>              break;
> +        case 's':
> +            sflag = true;
> +            file_name = g_strdup(optarg);
> +            break;
>          default:
>              qemuio_command_usage(&write_cmd);
>              return -EINVAL;
> @@ -1056,6 +1091,14 @@ static int write_f(BlockBackend *blk, int argc, char 
> **argv)
>          return -EINVAL;
>      }
>  
> +    if (sflag && Pflag) {
> +        printf("-s and -P cannot be specified at the same time\n");
> +    }
> +
> +    if (sflag && zflag) {
> +        printf("-s and -z cannot be specified at the same time\n");
> +    }
> +

Well, you also need to return from this function, just printing the
message is not sufficient to abort the operation.

Also, the shorter way would be something like:

if ((int)zflag + (int)Pflag + (int)sflag >= 1) {
    printf("Only one of -z, -P, and -s can be specified at the same
time\n");
    return -EINVAL;
}

Max

>      offset = cvtnum(argv[optind]);
>      if (offset < 0) {
>          print_cvtnum_err(offset, argv[optind]);
> @@ -1088,7 +1131,14 @@ static int write_f(BlockBackend *blk, int argc, char 
> **argv)
>      }
>  
>      if (!zflag) {
> -        buf = qemu_io_alloc(blk, count, pattern);
> +        if (sflag) {
> +            buf = qemu_io_alloc_from_file(blk, count, file_name);
> +            if (!buf) {
> +                return -EINVAL;
> +            }
> +        } else {
> +            buf = qemu_io_alloc(blk, count, pattern);
> +        }
>      }
>  
>      gettimeofday(&t1, NULL);
>

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