[SSSD] [PATCH] mmap_cache: Store corrupted mmap cache before reset

Michal Židek mzidek at redhat.com
Wed Aug 21 14:47:22 UTC 2013


On 08/21/2013 02:01 PM, Jakub Hrozek wrote:
> On Wed, Aug 21, 2013 at 10:27:38AM +0200, Lukas Slebodnik wrote:
>> On (21/08/13 09:50), Pavel Březina wrote:
>>> On 08/19/2013 09:56 PM, Michal Židek wrote:
>>>> +static void  sss_mc_save_corrupted(struct sss_mc_ctx *mc_ctx)
>>>> +{
>>>> +    int err;
>>>> +    int fd = -1;
>>>> +    ssize_t written;
>>>> +    char *file = NULL;
>>>> +    TALLOC_CTX *tmp_ctx;
>>>> +
>>>> +    if (mc_ctx == NULL) {
>>>> +        DEBUG(SSSDBG_TRACE_FUNC,
>>>> +              ("Cannot store uninitialized cache. Nothing to do.\n"));
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    tmp_ctx = talloc_new(NULL);
>>>> +    if (tmp_ctx == NULL) {
>>>> +        DEBUG(SSSDBG_CRIT_FAILURE, ("Out of memory.\n"));
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    file = talloc_asprintf(tmp_ctx, "%s_%s",
>>>> +                           mc_ctx->file, "corrupted");
>>>> +    if (file == NULL) {
>>>> +        DEBUG(SSSDBG_CRIT_FAILURE, ("Out of memory.\n"));
>>>> +        goto done;
>>>> +    }
>>>> +
>>>> +    /* We will always store only the last problematic cache state */
>>>> +    fd = creat(file, 0600);
>>>> +    if (fd == -1) {
>>>> +        err = errno;
>>>> +        DEBUG(SSSDBG_CRIT_FAILURE,
>>>> +              ("Failed to open file '%s' [%d]: %s\n",
>>>> +               file, err, strerror(err)));
>>>> +        goto done;
>>>> +    }
>>>> +
>>>> +    written = write(fd, mc_ctx->mmap_base, mc_ctx->mmap_size);
>>>
>>> Shouldn't sss_atomic_write_s() be used?

sss_atomic_write_s is probably better. I though that the function
is only useful for non-blocking sockets, but after reading it's code I 
see it is good to use it here too.

>>>> +    if (written != mc_ctx->mmap_size) {
>>>> +        if (written == -1) {
>>>> +            err = errno;
>>>> +            DEBUG(SSSDBG_CRIT_FAILURE,
>>>> +                  ("write() failed [%d]: %s\n", err, strerror(err)));
>>>> +        } else {
>>>> +            DEBUG(SSSDBG_CRIT_FAILURE,
>>>> +                  ("write() returned %zd (expected (%zd))\n",
>>>> +                   written, mc_ctx->mmap_size));
>>>> +        }
>>>> +        goto done;
>>>> +    }
>>>
>>> I think the file should be unlinked in case of error.

Ok. I added unlink() call for the case if write returns -1. If the
file was only partially written (for whatever reason) it can still
hold some useful information, so I would prefer to keep it.

>>>
>>>> +
>>>> +    sss_log(SSS_LOG_NOTICE,
>>>> +            "Stored copy of corrupted mmap cache in file '%s\n'", file);
>>>> +done:
>>>> +    if (fd != -1) {
>>>> +        close(fd);
>>>> +    }
>>>> +    talloc_free(tmp_ctx);
>>>> +}
>>
>> I think that function sss_mc_save_corrupted will never be called with patches
>> from thread "[PATCHES] mmap_cache: Skip records which doesn't have same hash"
>>
>> It is very likely that it is a dead code. I would prefer to ignore this
>> nitpicks, because patches have already been pushed.
>>
>> LS
>
> No, sorry, I would prefer to always fix and improve code. At the very
> least, existing code acts as a reference when developing new code.

Since the original patch was already pushed, this one just adds the
requested changes.

Thanks
Michal
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