Re: [PATCH v2 3/5] compact: preserve backup database until compacted database is in place

[Jani Nikula <jani@nikula.org>]

On Wed, 13 Nov 2013, Tomi Ollila <tomi.ollila@iki.fi> wrote:
> It is less error prone and window of failure opportunity is smaller
> if the old (backup) database is always renamed (instead of sometimes
> rmtree'd) before new (compacted) database is put into its place.
> Finally rmtree() old database in case old database backup is not kept.
> ---
>  lib/database.cc | 42 +++++++++++++++++++++++++-----------------
>  1 file changed, 25 insertions(+), 17 deletions(-)
>
> diff --git a/lib/database.cc b/lib/database.cc
> index 3530cb6..ee09c5e 100644
> --- a/lib/database.cc
> +++ b/lib/database.cc
> @@ -873,6 +873,7 @@ notmuch_database_compact (const char *path,
>      notmuch_status_t ret = NOTMUCH_STATUS_SUCCESS;
>      notmuch_database_t *notmuch = NULL;
>      struct stat statbuf;
> +    notmuch_bool_t keep_backup;
>  
>      local = talloc_new (NULL);
>      if (! local)
> @@ -898,17 +899,25 @@ notmuch_database_compact (const char *path,
>  	goto DONE;
>      }
>  
> -    if (backup_path != NULL) {
> -	if (stat (backup_path, &statbuf) != -1) {
> -	    fprintf (stderr, "Backup path already exists: %s\n", backup_path);
> -	    ret = NOTMUCH_STATUS_FILE_ERROR;
> -	    goto DONE;
> -	}
> -	if (errno != ENOENT) {
> -	    fprintf (stderr, "Unknown error while stat()ing backup path: %s\n",
> -		     strerror (errno));
> +    if (backup_path == NULL) {
> +	if (! (backup_path = talloc_asprintf (local, "%s.old", xapian_path))) {
> +	    ret = NOTMUCH_STATUS_OUT_OF_MEMORY;
>  	    goto DONE;
>  	}
> +	keep_backup = FALSE;
> +    }
> +    else
> +	keep_backup = TRUE;

*cough* I thought you were the style police around here *cough*

> +
> +    if (stat (backup_path, &statbuf) != -1) {
> +	fprintf (stderr, "Backup path already exists: %s\n", backup_path);

The user will be confused if he specifically didn't add --backup and
happens to get this. But maybe it's a corner case. *shrug*.

> +	ret = NOTMUCH_STATUS_FILE_ERROR;
> +	goto DONE;
> +    }
> +    if (errno != ENOENT) {
> +	fprintf (stderr, "Unknown error while stat()ing backup path: %s\n",
> +		 strerror (errno));

ret = ?

> +	goto DONE;
>      }
>  
>      try {
> @@ -924,14 +933,10 @@ notmuch_database_compact (const char *path,
>  	goto DONE;
>      }
>  
> -    if (backup_path) {
> -	if (rename (xapian_path, backup_path)) {
> -	    fprintf (stderr, "Error moving old database out of the way\n");
> -	    ret = NOTMUCH_STATUS_FILE_ERROR;
> -	    goto DONE;
> -	}
> -    } else {
> -	rmtree (xapian_path);
> +    if (rename (xapian_path, backup_path)) {
> +	fprintf (stderr, "Error moving old database out of the way\n");
> +	ret = NOTMUCH_STATUS_FILE_ERROR;
> +	goto DONE;
>      }
>  
>      if (rename (compact_xapian_path, xapian_path)) {
> @@ -940,6 +945,9 @@ notmuch_database_compact (const char *path,
>  	goto DONE;
>      }
>  
> +    if (! keep_backup)
> +	rmtree (backup_path);
> +
>    DONE:
>      if (notmuch)
>  	notmuch_database_destroy (notmuch);
> -- 
> 1.8.3.1
>
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