xfs
[Top] [All Lists]

Re: [PATCH 01/13 V2] xfs_db: Allow writes of corrupted data by optionall

To: Eric Sandeen <sandeen@xxxxxxxxxxx>
Subject: Re: [PATCH 01/13 V2] xfs_db: Allow writes of corrupted data by optionally skipping write verifiers
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Tue, 24 Mar 2015 08:07:23 -0400
Cc: Eric Sandeen <sandeen@xxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <551070CC.9040309@xxxxxxxxxxx>
References: <1426624395-8258-1-git-send-email-sandeen@xxxxxxxxxx> <1426624395-8258-2-git-send-email-sandeen@xxxxxxxxxx> <551070CC.9040309@xxxxxxxxxxx>
User-agent: Mutt/1.5.23 (2014-03-12)
On Mon, Mar 23, 2015 at 03:00:12PM -0500, Eric Sandeen wrote:
> Being able to write corrupt data is handy if we wish to test
> repair against specific types of corruptions.
> 
> Add a "-c" option to the write command which allows this by removing
> the write verifier.
> 
> Note that this also skips CRC updates; it's not currently possible
> to write invalid data with a valid CRC; CRC recalculation is
> intertwined with validation.
> 
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

> 
> V2: Fix whitespace, remove "if (argc)", and test for
> iocur_top->bp->b_ops before attempting to deref it.
> 
> diff --git a/db/io.c b/db/io.c
> index 7f1b76a..c5898f1 100644
> --- a/db/io.c
> +++ b/db/io.c
> @@ -457,6 +457,13 @@ write_cur_bbs(void)
>  }
>  
>  void
> +xfs_dummy_verify(
> +     struct xfs_buf *bp)
> +{
> +     return;
> +}
> +
> +void
>  write_cur(void)
>  {
>       if (iocur_sp < 0) {
> diff --git a/db/io.h b/db/io.h
> index 71082e6..31d96b4 100644
> --- a/db/io.h
> +++ b/db/io.h
> @@ -63,6 +63,7 @@ extern void set_cur(const struct typ *t, __int64_t d, int 
> c, int ring_add,
>                       bbmap_t *bbmap);
>  extern void     ring_add(void);
>  extern void  set_iocur_type(const struct typ *t);
> +extern void  xfs_dummy_verify(struct xfs_buf *bp);
>  
>  /*
>   * returns -1 for unchecked, 0 for bad and 1 for good
> diff --git a/db/write.c b/db/write.c
> index a0f14f4..655b618 100644
> --- a/db/write.c
> +++ b/db/write.c
> @@ -38,7 +38,7 @@ static int  write_f(int argc, char **argv);
>  static void     write_help(void);
>  
>  static const cmdinfo_t       write_cmd =
> -     { "write", NULL, write_f, 0, -1, 0, N_("[field or value]..."),
> +     { "write", NULL, write_f, 0, -1, 0, N_("[-c] [field or value]..."),
>         N_("write value to disk"), write_help };
>  
>  void
> @@ -79,6 +79,7 @@ write_help(void)
>  "  String mode: 'write \"This_is_a_filename\" - write null terminated 
> string.\n"
>  "\n"
>  " In data mode type 'write' by itself for a list of specific commands.\n\n"
> +" Specifying the -c option will allow writes of invalid (corrupt) data.\n\n"
>  ));
>  
>  }
> @@ -90,6 +91,10 @@ write_f(
>  {
>       pfunc_t pf;
>       extern char *progname;
> +     int c;
> +     int corrupt = 0;                /* Allow write of corrupt data; skip 
> verification */
> +     struct xfs_buf_ops nowrite_ops;
> +     const struct xfs_buf_ops *stashed_ops = NULL;
>  
>       if (x.isreadonly & LIBXFS_ISREADONLY) {
>               dbprintf(_("%s started in read only mode, writing disabled\n"),
> @@ -109,12 +114,34 @@ write_f(
>               return 0;
>       }
>  
> -     /* move past the "write" command */
> -     argc--;
> -     argv++;
> +     while ((c = getopt(argc, argv, "c")) != EOF) {
> +             switch (c) {
> +             case 'c':
> +                     corrupt = 1;
> +                     break;
> +             default:
> +                     dbprintf(_("bad option for write command\n"));
> +                     return 0;
> +             }
> +     }
> +
> +     argc -= optind;
> +     argv += optind;
> +
> +     if (iocur_top->bp->b_ops && corrupt) {
> +             /* Temporarily remove write verifier to write bad data */
> +             stashed_ops = iocur_top->bp->b_ops;
> +             nowrite_ops.verify_read = stashed_ops->verify_read;
> +             nowrite_ops.verify_write = xfs_dummy_verify;
> +             iocur_top->bp->b_ops = &nowrite_ops;
> +             dbprintf(_("Allowing write of corrupted data\n"));
> +     }
>  
>       (*pf)(DB_WRITE, cur_typ->fields, argc, argv);
>  
> +     if (stashed_ops)
> +             iocur_top->bp->b_ops = stashed_ops;
> +
>       return 0;
>  }
>  
> diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
> index 4d8d4ff..d527230 100644
> --- a/man/man8/xfs_db.8
> +++ b/man/man8/xfs_db.8
> @@ -711,7 +711,7 @@ and
>  bits respectively, and their string equivalent reported
>  (but no modifications are made).
>  .TP
> -.BI "write [" "field value" "] ..."
> +.BI "write [\-c] [" "field value" "] ..."
>  Write a value to disk.
>  Specific fields can be set in structures (struct mode),
>  or a block can be set to data values (data mode),
> @@ -729,6 +729,12 @@ contents of the block can be shifted or rotated left or 
> right, or filled
>  with a sequence, a constant value, or a random value. In this mode
>  .B write
>  with no arguments gives more information on the allowed commands.
> +.RS 1.0i
> +.TP 0.4i
> +.B \-c
> +Skip write verifiers and CRC recalculation; allows invalid data to be written
> +to disk.
> +.RE
>  .SH TYPES
>  This section gives the fields in each structure type and their meanings.
>  Note that some types of block cover multiple actual structures,
> 
> _______________________________________________
> xfs mailing list
> xfs@xxxxxxxxxxx
> http://oss.sgi.com/mailman/listinfo/xfs

<Prev in Thread] Current Thread [Next in Thread>