[SSSD] [PATCH] mmap_cache: Store corrupted mmap cache before reset
Michal Židek
mzidek at redhat.com
Wed Aug 21 23:20:26 UTC 2013
On 08/21/2013 04:47 PM, Michal Židek wrote:
> 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
>
Since this was not yet pushed I did one more cosmetic change. I think
calling the close() before unlink() is more readable. If the fd != -1 we
already know that we want to close it, so the conditional check for
unlink() just makes noise before it. And this order is probably more
natural for most cases.
Michal
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